Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 301349 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 949 AM EDT MON MAY 30 2016 .SYNOPSIS...
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Tropical depression Bonnie will stay near the South Carolina coast this afternoon into tonight, slowly working northeast to the North Carolina coast Tuesday. A cold front arriving from the west Friday will finally boot Bonnie out to sea.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 930 AM EDT Monday... Much of the area remains in between the deeper tropical moisture associated with Bonnie to the southeast per latest blended pwats, and a weak upstream shear axis along a faint cold front just west of the ridges. This has resulted in a weak convergence zone along the Blue Ridge per north/ne flow around the tropical low and the boundary approaching from the west. However latest short term guidance indicates only very weak support aloft today, with eastern showers driven via influx of tropical moisture from the south, and more orographic aided convection over the west where should see more heating once the remaining fog fades soon. This along with better forecast instability west would support best coverage across the far western mountains this afternoon, per more clustering of shra/tsra, then heading east toward the Blue Ridge late. Appears less out east where more spotty shra likely given subsidence zone on the back of Bonnie which should factor in per latest HRRR. Thus have cut back on pops central and east until later while boosting to higher chances far west where may need brief periods of likely pops pending later coverage. Again given weak steering between low level northerly flow and sw flow aloft, potential exists for bands to get stuck with some heavy rain potential given decent pwats. Overall highs of 75-82 look on track with perhaps the far east being the coolest pending clouds. Previous discussion as of 330 AM EDT Monday... Tropical depression Bonnie continues to track very slowly if at all between Charleston and Myrtle Beach. Water vapor satellite shows a plume of tropical moisture feeding into the NC coast then northward across the Virginia piedmont. Drier air is situated across the Appalachians with more moisture with a shortwave moving across the Ohio Valley. Early this morning a narrow band of showers had formed near I-77 in NC north along the Blue Ridge of Virginia. The 04z HRRR seemed to be picking up on this fairly well with subsequent 06z run also hitting the southern Blue Ridge into the NC foothills with best threat of showers this morning with isolated to scattered coverage to the east. At the same time fog was becoming dense where it had cleared along and west of the Blue Ridge from Fancy Gap north toward I-81 from Marion to Christiansburg. Think fog will be periodic based on in and out lower clouds and possible showers but enough coverage of lower visibilities to warrant a Special Wx Statement. For today, any fog will be diminishing by 9am. Following the HRRR into late morning and blending with the 00z GFS as it seemed to have a decent handle on synoptic features gives us isolate to scattered showers til lunchtime. Should see some sunshine enough to destablize the airmass. More thunder is expected this afternoon, but not expecting it to be widespread, as it will be dependent on how much sunshine occurs. This afternoon, thinking the better low level convergence stays near the Blue Ridge and the across the Piedmont roughly east of a LYH-DAN line and moreso east of our forecast area. Looking for high chance to even low likely pops along and either side of the Blue Ridge this afternoon and then east of South Boston to Charlotte Court House with low/scattered threat elsewhere. Given the flow from the sfc-7h mb will be mainly light from the NNE should see some heavy rain potential with slow moving storms and precipitable water values of 1.5". At the moment will not highlight this in the HWO as it will be isolated, but would not be surprised that a flood advisory or even a flash flood warning is issued later this afternoon for small scale area. With a little more sunshine or breaks expected went close to MAV guidance on highs with mainly upper 70s to lower 80s across a good deal of the region. Slightly cooler in the lower to mid 70s along the Southern Blue Ridge. Tonight, remnants of Bonnie still situated near the NC/SC coast. Models show deeper moisture well east of us but will still be in a tropical like airmass and think showers will linger all night, though coverage will lessen as will thunderstorm threat. Will go with isolated coverage most of the night and still looks like areas near the Blue Ridge may stay in more of a favorable low level convergence zone to keep isolated showers here through the overnight. Drier air will try to make it at least to the WV/VA border south toward the NC/TN border. This gradient will likely enhance fog potential with fog likely most areas overnight.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY/... As of 210 AM EDT Monday... Tropical Depression Bonnie will continue to linger over the Carolinas through Thursday. While Bonnie is inland, she will continue to weaken, losing her closed circulation aloft. However, she will maintain and generate spiral bands of convection, especially during the afternoon, fading in the evening. These bands will likely move east over the piedmont, possibly making it to the Blue Ridge each afternoon. Even if these bands do not track that far east, afternoon heating and easterly upslope in a tropical air mass should be enough to generate scattered showers and an isolated thunderstorm along and west of the Blue Ridge Tuesday and Wednesday afternoon. By Thursday, a closed low is expected to move over the Great Lakes and its associated cold front will enter the Ohio Valley. This front will give Bonnie a nudge out to sea. This cold front and remaining tropical moisture will bring a good chance for widespread showers Thursday and Thursday night. Temperatures will continue to warm by a degree or two each day until the front moves east of the area Thursday night into Friday. Temperatures will generally warm into the upper 70s to lower 80s. Overnight lows will remain muggy and in the 60s. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... As of 400 PM EDT Sunday... A cold front Friday will result in an increased threat for showers/storms...its passage bringing a less humid airmass to the region for the weekend. Until the frontal passage at the end of the week, temperatures, especially the overnight lows, will favor above normal readings. After the frontal passage, lower dewpoints and clearing skies will support lower nightime lows. Daytime highs are advertised to be close to normal. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... As of 737 AM EDT Monday... Fog was predominant over BCB/LWB and BLF this morning with less in the east due to cloud cover. Expect the fog will be lifting/dissipating by 14z with cigs running to vfr by late morning. As we head through the afternoon looking at mainly broken ceilings of cu/sc and ac. Models favor Roanoke and Blacksburg having better threat of storms in vicinity as well as Lynchburg. Any storms and showers will weaken and lessen after 00z with fog working in again late tonight, especially in the mountains where skies clear out. Dense fog is a good bet at LWB/BLF and BCB, with MVFR to IFR fog out east. EXTENDED DISCUSSION... What remains of Bonnie appears to stay situated over the SC coast with our area staying just close enough to keep a few showers around at night then scattered storms during the afternoon again Tuesday. This looks to possibly play out again Tuesday night into Wednesday. Finally an stronger upper trough will kick what is left of Bonnie out to sea Thursday-Friday. Thursday may be our driest day with frontal showers and storms Thu night into Friday. Overall looking at possible MVFR to IFR at night through Thursday morning, with mainly VFR during the day except in showers/storms. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...JH/WP SHORT TERM...RCS LONG TERM...PM AVIATION...WP

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