Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 161942 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 242 PM EST Sat Dec 16 2017 .SYNOPSIS... High pressure will build across the Southeast U.S. tonight and Sunday. Lows pressure over the Southern Plains will move northeast toward the Ohio Valley and weaken tonight and Sunday. Another low over the Southern Plains and lower Mississippi Valley on Wednesday will move east through the end of the week. && .NEAR TERM /THROUGH SUNDAY/...
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As of 230 PM EST Saturday... Surface high pressure was centered over central Alabama. A cold front extended west to east from southern Minnesota into New England. A trough of low pressure was deepening into an area of low pressure in the western portion of the Gulf of Mexico. As we progress through the next 24 hours, the center of the the high pressure will move eastward to off the coast of the Carolinas by this time Sunday. Anti-cyclonic flow on the west side of the high will help advect milder temperature into the area, as well as, help guide the developing low in the Gulf of Mexico into the Deep South. Associated moisture will start to stream into the area in the form of high level cloudiness Sunday morning. By the afternoon, we expect isolated to scattered showers to be across approximately the western half of the region, with clouds continuing to lower an thicken across the entire region. Lows tonight will reflect the scenario of the the higher elevations remaining mixed within the stronger breezes aloft, and thus milder than their neighboring valleys. Likewise, the Piedmont region will also remain cooler than the higher terrain to the west. Lows tonight will fall into the mid to upper 20s across most locations. The higher ridge tops will be milder with lows in the lower 30s. On Sunday, despite increasing cloud cover, the influence of increasing warming air advection should allow for high temperatures a few degrees higher than those expected for today. Anticipate mid to upper 40s across the mountains with low to mid 50s across the Piedmont.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 210 PM EST Saturday... Series of upper low will track out of Mexico and to the northeast through the week. The first upper low weakens in the confluent zonal 500MB flow over the eastern United States,. What is left of this short wave will cross over the Mid Atlantic region on Sunday night. By then the next closed low will be over the Southwest. Models is reasonable consensus on synoptic pattern and temperatures through this time frame. 850MB temperatures will take longer to warm up in eastern West Virginia, but even there by Tuesday will be above zero. Persistent westerly flow and downsloping will aide in warming temperatures in the foothills and piedmont Monday and Tuesday. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 210 PM EST Saturday... The second upper low also weakens as it moves northeast but takes a more southern track through the Tennessee Valley. This short wave crosses the Mid Atlantic region on Wednesday and Wednesday night. A third upper low reaches the Southwest United States late in the week with a larger spread in models solutions concerning location and intensity. The main track of the vorticity maximums will depend on the strength of the digging trof in the central United States and the upper ridging over the Southeast. Models were showing a spread of solutions for Thursday through Sunday. In-situ type wedge of high pressure may develop over the area on Thursday. Models keep the bulk of any precipitation south of Virgina. Will keep better probability of precipitation mainly on Friday night and Saturday. Decent plunge of much colder air advertised by the GFS and ECMWF on Friday and Saturday for the central and eastern United States. Air mass will cold enough to support snow in the mountains on Saturday. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... As of 1225 PM EST Saturday... VFR conditions are expected during the extent of the valid TAF forecasts, concluding at 18Z/1PM Sunday. A southwest surface wind around 10kts is expected at most locations through the remainder of the afternoon with some gusts approaching 20 kts. Winds will subside overnight, then increase a little through the morning hours Sunday. Extended Discussion... VFR conditions continue through Sunday afternoon. A weak frontal system approaching from the west may induce a brief period of MVFR with light rain showers across the mountains Sunday night. This may impact KBLF and KLWB. VFR cloud bases anticipated elsewhere. Little or no impact is expected to aviation for the central Mid-Atlantic through mid week as weather features remain well north and south of the geographic region. The greatest potential will be Wednesday night, but even here, guidance is still not consistent with its various solutions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...DS SHORT TERM...AMS LONG TERM...AMS/PH AVIATION...DS

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