Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 191649 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1249 PM EDT Tue Jul 19 2016 .SYNOPSIS... A weak cold front will drift south across the region this afternoon before passing to the south overnight. Additional showers and thunderstorms are expected along the front into early this evening. Weak high pressure follows the front with drier weather for mid and late week. && .NEAR TERM /THROUGH TONIGHT/... As of 945 AM EDT Tuesday... Main concern again with convective potential this afternoon as a weak front to the north pushes south into the area during peak heating and shortwave energy glides through from the northwest. Morning raobs do show deeper moisture now across much of the region with much drier air aloft supportive of better DCAPE once strong heating gets going. However forecast convergence remains weak until things coincide over far southeastern sections late with meso models again having a tough time in resolving where better storm clusters/bands will occur. Again appears per early clouds south will see differential heating aided convection to initialize along and just east of the Blue Ridge with coverage spilling east ahead of the front folding over from the north. This should focus more organized coverage along/south of Highway 460 in the east closer to the front, and bounded by the Blue Ridge in the west where pwats will start to lower later in the day. Forecast severe parameters also point to stronger convection over the south/east where moisture will be deeper along theta- ridging and perhaps far enough removed from ongoing downslope later to allow more organization to occur. Thus upped pops slightly where upgraded to slight risk for this afternoon given downburst potential despite weak winds aloft. Looks like most widespread coverage will quickly shift to the south by early this evening with drying filtering in from the north. Otherwise another rather hot day under intervals of clouds/sun with thickness again showing at least low 90s out east ahead of the boundary, and well into the 80s west pending early clouds and later convection. Previous discussion as of 327 AM EDT Tuesday... An upper level trough will move east across the Northeast today as a cold front advances southward into our region. Scattered showers and thunderstorms will form ahead and along the cold front especially this afternoon into this evening. SPC has most of county warning area in the marginal risk for Severe thunderstorms in the Day One Convective Outlook. The main threats will be gusty winds, hail and heavy downpours. Outside of the isolated convection this morning, scattered showers and thunderstorms will develop along the Blue Ridge Mountains by early afternoon, then translating into the east as the axis of higher pwats leans over along the front. High temperatures this afternoon will range from the mid 70s in the northwest mountains to the lower 90s in the piedmont. As a wave of low pressure pushes out into the Atlantic ocean this evening into tonight, the cold front will move south of our area reaching South Carolina by Wednesday morning. The convection will taper off as high pressure build south from Pennsylvania in the wake of the front. Low temperatures will drop into the upper 50s in the mountains to the upper 60s in the Piedmont. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 245 AM EDT Tuesday... During this part of the forecast, an upper ridge builds across the central portion of the country while expanding its influence eastward toward our region. We are expecting northwest flow aloft on the east side of this ridge across our region all while height build. Anticipate a trend towards higher temperatures each day with numbers on Friday some five degrees above normal for this time of the year. Precipitation chances will be minimal Wednesday and Thursday. Guidance varies on the degree to which isolated to scattered convection will develop. Any activity is expected to be confined primarily to orographical influence along and near the crest of the Blue Ridge. Wednesday coverage is expected to be confined to mainly the northern mountains of North Carolina with better expanse north through Virginia on Thursday. Friday an upper low/trough is progged to round the top of the upper ridge and travel into New England. Guidance offers a solution that brings its associated trough axis into and through our region on Friday and Friday night. Isolated to scattered showers and storms are forecast for areas along and west of the Blue Ridge, including southeast West Virginia, where coverage Wednesday and Thursday will be lacking. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 330 PM EDT Monday... As the upper trof over the Pacific northwest moves east late in the week it will flatten the ridge across the midsection of the country, leaving us in weak quasi zonal flow on the hot side of the jet stream. This will allow the heat to build throughout the weekend with air temperatures well into the 90s and heat index values over 100 east of the Ridge, a bit cooler to the west. Our chances for showers and thunderstorms will also be increasing through the weekend, especially as we head into Monday with a cold front approaching from the northwest. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As of 1230 PM EDT Tuesday... Weak cool front continues to sag toward the region from the north preceded by quite a bit of mid cloudiness along/east of the Blue Ridge in response to lift within weak difluence aloft. However expect this canopy to push southeast shortly while giving way to a developing scattered to broken VFR cumulus field between 4-6K feet this afternoon. In addition, heating combined with this low level moisture ahead of the boundary should result in development of at least scattered showers and storms during the afternoon. This should make for periods of MVFR/IFR espcly across eastern/southern sections with the KLYH-KDAN corridor, and points south/east the most likely area to have a tsra impact an airport directly into early this evening. Therefore inserting a tempo group for localized lower conditions in convection with some gusty winds also possible. More isolated nature coverage expected west of the Blue Ridge where will just include a vicinity mention of a shra/tsra this afternoon. Most organized convection if any should move south by sunset with drier air aloft spilling in from the north overnight. However moist ground conditions along with possible lingering higher dewpoints across the south/east likely to give rise to more fog/stratus east and patchy valley fog west late. This supports a period of MVFR/IFR in spots late with uncertainty at KBLF about seeing any low clouds/fog so including less there than models suggest. Drier air should win out on Wednesday with widespread VFR once low clouds and fog burn off during the morning. An isolated mountain shower or storm may still be possible with heating but not enough to include any mention Wednesday afternoon. Extended aviation discussion... Strong high pressure aloft will bridge east across the region Thursday into next weekend. Cant totally rule out an isolated storm each afternoon/evening through the period but appears overall VFR outside of the typical late night valley fog in spots.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/KK NEAR TERM...JH/KK SHORT TERM...DS LONG TERM...MBS AVIATION...JH/KK/RAB

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