Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251648 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1248 PM EDT Tue Jul 25 2017 .SYNOPSIS... A weak stationary front across northern North Carolina will remain in place this afternoon before sliding to the south overnight into Wednesday. High pressure building north of the region should keep overall dry weather in place through midweek. Another cold front approaches from the northwest Thursday into Friday exiting to our southeast by Saturday morning. && .NEAR TERM /THROUGH TONIGHT/... As of 955 AM EDT Tuesday... Surface front has dipped into far southern sections this morning with much drier air aloft working in from the northwest as seen in the latest water vapor loop. This along with continued weak dry advection under light low level northerly flow should keep things mainly dry through the afternoon under mostly sunny skies once any lingering western low clouds fade. Only exception perhaps will be near the front over northwest NC where guidance shows a sharp instability gradient and enough residual low level moisture under a weak passing wave to possibly spark a shower to two with heating. However many short term solutions remain basically dry with most convection just south of the CWA, so only keeping in isolated pops where ongoing for now. Otherwise expect subsidence in conjunction with very dry air aloft per the morning RNK raob to make for a little more comfortable afternoon with heat and humidity down a bit behind the front. This along with morning thickness supports highs mostly 80s mountains, to upper 80s to lower 90s from the Blue Ridge east. Previous discussion as of 320 AM EDT Tuesday... Have a little fog/low clouds banked up across southern WV into the Mountain Empire where an inverted sfc trough lingers. Expect these clouds/fog to erode after 8-10am. High pressure will bring drier airmass/dewpoints to much of the region today, with models showing deeper moisture shunted south of our forecast area. Still enough of a gradient plus some return flow and inverted trough along the southern Appalachians to maybe generate isolated storms across the NC High Country possibly moving into the NC foothills this afternoon. Otherwise enough subsidence for overall mostly sunny skies with highs low/mid 80s mountains to upper 80s to around 90 east of the Blue Ridge. Any convection weakens and shifts out of our ares this evening with skies staying generally clear. High pressure will be over New England late Tuesday night so some return flow may still generate lower stratus/fog along the southern Appalachians, but overall confidence is low and another day of drying should limit this. Lows running close to normal with upper 50s to lower 60s mountains, to mid to upper 60s east of the Blue Ridge, but including Roanoke- Lexington. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 330 AM EDT Tuesday... High pressure over New York Wednesday morning will slide east in the Atlantic ocean Wednesday night into Thursday. Some weak orographic lift may combine with solar heating to create isolated to scattered diurnal showers and thunderstorms mainly along the southern Blue Ridge. High temperatures Wednesday will range from the the mid 70s in the mountains to the mid 80s in the piedmont. Any convection will taper off quickly Wednesday evening with loss of solar heating. Under partly cloudy skies, low temperatures Wednesday night will vary from around 60 degrees in the west to near 70 degrees in the east. Low pressure with a trailing cold front will move east across the Ohio Valley Thursday into Thursday night. The timing looks a little faster than yesterday. Thus, increased pops on Thursday and bring likely into the western mountains Thursday night. High temperatures on Thursday will climb to around 80 degrees in the mountains to about 90 degrees in the Piedmont. SPC has placed most of the forecast area in a slight risk for severe weather Thursday afternoon into Thursday evening. The main threat is for fast moving bands with damaging winds. Also, any thunderstorm could produce locally heavy rains. With clouds and rain, low temperatures Thursday night will generally be in the mid 60s in the mountains to the lower 70s in the Piedmont. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 1245 PM EDT Monday... Upper pattern amplifies starting on Friday with the upper ridge over the western United States slightly retrograding and a trof digging in the east. An upper low may eventually close off somewhere over the Tennessee Valley or Mid Atlantic region by Sunday or Monday. This closed low solution was not supported by a majority of the extended guidance. Probability of showers and thunderstorms will increase on Friday and Saturday with some vorticity advection and lowering heights. Air mass ahead of the trough stays in the +16 to +20 range for temperatures at 850MB and will be a little cooler on Sunday and Monday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 1245 PM EDT Tuesday... Good flying conditions to continue this afternoon with VFR expected under some passing scattered-broken cumulus mainly across southern/eastern sections. Any convection later this afternoon will be isolated and stay confined to locations south and west of the terminals into North Carolina. West to northwest winds at 5 to 12 kts should prevail with ocnl gusts to around 20 kts along the ridges. Low level flow turns more easterly around high pressure to the north overnight providing some potential for moisture to bank up along the mountains late. This could result in a period of sub- VFR cigs if patchy low canopy forms per latest Nam. Otrw leaving out most low cigs given dry air for now and trending VFR overnight outside of any fog/stratus. However the fog threat late tonight again looks minimal, so only including a brief mention at KBCB/KLWB toward daybreak. If enough of an east wind develops, fog forming over the Greenbrier River could push into KLWB resulting in a period of MVFR or worse late. Should stay VFR under high pressure Wednesday though some scattered- broken VFR cigs possible in the mountains. Looks like most isolated convection will again remain mainly south/west of the taf sites later in the afternoon. Therefore leaving out any mention at this point, with any shra/tsra also likely not developing until after the valid taf period. Aviation Extended Discussion... Should start to see a front approaching with better threat of showers/thunderstorms Thursday into Friday. Outside of storms expect VFR conditions, with possible late night fog by Friday morning. Saturday looks drier with northwest flow, but could see lingering low end VFR/high end MVFR ceilings in SE WV along with a few added shra/tsra mainly southern sections Saturday afternoon. Expect widespread VFR to return Sunday under high pressure following the front. && .EQUIPMENT... As of 345 AM EDT Tuesday... The temperature sensor on the observing equipment at Lynchburg has failed, therefore no temperature data will be available until technicians can replace the defective part later this week. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...KK LONG TERM...AMS AVIATION...JH/RAB/WP EQUIPMENT...WP

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