Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 272315 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 715 PM EDT Thu Apr 27 2017 .SYNOPSIS... A cold front will early tonight. High pressure will then build off the Atlantic coast and begin a trend for warmer and more humid conditions, with a slight chance for a shower or thunderstorm, through the weekend. Another cold front will move through on Monday and bring a good chance for thunderstorms, followed by some cooler temperatures through the first part of next week. && .NEAR TERM /THROUGH FRIDAY/... As of 700 PM EDT Thursday... Updated forecast to account for radar coverage of showers and a few storms over the mountains, moving northeast at 40 mph. Mesoanalysis shows a more stable environment lee of the Appalachians so severe threat looks to be diminished and thunder chances should wind down as well after 8pm, with a few cloud to ground strikes still possible in the piedmont until late evening. Trended temps a few degrees cooler than previous due to shower cooled air. Short term models show best coverage of showers after 8pm in the piedmont then drying after midnight. Previous afternoon discussion... The latest models continue to slow the arrival of showers and thunderstorms from the Tennessee River Valley toward our forecast area. Throughout the day, surface heating has been trying to overcome increasing cloud cover from the west and an impressive cap as depicted in the 12Z RNK sounding. An old outflow boundary will approach the Appalachian Mountains this evening, which should provide enough lift to spark scattered showers and thunderstorms. The Storm Prediction Center still maintains a marginal risk of severe weather, but whether anything happens or not will depend on if the aforementioned cap can be broken. Strong wind gusts would be the primary threat due to a 40 knot low level jet ahead of a cold front in the Ohio River Valley. Any shower and thunderstorm activity that develops this evening will cross over the Blue Ridge early tonight before fading over the Piedmont by midnight. As the surface front crosses overhead later in the night, the models dissipate this front due to strong upper level ridging over the Southeast. Skies should clear toward early Friday morning, but it may allow patchy morning fog to develop in the river valleys. The fog should vanish quickly and give way to mostly sunny skies through the day. With less cloud cover and drier conditions for Friday, expect high temperatures to be a few degrees warmer than Thursday and about 10 to 15 degrees above normal for late April. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 345 PM EDT Thursday... Region remains under large upper southeast ridge. Broad subsidence and 850MB temperatures peaking around +20 will result in maximum temperatures as much as 10 degrees above normal. However, on Sunday high clouds blowing off from showers and thunderstorms well upstream may limit full potential of heating. Will be cutting back of probability of precipitation for Sunday. Bufkit soundings on Sunday showed a cap just above 5000 feet and not much of any lift. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 345 PM EDT Thursday... Progressive pattern as closed upper low continues northeast into the Great Lakes on Monday and Tuesday. Models keep the long wave trof over the east with another low closing off somewhere around the Tennessee Valley on Thursday. WPC was leaning more towards the ECMWF with split flow and a southern stream not as deep as the GFS by Thursday. The system on Monday and Tuesday brings a surface cold front through the Mid Atlantic states on Monday and Monday night. Once a short wave goes by on Tuesday night, the front sinks south and high pressure builds in keeping deeper moisture south of Virginia and Kentucky. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/... As of 712 PM EDT Thursday... Showery conditions near ROA/LWB/BCB and moving into LYH/DAN this evening with mainly VFR outside heavier downpours. Downpours should drop vsbys to IFR with MVFR cigs, so will have tempo groups in to account for this. Thunder threat should subside by TAF start time with mesoanalysis showing little to no instability. Appears threat of showers will exit the piedmont after 05z, then overnight will deal with fog potential given wet ground and clearing skies. At the moment seems BCB/LWB will have best chance of IFR or worse vsbys but could see MVFR at the other sites as well. All TAF sites should return to VFR after 12Z Friday with light south winds expected. Extended Aviation Discussion... High pressure should build off the Southeast coast during this weekend. Other than the potential for MVFR/IFR morning fog at the usual river valley locations, VFR conditions should prevail through Saturday. As a low pressure system approaches from the west on Sunday and Monday, the potential for afternoon showers and thunderstorms will increase. The cold front associated with this system should reach the Appalachian Mountains by Monday afternoon and depart offshore on Tuesday morning, so expect the best chance of MVFR conditions during the frontal passage. && .CLIMATE... Potential for high temperature records to be broken Saturday, April 29. Current record/yearForecast Roanoke 89/1915 89 Lynchburg 88/1974 89 Danville 91/1981 88 Bluefield 83/1996 85 Blacksburg 83/1974 84 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...PW/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...PW/WP CLIMATE...JR

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