Area Forecast Discussion
Issued by NWS Blacksburg, VA

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480 FXUS61 KRNK 280521 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 121 AM EDT Tue Mar 28 2017 .SYNOPSIS... Moist southerly flow will continue tonight into Tuesday, with several rounds of showers and thunderstorms possible. Low pressure in the Ohio Valley with a trailing cold front will lift east tonight into Tuesday. Behind the front, drier air will arrive for midweek. && .NEAR TERM /THROUGH TODAY/... As of 940 PM EDT Monday... Changes to the forecast this evening amount to mainly very short term adjustment to chances of additional showers and and storm through the next few hours. Adjustments will be based upon the latest radar trends, which place isolated to scattered coverage across the far southeast portion of the forecast area, and soon-to-be arriving scattered showers and a few storms across the far western portions of the area. As the night progresses, the forecast will reflect progressively increasing chances of showers from west to east as a cold front approaches the area through the Ohio and Tennessee Valleys. As of 350 PM EDT Monday... Isolated to scattered convection developing ahead of the cold front this afternoon in the warm and unstable air. This convection is developing ahead of a lead shortwave moving ahead of an upper trough. The convective outlook for Day 1 places the marginal risk of severe weather to our west with the best instability and dynamics. Highres models like the HRRR and ARW showed isolated convection developing this afternoon into tonight, especially along the southern Blue ridge. Models enhance lift and low level convergence across the Blue Ridge into the foothills after midnight into the overnight as the front approach the Appalachians. Low temperatures tonight will range from the upper 40s in the mountains to near 60 degrees in the Piedmont. A strong cold front will move across our region Tuesday into Tuesday night. Scattered showers and Thunderstorms will develop ahead and along this boundary. The SWODY2 has placed eastern portions of CWA in a marginal risk for Tuesday. The timing of the shortwave on Tuesday with a favorable area of forcing for ascent moving across eastern portions during the afternoon during peak heating. The shortwave should move offshore around 29/00Z. The strongest storms could produce hail and locally damaging wind gusts. High temperatures Tuesday will vary from the upper 50s in the mountains to the mid 70s in the Piedmont. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... As of 349 PM EDT Monday... A cold front will move across the region Tuesday night with showers exiting the piedmont during the evening. Some low level moisture may squeeze out a few showers along western slopes overnight as the theta-E boundary tracks south across the mountains. There is not much cold air air behind this front, so any precipitation along western slopes or across the mountains will be liquid and not frozen. High pressure will move south out of Canada Wednesday, then wedge down the east coast Wednesday night into Thursday. This wedge will initial be dry and mostly clear Wednesday. Wednesday afternoon temperatures will warm into the 60s west to 70s east. A strong area of low pressure will track out of the Rockies Wednesday then across the Midwest Thursday night. This system will throw warm moist air over the wedge, increasing clouds and eventually the chance for rain/drizzle. Saturation of the environment should not occur until late Wednesday night into Thursday morning. Isentropic lift increases during the day Thursday. With this in mind, we have delayed the onset of stratiform rain/drizzle until late Thursday morning and moreso along eastern slopes of the North Carolina High Country and Grayson Highlands. The combination of rain falling into a linger wedge will produce cool temperatures with highs in the 50s areawide Thursday. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 349 PM EDT Monday... A strong area on low pressure will track from the Midwest to the south-central Appalachian mountains Thursday night into Friday. This low will erode the wedge of cooler air that moved into the region Wednesday. Dynamics from this low and with a retreating wedge boundary, there is the possibility strong storms could develop across the region Friday into Friday evening. However, timing is everything with this event. Currently, models have dynamics and retreating wedge environment occuring during the morning, which lowers the threat for severe weather. If this event occurs later in the day, then the threat for severe weather will increase. With an eroding wedge, temperatures will increase Thursday night and into the day Friday. Lows Thursday night will occur around midnight (upper 40s), then rise into the low to mid 60s Friday afternoon. This low pressure system and associated showers will exit the mid Atlantic coast Friday night. Dry high pressure and near normal temperatures will follow for the weekend. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/...
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As of 113 AM EDT Tuesday... Expect a period of showers and isolated thunder in the BLF/LWB areas at the start of the taf period with area of showers moving into ROA/BCB by 08z, then DAN could see some as well by 09z, with LYH toward 11z. Attm will have VCTS in the tafs since instability has weakened. Showers will bring the cigs/vsbys to high end IFR at times especially BLF/LWB, otherwise should be VFR. A few gusts as well possible but too infrequent for tafs. Front is across southern OH into Wrn KY early this morning and should be moving across the mountains in the 12-18z time frame, exiting the piedmont by 21z. Most of the showers and thunderstorms will occur in pre-frontal trough ahead of it but some lingering showers are possible in the mountains this afternoon, namely BLF/LWB. Could see a brief gust to 20-25 kts after fropa. Any precip will be out of the CWA by dusk. Looking at period of MVFR cigs at BLF and possibly LWB after 00z into Wednesday morning. Extended Aviation Discussion... High pressure builds in from the north Wednesday into Thursday with next storm system moving in the Mississippi Valley. A threat for sub-VFR cigs appears likely as the high wedges southwest Wed night into Thursday for most sites. The highest probability of rain will be on Friday along with sub-VFR cigs/vsbys with the showers. Post-frontal northwest flow sub-VFR into Saturday with gusty winds possible.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...DS/KK SHORT TERM...RCS LONG TERM...RCS AVIATION...AMS/WP

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