Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 171632 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1232 PM EDT Fri Mar 17 2017 .SYNOPSIS... High pressure over the region will shift offshore this afternoon ahead of a warm front approaching from the south. This front will lift northeast through the area overnight before a trailing cold front pushes across from the west during Saturday. High pressure will follow the front on Monday, then another cold front crosses the Mid Atlantic region Monday night. && .NEAR TERM /THROUGH TONIGHT/... As of 955 AM EDT Friday... 12Z soundings and corresponding surface observations continue to show very dry air in place this morning ahead of deeper moisture quickly advancing in from the west. This precip remains along the leading punch of deeper warm advection aloft and aided by low level isentropic lift ahead of the surface warm front to the south. Latest HRRR continues to bring an initial swath of precip into the far west shortly after noon with the more widespread coverage holding off until late in the day per dry air in place. Thus have sped up the onset of at least spotty precip northwest despite dry air while beefing up clouds and eastward expanse of higher pops by early this evening given lift. Other concern with possible frozen precip, mainly over Greenbrier and Bath counties, as guidance shows a delay in exodus of the colder 850 temps later, while also expecting some evaporative cooling espcly if precip arrival is a bit sooner. This supports including a bit more sleet to snow over the far northwest before all go to rain as warm advection aloft wins out by this evening. Faster arrival of mid deck likely to put a damper on temps espcly west to start. Therefore lowered highs Blue Ridge west a few degrees for now, and left mostly 50s east, where should see a bit more sun per deep downsloping flow off soundings. Previous discussion as of 410 AM EDT Friday... Closed low develops today over the western Great Lakes and moves southeast. Relative humidity forecast from the models bring moisture in above 700MB ahead of warm front approaching from the west. These high clouds will reach the central Appalachians around 15Z/11AM. Low level moisture does not arrive in the mountains until after 18Z/2PM. Surface high pressure was overhead early this morning. This high will move southeast today and will be off the southeast coast this evening. Surface winds will turn southwest once the high moves offshore and the warm front goes through. Not seeing much support tin the forecast temperature profiles for cooling enough for snow. Only the Elkins WV Bufkit sounding showed the potential for snow this evening. Have removed nearly all the snow from southeast West Virginia for this evening and overnight. Used mainly the MET for guidance on high temperatures today. Stayed on the warmer side of guidance since the area will be south of the warm front tonight. && .SHORT TERM /SATURDAY THROUGH MONDAY/... As of 300 AM EDT Friday... A quasi-stationary surface front will reside over the foothills and piedmont Saturday. The front does not slide south of the area until the upper low over Lake Erie begins to track to the southeast Saturday night. With the slower movement and exit of the front Saturday evening, cold air will lag behind and so will the change over from rain to snow across the mountains. Models are some what in agreement with liquid precipitation amounts that when the P-type does become snow, one to two inches may accumulate along the western slopes of southeastern West Virginia late Saturday night into Sunday morning. Temperatures are not expected to be too cold with readings from the mid 20s along ridgetops to lower 30s across most mountain valleys. Majority of the snow should melt on roadways overnight as Saturday afternoon temperatures will warm into the 50s west of the Blue Ridge. Also as low pressure moves off the Mid Atlantic coast and high pressure enters the Ohio Valley, a pressure gradient will sit over the area Saturday afternoon into Sunday morning. This will bring breezy and gusty conditions to the area but speeds will not reach advisory criteria. Cool high pressure builds over the region Sunday. Sunday afternoon`s temperatures will be close to normal with 40s across the mountains and 50s east. High pressure will sit overhead Sunday night which will allow temperatures to radiate down into the 20s and 30s. Temperatures will warm into the 60s Monday following the exit of high pressure and the passing of a warm front. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... As of 245 PM EDT Thursday... On the heels of our weekend cold front, will be yet another cold frontal passage Monday night into Tuesday, with a weak warm front preceding it on Monday. Anticipate another round of patchy light rain on Monday, before a switch to rain showers Monday night. Enough cold air may arrive by Tuesday morning for a rain/snow mix across western Greenbrier Co, WV. The front is expected to head south of the area by Tuesday evening, with limited showers remaining across the southern half of the area Tuesday afternoon into the evening hours. After only another small break in the activity, another warm front is progged to lift north across the area Wendesday night into Thursday. This one will be different from the previous. Its parent low will have Pacific origins and will be making its way into the central portion of the country. We may have a precipitation type issue at the onset of the event based upon some of the early looks at model low level thermal profiles. At this point, we will keep the forecast simple with a basic rain versus snow forecast, with a surface temperature of 32 degrees or less the determination for rain versus snow. Temperatures during this portion of the forecast will average around five degrees below normal. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/...
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As of 1230 PM EDT Friday... VFR will gradually give way to deteriorating conditions from west to east this afternoon into this evening as lowering cigs and bands of precip spread east ahead of a warm front to the south. May also see periods of MVFR in rain/sleet around KBLF and perhaps a wintry mix at KLWB this afternoon before finally switching to all rain this evening. Rain will also be spreading toward KBCB/KROA where some sleet could also occur this afternoon but thinking mostly VFR until more widespread rainfall with the upstream cold front arrives this evening. Ceilings will continue to lower overnight with MVFR/IFR across much of the west and perhaps a period of MVFR east of the ridges this evening/overnight. Also expecting a few hours of MVFR vsbys in rain/fog mountains overnight and brief low end to MVFR out east. The low level jet increases into the 50 knot range south of the warm front which could lead to spotty LLWS. Since quite isolated and mostly late tonight wont include mention for now. Cold front moves across the region during Saturday resulting in improving conditions espcly by afternoon from the Blue Ridge east. Uncertainty remains over the west given developing upslope northwest flow behind the front but for now appears there could be a window of MVFR to even VFR at KBLF/KLWB before colder air aloft arrives late in the day. Extended Aviation Discussion... Gusty post frontal northwest winds along with upslope western mountain snow showers will develop Saturday night and continue into part of Sunday. Best chances for sub-VFR with snow showers at KBLF and perhaps KLWB will be Saturday night into Sunday morning. High pressure building in on Monday should yield VFR all terminals to start the week. However moisture ahead of another cold front and associated weak low pressure may arrive by Monday night, with sub- VFR possible later Monday night into early Tuesday before improving conditions take shape into midweek.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/JH NEAR TERM...AMS/JH SHORT TERM...RCS LONG TERM...DS/RCS AVIATION...AMS/JH

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