Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281758 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 158 PM EDT Wed Sep 28 2016 .SYNOPSIS... A weak frontal boundary will continue to meander east of the Blue Ridge through late week. A strong upper level area of low pressure will also drop south into the Tennessee Valley Thursday into Friday before lifting back north by Saturday. The combination of these features will lead to rounds of showers and storms through the rest of the week before drier weather arrives this weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1055 AM EDT Wednesday... Strong upper low to the north should continue to dig south into the Ohio Valley later today causing sharpening of the backing southwest flow aloft across the region. This should act to spill moisture back westward by afternoon ahead of perhaps another weak surface wave sliding up the residual surface front to the south. Already seeing a slight push in the deeper moisture on the total precipitable water graphics. Guidance suggests this will allow for a highly diffluent scenario to take shape aloft this afternoon with good shear including decent low/mid level flow of 30-40 kts espcly eastern third. In addition, arrival of cooling aloft should help overcome potential lack of good instability given low clouds lingering out east. Most solutions including the latest Cams tend to focus best coverage along/east of Highway 29 per high PWATS, then gradually fill in back into the Blue Ridge. Will also have a leading band of showers ahead of the upper low approaching the west late, but still appears will be a break between the two over the far west/southwest sections where drier air will remain nosed in. Therefore running with a gradient of likely/categorical pops east to likelys eastern slopes of the Blue Ridge to low/slight pops far west. Appears the east also has the best shot at isolated pulse/training storms given chilly temps aloft while QPF of 1-2 inches possible in spots but not widespread enough at this point for a watch today. Have increased maximum temperatures in some locations that are already getting sunshine. Lower clouds that extended from the foothills in eastern Wilkes County to the Henry County will eventually erode. Even those spots that get heating later today will warm into the mid 70s to lower 80s. Complex interaction of the residual front and bands of showers around the upper low will persist into the overnight with added potential for stronger storms north/east at least this evening per 00z ECMWF. Could eventually work into a dry slot aloft espcly western half later tonight as suggested by the latest HiRes-ARW but that remains iffy as features likely slower to exit than progged. Otherwise given expected good lift and continued deep moisture off models eastern half, will continue likely pops through around midnight and then slowly taper to mostly chance most sections late. With lots of clouds lingering and the front stuck across the region, expect lows to be warmer than earlier expected with mostly 50s mountains, while the east likely remains in the low/mid 60s overall. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 400 AM EDT Wednesday... A closed upper low is expected to stall across the Ohio River Basin during the day Thursday, while a series of disturbances, including an encroaching cold front from the west, will begin to interact with the deep atlantic moisture and pulse along the mid Atlantic Seaboard through the period. As a result, ongoing showers and thunderstorms are expected to continue across the eastern Piedmont counties of Virginia and North Carolina during the morning hours Thursday. Showers and storms will likely increase in coverage and intensity by mid afternoon, continuing the spread with the flow of moisture around the low and along the boundary. Some of the thunderstorms could be strong with hail, gusty winds, and heavy downpours. Impressive low level lapse rates coupled with unseasonably low freezing levels could aid in ultimate hail potential. Thunderstorm activity is expected to diminish in large part due to the loss of daytime heating and the subsequent instability axis overnight Thursday. Continuing light to moderate shower coverage will maintain through much of the overnight hours, with uncertainty remaining in just how much precipitation will fall. The NAM/ECMWF models continue to indicate very wet conditions while the GFS continues to keep the heaviest precipitation a bit north of the forecast area. Have tended to split the difference between the two model camps when it comes to QPF/POPs. Temperatures during the period continue to trend cooler for highs and warmer for lows. Expect daytime highs struggling to breach 70 degrees THU/FRI thanks to cloudcover. Low temps will remain cool, but trending a bit warmer than guidance due to abundant cloudcover and continued Warm Air Advection East of the Blue Ridge prior to the low pulling back North. Sub 50s to the west will be remain possible Overnight Thursday and especially overnight Friday. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM EDT Tuesday... Closed upper low continues to lift northward through the Ohio Valley into the weekend. The low center continues to push into the Great Lakes by Sunday evening and New England by Monday. The low will move into the Atlantic ocean on Tuesday. Meanwhile, the potential for tropical low development across the Caribbean may lead to a threat for the southeast early next week. This is being monitored by the NHC and WPC. Temperatures will start cooler for Saturday with continued improvement as precip/cloudcover comes to an end, then temperatures begin to moderate Sunday into Tuesday. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 155 PM EDT Wednesday... Scattered showers and thunderstorms were beginning to develop from KTNB to KBCB and northeast of KLYH. MVFR clouds from KFVX to KUKF were lifting and will improve to VFR by 20Z/4PM. Showers and thunderstorms will become widespread east of a KHSP to KDAN line after midnight. As an upper low moves south of the Great Lakes tonight and Thursday...a cold front will approach the Appalachians from the west. This front will merge with a stationary low pressure system over Virginia on Thursday. Medium to high confidence of MVFR to IFR ceilings and fog developing overnight. Little improvement is expected on Thursday. Extended aviation discussion... A deep upper low will remain over the Ohio and Tennessee Valleys through Friday night. This will keep variable clouds, MVFR cigs, and periods of -SHRA across the region through much of the period. Should finally see VFR return during Saturday and continue Sunday as the upper low lifts north and weak high pressure builds in. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/JH NEAR TERM...AMS/JH SHORT TERM...JM LONG TERM...JM/KK AVIATION...AMS/JH

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