Flirting with freezing late tonight, Wednesday morningPosted Apr29, 2008 at 04:13 PMWednesday may be the last day of April but temperatures will start out cold. The mercury will probably fall below the freezing mark in the New River Valley and points westward, so a freeze warning has been issued in that area. Temperatures will probably hover near or slightly above freezing from the Roanoke Valley south and east, so a less-stringent frost advisory is in effect for those counties. It would probably be a good idea for everyone to take in any sensitive plants tonight. For the record ... if Roanoke does happen to dip to 32 on Wednesday morning ... it would be the latest freeze in the spring since May 4, 1986. We had an April 28 freeze in 1998. This year's current last freeze date, April 16, matches 2005 as the latest since 1998. Latest frost/freeze advisories from the National Weather Service An official freeze in RoanokePosted Apr16, 2008 at 09:40 AMRoanoke's temperature at 7 a.m. was 31 degrees, meaning that the city officially experienced a freeze. The average last spring freeze from 1948 to 2007 was April 12, so this would only be 4 days later than average, provided there is not another freeze later in the spring. The latest date on record for a last freeze was May 11 in 1966, though it dropped to 33 on May 22, 2003, missing a freeze 11 days later by 1 degree. The earliest date for a last spring freeze was March 18 in 1978. The last spring freeze was very early that year even though it followed an extremely cold winter. Temperatures almost everywhere else in Southwest Virginia were below freezing for a few hours this morning. There is the potential for damage to anything that is budding or blooming, but that seems to be much less than last year, since our March wasn't as warm. A few areas may get to freezing again Thursday morning, though the overall trend the next several days will be for much warmer weather. Roanoke will have to drop fast to get to 32Posted Apr15, 2008 at 10:12 PMRoanoke is still sitting at 52 degrees at 10 p.m. The dew point is low, 18 degrees, so there is plenty of room for the temperature to fall. It will have to do so hurriedly in the after-midnight hours to get us to freezing. It can do it, but I would not be surprised if the urban areas of Roanoke escape with temperatures just above freezing. Still, a close enough call to get in some sensitive plants. We'll see how it pans out. Most outlying areas will drop below freezing by Wednesday morning, the second in a row for many locations. A freeze warning is in effect for most counties from Roanoke south and east. The counties north and west of Roanoke will get to freezing, too, but their growing season is not far enough long to warrant a freeze warning, according to the National Weather Service. Click here for current temperatures at stations across the area Frost could be widespread by Wednesday morningPosted Apr14, 2008 at 10:16 PMIt's been a little too warm for snow except in the higher elevations around Southwest Virginia ... we've just had chilly sprinkles with temperatures in the 40s in the Roanoke Valley. The real issue could be how much frost develops by Wednesday morning across the area. There could be some frost on Tuesday morning if the cloud blanket rolls away overnight, allowing radiational cooling to take temperatures near freezing. Tuesday night into Wednesday, however, clear skies and calm winds may take temperatures below freezing across almost all of the area, and this could allow for a widespread frost. A frost advisory is in effect for Tuesday morning and a freeze watch is in effect for Wednesday morning, which may be upgraded to a freeze warning sometime Tuesday. Though Thursday morning could be pretty cold, a warmup is expected to set in Thursday afternoon into Friday. One can never be totally certain, but there is a good chance this will be our last bout of near freezing weather this season. A few inches of snow possible in some higher elevationsPosted Apr12, 2008 at 10:06 PM
All of this is being caused by a series of disturbances -- pockets of very cold air aloft -- that will be moving southeastward during the next 48 hours over the Canadian air mass that has moved in at the surface behind the cold front that moved through today. These pockets of very cold air will allow somewhat warmer air with some moisture to be lifted upward and squeezed out, producing showers of rain and snow on Sunday and Monday. As is typical in setups like this throughout the winter, the western slopes of the mountains will be favored for the heaviest precipitation, as the northwest winds guided up the mountain slopes produce extra lift. But even the lower elevations, such as the base of the Roanoke Valley, may see at least some flakes flying through the air by late Sunday night or early Monday. It may seem a little weird to have snow this late in the season, but really, it's not an extremely unusual event. In fact, we had snow showers in mid-April just last year, and the highest elevations in our region sometimes see at least some snow into May. The cold, damp wedge is returningPosted Apr01, 2008 at 05:18 PMToday has turned out to be a warm and pretty day, and the showers and thunderstorms that were expected with an approaching cold front have largely washed out. We can't rule out a few showers tonight, but certainly no gullywasher is on tap. After a mild, breezy day on Wednesday, it does appear that Thursday will be much like a repeat of Sunday, as cold, damp air becomes trapped against the east side of the mountains. The result will be another dreary, drizzly, chilly day that might even include a little sleet or, at some cold spots in the higher elevations, freezing rain. To get this kind of setup twice within a week is certainly unusual for late March/early April. Once again, the wedge will slowly erode and temperatures will gradually warm into the weekend. Enjoy Wednesday's warmth while it lasts! Some more rain on the way, but not freezingPosted Mar30, 2008 at 11:37 PM
Temperatures will slowly warm Monday and then more quickly warm Tuesday. We will have a chance of rain each of the next two days, though it doesn't look like a lot is likely to fall. There could even be some thunderstorms by Tuesday evening as a new cold front approaches. The second half of the week looks drier and warmer. You've got to be kidding -- freezing rain?Posted Mar29, 2008 at 07:42 PM
The last flakes of the season?Posted Mar24, 2008 at 11:20 PMAbout 6:30 this evening I drove through a brief but rather intense snow shower in Southwest Roanoke County. A weak disturbance aloft allowed some puffy clouds to pop up as slight surface warming rose into cold air aloft ... almost like miniature versions of the random summer thunderstorms we get ... and these kicked out some spotty showers of rain and snow. I think these may very well be the last flakes the lower elevations see until late next fall -- higher ridgetops often see some snow into May. The upcoming couple of weeks looks pretty mild overall with occasional rain systems. Even if we get another run of cold air from Canada, it will be so late in the season that snow will be hard to come by anywhere below about 2,500 feet. It's spring, but it's a pretty slow-springing one. Potential winter storm looking wide right this timePosted Mar21, 2008 at 10:47 AMAfter an entire season of nearly every potential winter storm going wide left -- west of us, that is -- the Sunday-Monday low is looking to go wide right -- off the coast. For signficant snow to occur in late March or April, conditions usually have to be almost textbook perfect ... dense cold air forced southward by strong high pressure in Canada, a lot of moisture falling through that cold air, and a favorable time of day away from the most intense sunlight helps. This one is probably going to fall well short on the moisture end with the low heading off the coast. Some light snow or rain is possible Monday, but barring an unexpected shift in the pattern, probably no late-March snowstorm. Is a late-March snow in the offing?Posted Mar20, 2008 at 09:14 AMNext week is looking cold, as this map from the Climate Prediction Center shows. The pattern is shifting, at least for a few days, to one more conducive to forcing cold air our direction. What's more, there is an early-week storm system that we will have to keep an eye on for the potential to bring moisture into the cold air. Yes, there is some chance of snow around the Sunday-Monday timeframe. In any event, next week looks like it will be unseasonably cold, as winter tries to make a late return. The early call: Snow goes west of us againPosted Mar05, 2008 at 10:45 AMAt this point, it appears that a new low pressure system for Friday and Saturday will track far enough inland that the significant snow will pass west of us, which has pretty much been the way this winter has gone. This snowfall map from the Hydrometeorological Prediction Center illustrates the most likely area heavier snow. But it is closer than many of the previous systems, and will need to be monitored for any forecast changes that could jog this storm slightly eastward. That hasn't been the trend this winter, though -- most storms have ended up farther west than the early forecasts show. Quinwood, W.Va. wins again -- 15 inches of snowPosted Feb28, 2008 at 01:25 PMWithin the National Weather Service-Blacksburg office's forecast area that includes much of Southwest and Southside Virginia plus a few counties in southeast West Virginia and northwest North Carolina, Quinwood, W.Va., in western Greenbrier County is the typical winner in an upslope snow event. This time was no different coming in with 15 inches of snow from the intermittent snow showers and squalls that were squeezed out as northwest winds climbed the mountains the last couple of days. Below, in the extended entry, is a National Weather Service list recapping snowfall amounts from the snows of the last couple of days. In the Roanoke Valley, we just got a trace on a few snow showers Wednesday. Continue reading "Quinwood, W.Va. wins again -- 15 inches of snow" » A few speckles on radar kick out lots of snow for somePosted Feb27, 2008 at 05:56 PM
The snow showers and flurries will gradually dwindle overnight, and we'll be left with a cold but sunny Thursday before a gradual warmup through the weekend. A few flakes in the air today, no big deal in RoanokePosted Feb26, 2008 at 11:50 PMThe marathon upslope snow shower episode that is expected to deal up to a foot of snow in eastern West Virginia is off to a slow start tonight, but should pick up overnight and into Wednesday as strong northwest winds carry Great Lakes moisture up the western side of the mountains. On this side of the Appalachian spine, we may see a few flakes blowing through the air from time to time in the blustery breezes, but probably no significant accumulation. I wouldn't rule out a white ground in parts of the New River Valley, but even most places there should escape significant accumulation. Latest advisories and warnings from National Weather Service-Blacksburg Blustery winds will blow snowflakes in tonight and WednesdayPosted Feb26, 2008 at 12:24 AMAfter a cold front pushes through some showers today, strong northwest winds will kick in as a low pressure system develops in the Northeast. This is a familiar prescription for upslope snow showers, and this time, they will likely continue for so long that some of the higher elevation areas in eastern West Virginia could get 6 or more inches of snow. That's why winter storm watches were issued for a few counties over that way on Monday to cover the time from 6 p.m. tonight until 6 a.m. Thursday. There will be enough bleed-over from the upslope snows that some places in the New River Valley could get a dusting to an inch, and I wouldn't even be surprised to see a couple of the more vigorous snow showers amid off and on flurries in the Roanoke Valley briefly whiten the ground in a few places. Not a big snowstorm for the New River and Roanoke valleys, but enough snowflakes in the air to remind us that it's still winter. So now that this has piddled out, what's next?Posted Feb22, 2008 at 08:28 PM
It looks like we've dodged the icePosted Feb22, 2008 at 11:55 AMA couple of weak showers have moved through the Roanoke Valley with temperatures just above freezing, and more showers are on the way from the west, though they are diminishing somewhat in intensity and areal coverage. While we can't rule out a few icy spots on bridges and overpasses this afternoon, it would appear that we have essentially dodged this winter weather threat in most of Southwest Virginia. One late wave of rain coming -- but will it freeze?Posted Feb22, 2008 at 07:34 AMIt is now a race between the last piece of this very broken storm system, currently moving across Tennessee and Kentucky (click here for national and regional radar views), and whether surface temperatures can warm above freezing before it gets here. We will probably see some rain as that last spoke in the wheel moves through later this morning or early in the afternoon. Temperatures are well above freezing in the atmosphere above the surface level, so anything reaching the surface will almost certainly be liquid. It's just a matter of whether temperatures at ground level will be cold enough to allow any ice to build once that precipitation arrives later today. The National Weather Service in Blacksburg is hanging on to a winter weather advisory until noon just in case the last wave slaps us with a little ice. Precipitation will be tardy or absentPosted Feb21, 2008 at 08:52 PMUPDATE 12:55 a.m. Friday Feb. 22: New precipitation is firing over Arkansas, Mississippi, Alabama and Tennessee as I write this. This could move into our area later this morning, though it's still doubtful that this will be much more than a minor ice/sleet event. But it will have to be monitored in case heavier precipitation moves in while it's still below freezing. If rain arrives much later today, it could well warm above freezing. It's a very disorganized winter storm, sort of symbolic of a strange winter. 
Will precipitation keep doing the old spliteroo?Posted Feb21, 2008 at 03:23 PM
This split in precipitation we've been seeing was not entirely unexpected -- forecast models have been picking up on it for days. The question is whether or not overnight or on Friday a low moving east will drag more of the southern piece of moisture northward toward us. The two precipitation areas are connected now by a thin band near the Mississippi River -- we'll probably get that, if nothing else, and it will probably grow. But if we are going to get anything beyond an inch of snow/sleet and a thin glaze, the southern precipitation area will have to become more involved. Some of our moisture may well be getting eaten up by the thunderstorms along the Gulf of Mexico. As of now, it still looks some wintry precipitation will move into our area late tonight, probably after 10 p.m., but it's looking like a rather light event at this point unless something changes in the next several hours. The more mix we get, the less ice will build upPosted Feb21, 2008 at 09:49 AMWith the expectation that most of the area will see enough of a mix that the freezing rain portion of the event will not collect more than 1/4 inch, the National Weather Service in Blacksburg has gone the route of issuing a winter weather advisory for most counties in Southwest Virginia, including the Roanoke and New River valleys. Floyd, Carroll and Patrick counties, and a few more in northwest North Carolina, are under a winter storm watch for the possibility of getting 1/4 inch or more of ice on top of whatever snow and sleet falls to begin tonight's winter weather event. While it seems likely that wintry precipitation will occur across the area tonight, the amounts are the tricky part, especially weighing how much falls as snow/sleet and how much ends up as freezing rain, which all depends on how deep the cold air is being pushed from the north and how fast warm, moist air from the south can erode that colder air in the upper atmosphere. The local forecasters in Blacksburg, as this map shows, believe that counties along the Blue Ridge south of Roanoke have the best chance at getting more ice, owing to some southeast winds banking moisture against the eastern slopes of the mountains. But national forecasters at the Hydrometeorological Prediction Center favor areas from Roanoke northward having a better chance of getting 1/4 inch of ice or more, as this map shows. There is a question about the amount of moisture that will be available. This morning's radar shows the precipitation splitting up north and south, looking as if it might go on either side of us. I would expect that to fill in later today, as the split is primarily the result of separate pieces of energy in the northern and southern branches of the jet stream that will eventually become better aligned, though not perfectly. The moisture from the south is what is expected to spread northward, but thunderstorms down there could reduce the moisture flow. That's always an issue to watch when moisture is moving in from the Gulf. The flip side is that if fewer thunderstorms fire, we could see a surge in moisture that could push us into winter storm warning territory. My early guess: About an inch of snow/sleet on the front end in Roanoke with a quarter-inch of ice, pretty similar in New River with maybe a little more snow/sleet accumulation, just enough to get us on the edge of significant ice storm potential. I'm skeptical of any forecast or computer model that warms us above freezing before late afternoon on Friday ... the wedge of cold air from the northeast should hold tight and ice/snow accumulation will keep the air chilled near the surface at least a few hours longer than projected. Forecasting ice accretion is a slippery taskPosted Feb20, 2008 at 11:33 PMForecasters are facing a complicated storm system with a tricky forecast tonight and Friday. What seems very likely is that significant moisture will move over below-freezing air at the surface. Wintry precipitation is all but absolutely certain, and it could be quite troublesome -- at least a nuisance for travelers, but possibly a problem for trees and power lines if only a little more occurs than is forecast. That's not what we want to hear after the Feb. 10 windstorm and Feb. 1 ice storm power outages. One of the hardest things in winter forecast is projecting ice accretion. It's not as simple as saying "we're going to get a quarter-inch of rain, therefore we'll get a quarter-inch of ice." * The first complication is that much of the early precipitation may fall as snow or, especially, sleet. The more falls as snow and sleet, the less will fall as freezing rain, and therefore the less ice can accumulate. * Secondly, more of the rain will freeze if temperatures are a few degrees below freezing than will if it's very near freezing. The same level of freezing rain at 25 degrees is much more of a problem than it is at 32. * Temperatures aloft matter. If the air is very warm above the surface, the rain falling through it takes a longer to freeze at the surface than it would if it were falling through air just a few degrees above freezing. * How hard the rain falls also matters. A heavy rain may run off more and not freeze on objects as readily, whereas a steady, light to moderate rain runs off less and therefore has more of a chance to freeze on trees and power lines. Weighing all of those factors and many more as of late Wednesday night, forecasters were expecting up to two-tenths of an inch of ice on top of a layer of an inch or so of snow and sleet. That forecast could change many times today. If the National Weather Service believes there is a reasonable chance 1/4 inch or more of ice could accumulate, a winter storm watch or ice storm warning may go into effect. Expectations could change many times as the storm takes shape today. For the latest, click on the National Weather Service-Blacksburg's "Current Event" page. No watch, but a wintry mess likely on its wayPosted Feb20, 2008 at 05:18 PMThe National Weather Service in Blacksburg has, for the time being, declined to issue winter storm watches for the system headed our way Thursday night into Friday. It takes an expectation of 4 inches of snow or 1/4 inch of ice to trigger watches, and right now, the fast speed of the system may keep precipitation amounts light. Also, we may see so much mixing of snow, sleet and freezing rain that the ice won't get to 1/4 inch by itself (very little chance the snow would get to 4 inches under any circumstances -- an inch, maybe). So for now, it looks like a messy, mucky winter storm that could be a nuisance but not a particularly severe winter storm. New data could change expectations. Click here for the latest on advisories and warnings from the weather service office in Blacksburg. Meanwhile, snow continuing to fall in parts of Alleghany and Bath counties could accumulate a few inches, hence the snow advisories. Cold, windy weather will spread across the area later tonight, and those winds could carry a few snowflakes, but significant snow is not expected in most places tonight. Hopefully for watchers of the lunar eclipse, the clouds will at least become broken in the gusty winds by 10 p.m. A weird afternoon in Southwest VirginiaPosted Feb20, 2008 at 02:55 PMThe low passing through our area has drawn enough warm air northward to push our temperature in Roanoke to 51 degrees at 2 p.m.... yet just 90 minutes drive northwest there is heavy snow and 28 degrees at Hot Springs. A snow advisory is out for Alleghany and Bath counties westward into West Virginia. It's going to get weirder as cold air arrives across the area tonight and temperatures plunge across the area into the teens and low 20s This new Arctic air will set up the likelihood of a signficant winter weather event on Thursday night and Friday, with snow, sleet and ice all possible. I will be interested to see if the National Weather Service flies winter storm watches. We should know in the next couple of hours. Winter weather threat building for late this weekPosted Feb19, 2008 at 05:17 PMSome of you saw a few snow showers today with a passing disturbance, and a stronger one passing just north may bring some showers of snow and rain to the area on Wednesday. The bigger issue, though, is the potential for a winter storm in the Thursday night-Friday timeframe as disturbances in both the northern and southern branches of the jet stream move near the area. The Hydrometeorological Prediction Center is already calling for a moderate risk of substantial ice for our area on Thursday night and Friday. It's unusual to be in a moderate risk still 3 days out. That signals a pretty high degree of confidence by forecasters that wintry weather will affect the area, but it also allows 3 days time for things to change. The current thinking is that precipitation will start as snow and then change to sleet and eventually freezing rain. It looks as if cold air will be pushed down into our area by high pressure to the north as the precipitation moves in. Winter has not let go of its grip on the area just yet. First comes fire threat, then maybe some snowPosted Feb18, 2008 at 11:46 PMBefore we can really begin to pick apart the series of disturbances from Wednesday to Saturday and what they could bring in terms of winter weather, a few stronger gusts of wind combined with dry conditions could easily spread fires today. As a result, the National Weather Service has posted a red flag warning for much of the area from Roanoke south and east. A red flag warning signifies an enhanced fire risk. This should not be a repeat of Feb. 10, as the lower atmospheric winds are not as powerful as they were that day. But we could see some gusts topping 40 mph during the day. The first threat of snow comes Wednesday with an Alberta clipper diving southeast. If you've followed weather for a while around here, you know that most Alberta clippers do not produce accumulating snow for our area, but once in a while, one will. Additional disturbances pose a snow/ice risk through the weekend, with gradually warming temperatures. It remains a tricky forecast. Tricky weather for last half of weekPosted Feb18, 2008 at 10:23 AMThough we've started out warm today, a cold front will soon be moving through, and over the next couple of days we will be sinking back to cold wintry temperatures. The tricky part of all this comes in the Wednesday to Saturday time frame when a series of disturbances will be moving through, as well as a warm front lifting northward. The timing and placement of each disturbance, the thickness of the cold air and the speed of the warm front moving north will all come into play into determining precipitation chances. On one extreme, there could be off and on snow and ice throughout that time period. On the other extreme, the cold air could suppress the storms so much that little precipitation can occur until the warm front moves north, when it would only be rain for the weekend. Something in between those scenarios is most likely. Stay tuned. Probably no ice on Sunday, just some needed rainPosted Feb16, 2008 at 05:18 PMI think we're going to escape the freezing rain with Sunday's system. It's just not very cold and there's nothing to hold the cold air in place when the rain arrives, unlike last Tuesday night. As for rain amounts, looks like another decent but not especially soaking rain, as seen by the Hydrometeorological Prediction Center maps for the 24-hour period ending early Sunday evening and for the |
