Area Forecast Discussion
Issued by NWS Blacksburg, VA

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513 FXUS61 KRNK 201425 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 925 AM EST Sat Jan 20 2018 .SYNOPSIS... High pressure aloft and at the surface will build over the region into early Monday. Temperatures will continue to moderate from the recent Arctic cold as this occurs. A strong system will move from the Midwest into the Ohio Valley through Monday, passing through our region Tuesday. Widespread showers and gusty winds are expected to accompany this weather system, followed by much colder temperatures and mountain snow showers into midweek. && .NEAR TERM /THROUGH TONIGHT/...
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As of 925 AM EST Saturday... Made some minor adjustments to temperatures for late morning utilizing surface obs, their trends and shaped towards GLAMP. Adjusted cloud cover with satellite for late morning into this afternoon. Modified pops using 12z NAM for this morning. More changes later... As of 415 AM EST Saturday... Quiet weather expected today and tonight with a continued warming trend. Primarily a cloud and temperature forecast. Remnant Arctic high that brought our most recent cold temperatures was drifting slowly east off the southeast U.S. coast. Return moisture was tracking from the Gulf through the Midsouth and into the Ohio Valley, including adjacent West Virginia, up the west side of the Alleghanys. Models generally hold most of these clouds to our west, but could see some creeping as far east as JFZ, BLF, and HLX at times. Eastern sections should remain mostly clear again today. 850mb temperatures average around +8C across the region today, warming toward +10C by Monday. Clouds may temper max temperatures in the west a bit, while remnant snow cover from 1-4 inches eastern sections should hold temperatures down a few degrees from what otherwise would be expected. Leaned toward the cooler GFS/ECMWF for temperatures and undercut eastern areas 2-3F degrees today and 1-2F degrees for min temps Monday. Otherwise, look for a nice day with high temperatures in the 40s and 50s and lows tonight around freezing to near 40 with mainly west to southwest winds 5-10 mph.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As of 300 AM EST Saturday... The upper pattern will be in transition as a large closed low over the midwest opens up and moves into New England early next week. So aside from a slight chance of showers far west of the Blue Ridge for the first part of Sunday, the Appalachians and central mid Atlantic region will have fair but breezy conditions through the first part of Monday with temperatures well above normal. By Monday afternoon the chance for showers will be increasing in the mountains later in the day as a strong cold front approaches from the west. Guidance continues to advertise the front with a good deal of dynamic support, being driven by low pressure moving through the Great Lakes. The front is expected to be accompanied by widespread rainfall though lapse rates are not impressive and surface based instability is largely absent so chances for thunder look quite low. However, the low level wind field amplifies considerably and there is very healthy shear along the front so embedded convective elements may be able to mix down strong wind gusts without thunderstorms. While the likelihood of this is not great due to the lack of instability, the possibility can not be dismissed due to the energetic nature of the system. The front crosses the region Monday night with precipitation tapering off to lingering upslope showers west of the Blue Ridge on Tuesday. Winds behind the front will become quite gusty through Tuesday night and a wind advisory may be necessary. Also, with colder air moving in behind the front some wet snowflakes are possible at the higher elevations west of the Ridge. The lingering upslope snow showers will persist into Wednesday morning. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 200 PM EDT Friday... Overall airmass behind the cold front is not that cold as it has a Pacific origin, so not an arctic blast. Temperature start to rebound late in the week as we dry out with surface high building in from the TN Valley midweek, and off the VA coast by Friday. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... As of 700 AM EST Saturday... VFR conditions will prevail through the TAF valid period for areas east of the Blue Ridge. In fact through much of the TAF valid period these areas will be SKC, including KROA, KLYH, and KDAN. Further west, low-level moisture was tracking from the Gulf around the west side of the remnant Arctic high lingering over the southeast states. Ceilings were mostly MVFR in these areas, with KBCB still several hours east of the MVFR ceilings yet. Little change is expected through the day. The low clouds will gradually spread further east from their current edge location near the VA/WV border eastward toward the I-81 corridor by evening. Ceilings will remain mostly in the 020-030 range through the day, then drop into the 010-020 range after 00Z, with the exception of higher terrain, such as KBLF, which will see IFR-LIFR ceilings in the 003-005 range., Visibilities are expected to be mostly VFR through the TAF valid period. However, if the ceilings drops below 005 at KBLF, MVFR visibilities in fog/mist will be possible. Winds will be WSW-WNW through the TAF valid period at speeds of 7-12kts with low end gusts 20-25kts, mainly along and west of the Blue Ridge. Winds will diminish to less than 10kts after 00Z. With strong winds aloft on the west side of the high, some LLWS will be present, especially this morning until the air becomes better mixed and the strong winds come down closer to the surface as noted in the paragraph above. Medium confidence in ceilings through the TAF valid period. Medium to high confidence in visibilities through the TAF valid period. Medium to high confidence in wind speed/direction through the TAF valid period. Extended Discussion... Low clouds may linger much of the weekend west of the Blue Ridge with associated MVFR ceilings. Mostly VFR conditions are expected across the Piedmont. Sub-VFR conditions will start to return to the entire area Sunday night into and through Tuesday night as a cold front and its associated precipitation moves through the region. Strong convective showers are expected with this weather system, including a potential QLCS and isolated thunderstorms. Very gusty northwest winds return to the area Tuesday night into Wednesday on the backside of the departing system. Lingering sub-VFR conditions possible across SE WV thanks to strong upslope flow and residual low level moisture. && .EQUIPMENT... As of 325 PM EST Friday... NOAA Weather Radio, WXL60 (Roanoke Transmitter) which broadcasts at 162.475 MHz remains off the air. The phone company reported that the circuit line had been cut and will take until Monday January 22nd to fix it. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...KK/RAB SHORT TERM...MBS LONG TERM...MBS/WP AVIATION...DS/JH/RAB EQUIPMENT...WP

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