Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241648 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1248 PM EDT Mon Jul 24 2017 .SYNOPSIS... A weak cold front across the Ohio Valley will slide southeast toward the region this afternoon before slipping south into the Carolinas late tonight and early Tuesday. High pressure works east across the Great Lakes into New England behind the front Tuesday through Wednesday with our temperatures returning closer to normal. Another cold front approaches from the northwest on Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 945 AM EDT Monday... Much of the region has slipped into drier air aloft this morning between the residual outflow/trough axis in the foothills and the actual upstream cold front still lagging back in the Ohio Valley. This seen via lower PWATS off the morning RNK sounding vs the wetter GSO raob, and the latest water vapor loop showing much drier air aloft to the northwest. Latest short term guidance still remains on the dry side given lack of much forcing until the front to the northwest gets closer. Also expected mixing down of drier air aloft this afternoon should help dewpoints lower from west to east as the low level flow veers more westerly out east. However still cant completely rule out an isolated storm developing southeast pending location of the lee trough, and across the northwest where some weak convergence will develop late along the axis of instability over West Va. This supports adding in some isolated pops far west later on while keeping a mention southeast where expect overall coverage of deeper convection to remain to the south. Otrw appears enough surface- 7h northwest flow to help skies become sunny by afternoon per dry entrainment, with only some low clouds persisting a bit longer northwest slopes where aided by weak upslope. Kept highs a little above guidance east, low/mid 90s, as weak downslope kicks in with heating, while maintaining thickness supported mid/upper 80s west for now. Previous discussion as of 324 AM EDT Monday... Area of showers and storms have weakened east of the Blue Ridge early this morning with residual showers back over Southeast WV into the NC mountains behind sfc trough. Will see less coverage today as deeper moisture shift southeast with front arriving across the central Appalachians. SPC has pretty much cleared the area of severe threat and most models are in agreement on limited coverage, with isolated across the WV mountains with frontal convergence and in the far eastern CWA closer to lee trough and deeper moisture. Expect a little lower humidity today with west winds still providing a very warm day with highs ranging from the 80s west, to lower to mid 90s east. Tonight, axis of upper trough exits east while sfc front slides south into NC. Question remains how far south the front goes along with deep moisture. Appears any convection this afternoon should fade by mid evening. Skies stay clear to partly cloudy with lows in the 60s west, to lower 70s east. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... As of 325 AM EDT Monday... Looking a little drier Tue-Wed with northwest flow aloft and rising heights while sfc high wedges southward into our area from the northeast. Still could see some isolated showers or storms in the southern Blue Ridge and NC foothills/piedmont Tue, then a little more southeast flow may allow for convection Wednesday to fire further north along the Blue Ridge and foothills but confidence is low as latest models are trending drier. Return flow continues a little more Thursday ahead of next front moving into the Ohio Valley, but appears coverage will be isolated to widely scattered. Temperature will be close to normal this period, which is a little cooler than what we have been experiencing. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... As of 1100 AM EDT Sunday... A cold front will make its way across the mid Atlantic on Friday, triggering more organized/widespread shower and thunderstorm activity. Latest run of the weather forecast models indicate that the front will clear our area to the south by Saturday morning, bringing drier air in its wake. Have therefore lowered rain chances for next weekend, though isolated showers/storms cannot be ruled out. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 1245 PM EDT Monday... Overall conditions have returned to VFR across the region with only KBLF holding onto some lower MVFR cigs under upslope flow. Expect those lower cigs to finally scatter out shortly resulting in mainly cumulus VFR cigs beneath some high clouds above into early this evening. Cant totally rule out isolated convection developing mainly west of the KBLF-KLWB corridor after mid afternoon with an isolated storm or two possible around KDAN. However given uncertainty will leave out any mention with best potential over the western sites late this afternoon. Winds will be turning more west/northwest through the rest of the afternoon with speeds mainly 5-15 kts except for a few gusts above 20 kts over the ridges. Weak front drops southeast through the area overnight with any lingering convection over the west fading this evening. Looks like enough of a threat to include a VCSH mention perhaps at KLWB or KBLF early this evening but quite iffy in whether or not any shra/tsra to the west will actually make it to any of the terminals. Otherwise expecting VFR under clearing this evening before possibly seeing some filling in of low clouds/fog across parts of the mountains, and espcly around KBLF given continued weak upslope flow. Also appears with slightly lower dewpoints that temperatures fall enough to help develop dense fog across the valleys. Thus including a IFR/LIFR mention at KLWB late as well as brief MVFR to IFR late at KBCB/KLYH and perhaps KBLF. Any sub-VFR due to low clouds/fog will gradually improve Tuesday morning as drier air mixes out low level moisture under high pressure. Convective chances again appear quite low Tuesday afternoon with any threat mainly south of the taf locations so running with overall VFR under cumulus/cirrus for now. Aviation Extended Discussion... A frontal boundary should stall to the south, with high pressure wedging southward on Wednesday. Overall VFR but with flow turning more east, this could bring some MVFR/IFR ceilings, which should quickly dissipate by Thursday. Any convection also likely to remain isolated and south of the taf sites again later Wednesday. Next best threat for showers and storms arrives with another front Friday with perhaps some of this coverage lingering over southern/western sections into Saturday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/PW/WP NEAR TERM...JH/WP SHORT TERM...WP LONG TERM...NF AVIATION...JH/WP

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