Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 271949 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 349 PM EDT Thu Apr 27 2017 .SYNOPSIS... A cold front will move across the region with a good chance for showers and thunderstorms through 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 345 PM EDT Thursday... 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 /20Z THURSDAY THROUGH TUESDAY/... As of 225 PM EDT Thursday... VFR conditions should persist for most locations this afternoon, but there will be scattered showers and thunderstorms that could limit ceilings and visibilities to MVFR temporarily. An old outflow boundary ahead of an approaching cold front in the Ohio River Valley will reach the western Appalachian Mountains, which should serve as the focal point for any convection. The best confidence for timing of the showers and thunderstorms comes between 20Z Thursday to 02Z Friday. Winds will gust out of the southwest this afternoon due to a 40 knot low level jet. By tonight, shower and thunderstorm activity should dissipate as the outflow boundary exits to the east. Model guidance shows ceilings dropping toward MVFR and possibly even lower at BLF/LWB/BCB during the night, but confidence was too low at this time to push it downward as much. Patchy fog will also be possible at LWB and BCB by early Friday morning, while locations in the Piedmont should remain VFR. 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. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...PW SHORT TERM...AMS LONG TERM...AMS AVIATION...PW is the U.S. government's official web portal to all federal, state and local government web resources and services.