Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241504 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1104 AM EDT Fri Mar 24 2017 .SYNOPSIS... High pressure off the coast will establish a warmer and more moist southerly flow across the Appalachians and central mid Atlantic region into the weekend. A slow moving cold front will enter from the west on Sunday with a chance for showers and possibly a thunderstorm. Our weather then looks to remain unsettled through next week as a series of disturbances move across the central and southern part of the country, keeping a chance for showers and thunderstorms in our forecast through Wednesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1100 AM EDT Friday... The wedge has eroded over parts of SE WV this morning. A warm front in northwesterly flow continues to track across the Mid Atlantic region. With all this taking place, an isolated shower or two may track across western Greenbrier early this afternoon. As of 345 AM EDT Friday... It`s looking like a quiet end to the workweek as an upper level ridge is the dominant weather feature over the Appalachians, though there will be a fair amount of cloud cover around. At the surface, high pressure along the middle Atlantic coast will continue to push offshore today. Satellite imagery shows some lower clouds extending back from the NC mountains toward the Gulf coast, guidance supports return flow around the high drawing these clouds up into the region this afternoon along and east of the Blue Ridge into Southside. Additionally, a short wave will swing through the Ohio valley along a warm front on the rim of the upper ridge. This is generating some shower/storms well off to our northwest, but expect some showers to brush by to our north today with lower clouds extending southward into the region. Quiet weather then continues tonight as the ridge axis crosses the region and high pressure at the surface remains parked off the mid Atlantic coast. With a deepening southerly flow, temperatures will moderate considerably from readings yesterday with highs about 10 degrees warmer which will be above normal for late March.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... As of 400 AM EDT Friday... A very active, highly kinematic, westerly flow will be in place across the U.S. with the Pacific wide open. A parade of vigorous upper-level low pressure areas will march from west to east across the U.S. through the period. At least four such significant systems are noted during the 7-day period beginning Sunday. Saturday will bring one last day of dry weather to the area as an upper ridge briefly moves across the area and temporarily blocks the upstream system in the central U.S. A warm front will continue to lift northward through the northern portions of the Mid-Atlantic into NY and New England. The surface high that has been providing us with the cool weather the last few days will move to our southeast. The region will be solidly in the warm sector with southerly to southwesterly surface flow. 850mb temps will soar into the double digits allowing surface temps to warm well into the 60s west to the 70s Piedmont. These readings are about 10-15 degrees above normal for late March. By Sunday, the first of the Pacific system will arrive. Models are in general agreement on the details. Timing is faster than has been indicated in recent days with this system now arriving in the western part of the CWA Sunday morning and then into the Piedmont by Sunday afternoon. The faster arrival of these system also heralds better dynamics as well. Models are in pretty good agreement on a near solid line of showers and thunderstorms translating from the TN valley into western VA. The risk of severe weather with this system appears low as instability is meager at best with capes below 500 J/kg. Have included a slight chance of thunder western areas, but left as showers east of the Blue Ridge at this time. Rainfall amounts are expected to range from 1/2 to 3/4 inch west of the Blue Ridge to 1/4 to 1/2 inch east of the Blue Ridge. Temperatures will remain warm Sunday, but the clouds and precipitation will keep readings on the order of 5-7 degrees cooler than Saturday. The clouds, southerly flow, and warm, Gulf air in place will keep overnight minimums very balmy, well into the 50s most areas. On Monday, the first upper low will lift northward toward the Great Lakes and weaken as yet another upper-low follows quickly on its heels moving out of the Central Plains. This system promises to be somewhat more progressive and transition into an open wave as it moves into the eastern U.S Tuesday. This leaves the CWA in an unseasonably warm, humid air mass Monday between systems with little in the way of dynamics or forcing, yet with lots of clouds and high RH. Any breaks in the sun could trigger isolated pop up showers and thus have left in chance pops west to slight chance pops east with no thunder. Temperatures will be warm Monday with lows in the 50s and highs mostly in the 70s, except 60s western mountains. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 415 AM EDT Friday... As noted above, the next in the series of upper-level low pressure system will arrive in our region early Tuesday. Dynamics are marginally more favorable for thunderstorms than the Sunday system, but instability is notably better. Consequently, have included a chance of thunder for the entire CWA. Still not impressed with this being a widespread severe event for the CWA, but with the upper trough affecting eastern portions of the CWA during afternoon heating, a few stronger storms cannot be ruled out. The lack of shear, but greater instability, suggests that hail would be the main threat. Temperatures are expected to be close to those observed Monday, mainly in the 40s and 50s for lows and the 60s to lower 70s for highs. Wednesday will bring a brief break from the active weather before the next upper-low moves from the Southern Plains into the eastern U.S. Thursday, which is about 24 hours faster than previously expected. Weak high pressure should provide the region with a mostly dry and slightly cooler day Wednesday, but still with lots of clouds in place and possibly even a few showers or sprinkles, especially during the morning. Temperatures will still be well above normal ranging from the 50s in the morning to mostly 60s during the afternoon. By Thursday, the Southern Plains system will move northeastward into the TN and OH Valleys. Upper diffluent flow will begin to impact the western parts of the CWA by afternoon and evening. Of the three systems slated to impacted the CWA next week, this one brings about the greatest threat of severe weather as notable shear and instability will be in place. A line of strong to severe thunderstorms would certainly not be out of the question Friday afternoon. Expect little change in temperature Thursday from previous days. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... As of 745 AM EDT Friday... High pressure along the Mid-Atlantic coast will continue to push offshore today allowing winds to come around to the south and southwest. The gradient will tighten allowing wind speeds to increase and become fairly gusty during the late morning and afternoon, especially east of the Blue Ridge. Extensive mid and high clouds were spreading across the region as a result of mid-level warm advection. The southerly winds will also allow low-level moisture to increase resulting in increased potential for MVFR ceilings overnight/early Saturday. Otherwise, ceilings should remain VFR until after 00Z with ceilings through the day generally AOA 050. Visibilities will not be an issue through the TAF valid period remaining VFR. Medium confidence in ceilings through the TAF valid period. High confidence in visibilities through the TAF valid period. Medium to high confidence in wind speed/direction through the TAF valid period. Extended Aviation Discussion... Moisture continues to increase over the weekend ahead of an upper-level low pressure area moving northeast from the Southern Plains. Precipitation is not expected until Sunday when sub- VFR conditions become more of a possibility. Otherwise looking at overall VFR to start the weekend with most lower cigs remaining west of the area until later Sunday at this point. Periods of unsettled weather will continue into the first half of next week as a series of upper-level lows track from west to east across the U.S. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS/RCS SHORT TERM...RAB LONG TERM...RAB AVIATION...AL/MBS/RAB

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