Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230716 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 316 AM EDT Wed Aug 23 2017 .SYNOPSIS... A cold front will move across the Appalachians and central mid Atlantic region today, bringing some showers and thunderstorms to the region, especially east of the Blue Ridge. A large high pressure system will move out of central Canada and build eastward behind the front tonight, bringing significantly temperatures to the region into the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 300 AM EDT Wednesday... Showers/some thunder out ahead of a cold front approaching from the northwest are having little success advancing into the region. Given the lack of upper support believe this will continue to be the case until the actual frontal boundary arrives later this morning and starts working across the area. This timing will allow for diurnal heating to generate some surface based instability and help reinvigorate convection along the front east of the Blue Ridge this afternoon. However, the best low level winds and dynamic support will be moving by to our north which will greatly limit the potential for any thunderstorms to become severe. There may be a window later this afternoon when enough surface based instability can pool just ahead of the front to give storms a boost in the far southeastern portion of the area, but this potential is marginal at best. Will trend convection in the grids from west to east with improving conditions indicated behind the front as winds become northwest. A large high pressure system will move out of central Canada and build eastward behind the front, bringing an end to any lingering showers early tonight. Slackening winds west of the Blue Ridge and a cooler airmass should help generate some late night valley fog. Highs today will generally be in the upper 80s east of the Ridge, while the earlier passage of the front keeps readings in the mid/upper 70s to the west. Lows tonight will be notably cooler with mid 60s east, low/mid 50s west. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... As of 230 PM EDT Tuesday... Best convergence moves past Danville and to the southeast early Wednesday evening. Will stay close to a blend of the GFS and NAM for timing on the clearing. Sharp drop in precipitable water values to less than one inch in the mountains on Wednesday night. Expect precipitation to be gone well before the clouds finally clear. Another short wave Thursday night and Friday morning. This will re- enforce the subsidence, drying and cooler air mass. By Friday morning the upper trof axis will be approaching the East Coast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 1230 PM EDT Tuesday... Friday night and Saturday surface high pressure will be centered over the Great Lakes. Saturday night through Sunday the high will progress down the east side of the Appalachians. Short wave crossing the northern tier states Friday and Saturday will turn south into the Mississippi Valley on Sunday. Nothing close to consensus in the models after Sunday reguarding any interaction between this troughing and the tropical system moving north through the Lower Mississippi Valley. Not expecting any impact in the Mid Atlantic region from neither of these systems before Monday at the earliest. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... As of 245 AM EDT Wednesday... Showers/some thunder and associated MVFR/IFR conditions out ahead of a cold front approaching from the northwest are having little success advancing into the region. Believe this will continue to be the case until the actual frontal boundary arrives later this morning and starts working across the area. This timing will allow for diurnal heating to generate some surface based instability and help reinvigorate convection along the front east of the Blue Ridge this afternoon. Will time convection in the TAFs from west to east with improving conditions to VFR indicated behind the front as winds become northwest. A large high pressure system will move out of central Canada and build eastward behind the front tonight. Model soundings indicate a nice low level surge of northerly winds east of the Blue Ridge early tonight as the high starts to build in. Will indicate this at both KDAN and KLYH by keeping winds up around 10kts as northerly flow at these sites can amplify. Extended Aviation Discussion... Flying conditions will improve Wednesday night and generally VFR conditions are expected into the weekend as high pressure builds over the region. There will also be a diurnal trend for late night fog/stratus especially west of the Blue Ridge with KLWB and KBCB the most likely TAF sites to be affected. && .EQUIPMENT... As of 735 PM EDT Tuesday... KFCX doppler radar is expected to be back in operations as early as midday Wednesday (Aug 23rd), but most likely Wednesday afternoon/early evening. Technicians replaced the bull gear Sunday and reassembled the radar today, and calibration work will continue through the day Wednesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...AMS LONG TERM...AMS AVIATION...MBS/PH EQUIPMENT...RCS

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