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So far, other than a couple of damaging hailstorms around the Rocky Mount-Smith Mountain Lake area, this hasn’t been an especially notable spring for severe thunderstorms in most of Southwest Virginia east of Interstate 77 (west of there got in on some of the same big early March outbreak that crisscrossed Kentucky, Indiana and Ohio). It certainly has been a far cry from the tornado frenzy of April 2011. Storm systems affecting us have not been especially wound up nor have they been traveling as far south across the nation, so we haven’t had the strong shearing winds (changing direction with height) develop as often or as intensely as a year ago. Also, there has been a recurring and persistent tendency for cool air “wedges” to develop east of the spine of the Appalachians, sapping storms’ energy as they move eastward. Some of this again appears likely to come into play on Tuesday afternoon and evening, when some strong storms will be possible as a cold front moves into warm and moist air ahead of it. But a few ingredients are likely to be missing or, at least, not very strong, such as shearing winds and instability. Lingering effects of Monday’s wedge that kept low clouds and drizzle hanging around from the Blue Ridge eastward, plus possible debris clouds from morning showers moving in from the west, will likely limit daytime heating, though temperatures in the 70s and dew points in the 50s and 60s are often sufficient for some stronger storms provided there is enough lift from the cold front. Shear aloft does not appear to be substantial, and temperatures aloft are not extremely cold, which will limit instability, or warm air rising into colder air higher up.  Anywhere the sun breaks out for a longer time on Tuesday will have a better chance of severe weather, which would primarily consist of a localized damaging wind threat, and perhaps some hail. Tornadoes are not likely on Tuesday afternoon or evening. By late Tuesday into Wednesday, a more general rain area may develop as the front sluggishly moves through and a weak surface low to the south spreads some moisture up over the cooling air mass.

Depending on how things develop, it would not entirely be out of the question for some or all of the region to be upgraded into a slight risk of severe weather, or for a watch to be issued. You can follow those developments on the Storm Prediction Center website – or on the Radar/ Futurecast at right, by clicking on “Alerts” for the latest watches and warnings.

UPDATE 7:30 AM, 5/7: Easterly breezes have banked moisture against the mountains in what has become a frequently recurring “wedge” pattern this morning. If and where the sun and break through the low clouds with scattered drizzle, it could turn into a rather sticky Monday with highs in the 70s and dew points. The moisture present will set up the arrival of a cold front late Tuesday or early Wednesday, with rain and storms becoming likely. It’s still looking like there will be chilly mornings by late week, with widespread 40s Friday and Saturday mornings, perhaps even some 30s.

We have at least three cold frontal passages coming in the next 7 or 8 days, as a significant weather pattern shift occurs that will put this past week’s summer fling on the shelf. The first front is moving through overnight, as a “backdoor” cold front slides southward from the Northeast U.S. and pushes through most of the Carolinas by Sunday morning. A cooler, drier air mass will push in, with highs the next couple of days only in the 60s to mid 70s across Southwest Virginia, and chances of showers greatly reduced to only a slight chance on Sunday. Monday may be a few degrees cooler. A quick retreat of this backdoor front as a warm front late Monday or early Tuesday will set up the arrival of a vigorous cold front from the west late Tuesday or early Wednesday. It may briefly become warm and humid enough ahead of this front for a significant chance of strong to locally severe storms — something to monitor in the days ahead. The latter half of the week will feature temperatures near to slightly below normal, with highs in the 60s to low 70s and lows in the 40s to low 50s. (Normals by mid to late week are 75/52 for high/low at Roanoke, and 70/45 at Blacksburg). Another cold front is due to arrive by Saturday to reinforce the somewhat cooler air mass.  (Linked here, a NOAA weather map showing us between the cold fronts, near the center of high pressure). With high pressure expected to dominate in the West Coast region as the Pacific-North Atlantic pattern flips to a positive phase, it appears that for most of the next 10 days to 2 weeks, seasonable to somewhat cooler than normal weather will be on tap for Southwest Virginia as we that high’s clockwise circulation pushes in cooler weather from the northwest. A negative shift in the North Atlantic Oscillation, meaning high pressure near Greenland is forcing the jet stream southward into the Eastern U.S.with more Canadian air, is also at play. A frosty morning or two may be possible for some areas  if there are clear, calm nights near the peak of one of these cooler air masses, perhaps late this week or early the following week, though it does not appear a radically cold, widespread frost/freeze situation is likely.

UPDATE MIDNIGHT, 5/4: An area of storms in West Virginia, Kentucky and Ohio is sliding toward us overnight. Some parts of Southwest Virginia may experience a period of rumbles and heavy rain in the early morning hours, with chances being greater the farther west you are in the region. (Follow the overnight storms on the Weather Journal’s new radar display, linked here.) There will be likely be some break in rain after this passes, but new scattered storms could develop in the afternoon, as daytime heating, humidity, a weak front from the north and a rather potent upper-level disturbance interact. Sunday looks to be similar, perhaps a few degrees cooler behind the “backdoor” cold front. No real change in the general weather until a stronger cold front pushes in about midweek. END UPDATE

90 degrees will have to wait — maybe til late May or even June, when we would more typically expect it. Roanoke’s high fell a degree short of 90 again Thursday, while Blacksburg soared to a new record high for May 3, 87 degrees. The heat and humidity — dew points well into the 60s — cooked up some afternoon thunderstorms, some of which became severe with some hail reports. We’ll likely see somewhat more numerous showers and storms in Southwest Virginia both Friday and Saturday, as the warmth and humidity combine with (a) an upper-level disturbance moving northeastward from the Gulf of Mexico and (b) a “backdoor” cold front that will slide southward to near the North Carolina-Virginia border or a little farther south on Saturday. These systems will assist the unseasonable warmth — highs are likely to back off into the upper 70s to mid 80s most places with more clouds, but that’s still 10-15 degrees above normal for early May — in creating more lift and instability to create thunderstorms, some of which may contain gusty winds and hail. (Inset image at left is the Weather Central “Futurecast” for 3 p.m. Friday, showing scattered green blobs for showers and storms, as seen on Weather Journal’s new Radar/Futurecast display linked in the right margin.)   Periods of showers and storms and continued warmer than normal temperatures appear to be likely through about the middle of next week, when a strong cold front is expected to push through, leading to several days of much cooler weather. Whether that just means cooler than what we’re seeing now — i.e. back to normals in the upper 60s/low 70s for highs and lows in the mid 40s to low 50s — or something a bit colder that could raise frost concerns, at least in outlying areas, late next week remains a bit blurry.

Follow the development of storms Thursday on Weather Journal’s new radar / futurecast display linked here

UPDATE 6 PM: Blacksburg set a new record high for May 3 today, hitting 87 degrees — the previous record was 85 set in 1962. For the second consecutive day and third time this spring, Roanoke came up a degree short of 90 at 89, also 3 degrees short of previous May 3 record of 92 set in 1953. Storms in parts of the New River Valley and southward this afternoon have provided some heavy rain and scattered hail reports, and clouds blowing off from these storms have stopped the warming for the day even into the Roanoke Valley. Remember, you can follow the storms on the Radar / Future Cast link at right. END UPDATE

Roanoke hit 89 degrees on Wednesday, as it did on April 16. There’s a pretty good chance that Thursday will be the first 90-degree high temperature of the season for Roanoke, with widespread 80s across Southwest Virginia and low 90s in Southside. Over the past 10 years, the average date of the first 90-degree high temperature for Roanoke has been May 19.  It wasn’t until May 30 last year, but occurred in April the two years prior to that. The major obstacle in the way of a 90-degree day would be the threat of scattered showers and storms, like those that popped up and hailed on parts of Bedford, Patrick and Henry counties on Thursday afternoon. Heat, humidity, terrain influences and leftover outflow boundaries from Wednesday’s storms will be sufficient to fire a few storms, but an upper-level impulse will also be approaching from the southwest late in the day, and will increase the chances of storms, especially west of Roanoke. Leftover debris clouds from more numerous evening/overnight showers/storms with the upper-level disturbance will probably hold temperatures down about 5 degrees or so come Friday. Temperatures will gradually pull back into next week as a backdoor cold front may slip southward from New England, with the possibility of a much stronger cold front about the middle of next week returning temperatures to near normal or possibly even below normal.

Weather Journal gains an exciting new feature today — a radar display, provided by Weather Central, utilizing Bing maps. I wrote rather extensively about it in today’s Weather Journal column, linked here. You can find a small version of the radar display permanently inset on the right margin of the blog.  Here’s a very brief tutorial. By clicking on the Radar /Futurecast label above this display, a much larger display comes up that has several features. In the upper left are buttons for “Radar,” “Futurecast” and “Alerts.”  Directional controls below these buttons allow you to move the display anywhere you want to see, in our region or elsewhere in the nation,  zoom in to your neighborhood or zoom out to the entire continental United States. The magnifying glass in the upper right allows you to pick a location, even to a specific address, upon which to anchor the radar view. The “?” is just what you think, answering numerous questions and providing a much more in-depth tutorial than I am providing here. The four-arrows icon in the upper right expands the radar to cover your screen. Beneath these icons is a control to animate the radar or futurecast, and below that an expandable “Options” menu that has many different choices of what can be seen and animated on the display. One particularly useful item is the “Storm Cells” option, that places an icon on individual storm cells on radar, indicating whether they are likely to contain heavy rain, hail or high winds (or even a possible tornado), and by clicking on each storm cell, it will show you direction of movement and expected arrival times at given locations. The best way to learn how to use it is to do what I’ve been doing a few days, just play around with the features yourself. I will say in advance that the “Futurecast” is a handy little feature, but represents only one computer-generated scenario for what the weather will do in advance — and there will be times that I or the National Weather Service or other forecast entities see it a little differently.

There will probably be just a few showers and storms for the radar to pick up in our region today through Friday, as a very summerlike pattern again sets up. Highs in the 80s to possibly some low 90s will occur each of the next three days, with that heat cooking up just a few scattered showers and storms in the afternoon, most numerous in the mountainous areas west of Roanoke. This is much like the weather we commonly see in July. It still appears likely we see a sharp reversal to cooler temperatures for a few days next week.

UPDATE 11:15 AM, 5/1: The wedge has broken and sunshine is driving temperatures upward, with 80s possible in many areas of Southwest Virginia today. Some storms moving out of eastern Kentucky and southern West Virginia will affect some areas this afternoon, especially along and north of the U.S. 460 corridor (Bluefield-Blacksburg-Roanoke-Bedford-Lynchburg) this afternoon. Afternoon warming and humidity may give them a boost of intensity, with a few strong to severe storms possible.  Latest National Weather Service radar linked here. END UPDATE

Damp air trapped against the mountains by light east to southeast winds kept locations along and east of the Blue Ridge in drizzle, low clouds and fog on Monday. As a result, there was a wide and unusual disparity in temperatures, with Roanoke and Lynchburg hanging near 60, Blacksburg topping 70 and Bluefield topping 80. That wedge effect is continuing overnight and early Tuesday, with a dense fog advisory from Roanoke east through Bedford County to Lynchburg, and north and northeast through Botetourt, Amherst and Rockbridge counties. Beware if driving of potential for pockets of 1/4 mile or less visibilities due to fog.

Finally, on Tuesday, the flip-flopping front that has created unpredictable day-to-day weather since Saturday will lift well northward. This movement of the front will usher in a several days period of very warm to hot  temperatures (80s to low 90s). Tuesday and maybe even Wednesday could have some showers and storms dotted around, but the days are likely to become increasingly dry as we approach the weekend. It still appears as if this summerlike period will come to a screeching halt sometime early to mid next week with a cold front that may usher in a period of normal to below normal temperatures for at least a few days.

UPDATE 4:30 PM: Take a look at a visible satellite photo from this afternoon, linked here, to see why Roanoke and points east are staying in the low 60s with drizzle and fog under dense low cloud cover, while locations to the west are in sunshine and rising into the 70s and low 80s — enough to cook up at least one thunderstorm that has led to a severe thunderstorm warning in parts of Wythe and Grayson counties (current radar linked here). END UPDATE

Kind of a weird day Sunday, though a beautiful one, with Blacksburg having a high temperature (78) that was 7 degrees warmer than Roanoke (71). It wouldn’t be odd to see something like that when Roanoke is socked into fog that clears farther west, or some kind of rain band or storms moving in a way to affect Roanoke but not Blacksburg, but it is quite unusual to see a +7  temperature differential in Blacksburg’s favor when both sites are in sunshine. The trick was that a high pressure system pressing in cooler air held in just a little longer to the east, so Roanoke’s temperature was more stubborn to rise.

Through the next two days, we’re still near a back-and-forth front that has been sliding north and south for several days, and there will be continued upper-air disturbances zipping by. This will keep a chance of showers and storms around that will be hard to time on days that may just as easily be mostly sunny and warm, like Sunday (perhaps very warm on Tuesday, well into the 80s possible). By Wednesday and Thursday, the front finally gets a good shove northward as a warm front and, a very warm, mostly dry air mass takes hold for several days. Expect widespread 80s for the latter half of the week, with a 90-degree reading or two not impossible somewhere in our general region on a day or two. Don’t get used to it though, as there are signs that the pattern may collapse rapidly at some point next week, and turn around to an unseasonably cool scenario for several days after the hot spell. The North Atlantic and Arctic oscillations are projected to dip into a negative phase for early to mid May, meaning more blocking high pressure in the far north forcing cooler air south, and several forecast models show a southward-dipping jet stream developing. Sunday’s computer-generated temperature forecast maps from the Climate Prediction Center (inset at left: 6 to 10 day map at top, 8 to 14 day map at bottom) show the potential temperature contrast vividly. So our short-term flip-flopping may stop for a few days with a warmup later this week, but a big flip-flop back to cooler weather may well occur in the longer term next week.

UPDATE 9:45 AM: The flash flood watch is no longer in effect, and there is nothing of significance on National Weather Service-Blacksburg radar this morning. A partly cloudy day with highs mainly in the 60s, maybe some low 70s, is on tap, with a chance of showers and storms, as we remain near the influence of a back-and-forth front and periodic upper-level impulses. END UPDATE

Saturday didn’t quite work out as planned. Oh, it stayed mostly dry in most places – radar composite shows less than a tenth of inch rain in much of the region, and no more than three-quarters of an inch even if the heavier thunderstorm paths, mainly the east-west track a few miles north of Roanoke. But the storm cluster from West Virginia that slowly dissolved into the cooler, drier air over Virginia was enough to splatter midday raindrops (and a few small hailstones) on many outdoor events and the resulting evaporational cooling dropped temperatures into the chilly 40s for a while over much of the region. Late this afternoon, temperatures are recovering into the 60s as the sun has broken out in many parts of Southwest Virginia.

The National Weather Service in Blacksburg has issued a flash flood watch overnight and early Sunday — expiring at 9 a.m. — for the counties immediately north and west of Roanoke and Blacksburg — Bland, Giles, Craig, Alleghany, Botetourt and Rockbridge — extending into much of southern West Virginia. This has been issued because many of these areas have seen the most rain in the past several days and are most in line to see a few heavy downpours overnight and early as another storm cluster, forming now in Illinois and Indiana, may make a run at the region. Like Saturday morning, the bulk of it is expected to stay primarily to the north of the U.S. 460 corridor (Bluefield-Blacksburg-Roanoke-Bedford-Lynchburg), but there will be a chance of showers and storms most anywhere. This does not reflect a likelihood of widespread heavy rain, but rather localized downpours that could lead to some streams out of their banks where rain has filled them in recent days. The flip-flopping front edging northward as a warm front on this Saturday will again get pushed south and we’ll have a break, with only minimal chances of showers, by Sunday night and Monday. That front is going to be hanging around just south of us for the next 2 or 3 days, always lurking as a possible contributor to rounds of showers and storms, until it finally gets pulled northward past us around midweek. That may be the start of a several-days warmer, drier period for our region and much of the central and eastern U.S.

UPDATE 10 AM: Latest National Weather Service radar shows a cluster of showers and storms moving out of West Virginia, which will hit drier and more stable air headed eastward, but may rain on some areas, especially west of Interstate 81 and north of U.S. 460. Expect some showers in the Roanoke Valley by midday as it heads east. Won’t wash out the whole day, but may make things showery for a bit. END UPDATE

Dry air pushed in by high pressure behind a cold front that sank to the south allowed for a picture-perfect Friday across much of the region — a stark contrast to April 27 a year ago, a sticky day capped by severe storms and tornadoes. That dry air will be stubborn to leave on Saturday, as high pressure continues to push it in while only slowly moving eastward, and the stalled front in the Carolinas late  resists the northward tug of a weak surface low-pressure system and upper-level disturbances moving along the front. Temperatures will start out Saturday a bit chilly in much of our region, with widespread lows in the 40s — and some 30s, especially outlying rural valleys and locations north of I-64, where frost advisories are in effect. As the front tries to move northward and upper-level energy moves closer, some scattered showers or storms can’t entirely be ruled out, but it will be difficult to get much rain to the ground in the dry air that’s in place. It will probably take most of the day to moisten the air enough for a better chance of showers and storms by late afternoon and evening, with the greatest chances, like on Thursday afternoon/evening, staying along the Virginia-West Virginia line and south along the I-77 corridor. The Hydrometeorological Prediction Center is expecting rainfall amounts to average a tenth of an inch or less across most of the region through Sunday evening, while Friday night’s North American Model actually cuts rainfall off entirely for the New River and Roanoke valleys and eastward. We’ll still have the flip-flopping front and occasional upper-level disturbances to deal with for the next few days, so additional bouts of showers and storms are possible, hard to time and locate until about 12-24 hours away. For now, it appears Saturday will be a good day for most outdoor activities, with highs similar to Friday, in the 60s to low 70s, but keep one eye to the sky for that brief shower or storm, with chances increasing the later in the day it is and the farther west you are.

Friday marks the anniversary of the peak day of the 2011 Super Outbreak, when 316 people were killed in tornadoes across the South and East, the fourth deadliest day of tornadoes in U.S. history. Glade Spring, Virginia, on Interstate 81 south between Wytheville and Abingdon was hard hit by an EF-3 tornado during that outbreak, and the scars haven’t entirely healed a year later. One way to recall that terrible week is to look back on Weather Journal entries in late April 2011, many of which deal with the severe weather outbreak, as it was happening and in the immediate aftermath.

Thankfully, we do not have anything that ballistic to deal with this year. We do have a flip-flopping front that will move north and south like a jump rope the next several days. It lifted north as a warm front late Wednesday and early Thursday, helping trigger the round of showers and storms we saw, in association with an upper-level impulse sliding east-southeastward. (Linked here: A list of regional rain totals, through 9 p.m. Thursday.) That will push it south for Friday, which means a dry day is likely. But a new disturbance approaching Saturday could lead to another round of showers and storms across much of our region. There will be some potential for heavy rain and/or strong storms, depending on how the pieces come together, and when they do. Timing, placement and intensity of each new round of showers and storms resulting from upper-level disturbances interacting with this back-and-forth frontal boundary are difficult to forecast until just a few hours before each new event. Saturday is not likely to be a total washout for most people, but it’s also unlikely to be totally dry. Something in between is the most likely outcome for those planning outdoor activities. (As of Thursday evening, the Hydrometeorological Prediction Center is leaning more to the dry side for our immediate region.) Sunday may also have some showers and storms before the front slides back to the south. It will come north yet again in the early to middle part of the coming week, but appears likely to eventually push far enough northward that a warmer and drier weather regime will take hold, with several days topping 80 next week as we move into May.