Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 240104 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 904 PM EDT MON MAY 23 2016 .SYNOPSIS... Low pressure off the Mid Atlantic coast will drift northeast and away from the region overnight, followed by high pressure building in from the west into Tuesday. As the high pressure center settles over the Southeast states, west to southwest winds on the backside of the system will bring above normal temperatures to the region by midweek. && .NEAR TERM /THROUGH TUESDAY/... As of 845 PM EDT Monday... Upper low just east of the Delmarva remains very slow to exit with added spokes of energy resulting in widely scattered convection that continues to fade with loss of heating. Expect this trend to prevail over the next few hours with any residual showers dissipating well before midnight as latest analysis shows only faint instability remaining. Once the showers end, main question with the coverage of lingering mid deck on the back of the upper low as most guidance shows slow clearing overnight as weak high pressure starts to edge eastward. Appears best shot at seeing skies completely clear will be over the west where light winds should lead to more widespread fog late espcly where showers have occurred over the last couple of days. Think clouds may linger longer east of the Blue Ridge but even there looks like enough clearing for patchy fog by daybreak. Otherwise pops ending this evening with decreasing clouds overnight. Temps to remain on the cool side for at least one more night with lows 40s to lower 50s overall. Previous discussion as of 320 PM EDT Monday... Low pressure off the Virginia coast this afternoon will lift northeast tonight and be off the New England coast Tuesday. The combination of solar heating and cool air aloft associated with the upper low will result in scattered showers and thunderstorms this afternoon into tonight. SPC mesoscale analysis at 18z showed Surface based CAPES around 500 j/kg especially across northern portions of the forecast area. The most unstable air this afternoon was also located across northeast corner of area as seen in the LIs. The latest KFCX images indicated scattered showers across northern portions of the forecast area moving southward. Some of the strongest storms this afternoon into tonight will have the potential to produce some very small hail considering the relatively low wet bulb zero levels, and possibly some locally gusty winds and heavy downpours. Training of storms could result in local water problems. However, there is not enough lift and shear to create severe thunderstorms. Used a blend of RNK WRF ARW, Hiresw-arw-arw and HRRR to create pops for this afternoon into tonight. The higher resolution models imply that the a best location for stronger storms will be along/near a corridor from the Alleghany Highlands southwest through the New River Valley. Expect to see a rapid dissipation of any lingering convection this evening with loss of daytime heating and as upper low pressure finally moves away from the area. Arrival of surface ridge and clearing skies under weak subsidence may set the stage for the development of some patchy late night fog, most notably in the deeper mountain valleys, and perhaps some of the more sheltered low lying areas of the Piedmont. Low temperatures will range from the mid 40s in the mountains to the lower 50s in the piedmont. The closed upper low pulls away from the region on Tuesday. An isolated shower may be possible across northern portions of the county warning area. Morning low clouds and fog should lift by mid morning allowing sunshine to return. High temperatures Tuesday will vary from the upper 60s in the mountains to the lower 80s in the Piedmont. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 320 PM EDT Monday... Dry weather continues on Tuesday night with patchy fog possible in the mountain valleys. Low temperatures Tuesday night will be mild than tonight with readings from the upper 40s in the mountains to the upper 50s in the Piedmont. Afterward, we will be transitioning to a summerlike pattern with broad ridging aloft and a Bermuda high off the Southeast coast. High temperatures on Wednesday will climb into the lower 70s in the mountains to the mid 80s in the Piedmont. Maximum temperatures on Thursday will moderate to the mid 70s in the mountains to the upper 80s in the Piedmont. Humidity will also be on the rise so conditions will start to feel a bit uncomfortable and may require running the air conditioner or fan. The heat and humidity will also create diurnal instability and give us a chance for mainly afternoon showers and thunderstorms through the middle of the week with the best chances from the Blue Ridge westward. By Thursday night, low temperatures across the region will generally be in the 60s. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 325 PM EDT Monday... Summerlike weather with mid to late June temperatures and scattered diurnal afternoon and evening convection continues into the holiday weekend as an upper ridge builds over the Southeast U.S.. The combination of topography, instability and moisture each day across the Appalachians will generate scattered showers and thunderstorms, with a lesser threat in the Piedmont. Highs Friday through MOnday will range from the upper 70s to lower 80s in the mountains to mid to upper 80s in the piedmont. Lows will generally run from the upper 50s to lower 60s mountains to mid 60s Piedmont. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... As of 640 PM EDT Monday... Additional widely scattered clusters of convection will continue to drift southwest across the area until shortly past sunset when should finally should coverage fade with loss of heating. This will result in only brief MVFR cigs/vsbys with the majority seeing VFR into this evening. Thus will continue to cover with a VCSH mention most spots until a shower or storm looks to directly impact a specific airport when will amend for lower conditions. Most of the threat for storms will end before midnight given loss of daytime heating and the exiting upper low/cold pool offshore. Dense valley fog is possible overnight under slow clearing. In the west, and a bit more removed from upper low, partial clearing over a moist ground combining with light winds support the development of patchy fog in the SW VA and SE WV mountain valleys. This supports including a period of IFR/LIFR at KLWB/KBCB before daybreak and at locations such as KLYH that saw earlier rainfall. Patchy fog also possible around KROA but wont include for now. Also weak upslope flow may result in stratus/fog at KBLF with sub- VFR possible there per latest guidance but lower confidence at this point. Overall expecting improving aviation weather after the upper low lifts out by Tuesday and high pressure builds in. Light and variable winds tonight will become west around 10 mph Tuesday afternoon under scattered to broken VFR cloud canopy. Medium confidence in ceilings, visibilities and winds during the taf period. Extended discussion... We will be going to a more summer like pattern mid to late week with high pressure offshore providing south to southwest flow. Thus, mainly VFR weather expected. However, the potential exists for late night/early morning fog at times around KLWB/KBCB and in some of the deeper mountain valleys. Also some convection could pop up each afternoon in the mountains Thursday into Saturday, making for localized afternoon/evening MVFR restrictions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/KK NEAR TERM...JH/KK SHORT TERM...KK LONG TERM...KK/WP AVIATION...JH/KK/WERT

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