Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 151143 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 743 AM EDT Fri Sep 15 2017 .SYNOPSIS... High pressure will build over the Mid Atlantic region tonight and cover much of the eastern United States through Sunday. A cold front will approach the region from the northwest on Monday and Tuesday. A gradually warming trend to slightly above normal temperatures is expected through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 310 AM EDT Friday... High pressure has nudged in from the west and allowed for the development of patchy dense fog across much of the region. Expect the fog to persist before gradually dissipating after sunrise. Expect a little sun after the fog burns off, but short wave energy undercutting a weak upper level ridge will combine with orographic affects to bring just a slight chance for a shower to the southern Blue Ridge into the mountains of NC and also for the Alleghany Highlands. Expect coverage to be quite sparse. Any showers will fade away early this evening, leaving us with conditions favoring a repeat performance of overnight fog. Highs today will be in the lower 80s east of the Blue Ridge with low/mid 70s to the west. Lows tonight will be in the upper 50s/lower 60s est to low/mid 50s west. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... As of 330 AM EDT Friday... Weather pattern in place through the period much like a typical late August pattern with a broad ridge of high pressure extending from the Southern Plains northeast into southeast Canada. Hurricane Jose is forecast to be off the NC coast several hundred miles and there is also evidence of a weak easterly wave along the central Gulf Coastal region. Moisture content will be relatively high over the area for mid-September with dewpoints in the 60s most areas. However, there will be little to no triggering mechanism in place through the period. Isolated to scattered diurnal convection appears possible, mainly driven by differential heating, thus most numerous across the mountains. The proximity of Jose may support a weak backdoor front sagging southward through the northern parts of the CWA Monday, which could support slightly better coverage of precipitation across northern parts of the CWA during the afternoon. For the most part any precipitation would just be showers. Enough instability is present according to several models for isolated thunderstorms near the I-64 corridor Sunday. Have kept all precipitation chances through the period less than 30% as confidence is low in any precipitation given the weak, diffuse pattern and lack of meaningful dynamics. Temperatures will be above normal through the period with 500mb heights in the 585+ range and 850mb temperatures in the +12C to +16C range. Northeast flow much of the time, especially once Jose starts moving north off the eastern seaboard, will temper max temps, but most locations will still average 5-8 degrees above normal for both min and max temperatures. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 350 AM EDT Friday... A broad ridge of high pressure will remain in place through the period. Hurricane Jose is forecast to be tracking north through the Atlantic off the east coast several hundred miles per official NHC track. However, it is important to note that some models, both the GFS and ECMWF for example, do impact portions of the northeast U.S. coast with Jose by the end of next week, and the ECMWF even tries to loop the system back through northern VA, similar to what the GFS did a couple of runs back. With high pressure aloft across the eastern seaboard and weak winds aloft, steering currents will be weak, so we will need to keep a close eye on Jose. But for now, at least, it does not appear that it will impact our CWA and so far most model tracks are too far east and north for it to impact us much under any possible track. Jose may help to increase subsidence across our region, but by- in-large, the pattern will remain much the same as in the short term, namely partly cloudy, warm, and seasonably humid with isolated to scattered diurnally driven showers. A dissipating frontal system will drift into the Ohio Valley late in the period, but likely wash out under the ridge of high pressure and subsidence on the back side of Jose at that point. This may help to increase shower chances some across the western mountains on Wednesday. Above normal temperatures can be expected with maximum temperatures in the 70s west to the 80s east with lows in the 50s west to the 60s east. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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As of 745 AM EDT Friday... Patchy IFR-LIFR conditions in BR/FG will improve to MVFR or better by 15Z. A layer of moisture remains trapped around 050, so expect BKN-OVC mostly low end VFR or high end MVFR cigs through the day. VFR cigs are expected for most sites east of the Blue Ridge after 14Z, with MVFR to low end VFR conditions to the west. Fog development is expected again after 06Z tonight as low cloud diminish some. Short wave energy undercutting a weak upper level ridge anchored across the region will combine with orographic affects to bring just a slight chance for a shower to the southern Blue Ridge into the mountains of NC and also for the Alleghany Highlands. With sparse coverage expected will keep all TAFs VFR/dry through the end of the valid period. Winds will be light and variable through the period with surface high pressure across the area. Extended Aviation Discussion... Some MVFR showers are possible on Saturday with another short wave. The chance of precipitation remains low for Sunday and Monday. Expect diurnal isolated showers and thunderstorms across the terrain. Aside from valley fog in the early morning, conditions overall should be VFR. Tuesday may feature some isolated MVFR showers in the mountains. Hurricane Jose is expected to remain well east to well northeast of the CWA at this time.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...MBS SHORT TERM...RAB LONG TERM...DS/RAB AVIATION...MBS/RAB is the U.S. government's official web portal to all federal, state and local government web resources and services.