Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 270536 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 136 AM EDT Fri Apr 27 2018 .SYNOPSIS... An upper level trough will cross over the Mid Atlantic and provide rain showers for tonight. High pressure should arrive to provide drier conditions for the upcoming weekend and into early next week. && .NEAR TERM /THROUGH TODAY/... As of 930 PM EDT Thursday... Current set of grids still look good. At time of this update,showers have overspread much of the Blacksburg forecast area. Have adjusted hourly temperatures and dew points to reflect latest trends as onset of rain and wet bulbing drive temperatures downward - only to level off as the evening progresses as boundary layer saturates. Minimum overnight temperatures still look reasonable, so left unchanged. Otherwise, just enough weak instability may try to sneak in across the extreme southeastern portion of the forecast area in advance of the approaching short wave to support a brief rumble of thunder, but not sufficient enough in either time or space to warrant infusion into forecast at the present time. All indications are that best instability will remain locked to areas further to the south and east through the night. As of 315 PM EDT Thursday... A potent upper level shortwave trough will approach northwestern North Carolina this evening and cross overhead tonight. Showers will spread northeastward along the reflected surface low pressure area from this trough. Details are still a little sketchy on the exact QPF and timing of the rainfall. The GFS is a little quicker and wetter, while the ECMWF is slower and drier. The consensus of the high resolution guidance favors the GFS solution more but appears to be driven too much by convection, and instability is barely there to support it according to model soundings. We will need to monitor rainfall rates for any possible minor flooding or any aggravation of the ongoing river flooding situation in Southside Virginia. Confidence was not high enough to warrant a Flood Watch at this time, so the flood threat is mentioned in the HWO. Overall, about a half to one inch of rain is expected tonight, but there should be locally higher amounts if any banding or training takes place. The showers should gradually fade during the early morning hours of Friday, but the lingering moisture should provide low clouds and patchy fog toward sunrise. As the area of low pressure departs from the Mid Atlantic, winds should shift toward the northwest and steadily increase during the day. This mixing should scour out any fog and low clouds across the Piedmont by midday. However, lingering moisture could keep low clouds a little longer along and west of the Blue Ridge. In addition, the upslope flow should provide showers along the higher elevations west of a line from Lewisburg to Boone through most of the daytime hours. It will be slightly cooler on Friday compared to today, but temperatures should remain near seasonal values. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 230 PM EDT Thursday... A disturbance over the Great Lakes Friday night will slowly track east to New England by Saturday night. An inverted trough emerges ahead of this system and along the western slopes of the Appalachian Mountains Friday evening. This trough should only result in some low clouds passing over the mountains into Saturday morning. Also ahead of this system, winds back across the Tennessee-Ohio Valley. With weak forcing and limited moisture as Gulf is blocked, light showers are possible along western slopes and isolated showers across the rest of the mountains Saturday afternoon into the early evening. Showers will end quickly as the front slides across the area Saturday evening. Even though dry air entrains into the region, some light upslope rain/drizzle is likely along western Greenbrier as short waves rounding the low to the north pass over the area. Upslope precipitation will come to an end Sunday morning, then dry high pressure builds over the region. Being ahead of the front Friday night and Saturday, temperatures will remain mild. Overnight Friday, 40s will be common to near 50F across the piedmont. For Saturday, near seasonal temperatures expected with low to mid 60s west and low to mid 70s east. Following the front Saturday evening, temperatures drop into the 30s across the mountains and low to mid 40s east. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 230 PM EDT Thursday... Dry high pressure will be overhead Monday. With dry air and abundant sunshine, temperatures will warm to near normal levels. The center of the high will slide off the southeast coast on Tuesday. The addition of southerly flow will push afternoon temperatures well above normal Tuesday into Thursday. Expected temperatures through the middle of the week to run 10F warmer than normal. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 136 AM EDT Friday... Poor flying conditions this morning in low clouds, fog and convection will improve this afternoon into tonight. The upper level and associated widespread area of showers will continue to slowly move east across the region today into tonight. VFR/MVFR conditions will low to IFR/LIFR in low clouds, fog and showers this morning. Gradual improvement back to VFR conditions expected by late this morning with passage of trof and with onset of daytime heating/mixing. Winds will remain too light throughout the valid forecast period to present any flight-related concerns, but could pick up a little as the afternoon progresses. Medium confidence in ceilings, visibilities and winds during the taf period. Extended Aviation Discussion... High pressure should build overhead tonight into Saturday to bring VFR conditions for all sites by Saturday afternoon. Good flying weather will persist through the remainder of this weekend and into early next week.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW/WERT NEAR TERM...PW SHORT TERM...RCS LONG TERM...RCS AVIATION...KK/WERT

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