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Kevin Myatt grew up in Arkansas to the tune of tornado sirens and the rhythm of hailstones. Chasing twisters like he did in 1999 and getting within a quarter-mile of one was exciting, but he finally tired of 5-month-long summers and 2-inch snowstorms and moved to the cooler climes of Southwest Virginia's mountains in 1999. Kevin thought he was going to be a meteorologist growing up but he credits divine intervention with continually detouring him to a newspaper career instead, landing him in an managing editor job of a small Arkansas paper before coming to The Roanoke Times as a copy editor in 1999. But his love of weather continues to this day, and at the beginning of 2003 he began this weather column in addition to the hiking page he has updated occasionally on Roanoke.com since early 2000. He now works the copy desk for The Roanoke Times and is its principal weather geek, offering weather reporting training classes to reporters and advising the newsroom on upcoming weather stories. He updates this column most Tuesdays and Fridays -- and other times as conditions warrant. Email your weather or comments questions to kevin.myatt@roanoke.com For more on Kevin |
WEATHER JOURNALClick here for the latest winter weather warnings from the National Weather Service in Blacksburg. Click here for ski slope conditions Jan. 9, 2004 @ 1 p.m. IT KEEPS GOING AND GOING AND GOING ... The snow area rather unexpectedly redeveloped over much of the area during the late morning, and steady light to moderate snow has continued into the afternoon. At 8 a.m., Roanoke Regional Airport already had 3 inches on the ground and will probably end up with 4 or more considering the snow that continues to fall. This is above and beyond all expectations as of yesterday by about every weather-knowledgeable person out there. The system has had a few unexpected tricks up its sleeve, and certainly found more moisture than we thought it could find. We'll probably see off and on light to moderate snow through the afternoon with flurries stretching into the evening. Then, with the coastal low developing that could whiten the Outer Banks and the Tidewater, expect brisk northwest winds to key up some more upslope snow showers in the favored western mountain slopes. Tomorrow, it won't get anywhere near freezing as bright sunshine must fight stiff northwest winds bringing in Arctic air and widespread snow cover. It is a lovely snow, with nary a pellet of sleet or a drop of freezing rain. Enjoy it. January 9, 2004 WORLD IS WHITE, ONCE AGAIN Storm systems to the south and north have connected more solidly than appeared likely yesterday and we've had a decent snow here in the Roanoke Valley overnight. Amounts across the area will vary some as a few areas get caught in heavier snow bands. Radar trends suggest snow amounts may even vary quite a bit across the Roanoke metro area, with the southern side getting more than the northern side. But it looks everyone in the metro area is in for 2-3 inches this morning, a bit a more than the original National Weather Service forecasts and a whole lot more than I anticipated with what looked like a ragtag system. I would not be surprised if someone in the area just to our south -- Pulaski, Floyd or Franklin counties, for instance -- doesn't come out with 4-5 inches, maybe an isolated 6. The heaviest snow band has been moving across that area for a few hours now. The northern piece of the system, an upper level low over Kentucky, will move across later today and the steady snow should end by noon, with occasional flurries or a few snow showers continuing into the afternoon. After that, we get a reinforcement of the Arctic air this weekend that will be made a bit colder by the existing snowpack. Then we wait to see next week about additional Arctic air shots and any storm threats. The jury is still out. January 8, 2004 WET ENOUGH TO BE WHITE? It's cold enough for snow -- that's a given. Will it be moist enough? We're watching a couple of pieces of upper level energy today and Friday to see what kind of snow they can squeeze out on us. The biggest question is how much moisture can get packed into our cold, dry atmosphere before the upper level systems move away. There is quite a bit of rain in Mississippi and Louisiana, which represents moisture from the Gulf of Mexico. Should this thick moisture get more entrained into the systems, the snow totals could be higher than the 1 to 2 inches forecast by the National Weather Service. If not, we're left with whatever the systems can bring with them moving over land through very cold and dry air, and whatever can get over the mountains. Unless the radar trends over the next few hours show the moisture from the Deep South making more of a move to the north, I'm just not jumping on this bandwagon. Been burned too many times by the weak systems coming over the mountains. Really, I don't expect much, a few snow showers to maybe a dusting, here in Roanoke that is -- a bit more in the New River Valley and farther west. That's still enough to cause some driving problems, so be careful. January 7, 2004 COLD AND SNOW RETURN In my 6-day absence from the area, the first chunk of Arctic air hinted at here earlier has arrived, with widespread temperatures in the teens this morning just a few days after record warmth (Saturday's 74 degrees and Sunday's 73). There's also a hint of snow with a couple of weak systems moving across the area over the next 72 hours. Besides the strength of the systems, there are big questions about the amount of moisture available for snow. The air mass over us is very cold and very dry. How much the Gulf of Mexico can become a player in these systems and provide some moisture will make the difference between flurries or even just some clouds and a ground-covering blanket of white. In any event, it appears almost certain that this won't be a big snowstorm for us, and at this point I'm really doubtful about any accumulation. It does look like additional chunks of Arctic air will move our way next week with occasional upper level lows threatening snow or ice. Winter will not be denied. The springlike warmth seems like a mirage now. Dec. 31, 2003 AN ACTIVE YEAR Southwest Virginia was on the sidelines of the biggest weather events in 2003. We were close enough to hear the pads popping, but we didn't take a hard hit. Hurricane Isabel and the President's Day snowstorm were the historic weather events of 2003 in our region. We were affected by each of them, but not the way most other parts of the state suffered. For most of us from the Roanoke and New River valleys southward, Isabel was nothing but a few gusty showers, its winds easily surpassed in most cases by a tree-toppling cold frontal passage just three weeks later. The President's Day snowstorm buried cars in Northern Virginia, but here, it just left an annoying enamel-like coating of sleet and ice. It was the weekend after that sleet storm that summarized the year: a mild, moist system moved through, and combination of melting ice and heavy rain sent creeks and rivers over the banks. The 2003 New Year's Baby was wet behind the ears from birth and never really dried out even as the months grew on him. Roanoke finished with 54.24 inches of rainfall, nearly a foot more than normal and about 20 inches more than dry 2002. Nine of the year's 12 months were above normal in precipitation, topped by May's 10.13 inches and 21 days of rain. Mountain Lake and Carvins Cove both filled to the brim this year. Almost no one would have predicted that 18 months ago. The Roanoke Valley's biggest weather of 2003 was decidedly local. A May thunderstorm caused widespread urban street flooding in the city's core, but almost none anywhere else. An August tornado dropped out of an early morning thunderstorm, ripping the roof off of ITT's building and doing other damage near Interstate 81 at Hollins. Breaking the pattern of recent years, we had a real winter weather. In Roanoke, it never snowed more than 6 inches in any single storm, but snow was persistent. In January and February, we had seven accumulating snows. And on March 30, a 6-inch wet snow broke many of spring's blooming trees. Winter made a quick return in December, with nearly 10 inches total of sleet and snow in the final month of the year. 2003 was not a hot year. The daily high temperature never got above 93 in the summer. Eight of the year's 12 months were below normal in temperature. What lies ahead in 2004? Year-long weather prediction is out of the range of modern science, other than some broad, vague trends that often fail to verify. It's probably a safe bet through the law of averages that 2004 will not be as wet as 2003 nor as dry as 2002. With no overpowering El Nino/La Nina patterns in the Pacific with subtle sea surface temperature changes, we may revert to a more "normal" pattern influenced more by the variable factors that usually shape our seasons. Perhaps we see a year of balance between the hot and the cold, and the wet and the dry. Over the past year, we've been seeing more strong Eastern U.S. low pressure areas spin up than we did in recent years, and more intrusions of Arctic air than in those bland late 1990s-early 2000s winters. It's been eight years since a foot-deep snow or a below-zero temperature in Roanoke. Could that be right around the corner? It's also been a while since we've locked in a high pressure long enough in the summer for a heat wave. Specifically, we haven't been higher than 97 degrees on any day since 1999, the last time we saw 100-degree weather here in the valley. Does it seem we might be due for that? I'm sure the next 366 days (it's a leap year, remember) will hold some surprises in our weather. Otherwise, I wouldn't bother writing about it. BIG CHILL, OR NIL? Vicious cold is gathering in northern Canada. Now we wait to see if the dam will break and this frigid cold will ooze across the continental United States, or whether it will stay bottled up in Canada and get pushed eastward or back across the pole to Siberia. Much hangs in the balance for the entire winter weather pattern. A flood of this Arctic air in the first couple of weeks of January, especially if it were enhanced by abundant snowpack over North America, would be hard to move the rest of the winter. Arctic air is the dense, thick-necked bully of the meteorological playground, and doesn't put up with getting shoved around. This is what happened last year, when Arctic air poured south in the second week of January, and didn't really get completely uprooted until very late February. It wasn't bone-chilling cold everyday, but it seldom topped 50 in between the colder shots that brought frequent snow and ice. But if the Arctic air doesn't come down the next few weeks during the peak of winter, it becomes more and more difficult for it to establish. As the sun angle rises, the days get longer and the warmer air from the south starts getting more brave against winter. The "dam" in this case is a persistent zonal jet stream pattern energized by an unusually powerful jet stream out of the Pacific. This burst of high upper level winds has been keeping storm systems moving from west to east rapidly, and it's kept the extreme cold from bulging south into the United States. It did buckle enough to let some cold air in during December, but those air masses moved in and out quickly as did the storm systems that caused the ice and snow for us. Many computer forecast models are showing the Arctic air expanding across the Canadian border into the Dakotas and Minnesota by next weekend. Beyond that time, many complicated, interconnected issues worldwide will come into play: Will massive high pressure areas in the north shove this frigid blast down our throats? Or will the Pacific jet, with some help from a southeastern U.S. high pressure ridge, keep the bulk of it in Canada? Best guess now is that chunks of this Arctic air will begin to break loose and move our way 10 days down the road, but the full honking refrigerated truckload doesn't careen out of Canada. In other words, some really cold periods but probably no constant chill or pipe-freezing blast, at least in the next 2-3 weeks. One thing about major Arctic outbreaks is that the air is incredibly dry. When the core of the cold high pressure is overhead, it's usually clear with no snow and lots of cracking skin. The real action in terms of precipitation occurs around the edges of the air mass, where the Arctic air may interact with milder, wetter Pacific systems or steamy Gulf of Mexico mositure. Big winter storms are more likely to occur near the start and the end of Arctic outbreaks rather than during the middle of them. That's why the possibility of Arctic air poking its head into a fast-moving Pacific jet stream could yield some weather fireworks down the road. But 2004 will start mild and calm. Whether this is a pattern or a respite remains to be seen. December 22, 2003 WINTER RELAXES You can tune out the Bing Crosby. Here in the Roanoke Valley, a white Christmas isn't happening. December 19, 2003 ALBERTA CLIPPER, BAH HUMBUG! Never play cards with a man whose first name is the same as a major city. Never pick a NFL team from Florida on the road against Buffalo or Green Bay in winter. And never, ever call for accumulating snow in the Roanoke Valley with an Alberta clipper. Folks in the New River Valley got a little snow with the clipper, and the mountains of West Virginia, far Southwest Virginia and North Carolina are getting clocked in the continuous upslope snow machine. But other than a few flurries and, of all things, some drizzle, Roanoke and points east came up empty on Thursday. It simply dried up east of the mountains. National Weather Service-Blacksburg describes it well in its forecast discussion this morning: "If you look at the regional radars ... activity looks like it is running into a wall with only spill-over snow showers and flurries occurring east of the higher terrain." If you want to see snow, drive west. Here in the valley, we can turn our attention to the Christmas week drama about to unfold. Big system comes our way toward mid-week. Is it a mild rain? Is it a big snow? Is it rain turning to snow? All options are on the table at this point, and this will be one of the most difficult forecasts we've faced in a long time with such wildly divergent possibilities. Hopefully we'll have a little less blurry focus on it by Monday. See you then. Dec. 18, 2003 CLIPPING US? Today's question is how much snow makes it over the mountains with the Alberta clipper coming our way. Best guess now is maybe an inch here in the Roanoke Valley, more in the favored upslope areas of West Virginia, where it'll probably keep snowing until Saturday morning. An Alberta clipper is a common winter feature, a low pressure area that moves southeast out of south-central Canada toward the East Coast. They're called Alberta clippers because, well, they usually develop in or near the province of Alberta. (Nicknames like Saskatchewan screamer and Manitoba mauler have been developed for similar systems that develop in adjacent Canadia provinces, but for simplicity, we'll just call them all Alberta clippers.) They're called clippers because they typically move rapidly. In Western Virginia, I would say they could be called clippers because all they usually do is clip us. Most Alberta clippers sail harmlessly north of us across the Great Lakes into the Northeast. They'll drag a cold front through, changing our winds to the northwest, chilling us out a bit and maybe kicking off a few snow flurries or even rain showers. A few come right at us, but even most of these have little effect on our side of the mountains. The moisture is hard pressed to make it over the mountains, getting squeezed out in the upslope flow on Beckley and Bluefield. Mountain Lake gets some, maybe even Blacksburg or Clifton Forge or New Castle, but often it doesn't do much but spit a few flakes this side of Catawba and Fort Lewis mountains. It's when the clippers dive south of us that there is more of a threat of a widespread accumulating snow in Southwest Virginia, including the Roanoke Valley. Most of the precipitation tends to fall north of a low pressure system, and this is also where the coldest air is. In our neck of the woods, there is even some chance that a deeply south-diving Alberta clipper can tap Gulf of Mexico moisture, though this is rare. Because these systems are fast-moving and come at us across not-very-moist terrain, snowfall amounts are usually light with clipper systems, rarely more than a couple of inches here in the Roanoke Valley. Most go by dry or with only flurries or sprinkles. A stronger system, once in a great while, can spin up a stronger surface low that pulls Gulf or Atlantic moisture into the mix -- but really, at that point, it quits being a clipper and becomes a coastal storm. The clipper for this afternoon and evening dipped as far south as Missouri last night before heading our way. You can be the judge on what this clipper does in your backyard. WARM OR COLD? The U.S. government's Climate Prediction Center is predicting above average temperatures in the 8- to 140day range, which would include the period of time between Christmas and New Year's. They're basing their forecast on lots of computer model guidance that suggests a "zonal" flow will develop, a jet stream from west to east across the country with little wiggle in it either way. Delightful, pleasant weather or uneventful, boring weather, depending on your perspective. They admit their confidence is low. A large number of private forecasters online have been calling for an Arctic outbreak, expecting high pressure to build over Greenland and over the western U.S, with the jet stream buckling south between them. The battle lines are clearly drawn. We'll revisit this subject some next week when a Christmas week storm bears down on us. Dec. 17, 2003 SNOW SHOWERS I saw a few flakes of snow flutter down at the end of the rain this morning in Roanoke. Some places at higher elevations or to our west perhaps saw more. That's going to be about it for this round, as the moisture mostly got out of the way before the cold air could catch up to it. The next 48-72 hours will offer blustery conditions across our region, and the upslope snow machine will get going in full gear across West Virginia. Here in the Roanoke Valley, we might catch some light snow on Thursday as a stronger disturbance races southeast toward us. Probably not much accumulation. Favored west-facing slopes of West Virginia, however, may get several inches by Saturday as constant light snow, interspersed with some sporadic heavier snow, begins by this evening and doesn't stop until the weekend. National Weather Service-Blacksburg has even mentioned in passing the possibility that somebody over that way might get a foot. Christmas week has many questions that are just too complicated to dive into now. Dec. 16, 2003 CLOSE CALL The concerns for Wednesday are still "How fast will the cold air get here?" and "How much moisture will be left when the cold air arrives?" These situations are often nail-biters for meteorologists. A few flurries or a few hours of moderate to heavy snow? One computer forecast model is vigorous with a quick shot of a heavy snow, but others are saying most of the rain moves out before the cold air arrives. Do not be surprised to see some flakes, and probably some fat, wet clumps of snow at that, on Wednesday afternoon as the rain ends. Best call now is that any accumulation will be light here in the Roanoke Valley. Western upslope areas of far Southwest Virginia and particularly in West Virginia are going to get hammered over the next 72 hours with several inches of snow. Strong winds -- and potentially high winds with 50 mph gusts -- developing behind the front and on the back side of our latest nor'easter will kick the upslope snow machine into full throttle come Wednesday night, running all the way into Friday. It's great news for ski resorts. Here on the downslope side, a disturbance moving through Thursday may be strong enough to squeeze out a white ground, if we don't already have one after Wednesday's episode. Christmas week is offering put frightening travel implications almost coast to coast. More on that later. Dec. 15, 2003 A LITTLE CHILL GOES A LONG WAY Two winter storms before Christmas ... and we still haven't had a true blue Arctic outbreak, the kind that freezes everything solid for a week or two. If you had told me a month ago that we would have two significant winter storms in the first two weeks of December, I would have just presumed that a major early-season Arctic outbreak must have occurred. Instead, we've got all this ice and snow out of some transient and not particuarly severe cold air masses, timed just right to dam against the mountains as major upper level low pressure areas cross the nation and shovel moisture into the chill. The scary thing is this: What if this train of storm systems stays on the tracks and we get a serious intrusion of Arctic air? That could happen down the road. But first, let's examine our midweek scenario. Another strong upper level low pressure system will be moving across the country on the persistently strong jet stream coming out of the Pacific. For the past several days, it has been widely assumed that the warmup that begins today would make this an all-rain event for us. But now that is not as certain. We will almost certainly begin with rain on Wednesday, but how we finish is now an intense subject of debate in weather geekdom. In our first two winter storms, warm air has overrun the cold air at the surface to produce a progressive buffet of precipitation ranging from snow to sleet to freezing rain, in that order. The potential problem on Wednesday is totally opposite, a worry that advancing cold air will catch the precipitation and change it to snow. Another concern is that this upper-level low will trigger yet another hyperactively wound-up surface low pressure in the eastern United States. Some computer models show this; many do not. This is rapidly turning into the season of the big Eastern U.S. low pressure system, which is a departure from the relative tranquility of many recent years, when few systems blew up into big storms. There's already been two nor'easters this month, mostly hammering New England. Plus, we've had at least three intense inland low pressure areas run through the Midwest to the Great Lakes since October. Remember the big windstorm in October? That was the first in this ominous series. So some computer models are now showing a low exploding over the Carolinas just in time to pull cold air into it from the northwest, catching the back edge of our rain on Wednesday and developing a heavy snow burst for us. Right now, it's speculation, but just enough to increase forecasters' antacid dependency. What about big-time Arctic cold? Well, there is a good amount of discussion out there about the possibility of a large high pressure system developing over Greenland in upcoming weeks. So what, you ask? If this happens, it's the negative phase of the North Atlantic Oscillation, which means the jet stream buckles around the high southward from Canada into the United States. This causes two things to happen: (1) Arctic air invades from the north and (2) storm systems dig farther south, perhaps into the Gulf of Mexico. This is several days if not weeks out, if it happens at all. But if it does and the storms keep rolling in faithfully out of the Pacific across the nation, then intensify in the East, the stage is certainly set for some really big snowstorm action in our neck of the woods. A grand slam snowstorm is not guaranteed by any of this, but the slugger would be at the plate with the bases loaded. Dec. 14, 2003 HURRY -- GO BUILD A SLEET-MAN The bulk of our precipitation from winter's latest hit on our area was sleet. Sleet really has the least impact of all winter precipitation, as it doesn't pile up as fast as snow and it doesn't collect on power lines like freezing rain. But it's still been quite a mess in the season's second winter storm. Sleet and snow piled from 1-5 inches across our area, about 1 1/2-2 in most of the Roanoke Valley, with glaze on top. The heaviest totals were in Bath and Rockbridge counties, where more snow fell before changing. Some parts of Southside Virginia experienced a signifcant ice storm with power outages. That, in my opinion, is the worst-case scenario with any winter storm. Two feet of snow, in the long run, is less trouble than just an inch of ice. It takes a few days to get the roads clear, but it can take weeks to restore power after a major ice storm. Thankfully, most of us dodged that. Warm air got sucked in aloft fast and furiously to cut off our snow and change it to sleet and ice. Places all up and down the Eastern Seaboard are seeing this happen today, much farther inland than earlier forecast. Warm air advection, it's called, or WAA for short. The good news is that the icy muck should be melted, except on densely shaded north-facing hillsides, by this time on Monday. A new system comes our way for Wednesday and Thursday. Until Sunday, it went without argument that this next system would be all rain, but at least one computer forecast model and a couple of prominent private long-range forecasters have cast doubt on that with speculation that the next system could dig farther south and stir up yet another winter storm for the East Coast. I'm not ready to bite on that yet and have lots of doubts, but I'll keep an eye on it the next couple of days. 12/13/2003 9:30 AM SHAKY FORECAST? After looking at the radar trends this morning, I'm not impressed with our upcoming winter storm. It looks like it's weaker and faster than I expected, certainly less impressive than it was on radar 12 hours ago over Oklahoma and Texas. Only light precipitation is showing up in Kentucky and Tennessee. Weather service offices to our west are noting the upper level low approaching has been weaker than expected and has failed to really draw in the moisture that was forecast. Places in Missouri and Arkansas that were under winter storm warnings are getting 1-2 inch amounts instead. Some places barely saw any precipitation as hours of moisture evaporated in the dry air and then a "dry slot" swept in to stop it all together. But the system will get wetter as it continues to draw in Gulf moisture. This moisture will "overrun" the cold air dome created by a high pressure system to the northeast -- a cold-air damming setup. The cold, dry air will eat away the precipitation for a time, as it evaporates before hitting the ground, but eventually the atmosphere will be saturated and it will reach the surface. On Sunday, a coastal low will develop to our east and become the primary driver of the storm system. When this low strengthens and moves up the coast, we will be shut out of the moisture and the precipitation will end, except for some freezing drizzle or snow showers. How much we get until that occurs will determine our amounts, and then there's the thorny question of snow vs. sleet vs. freezing rain. Odds are now that a deeper layer of cold will create more of a snow/sleet event. One thing to wonder about is whether thunderstorm activity along the Gulf coast will rob the system of moisture farther north. This happens sometimes, and can reduce snowfall amounts. There appear to be heavy thunderstorms in Louisiana and Mississippi, moving east. All in all, this is looking more like a nuisance event for us rather than a major winter storm. The 5 inches I suggested last night might be at the top end of what will occur, so I'm going to back off to 2-4 inches. If sleet gets involved early, it will be near the bottom of that range. Dec. 12, 2003 REPEAT PERFORMANCE? As time goes along, Saturday night's storm looks more and more like last week's. The models have been trending colder in the upper atmosphere today, which means probably more snow than thought earlier. That said, there should still be enough warm air aloft to eventually change things to sleet, possibly freezing rain. The National Weather Service has issued a winter storm watch for 1-4 expected inches of snow/sleet. This sounds like last time, too. We ended up with 6 in Roanoke, up to 10 in some places. The cold air held longer and deeper than thought. A trend? Sometimes, it seems storms repeat themselves. The high pressure to the north may not be as strong this time and the warm air influx aloft may be a bit stronger, so it may change over more quickly than last time. It does look like a decent amount of moisture will get pulled in ahead of the system from the Gulf of Mexico. That could mean some heavy snow or sleet that accumulates rapidly. So, like the 5-6:30 p.m. blast on Dec. 4, it might not take long to put down several inches. My call is 5 inches combined sleet and snow in Roanoke. More snow to the west, more ice to the east. Approximate start of precipitation: 5 p.m. Saturday in Roanoke. Earlier to the southwest, later to the northeast. You'll probably see the radars turning green over your town hours before it starts. The air will be very dry, and it will take a while to moisten it up enough for precipitation to hit the ground, but once it does, it will get messy quickly. Dec. 11, 2003
WINTER PUZZLER
It's another classic winter puzzler this weekend, and it all depends on how strong the high is and where the low goes.
A strong low pressure system now in the western states promises to slide across the southern United States over the next 48 hours and make a beeline for our neck of the woods.
What appears likely is that a surface low will develop somewhere near or along the Gulf of Mexico. It's over what happens next that there are two camps, each composed of flesh-and-blood forecasters and metal-and-plastic computers. Think of it as a battle of East vs. West.
Will the low move up the East Coast? Or will it ride farther west along the Appalachians?
Generally speaking, the milder air is on the south and east sides of a low's track, while the colder air is on the north and west side. If the surface low goes up the coast, we stay in the cold air, leaning more to a wintry weather solution, probably a good bit of snow. If it goes north and west, then things warm up during the precipitation and we end up as rain.
That seems simple enough, but there are complicating factors.
One is a hybrid solution to the puzzle where a low moves northeast into eastern Tennessee and weakens, and then another forms on the coast of the Carolinas and strengthens. With this kind of event, we could go from snow to ice to rain and then back to snow.
The second and biggest complications is those three words you are already sick of reading here: cold-air damming. This is where the strength of the high pressure comes in.
If the high is strong, then the cold air will bank up against the mountains and be hard to move. If it's strong enough, it could hang tough at the surface even if the low pressure area passes to the west and drags warmer air over it. This is the worst-case scenario, and could lead to an ice storm.
If the high is strong and the low passes south and east, then the likelihood is of a mostly snow event, with maybe some sleet.
Weaker high pressure areas could allow quicker erosion of the cold air, allowing a transition to an above-freezing rain.
So what's the best guess now? Probably something similar to what happened last week, with snow changing to sleet and ice. Saturday night and Sunday look to be the bullseye for this event, but even the timing is uncertain with so many factors in flux. Get used to this. There's probably at least two more systems in line behind this one, about four days apart. The overall weather pattern is unstable and changeable, so keep expecting these if-and-but forecasts keeping your local weather folks on their toes.
FARMER'S ALMANAC UPDATE
Giving credit where credit is due, the Old Farmer's Almanac is entitled to some bragging rights for calling for a eastern U.S. snowstorm in the period Dec. 5-10, since there was one from Dec. 4-7.
After finishing 10-20 on its day-by-day forecast for November, and badly missing a month prediction of below normal temperatures and below normal precipitation (both were above normal), the almanac is off to a respectable 8-2 start through Dec. 10 with its calls for lots of cold weather. That makes it 18-22 for the season, still below .500.
The almanac is calling for sunny weather from Dec. 11-16. With a winter storm likely on the way, its record may take a hit over the next few days. Dec. 8, 2003 MORE WET STUFF COMING
This week's weather threat: flooding. +++ Dec. 6, 2003 IT'S OVER Some of you got one last burst of snow last night between about 10 p.m. and 1 a.m. Some of you may not have. Driving in south Roanoke city and adjacent Roanoke County near my apartment, the snow was quite impressive at about 11-11:30 last night. Huge conglomerations of flakes, some 2 inches wide, came blasting out of the sky, quickly turning roads white. It stuck to every little limb on every tree, though if you didn't see it last night after it fell, you may not have seen it at all, as it's blown off and melted this morning. The Roanoke Regional Airport officially reported an inch; on this side of town, more like an inch and a half, maybe 2. As the upper low moving from the west transferred its energy to the coast, the snow area associated with the upper low began diminishing into several squally areas as shown on radar. As a result, instead of widespread snow across the area, it was quite spotty, with some areas getting one last hurrah and other areas little more than flurries. One lump of dark green on the radar passed over Roanoke, and this is where the final heavy snow burst emanated. This morning, it appears Roanoke has warmed up unexpectedly, perhaps on a local downslope wind effect. At 9 a.m., the temperature is 39 degrees at the Roanoke Regional Airport, while other cities in the region are not nearly as warm. The snow melt has begun here, as the coastal surface low pulls away giving parts of the Northeast a legitimate blizzard. Some areas of the Washington, D.C., area and Maryland are missing out on what was expected to be a foot-plus snow there. It's hitting farther up the coast, where some places will top 20 inches. So now we move into what should be a gradually warming early week, with a mild rainstorm at midweek, then more cold weather toward the end. For two years straight, we've had a big winter storm in the first week of December. Does this mean this winter will be cold and snowy like last one? We shall see. Dec. 5, 2003 The big snowstorm will not be one we can claim as our own, and our piece of the action appears to minimal. The best atmospheric dynamics are going to pass well north of us. We'll probably get one band of decent snow in the area late tonight into Saturday morning, but it will be speeding through and, quite likely, dying out as the developing low pressure system off the Delmarva Peninsula takes over and then pulls away from us. Historically, we don't get a lot of big snows in Roanoke from upper level systems coming across the mountains from the west. We don't even get a lot of little snows like this, but the upper level low is so strong, it may overcome some of the downslope factors. Still, there's a pretty large precipitation area in eastern Kentucky and Tennessee that will pull across us. It's mostly rain there, but the atmosphere should be primed for snow when it arrives here. How much we can squeeze out of this band before it blows by or dries out will determine our snowfall amounts. Right now, computer models are spitting out even less than they were this morning. I wouldn't be surprised if some localized area caught a heavier band and grabbed another inch or two, but overall, it looks like a 1-2-inch storm for us. Favored upslope areas of West Virginia will get nailed by northwest winds tomorrow, adding more inches to their totals, but we'll be safely on the downslope side by then. A few flurries at best tomorrow. I expect to see the sun before the day is out. Did you know Tropical Storm Odette has formed in the Caribbean and is expected to affect Jamaica? Hard to believe with half a foot of slush slowly melting away. A BREATHER Round 1 was much more of a blow to the area than almost anyone expected. Widespread 4-10 inch snowfall amounts, including 6.3 inches of combined snow and sleet at the Roanoke Regional Airport, and 6.8 inches at the National Weather Service office in Blacksburg. Dec. 4, 2003 MORE SNOW? First, tonight. The snow hung on longer than we thought today, leaving up to 8 inches in the mountains near the North Carolina line. Here, in Roanoke, looks like about 2 inches, but mercifully, it hasn't stuck to the roads much. Can't say the same farther south, or even in the higher elevations immediately surrounding the Roanoke Valley, where a number of accidents have occurred. We are now beginning to see more freezing rain and sleet getting started in our area, and this could spell bigger problems as the night continues. Ice is nobody's friend, and with darkness, road conditions could worsen. It's not going to the really cold and freeze everything solid, but patchy ice could be an issue. Depending on the amounts that fall, power line problems could develop, too. Friday, we'll see a break, and likely get above freezing, though I'm still doubtful about any low 40s. And then comes what could be the big dog of this litter, the strong upper low from Canada that could spin up a major Eastern U.S. winter storm. Will it be our storm, though? Here are five things to watch for as this situation develops to determine whether we'll get more substantial snow Friday night and Saturday. The track of the large upper level low This, more than anything else, will determine if we get a big snow (which I'll arbitrarily define as 6 or more inches), a medium snow (3-6 inches), a little snow (under 3 inches) or none at all. This thing is diving southeast at us from Canada. Computer models have been in two camps through the week, one showing a more northerly track with the upper low passing right over us or a little to the north, and the other group showing the system diving all the way to the Carolinas, even Georgia. On Wednesday night and Thursday, the models appeared to be converging on a more northerly path. Because the heaviest snow usually occurs 100-200 miles north of the upper level low's track, that would push the heavier snow north of us and leave us in a light-medium area. Or possibly nothing if it goes far enough north. Cyclogenesis This is just a fancy way of saying "low pressure formation off the coast." It is really related to item No. 1 above, as the energy of the upper low will help trigger the surface low. The earlier and farther south a surface low pressure system forms in the Atlantic, the bigger our snow risk. If it develops off South Carolina, we get in the rotation of Atlantic air quicker where the moisture will ciculate on top of us on cold north winds. If it forms farther up the coast, then places to the north are more favored, and we get cut out of the moisture quicker. Right now, it seems the middling answer of forming between Cape Hatteras and the Delmarva Peninsula is likely. Track of surface low Does it storm up the coast, or hang around for awhile off the coast? Best bet now is the first one, cutting us out of the moisture by Saturday night. A dawdling system could keep the snow hanging around longer into Sunday. Dry slot The biggest snow killer of them all. Do we get caught in the zone between where the upper low leaves off and the surface low takes over? This has happened a lot in our weather history. Does the downsloping northwest wind dry us out as the low pulls away? If we miss entirely tonight and Saturday, getting "dry-slotted" could be the reason. Temperatures aloft Never mind if it's a little above freezing on the ground. The upper level low is a deep pocket of cold air aloft that will ensure anything falling as snow, after maybe a dab of rain early, and as the precipitation falls, a quick drop below the freezing mark on the ground. Temperature does not appear to be an issue with tonight's system. Adding all these factors up, it seems unlikely this will be a total miss for us, but it looks like Maryland, Pennsylvania and points north have the best chance at a foot-deep or more "big 'un." With such a vigorous system coming right at us, though, it seems a few inches, 2-4 perhaps, could be on the way on top of whatever's left from today's storm, especially over our mountains to our west. But keep up to date as the forecasts can change rapidly, or miss entirely, on a complicated system like this. Dec. 4, 2003 DÉJÀ VU Winter 2003-04 has started remarkably similar to Winter 2002-03, with a snow to sleet to ice storm in many ways like the one we experienced a year ago today. Dec. 3, 2003 WARNING The puny little guy I wrote off has been pumping some iron. From observations and computer model forecasts, it's increasingly obvious that we are likely to have a 1-2 punch of wintry weather this weekend as opposed to one big 'un. Winter storm warnings are now in effect for much of Southwest Virginia on Thursday in anticipation of snow/ice totalling 1-5 inches. What a way to start winter, huh? Wasn't it 70 degrees just a few days ago? What we have is an upper level low moving east that will suck up lots of juicy Gulf moisture over the cold dome of air at the surface. At first, it will be cold enough from cloud to ground for snow, but as the upper air warms but the surface stays cold, the snow will turn to sleet and freezing rain. Could be a big mess by this time tomorrow. If you've looked out any at all today, you've seen a leaden gray sky that just screams "Snow!" In fact, it has been snowing much of the day high in the atmosphere over Southwest Virginia, but very little if any of it has made it to the ground because of the cold, dry air at the surface. Still, this virga snow has helped moisten the atmosphere, to prepare the next thicker batch of moisture coming through after midnight tonight and through Thursday to make it all the way to the ground. Let's leave Saturday on its own for now, as we have enough to get through on Thursday. But there is another threat then. Friday may see us get above freezing a while to melt off some of the mish-mesh, but Saturday could undo that in a hurry. Remember I said no accumulating snow before Christmas? Pretend I didn't. Dec. 3, 2003 HERE WE GO Never call a storm "puny." I've been kicking sand in the first upper level wave's face all week while keeping an eye on the muscle man coming in behind it, and the feisty little guy is raring back to punch us in the gut with what could be a significant ice storm on Thursday. The National Weather Service in Blacksburg has issued a winter storm watch for the expectation of 1/4 inch or more of ice on top of an inch or so of snow and sleet. You may already notice lots of colors on the radar to our west and southwest. But the lower atmosphere is so dry that the cold air just eats it the moisture. Eventually, the air will get moist enough to let the precipitation reach the ground, and then the trouble begins. We have cold-air damming to blame for this, as the cold air is wedged snugly against the mountains and ain't moving. The moist air from the Gulf of Mexico will flop on top of it and begin to fall. By Friday, the approaching storm may pull enough warm air from the Gulf to nudge us above freezing, grudgingly, but don't count on it. Then we may still have the big guy to deal with. Or maybe he'll go bully someone else. What we have is a battle between Europe and America. The European computer forecast models show the big upper level low coming right on top of us, which would mean that the bulk of the heavy snow would occur well north of us. If these models pan out, we could even get into a "dry slot" and miss out on accumulating snow altogether on Saturday while areas to the north get buried. The American model paints a different picture, pulling the upper level low much farther south into Georgia and South Carolina. If this happens, we'll need the shovels by Saturday. Stay tuned. So much drama for the first week of metorological winter. Would you laugh at me if I told you there's a chance a tropical storm may develop in the Caribbean? Dec. 2, 2003 INCREASING CONCERNS Some computer forecast models are playing up a very big nor'easter for the weekend, the kind that washes away beaches and dumps snow measured in feet where it's cold enough inland. Some are showing nothing more than a routine band of rain showers ahead of a cold front, then blustery weather and snow showers behind it, not unlike what we had late last week. Some private forecasters on the Web are beginning to toot lightly on the horn about the potential for a major East Coast storm this weekend. The National Weather Service, wisely at this point, in my opinion, is being more vague and circumspect, for there are a number of scenarios that could play out and it's really too early to commit to one. I'm not committing yet, either, but be aware. Even it develops big and bad, its implications for us are complicated and still uncertain. The right chess pieces are in position, but will they move into the right squres for an early season winter checkmate on us? Stay tuned. In the meantime, don't be surprised if you see an ice pellet or a snowflake Wednesday night or Thursday morning. The "puny little system" I talked about yesterday will be moving through, but it is puny. Dec. 1, 2003 IT'S WINTER The start of December is also the start of meteorological winter. Unlike the astronomical calendar that waits for solstices and equinoxes to start seasons, meteorologists just start them at the beginning of the month. December, January and February are winter. So be it. Right off the bat, we have several classic winter case studies to talk about. We had a textbook case of upslope snow showers Friday and Saturday, dumping up to 5 inches in southern West Virginia and even blowing a few snowflakes into the Roanoke Valley. We've got our old friend cold-air damming setting up this week to keep things chilly a few days. Perhaps, most ominously, a couple of disturbances are moving through that just might squeeze out some snow or ice on us. First, a quick note on the weekend snow. I took a drive west on Saturday morning to examine the snow. When I left Roanoke a few flakes were fluttering past under partly cloudy skies. As I crossed the mountain to Catawba, the snow showers were pretty thick and collecting on the ground in a few spots. When I got west of New Castle onto Potts Mountain, I hit the Arctic Circle. I saw 1-3 inches of snow there and west into West Virginia, with a steady light snow falling. By the time I got to the Princeton-Bluefield area of West Virginia, there was 3-5 inches on the ground. Up at little overlook park on East River Mountain at Bluefield, there were foot-deep drifts in spots. Now, on to cold-\air damming. You're going to get sick of reading about it in this column, because it's a bugaboo that sets up on a regular basis each winter, and sometimes causes big problems. It's caused by high pressure to our north and northeast that pushes cold air down the eastern United States, with the cold air banking up against the mountains. Were the mountains not there to keep it in place, the cold air would spread out and disperse. Or, approaching weather systems from the west could scrape it away. This week we'll see a true Arctic air mass set up over our area, and cold-air damming will keep it over us for the most of the week. Expect lows in the 20s and highs in the 40s. Winter has arrived, indeed. But the air mass will also be quite dry, so the sun will shine nearly every day and there will be no precipitation. Or will there? A puny system will squirt east-southeastward out of the Plains on Wednesday. Right now, it looks like the cold air in place will be too dry for any precipitation here. The storm might roam farther south,and weaken. With the right trajectory and enough moisture, it's the kind of system that could be a snow-maker for us ... but probably not this time around. Maybe a few extra clouds as it skips to the south. For the weekend, there are forecast complications galore. A much stronger upper low will move across the nation on the jet stream. Computer models are all over the board on the track and strength of this system. As a result, many forecast discussions are saying "confidence is low" as to what it will end up doing. Best guess is that it comes across the Ohio Valley, pulls up warm moisture ahead of it for some rain, then kicks off a surface low somewhere on the coast and we get another round of mountain snow showers as that low pulls away. But be warned that there is enough uncertainty with it that other more ominous scenarios are possible, and yes, some of them would involve shovels and scrapers. It's that time of year. The forecast can change on a whim.
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