Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 271737 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 137 PM EDT Tue Sep 27 2016 .SYNOPSIS... A cold front will move east of the Blue ridge this morning, then stall over the piedmont this afternoon. A wave of low pressure moving along this front will keep the chance for showers across foothills and piedmont counties on Wednesday, before finally exiting Wednesday night. && .NEAR TERM /THROUGH TONIGHT/... As of 1020 AM EDT Tuesday... A cold front had advanced to the east side of the Blue Ridge as of 10AM. Lower dew points, in the mid 50s, had reached the border between West Virginia and Virginia. Have trimmed back the Probability of precipitation west of the Blue Ridge, in locations behind the front. Instabilities will increase some across Southside this afternoon, as a weak short wave tracks along the front across central North Carolina. A closed upper level low will track from the Great Lakes today to the Ohio Valley tonight. As this low sinks south, the front and its showers will get pushed to the east. Temperatures will be close to seasonal averages ranging from the low to mid 70s west to mid to upper 70s east. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 400 AM EDT Tuesday... By early Wednesday, an upper low situated across the corn belt is expected to begin meandering south and east toward the northwest portions of our forecast area. Around the same time, a short wave is expected to ride the residual frontal boundary just to our east, reinvigorating the fetch of deep moisture. Scattered showers with potentially a rumble of thunder should remain east of the Blue Ridge Mountains through Wednesday evening as the low begins to dig further south. An isolated shower will be possible across the western slopes of the Appalachians just after sunset. At this point, solutions begin to differ rather greatly. The latest few model runs continue a moistening trend, with the ECMWF leading the pack. The bulk of the precip tends to stay north and east of the forecast area for now, but have once again introduced higher POPS out east out of respect to the very wet ECMWF which seems to emphasize the short-waves effect rather stoutly. Have re- introduced thunder into the forecast for the same portion of the forecast area Thursday, as impressive low to mid level lapse rates look to combine with very low freezing heights across the area. This should allow for a small hail threat to develop, even in an environment only favorable for shallow-type convection. Heavy rain in the showers/storms that do form will be the main threat. Temperatures during this portion of the forecast will remain at or below normal, limited greatly by cloud cover and rapid cold air advection around the low pressure system. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 130 PM EDT Monday... The slow moving upper low will continue to impact our forecast into Friday, however, the trend will be for the low to start heading north in response to a building upper ridge across the center portion of the nation. Progressively each day through Sunday, the concentration of showers will will trend more toward the northern sections of the forecast area, following the track of the low. While no thunderstorms are forecast, isolated hail will again be possible within the stronger showers given a continuation of a relatively low freezing level through Saturday. Sunday into Monday, a dry forecast is expected along with moderating temperatures as the upper ridge strengthens and its axis shifts eastward. At best some isolated showers may be possible across the Northern Mountains of North Carolina on Monday where Temperatures during this portion of the forecast will trend only slightly milder on average than the early part of the week. While highs may climb a bit higher, lows are expected to trend slightly cooler as the diurnal range increases thanks to decreasing dew point values across the region. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/...
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As of 120 PM EDT Tuesday... A front extended from central Virginia to western North Carolina this afternoon. There will be little movement of the front tonight and Wednesday. Showers and thunderstorms will develop this afternoon east of the front, with the best probability of precipitation at KLYH and KDAN. Medium to high confidence that the showers and thunderstorms will form around 21Z/5PM. Gusty winds are possible with any of the stronger storms but the chance is too low at any individual TAF site to include in the forecast at this time. Models, especially the NAM, showed IFR to LIFR ceilings east of the front overnight. High confidence that KLYH will have LIFR ceilings after midnight. LIFR ceilings are possible at KDAN too but confidence was too low to include in the forecast. Over the mountains with little cloud cover, fog will form in the river valleys. Expect LIFR fog and stratus at KLWB after 2AM. Low confidence about how long it will take the low clouds in the foothills and piedmont of Virginia and North Carolina to lift after sunrise. Extended aviation discussion... A deep upper low will remain over the Ohio and Tennessee Valley through Friday. This will keep variable clouds, MVFR cigs, and periods of -SHRA across the region through much of the period. Saturday is the most likely day to be drier and have VFR conditions.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RCS NEAR TERM...AMS/RCS SHORT TERM...JM LONG TERM...DS AVIATION...AMS/PM is the U.S. government's official web portal to all federal, state and local government web resources and services.