Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131408 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1008 AM EDT Wed Sep 13 2017 .SYNOPSIS... The remnants of Irma will track north across the Ohio Valley today and into Pennsylvania Thursday. High pressure will move east today into the Atlantic Ocean. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1005 AM EDT Wednesday... Southern edge of clouds had advanced up through Roanoke and will continue to progress north. Fog has dissipated. Winds will pick up from the south as mixing deepens this afternoon. Irma remnant low will continue to weaken as it moves northeast through the Ohio Valley tonight. There appears to be enough lift and moisture to support scattered showers with the best chance in the west. Patchy fog is possible late tonight into Thursday morning with light winds and low level moisture. Low temperatures tonight will vary from the mid 50s in the west to the lower 60s in the east.
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 230 AM EDT Tuesday... The remnants of Hurricane Irma will become absorbed within an upper trough located over the Ohio Valley and be lifted northeast with time into PA Thu, then to off the New England coast by the weekend. Meanwhile, high pressure aloft will begin to build across the eastern U.S. with troughing in the western U.S., somewhat of a flip-flop from the pattern over the past several weeks. A relatively quiet period for the forecast area with generally near to above normal temperatures. On Thursday, a fairly good chance of showers and possibly an isolated thunderstorm as the remnants of Irma lift just to the northwest of the CWA as the air mass will be marginally unstable and moisture levels will be high with dewpoints well into the 60s. By Friday, the upper trough and remnants of Irma will be well northeast of the area with upper ridging building in to the region from the west and east. A fairly typical summertime pattern will be in place for a change with precipitation confined mainly to diurnal activity across the mountains driven by differential heating. Saturday appears to be bring a slightly better chance of showers and possibly a thunderstorm to the CWA, but there are definite uncertainties regarding a tropical/subtropical low lifting north from the southeast states. The GFS has deep moisture tracking as far north as the central Appalachians, while the ECMWF is keeping this moisture closer to the GA/TN/NC border, although this is a slight drift north from what was indicated in the previous run. Will increase pops slightly across the mountains and indicate a slight chance for most parts of the CWA. Overall the upper-level pattern will feature a broad upper high across the central and eastern U.S. with a broad area of diffuse low pressure and tropical moisture anchored across the south central and southeastern Gulf coast states. The pattern becomes much more like summer during this period than we have seen in the past 2-3 weeks. This will allow temperatures to creep to above normal levels, especially min temperatures with lows rising into the 60s, 50s mountains, and highs in the 70s west to the 80s east. These temperatures are 5-10 degrees above normal for the first half of September. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 245 AM EDT Wednesday... A strong ridge of high pressure aloft will be anchored just west of the forecast area during the period, with a broad area of low pressure aligned along to just east of the east coast. Of interest in the tropics will be Hurricane Jose, that is progged to continue to meander around off the east coast of the U.S. The official forecast, as well as the Canadian, ECMWF, and earlier runs of the GFS keep Jose off the coast with any U.S. landfall appearing unlikely, except perhaps across the northeast U.S. However, the 00Z run of the GFS wants to loop Jose back into VA before taking it out to sea. As far as can be seen at this point, Jose will not have an impact on our forecast, but will remain a feature to watch closely in the days ahead. Otherwise, look for partly sunny, warm, and fairly humid conditions during the period with temperatures averaging 5-10 degrees above normal. There will be a slight chance to potentially low chance for showers and a few thunderstorms during the period as tropical low pressure lingers over the southeast states. Confidence in this scenario is low and becomes lower as Jose draws closer to the coast and induces subsidence across the eastern seaboard. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... As of 745 AM EDT Wednesday... Area of LIFR clouds receding north through Virginia this morning. Ensemble guidance showed southern edge of clouds north of Lynchburg and Lexington by 14Z. IFR to LIFR clouds were also along the southern Blue Ridge from KMTV into northwest North Carolina. Patchy fog was over southwest Virginia and northern North Carolina with MVFR to LIFR visibility. As mixing begins this morning and winds increase from the south conditions will improve. Medium confidence that ceilings and visibilities will lift to VFR by 15Z/11AM. The chance of showers increases late this afternoon into tonight as upper low/remnants of Irma start moving in from the west. Expected coverage of showers to be scattered over the mountains. Pockets of fog may also develop tonight. Extended Aviation Discussion... Scattered showers may continue into Friday. Some MVFR showers are possible on Saturday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...AMS/KK SHORT TERM...RAB LONG TERM...DS/RAB AVIATION...AMS/KK

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