Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 141756 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1256 PM EST Thu Dec 14 2017 .SYNOPSIS... A low pressure system sliding by to our north will bring strong gusty winds to the Appalachians and central mid Atlantic region, along with upslope snow showers for the higher elevations west of the Blue Ridge. High pressure will then build over the eastern part of the country and bring us fair weather with a warming trend as we head into the weekend. A low pressure system will then move out of the lower Mississippi valley late in the weekend and bring a chance of rain to the forecast for Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 1255 PM EST Thursday...Update to expire the wind headlines in effect. Even gusts at this point are becoming less frequent, though still gusting to 25 mph at Roanoke from the northwest. Also increased temperatures in the Piedmont and Southside areas by 2 degrees. This raises highs in these areas into the upper 40s to low 50s. Otherwise, forecast essentially unchanged with the early-afternoon update. Previous discussion issued at 220 AM Thursday... Clipper type low pressure system will slide by to our north early this morning. The low level wind field associated with this system is quite robust and looks like it will peak just before daybreak, about the time cold air advection becomes established and helps force higher momentum air from the hilltops to the lower elevations. This will result in strong gusty winds primarily at the higher elevations along and west of the Blue Ridge through early this morning where a wind advisory is in effect until Noon. A high wind warning is in effect from the mountains of NC into the Grayson highlands of VA where gusts to 60 MPH have been common. The wind field will gradually slacken and the high wind threat will diminish by Noontime. The brisk wind flow will also result in upslope clouds and snow showers west of the Ridge. Some of the higher elevations may pick up a fresh coating of snow with a couple of inches possible for western Greenbrier county. This will combine with the wind to create some areas of blowing snow early this morning. Moisture abates after daybreak with just some lingering flurries late this morning. Much quieter east of the Ridge with generally fair and blustery conditions for today. High temperatures today will generally be in the middle 40s east to low/mid 30s west. High pressure will settle over the region tonight with quiet weather expected, though there appears to be enough moisture to keep some cloudiness around especially west of the Ridge. This will keep temperatures tonight from reaching their full potential. Lows tonight will be in the middle 20s east to teens/lower 20s west, though if cloud cover is less than expected these temperatures may be adjusted downward. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 245 AM EST Thursday... Split flow Friday will feature passage of northern/southern stream energy. These features are forecast to remain out of phase with deeper moisture remaining to the east Friday with a surface wave developing offshore, while just ahead of the northern shortwave trough. Guidance showing lots of mid/high clouds from Friday but with little precip. Forecast will reflect spotty upslope snow showers and flurries far northwest sections Friday night, but only 20ish pop for now given lack of moisture with this system. MOS is cooler than normal Friday given progged clouds for much of the day which should hold the mountains in the 30s and low 40s east. Fast west/northwest flow to continue behind this system into the weekend with slowly building heights by Saturday as the 850 mb cold pool starts to lift out. This warm advection wont deepen enough to be realized at the surface until Saturday afternoon with sunshine helping to push highs into the 40s to perhaps around 50 southeast. Some increase in high clouds possible Saturday night but likely thin enough to still allow lows to reach the 20s to around 30. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 324 PM EST Wednesday... Warming trend will continue late in the weekend into early next week as weak southeast ridging keeps a more zonal trajectory in place until Wednesday when a passing trough aloft digs back into the region. However with the warm advection will see moisture return perhaps by late Sunday but moreso Sunday night into early Monday with a residual upper low ejecting northeast across the Gulf states. Appears much of this precip would be light and mostly liquid given westerly flow and well above freezing 850 mb temps. Models then diverge on whether or not this feature helps develop a weak low offshore, aided by yet another shortwave headed out of the southwest states, or things remain more progressive and drier into Tuesday. Given somewhat wetter trends will continue chance pops Sunday afternoon into Monday while leaving in low pops northwest Monday night/Tuesday for showers ahead of the next front and over the south per lingering shortwave energy. Drier and colder air should follow the front for Wednesday as deeper northwest flow kicks in. Otherwise looking at highs rebounding to above normal Sunday-Tuesday and well into the 50s east for early next week. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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As of 1256 PM EST Thursday... General mix of VFR/MVFR ceilings across the TAFs, though MVFR upslope stratus mainly for Lewisburg and Bluefield. Ceiling trends should continue through midnight. Northwest winds initially 6-12 kts gusts to 20 kts abate through early evening to light and variable as boundary layer winds ease. Until then, potential for mountain wave clouds/turbulence in and around the Blue Ridge. Aviation forecast then trends less certain looking into the overnight and midday Friday period. Another mid-level disturbance traverses the region around 07z. Recent 12z GFS and NAM solutions are at odds in terms of precipitation as this upper-level system ripples through our area. The NAM is the wettest, and examination of forecast soundings support potential for light snow/flurries or freezing drizzle between 07-15z along the Blue Ridge and adjacent terminals. Have sided toward the worst-case NAM with -FZDZ indicated in most TAFs except Bluefield and Danville. Freezing drizzle would produce slick runways and greater mixed-ice accumulation on wings. Ceilings trend MVFR most TAFs except at Danville where VFR conditions should prevail. Light and variable winds, tending light east/northeast through the rest of the TAF period. High confidence in aviation elements through midnight. Medium confidence on ceilings and winds after midnight, Medium to low confidence on weather type and visbys after midnight. Extended Discussion... Should see conditions improving toward VFR late Friday afternoon into the evening as aforementioned upper disturbance/weak surface low moves off the Atlantic coast. VFR conditions should prevail until Sunday night. A better shot exists for sub- VFR conditions from a system system forecast to emanate from the mid-Mississippi Valley Monday into Tuesday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...AL/MBS SHORT TERM...JH/PM LONG TERM...JH AVIATION...AL

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