Area Forecast Discussion
Issued by NWS Blacksburg, VA

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350 FXUS61 KRNK 161915 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 215 PM EST Sat Dec 16 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH SUNDAY/... As of 1220 PM EST Saturday... Very little change is expected concerning the forecast the remainder of the afternoon. The only notable change will be a slight decrease in the forecast high temperatures across the far western sections of the region. Have adjusted hourly temperature, dew point, wind, and sky cover to reflect the latest observations and expected trends through the remainder of the afternoon. As of 930 AM EST Saturday... Morning update will reflect very few changes to the ongoing forecast. Hourly temperature, dew point, winds, and sky cover are being tweaked to match the latest observations, and expected trends into the early afternoon hours. The biggest change here will be the allowance for a small area of cloud cover to pass to the east across the I-64 corridor through roughly noontime. As of 345 AM EST Saturday... Persistent Western CONUS Ridge and Eastern CONUS trough which has been the predominant set-up for the past week is now in the process of changing. As the break-down of the pattern takes place, the cold air in the eastern U.S. will retreat north with a slow but steady moderation of temperatures over the next several days. Today will start off cold, but unlike yesterday, lack of meaningful cloud cover and increasing warm air advection will lead to a wholesale increase in temperature this afternoon, highs a full 10 degrees warmer than yesterday. Winds will continue to be a bit breezy, so there will still be a bit of a wind chill to contend with. No threat of precip through Noon Sunday. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
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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.
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&& .LONG TERM /WEDNESDAY THROUGH FRIDAY/...
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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.
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&& .AVIATION /19Z 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/PM SHORT TERM...AMS LONG TERM...AMS/PH AVIATION...DS

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