Feb. 23, 2003, 9:20 a.m.
WILD, WILD WEATHER
A week ago at this time, we were watching the roads turn icy white as sleet pelted down at 18 degrees. This morning, we have rain-engorged streams, mudslides, thunderstorms, and 60 mph wind gusts. And there is a snow threat by mid-week.
In a setup very similar to 1996, heavy rain followed close on the heels of heavy snow/sleet. That's a dangerous 1-2 punch, as the first saturates the ground and the second just runs off. The rains ended up being of the torrential kind, with over 2 inches at many Western Virginia locales on Saturday alone. We had some more downpours accompanied by lightning and thunder overnight. With the runoff, I see no reason Carvins Cove shouldn't finally fill up in the next few days. It's only 4 feet down this morning.
The culprit is our old friend, the subtropical jet stream, which became a player again last week with the blizzard/sleet storm. This week's storm was actually stronger than that one was, but this time brought so much warm air (mostly aloft here; Norfolk, however, hit 77 degrees) that winter weather was not a factor except in parts of the Ohio Valley late last night. This moisture gravy train shows no signs of slowing down, as it is enhanced by El Nino (he's still kicking out there) and no longer blocked by the Arctic high pressure systems that have been persistent since early January.
That's not to say it can't get cold. Mid-week offers a tricky forecast. A cold air mass appears likely to set up in time for another of these moisture-laden systems to cross the southern United States. The question is whether enough will hang in for a snow -- potentially a big one -- or whether the approaching low will scour out the cold air and turn us to rain.
Much depends on the track of the storm -- farther west would mean more warmth and less snow -- and the strength of the high pressure to the north. A cold air damming situation similar to what occurred last week appears possible, where cold air is pushed south and southwest up against the mountains down the eastern United States.
One thing's for sure: An encore of last year's drought doesn't appear to be in the plans anytime soon.
Feb. 21, 2003, 8:20 a.m.
WET WASHES AWAY WHITE
I told you that sleet would hang around for awhile. We've had two days of temperatures in the mid- to upper 40s and in many places the ground is still solid white. Remember that it takes the same amount of frozen water to create 4 inches of sleet as it would have 12-16 inches of snow. So even though it was 4 inches deep, it's really like melting off a foot snow. 4 inches of snow would have been long gone by now.
We have a mild rain coming this weekend that should help finish it off. A decent-sized low pressure system will likely follow up the Appalachian chain, putting us to the east and unambiguously in the "warm sector" where snow/ice issues are out of the question. Might even hear a crackle or two of thunder.
Later thinking is that this might not be the big flooding storm earlier thought, but where it's washing away 3 feet of snow north of us I wouldn't be so sure. Probably an inch or two of rain for us. Carvins Cove is now within 6 feet of the spillway. Slight chance that this could finish 'er off, making the 15 percent of those of you who voted for February in our "Fill 'er up" poll look like geniuses. I think it'll take at least one more rain/snow in March to do it.
Remember back in October and November when we had a steady parade of rainstorms every three-five days? Did wonders for the drought. It looks like we're getting back into that pattern now. Two more storms crash onto the California coast next week and head our way on the subtropical conveyor belt across the South next week. Trick is, which ones catch the cold air and which ones don't? We're getting late in the season so cold air comes in spurts rather than hanging around. Still, as we all know, those March snowstorms of our memory are often the biggies.
Both systems next week are on the bubble for rain and snow for us, one early in the week and one mid- to late week. We're probably done with the cold powdery stuff and, should we have more snow, we'll probably get the heavy, wet kind that clings to everything.
I've ratcheted down our chances of a foot-plus snow in Roanoke before the winter ends from 50-50 to only a 20 percent chance that it will happen. My reasoning is that that we missed out on a twice-a-decade type opportunity for a major snowstorm last week. We might have to wait around to 2008 or so for another setup like that. Then again, we might be within two weeks of it in this weather pattern. One big California-crasher hits a Canadian-chiller just right over us, and we'll be shoveling.
Feb. 17, 2003, 1:15 p.m.
SLEET, SLEET GO AWAY
It sleeted hard again last night, adding another inch or two of sleet. Sleet amounts ranged from 2-5 inches across the area; looks like about 3 in the Roanoke Valley. If you didn't know better, you'd think just by looking it was all snow, giveen how pretty and white it is. If it were snow, it would have been on the order of 9-12 inches. Many areas also got an added coating of freezing rain.
The storm is now moving northeast spreading 1-3 feet snow. Now that some areas have been under blizzard warnings and experienced gusty winds whipping the snow, it will likely carry the moniker of Blizzard '03.
The victory of the warm air aloft that gave us sleet instead of snow also signals an important pattern change that will bring us overall milder weather.
We are about to be in a "zonal flow," which means winds aloft blow west to east across the country, instead of coming from north to south out of Canada bringing cold. That's not to say it won't still get cold on occasion or that we're definitely through with ice and snow, but it won't be a constant part of our weekly lives as it has seemed to be since early January. Like yesterday's storm, this winter has been notable in Roanoke not so much for its volume but its persistence.
While the zonal flow promises to bring tempeatures in the 50s by Thursday, it will also bring about Pacific-origin storm systems. Many of them will be rain-makers, but there is always the potential for something like this weekend happening again ... if not with the same magnitude. I will dare to say that we will have at least one more big winter storm threat before this winter is over.
The sleet will indeed go away this week, and it was a sufficient volume that the melting should push Carvins Cove closer to the "full-pond" stage, maybe just one good spring rain away from flooding over the dam. It's been my experience that sleet melts more sloppily and disappears more slowly than snow, turning into a mushy, slushy mess, kind of like a melted snow cone. Today, it' s not going anywhere, as temperatures will struggle to hit 30, and we might even squeeze out a little freezing drizzle or snow flurries.
Just don't try to throw sleet-balls or build a sleetman.
Feb. 16, 2003, 5 30 p.m.
SNIZZLESTORM, '03
This a truly historic winter storm ... but not for Roanoke. Just a nuisance here. While Northern Virginia and the DC area cope with more than a foot of snow with the storm nowhere near over yet, we slide around on 1-2 inches of ice pellets.
What went wrong? In the broad picture, nothing. The storm developed, or rather, is developing marvelously close to expected on the large scale. That such a large storm could even be projected days in advance is a testament to modern forecasting acumen. But in the details, a few key things happened to keep us out of the deep white today.
(1) The warm jet aloft was just too strong to allow any real serious snowfall to get going. Temperatures in one small part of the atmosphere were in the 40s. The storm never could overcome this gap in the cold, and it melted all the snow falling through it, before refreezing in the lower atmosphere as sleet or on the surface itself as freezing rain.
(2) Thunderstorms along the Gulf Coast used up some of moisture that was expected to flow into our area, cutting the flow. That eliminated our projected 3-inch liquid equivalent, which would have been a ton of sleet.
(3) The main shield of precipitation shifted subtly north this morning, leaving us in light stuff.
You may have noticed today that in between the periods of heavier sleet we had a thin fall of very light snow and icy bits. For a lack of a better word, this is sometimes referred to as "snizzle" because it is like drizzle in that it forms in moist clouds low in the atmosphere. The icy crystals condense much as snow does -- in fact, I found a few well formed flakes amid the hundreds of odd-formed icy bits -- and then fall to the surface, floating in the breeze. They didn't add much to the accumulation, but because of the persistence of snizzle all day I have dubbed this storm for Ronaoke as the "Snizzlestorm."
The storm isn't over yet. Besides some more "snizzle" and perhaps freezing drizzle tonight, we could still grab another inch of sleet as more moisture bands currently in Tennessee move across. Also, an additional piece of upper level energy will come across on Monday and cause some sleet and maybe even some real honest-to-goodness snow. Not much accumulation is expected Monday ... but we've been surprised before by this thing.
Travel conditions will remain treacherous across the area tonight. Glazed roads have been reported to our south, and snow/sleet totals increase headed north. Snow is 17 inches deep in the Winchester area, and it's not done yet!
We will get back into the 50s by midweek. More storminess is ahead next weekend, but now it looks more like rain. The pattern favors up and down temperatures and occasional storm systems. Would not be surprised to go through another round of this will-it-snow-or-won't-it before spring comes.
Feb. 16, 2003, 9 a.m.
ICER-SLEETER
The tropics are winning the battle of the upper atmosphere, while the Arctic has clearly taken the surface level as expected, so it looks like for much of Southwest Virginia, this is an ice-sleet situation more so than snow, at least through today.
In Roanoke, we're working on an inch of sleet; up to 2 has been reported to the north. To the south and southwest across parts of the New River Valley eastward to the heights of the Blue Ridge, there has been as much as half an inch of glaze ice. That's not good, because it's just beyond that point that tree and power-line damage begins to happen. Some parts of West Virginia are experiencing heavy ice storm problems this morning, according to the National Weather Service in Charleston, W.Va.
While it's a disappointment for those craving a foot-plus snow like some of Northern Virginia is already getting, Roanoke has navigated the storm just right to avoid extreme problems. The roads will be treacherous all day and well into Monday for sure, but we have had only a light glaze from freezing rain, so no power line difficulties. And we have no drifting snow, either.
My 8-inch call looks in serious jeopardy, becausee you get only 3 or 4 inches of sleet for every inch of liquid, where as you get 10-20 inches of snow for that same amount of H2O. But it's too late to back down so I'll fall on my sword if we fall short.
We may very well see snow on the backside of the storm late tonight and Monday but it may not be enough to push us over the 8" bar. Furthermore, with so much warm air aloft, we stand a chance of going back to freezing rain and building a dangerous ice layer. The warmth aloft might even be strong enough to switch places like Washington and Philadelphia, expecting 1 to 2 feet of snow, back to sleet themselves and bring them under snow expectations. (More inland, though, 2-3 feet of snow will be achieved many places.)
This is a mighty and complex storm that could still throw some unexpected punches at us. A convective downburst -- maybe even in a thunderstorm -- could pull enough cold air from the very highest levels of the atmosphere, where it's always cold, through the warm air to trigger heavy snow. That's a big "if" but something to watch for.
If the dynamics do something unexpected and switch us to snow, we could pick up a lot in a hurry. So any way you cut it, this is still a dangerous and unpredictable winter storm even now that it's begun.
As the rattle of sleet pecks on my window, I wish you a safety and coziness on a day not fit for man nor beast. I'll update again later today or early this evening.
Feb. 15, 2003, 7:15 p.m.
SNEETSTORM '03
It is almost showtime for Roanoke on this major winter storm. Temperatures have dropped to just above freezing and a steady rain has been falling. Lynchburg is already reporting freezing rain.
Roanoke marks the center of the battlefield between the tropics and the Arctic. The Arctic air will try to flood southward and change this to all snow; the tropical air will try to keep overrunning the Arctic air and turn us back to rain, which would be freezing rain at the surface.
The stalemate, and the one the National Weather Service is buying into wholeheartedly now, is an unprecedented severe sleet storm, where ice pellets collect 4-8 inches deep, mixed with a little snow. It's rare to get more than an inch of sleet. This would be a notable weather event if it verifies.
If the tropics win the battle in the upper atmosphere, we'll have something far worse: a crippling ice storm, resulting from the upper layers staying warm while a razor thin freezing layer develops at the surface. If the Arctic wins, we will have a wind-whipped blizzard with snow easily topping a foot. Chances are that we will have freezing rain, sleet and snow at different times over the next 36 hours, possibly lasting into Monday.
So what is going to happen? Your guess is as good as mine, or any experts. We're probably within a couple of hours of the first frozen precipitation in Roanoke and the forecast is still about as much of a crap shoot as it was two days ago. But you gotta take a stand on a battlefield!
I believe that there will be a period of a few hours on Sunday when the Arctic will take the flag and we will experience heavy snow. This snow may come at up to 3 inches per hour at its climax, so it could collect fast. I believe this will happen as the low pressure south and east of us wraps up and pulls the brunt of colder air into it, and also because of heavy precipitation eventually cooling the middle layers that will resist the cold. Before and after, we'll have a snow-sleet mix -- hence the name "Sneetstorm."
I think the National Weather Service is slightly under the total amounts we'll get. I think we can just consider 8 inches the over-under line .... I say more, they say less. 8-15 inches of snow/sleet is my call.
Believe me, it's a tightrope walk, and we could all be wrong and have ice-coated trees laying on the ground in the morning. Or, we could be knee-deep in snow headed for waist-deep. We're not expecting border-line cold, but eventually low 20s, so an all-rain scenario looks just about impossible.
Private forecasters are all over the board. A few samples: Gary Grey of www.millenniumweather.com agrees with the NWS call for 4-8 inches. David Tolleris of www.wxrisk.com puts us right smack dab on the 15-inch line. Joe Bastardi of Accuweather Professional, which I'm not going to link to because it's a subscription site, includes us in a 12-plus zone. All of them paint a hefty 2-foot-plus zone to our north, generally centered on Winchester, Va. Some mountaintops in Shenandoah National Park may report a 40-plus amount of snow before it's over. Washington DC, New York, Philadelphia and Boston may be paralyzed by this monster. This is one for the ages.
Be it ice, sleet or snow, this is going to be a severe winter storm and travel will become extremely difficult if not impossible on Sunday. The farther north you are from Roanoke the more snow; the farther south, the more ice. This will be a much different storm in Lexington than it will be in Martinsville. Or at least that's what we expect.
Feb. 15, 2003, 9:40 a.m.
HISTORY IN THE MAKING
I'm going to quote the National Weather Service-Blacksburg's morning forecast discussion to wake you up and get your attention:
"Confidence is highest across the northern CWA (County Warning Area) where sleet should change to snow early on ... creating the potential for several feet of snow to fall in the Highlands of Virginia and into the Shenandoah Valley and Greenbrier Valleys (tonight through Monday morning)." Click here to see the full discussion:
This would be Bath County, Lexington, and northward. But the entire "County Warning Area," which stretches from Lexington, Va. to Mount Airy, N.C., and from Appomattox to Tazewell, is under a winter storm warning tonight and Sunday for an expected epic event of winter weather mayhem.
This is a forecast discussion, not an actual forecast as of yet, and the operative word is "potential." But it shows what we're up against this morning. Computer models are showing what would be the equivalent of 3 inches of rain falling over much of the area tonight through Monday morning, as a tropical moisture train slams into Arctic air.
As snow, that would translate to 2-3 feet -- hence the concerns to our north where more of it will be snow.
As ice, that would be catastrophic to utilities. Most areas will get some of both, perhaps a lot of sleet, which doesn't collect on power lines and doesn't drift like snow (but does collect heavily on roofs and can cause damage that way). Even if we get only half of that level of moisture, this would still be a major winter storm.
For Roanoke: Looks like we're in for a "sneetstorm" beginning this evening as the Arctic air mass, already making its move across Northern Virginia this morning, roars in. Lots of sleet and snow piling up -- probably more sleet at first, then more snow later. I think there'll be at least 10 inches of white by tomorrow evening. Some snow may hang on to Monday.
This will be a paralyzing and historic winter storm for a large swath of the eastern United States.
TRAVEL IS NOT RECOMMENDED SUNDAY AND MAY BECOME NEARLY IMPOSSIBLE IN SOME AREAS.
Also understand that this a complicated forecast subject to changes. Slight shifts in the track or intensity of the system could result in the balance skewing more toward snow or more toward ice. The depth of the cold air mass moving toward us almost completely rules out above-freezing rain past about mid-evening (and probably a few hours earlier). We have fog right now, and I would not surprised to hear thunder during the episode tonight and Sunday.
Stay tuned ... and stay safe.
Feb. 14, 2003, 2:50 p.m.
RAIN FOR NOW
Light rain has begun in Roanoke. With a temperature of 42 degrees and a dewpoint of 30, it now looks doubtful to me that we will see much frozen precipitation this afternoon or evening. Maybe a touch of sleet or snow, little or no accumulation. We'll probably fall back into the mid to upper 30s, but not much lower.
When the Arctic air arrives Saturday evening, that's when the strangeness begins.
It's the harbinger of a long, difficult forecasting weekend.
The big storm for Sunday is still living large on computer models, and very confusing. Best guess is still the "triple play" storm with significant ice, some heavy sleet, then heavy snow. Someone on the East Coast probably will get a 2-foot wallop out of this, but probably farther north and east than us. A 1-foot wallop here? I give it a 50-50 chance. The sleet storm scenario is intriguing as well.
What a mess.
Feb. 14, 2003, 9:25 a.m.
SERIOUS SITUATION
Oh, man.
This is HUGE, folks.
I'm not going to belabor this or hype it too much, because this is more than 24 hours out, but it does appear to be a very serious situation with potential for major travel / utility disruption over a wide swath of the eastern United States.
Good news first: Tonight and Saturday morning look to be less ice and more rain for Roanoke, and I'm very skeptical of the National Weather Service's call for 1-3 inches of snow before the rain. We'll probably see some wet snow for a while, maybe sleet, then go to about a 35-degree rain for several hours. A few Northern Virginia-DC areas will be a different story, with heavy snow and then some ice. They get a double whammy this weekend.
The Arctic air doesn't start flooding in until late Saturday, just in time for the monster mother ship low pressure to begin winding up and moving to the south of us. A strong, moist Pacific-origin low intersecting an Arctic high pressure system with perfect timing. That means big trouble.
There are still other scenarios for Saturday night-Sunday but none of them are warm and toasty. It looks now as if the cold air may sweep in fast and deep enough to cut off the freezing rain and go to more of a sleet/snow situation late Saturday night. It could still rain hard enough and long enough into a shallow layer of cold air for enough ice to cause some damage.
An early guess for Roanoke:
- 1/4-1/2 inch glaze ice Saturday-Saturday night
- 8-plus inches snow/sleet mix late Sat night through Monday AM
If the ice is more, the snow will be less, and vice versa. If the sleet is more, both the snow and ice will be less. A sleet storm with 4-6 inches of ice pellets (National Weather Service forecast discussion out of Blacksburg mentions that possibility) might be the best-case scenario for travel/utilities from this storm, because sleet does not accumulate on power lines or drift as much as snow.
The National Weather Service will probably post a winter storm watch for Saturday night-Sunday by mid to late afternoon -- it's outside their regular forecast period at this point. We have a winter weather advisory tonight for whatever snow/sleet/ice we get. An interesting but dangerous weekend is in store.
Stay tuned here
Feb. 13, 2003, 8:15 a.m.
SPRING VS. WINTER, ROUND 1
If there were a theme song for this weekend's weather, it would have to be Avril Lavigne's "Complicated." "Why do you have to go and make things so complicated?" Forecasters everywhere in the mid-Atlantic region are singing that this weekend as they fill their stomachs with antacids and caffeine.
In my second corny pop culture reference in as many paragraphs ... have you seen the Christmas cartoon "The Year Without A Santa Claus" where Heat Miser and Snow Miser duke it out for atmospheric supremacy? That's a great metaphor for what is happening this weekend.
Snow Miser will open up with full control of our skies, then Heat Miser will make a charge, but Snow Miser will ultimately triumph in this first round of their battles that will eventually lead to April showers and May flowers.
In a nutshell, here is the order of precipitation generally agreed upon by forecasters this weekend:
- Friday: Snow
- Friday night: Snow to sleet to freezing rain
- Saturday: Freezing rain to rain
- Saturday night: Rain to freezing rain/sleet
- Sunday: Freezing rain/sleet to snow
How did we get to such a mind-boggling forecast? A series of atmospheric impulses, including that stalled low off the California coast I told you about earlier this week, will ride a moisture-charged southern jet stream our way.
Initially, this will cause "overrunning" precipitation as the warm moist air overrides the surface cold air. For a time on Saturday, it appears the warm moist air will win the battle and we'll have plain old-fashioned rain for a while -- it may even be heavy rain.
Toward the end of this mess, a surface low pressure system will intensify south of us, and as it passes by, it will pull colder air back on top of us Sunday for another wintry round.
The "how much" part is the hardest, because the duration and intensity of any part of this pattern is so variable. My call is 2-3 inches of snow/sleet on the outset, then significant ice accumulation, followed by maybe as much as an inch of rain, a light "re-icing," then 3-5 inches of snow at the end. This is little more than a guess at a slushy mess.
The danger points in this forecast are Saturday during the day and again on Sunday. The extreme possibilities are a major damaging ice storm Saturday, if the cold air holds in longer than expected, and near-blizzard conditions Sunday, if the surface low wraps up earlier, faster and stronger than expected.
Let me stress that these are extreme "worst-case scenario" possibilities and not what is expected in either my amateur opinion or in the learned opinion of major government and private forecasters. But they're not impossible.
The ice storm possibility on Saturday does raise a few hairs on my neck, because even a few more hours of freezing rain could cause big-time problems. Forecast models often handle the "cold-air damming" setup very poorly, underestimating the depth of the cold air and its resistance to being moved. This is one time that being in the Roanoke Valley is a disadvantage. Roanoke will be one of the last places in Southwest Virginia to warm above freezing in this setup.
For those of you ready for spring, this is spring's first attempt to conquer Western Virginia. In recent years, winter has gone quietly into that good night with nary a fight. But this year, winter's entrenched and will have a hard time being moved. When spring's warm wetness and winter's hard cold reality tangle, all kinds of weather mayhem can result. This will be the first episode of multi-part drama that will only conclude when we start talking about the heat index again.
Feb. 11, 2003, 8 a.m.
BIG PROBLEMS DOWN THE PIKE?
I admit that the rush of winter storms, small as they have been, has left me a bit fatigued. Because of the active winter weather pattern we've had, I've had little time to vary the column much beyond day-to-day weather. We'll hit a respite sometime down the line and we can discuss other weather-related things. But not this week.
The weekend is a cause of some concern. In a nutshell, a large low pressure system has been stalled hundreds of miles southwest of California for more than a week now, essentially shoved aside like the loner at a party as our weather pattern has gone about its merry way with cold outbreaks and little snow makers. The pattern has shifted just enough now that this swirl of deep moisture will finally swing into California and then cross the country. Exactly how far north or south it rides will have major implications for our forecast.
The threat for our area is that this huge low, further engorged by Gulf of Mexico moisture and additional pockets of upper level energy, will run right smack dab into a cold air mass being pushed by a high pressure system to the northeast. It won't be brutal cold but it doesn't have to be to cause problems. This is a setup known as "cold air damming," a fairly common occurrence in winter when a high pressure system pushes cold air down the eastern U.S. The Appalachians act as a dam. Roanoke, Va., is in a prime location to be under the pool of cold air that the dam blocks.
The system coming out of the Pacific will almost certainly be our juiciest precipitation maker since Christmas. The questions involve how much cold air will be present when the moisture arrives, and how deep that cold air will be. This will be determined by the strength of the cold air damming and the track of the low. A track farther north would allow more warm air from the Gulf to flow our way, maybe making it nothing but a big rain maker. A more southerly track means more cold air seeps down, which could spell big-time ice and snow.
Friday-Saturday is the time frame on this storm. We have three days to watch its development. There are already various theories being expounded on it out in weather-nerd cyberspace, and forecast models are showing every answer under the sun. My early guess is some kind of snow/ice mix changing to rain, with bigger problems farther north. That's not my final answer, yet. What this most likely will NOT be is another puny inch of snow or some light drizzle. Whatever happens, there will probably be a lot of it, unless the thing completely misses us, which seems highly unlikely.
Stay tuned.
Copyright 2003