Area Forecast Discussion
Issued by NWS Blacksburg, VA

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182 FXUS61 KRNK 152312 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 612 PM EST Fri Dec 15 2017 .SYNOPSIS... Chilly conditions with blustery northwest winds expected for tonight as high pressure begins to build back into the region. It will usher in a warming trend to temperatures with mostly sunny skies for Saturday into the first part of Sunday. Weather then turns more unsettled with cloudy skies developing Sunday night and rain chances on the increase into early next week. && .NEAR TERM /THROUGH SATURDAY/... As of 603 PM EST Friday... Winds pretty stiff out there in the mountains, so bumped up gusts a bit and put a Special Wx Statement out to cover stronger gusts from Floyd VA to Boone NC. Otherwise will forecast on track with limited moisture in the mountains of WV which could produce a few flurries/very light snow over northwest Greenbrier County this evening. Previous discussion from early afternoon... Still under a considerable amount of overcast low cloud cover this afternoon, stuck between an organizing surface low off the coast of eastern Virginia and an approaching surface trough advancing across southeast West Virginia. Visible satellite imagery and METARs are starting to reveal breaks in the overcast in the foothills and Piedmont of North Carolina. Overall it`s been a rather chilly, raw day with current temperatures only in the 30s this afternoon. Surface trough associated with a zone of 850-700 mb cold advection will continue to advance eastward through the rest of the afternoon/early evening. Lingering cloud cover should begin to thin out even more as westerly winds become a little more enhanced given modest surface pressure rises, with gusts as high as 30 mph along and west of the Blue Ridge. As lower-level flow turns northwesterly this evening, forecast guidance responds by building cloud cover/stratus in the favored northwest upslope areas in southeast West Virginia, far southwest Virginia and the mountains of northwest North Carolina. May see a few flurries underneath the upslope stratus at times, but the best chance at a coating of new snow would be in northwestern Greenbrier County late this evening into the wee hours of the morning. In both instances the moisture layer is shallow. Cold advection should maintain west-northwest gusts at elevation but overall diminishing trend to wind speeds and gusts after midnight. As for low temperatures tonight, I sided closer to the lower end of the guidance spectrum since we`re starting the evening colder, the cold advection aloft (-3 to -8C at 850mb by 12z), and with the expectation that clouds will clear in most areas except for the above-mentioned areas. This results in lows in the upper teens to the mid/upper 20s. Saturday then starts the warming trend and should otherwise be a pretty nice day overall. We finally get into synoptic-scale ridging aloft for the first time in over a week, ridding ourselves from the parade of Clipper systems and the periodic cold air shots they usher in. Surface high anchors itself across the entire forecast area and westerly warm advection boosts 850 mb temperatures to around 0 to +2C. So after a chilly start, temperatures should finish strong with many areas reaching the 40s under lots of sun with a few low 50s possible in the Piedmont/Roanoke areas. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 253 PM EST Friday... High pressure to settle over the region Saturday night as upper heights build across the southeast states ahead of ejecting shortwave energy from a residual Mexico upper low. This should make for decent radiational cooling under light winds but likely with some increase in mid/high clouds late per model cross sections. Also continued warming aloft within a backing wind profile should keep the ridges a bit warmer, while elsewhere slides back into the 20s with a few upper teens valleys. Warm advection regime continues Sunday into Monday under flat ridging and westerly flow aloft. Initial weak shortwave energy will fracture while running around the ridging aloft by Sunday night with added faint impulses attempting to slide through the higher heights into Monday/Monday night. Guidance remains uncertain to the degree that deeper moisture will make it into the area with some solutions basically showing little more than clouds after the initial system late Sunday into Sunday night. Appears best chances will be across the western mountains late in the weekend and then over the south/southwest early next week. Therefore tweaked pops down to very low chances western third late Sunday into early Monday, and mostly southern/southwest sections Monday night but all liquid without any ptype issues at this point. Continued 850 mb warming combined with westerly flow should allow temps to warm to around 50 west Sunday and 50-55 east before zooming well into the 50s to around 60 Monday pending clouds/showers espcly west. Lows also milder under clouds and higher dewpoints with readings in the 30s Sunday night and perhaps staying in the 40s Monday night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 253 PM EST Friday... Overall period to be dominated by flat ridging across the southeast states with a midweek perturbation resulting in brief eastern troffiness that should swing across and to the east on Wednesday. However second in a series of residual shearing southern upper systems to ride up from the southwest just ahead of this northern stream shortwave trof to perhaps produce a round of showers Tuesday. This still remains uncertain in both timing and coverage with some models keeping deeper moisture south on Tuesday closer to the dampening southern wave, while others including the GFS slide a few bands farther north. Thus keeping in some low pops mainly south/west with more clouds espcly southern sections. Cold front crosses Tuesday night followed by a brief shot of cold advection on strong and perhaps near advisory level northwest winds overnight into early Wednesday. High pressure then looks to build in from the west Wednesday night and quickly offshore Thursday. Lack of moisture looks to preclude much post frontal upslope snow showers with dry weather from later Tuesday night through Thursday night. Ridging to work farther east Friday ahead of the next cold front that could bring some chance of showers to mainly western sections pending timing on Day 7. Main aspect will be with the mild temperatures including highs that will be 10-15 degrees above normal espcly Tuesday per warmth aloft and ahead of the front on Friday. Some cooling in between behind the passing cold front but still a bit warmer than average for midweek. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... As of 610 PM EST Friday... MVFR cigs will stick around overnight at BLF/LWB with VFR elsewhere. Anticipate gusty winds at most sites, except for LYH/DAN. Winds will begin to wind down toward dawn. VFR conditions anticipated for Saturday with winds west- southwest 4-12 kts. Forecast confidence high thru the period except medium on cigs this evening. Extended Discussion... VFR conditions continue through Sunday afternoon. A weak frontal system approaching from the west may induce a brief period of VFR/MVFR with light rain showers mainly for western terminals Sunday night. Better opportunity for sub-VFR is Monday as ceilings lower ahead of another disturbance coming out of the Gulf of Mexico. Should start seeing some showers Monday night through Tuesday night in association with this system. VFR then returns for Wednesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL/WP SHORT TERM...JH LONG TERM...JH AVIATION...AL/PM/WP

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