Area Forecast Discussion
Issued by NWS Blacksburg, VA

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643 FXUS61 KRNK 221756 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1256 PM EST Wed Nov 22 2017 .SYNOPSIS... A cold front will continue heading southeast of the region this afternoon, all while an area of low pressure heads northeast off the Mid Atlantic coast. High pressure builds back into the area by Thanksgiving Day. Another cold front will cross the area this weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1245 PM EST Wednesday... Sunny skies prevailed, and will continue to prevail, across our Virginia and North Carolina counties. Across southeast West Virginia, cloud cover continues to erode, and any sprinkles or flurries from earlier are becoming much less likely anymore today. Have made some minor adjustments upward to the forecast high temperatures across the area. Otherwise, no notable changes are forecast for the remainder of the afternoon hours. As of 955 AM EST Wednesday... The morning update will reflect primary a pump upward in the current wind speeds and gusts across the area. Values have been trending a little higher than earlier forecast, but the trend toward decreasing speeds this afternoon is still expected. Have also tweaked hourly temperature, dew point, and sky cover based upon the latest observations and expected trends heading into th early afternoon. As of 630 AM EST Wednesday... Showers have moved off to the east of the forecast area, while leaving very light patchy fog in isolated locations to the west edge of the mid deck of clouds still across the far eastern counties. Winds should begin to mix that out any hour now as the cold front moves through. Winds have already started gusting in the New River Valley. Stratus behind front barely starting to sneak into western Greenbrier Co as of 630 AM, but no signs of any precip on radar. Will leave a slight chance for a few hours this morning mainly in that small corner. Made some adjustments to sky cover based on latest satellite images, and reduced coverage of fog slightly before dissipating totally by 8am. Also temps and dew points are running a little milder than previous forecast for early morning to adjust those slightly as well. Prev discussion as of 340 AM EST Wednesday... Upper trough and associated surface cold front to sweep through early this morning, frontal boundary at 08 UTC was nearing Blue Ridge already but with gustier winds still back in West Virginia. This is mainly a dry front with very light upslope precip along far western slopes, mainly very light snow showers behind front through the morning hours only. Low chances for any measurable precip however. Through about 5am scattered showers along western edge of baroclinic leaf from cyclogenesis just off of NC coast will still impact extreme southeastern portion of forecast area but will move east before day break. As western edge of mid cloud deck moves east and some clearing takes place, patchy fog is forming in foothills and this may temporarily spread east where it has rained overnight before winds behind the front begin to pick up and mix it out. Not sure how dense or widespread this will be so left it patchy and really just for a few hours mainly during the pre-dawn period. Otherwise for the day high pressure begins to push in from the west with clearing skies and gusty NW winds, as high as 25 to 30 mph along ridges, which gradually diminish by late afternoon. Far western slopes could see a flurry through the morning, mainly West Virginia, and skies will eventually clear there as well by the afternoon. With cold advection today and clouds lingering along far western slopes during the morning expect temperatures to rise only between 5 and 10 degrees by afternoon. East of the Blue Ridge temps should still climb into upper 50s to near 60 with full sun, although in most locations. Tonight a short wave weak upper ridge moves over with surface high pressure centered over the Appalachians by morning, and with clear skies this will allow for good radiational cooling and chilly night. Went closer to colder MET guidance for lows, with low to mid 20s mountains to upper 20s Piedmont. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... As of 226 AM EST Wednesday... An overall quiet holiday period in store with the area basically under weak high pressure within an upper split flow regime through the end of the week. Surface high pressure will keep the region dry for Thanksgiving, but cool under passing mid/high clouds as another weak northern stream shortwave trough boots across from the northwest. This along with the lingering 850 mb cool pool should interact with only light mixing to result in chilly highs in the 40s, to possibly a few warmer 50s east per weak downsloping and pending the degree of insolation given proximity of the wave off the southeast coast. Trough lifts out Thursday night into Friday with more zonal flow developing allowing surface high pressure to slide offshore. However guidance usually too fast to exit ridging in this setup at night which should result in another rather cold overnight under mainly clear skies as a weak extension of the parent ridge remains overhead. Thus went with lows on the cold end of MOS, mainly 20s, although may rise late along the ridges as warm advection starts to increase. Quick warmup then looks to ensue on Friday in response to increasing southwest flow behind the departing ridge and ahead of the next upstream 500 mb trough. Latest thickness values under sunshine support highs mostly in the 50s with values possibly reaching 60 southwest. Weak leftover subsidence region between the approaching upstream cold front and low pressure off the Carolinas will continue to get squeezed out Friday night despite lack of any phasing aloft. This should allow for some increase in clouds, especially southern and northwest sections but still dry. However continued mixing/warm advection should at least act to keep lows a bit milder with most seeing overall 30s with only the deeper valleys below freezing early on. With a mild start to the day and southwesterly flow increasing ahead of our next frontal passage, Saturday`s temperatures will warm above normal with readings in the 50s west to lower 60s east. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... As of 130 PM EST Tuesday... Fast split upper flow will again show more amplification to start the period with the translation of another deep 5h trough across the region next weekend. This should swing the next rather strong cold front across the area Saturday night and offshore on Sunday. Boundary again lacking moisture given low pressure off the Carolinas so mainly looking at perhaps a band of rain showers west late Saturday and increasing clouds elsewhere. This then to be followed by a few snow showers/flurries northwest mountains overnight into early Sunday as much colder air arrives. Flow should quickly flatten into early next week allowing for dry/sunny weather under moderating temperatures as surface high pressure slides overhead Monday and offshore into Tuesday. Mild high temps ahead of front with some 60s possible Saturday to dive back into the 30s/40s Sunday before slowly recovering to more seasonal levels by day 7. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 1230 PM EST Wednesday... The last of the MVFR/low end VFR strato-cu continues to dissipateover portions of southeast West Virginia. KLWB is the last terminal to report the cloud cover with skies scattering there currently via satellite imagery. As high pressure begins to nose into the region, look for little if any cloud cover the next 24 hours, post-dissipation in the far west. Also, winds will be on the decrease that from sunset this evening through the remainder of the valid TAF period light and variable winds are expected. Until then, gusts of 15 to 25 mph will be common at most terminals until a little after sunset. The only sub-VFR conditions expected may be some brief, light fog around KBCB early Thursday morning. Extended Discussion... High pressure will provide for primarily VFR conditions Thursday afternoon through Friday. Guidance from one model is hinting at precipitation and sub-VFR conditions may impact the area Friday night into Saturday thanks to a coastal low. This is an outlier at this point, and high pressure continue to control our weather pattern is more probable. A cold front will cross the area this weekend. Currently it is looking moisture starved, and may be more of a wind maker for the area. Anticipate gusty winds Saturday into Sunday in the 15 to 25 mph range for most areas, higher gusts at higher elevations. High pressure returns on Monday with weaker winds, and no precipitation forecast. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS/RCS NEAR TERM...DS/SK SHORT TERM...JH/RCS LONG TERM...JH AVIATION...DS is the U.S. government's official web portal to all federal, state and local government web resources and services.