Area Forecast Discussion
Issued by NWS Blacksburg, VA

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006 FXUS61 KRNK 261901 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 301 PM EDT Sat May 26 2018 .SYNOPSIS... High pressure centered offshore will maintain a moist southerly flow of air into the region for the next several days. Subtropical Storm Alberto moving into the Gulf of Mexico this weekend will move ashore and into the lower Mississippi Valley early next week. Tropical moisture will stream north into the region making for very rain efficient showers and thunderstorms. && .NEAR TERM /THROUGH SUNDAY/... As of 245 PM EDT Saturday... Heavy rain producing convection continues to develop north and east toward ongoing better instability and expect this trend to prevail with coverage tapering off to more isolated nature over the west into early this evening. However will need to keep high pops going east/north into early this evening as a mid level wave crosses the mountains and exits overnight. This along with loss of heating should bring an end to most showers this evening given lack of support in the wake of the shortwave and waning instability. Latest short term models do show weak convergence far west overnight again with perhaps a need for low end pops late. Otherwise expect may see some locally dense fog given earlier rainfall but usually see less fog within this tropical type airmass so only including patchy in spots. Lows mostly muggy 60s and may struggle to fall below 70 given moisture around. Shortwave trough works by to the north on Sunday with most support aloft staying to the northwest for most of the day. However seeing another slug of higher PWATs return northeast and expect this combined with more heating than today to help spark added convection in the afternoon. Since appears best convergence to line up over the higher terrain will focus likely pops there on Sunday and leave chance coverage in the east where weak subsidence may reside longer in the wake of the current impulse. Heavy rain again a concern despite slightly stronger steering with more linear nature to showers/storms per deeper unidirectional flow aloft. May need a watch over the west for later Sunday pending later model runs given saturation from heavy rain from today but wont hoist at this point. Otherwise provided more sunshine looks like warmer highs in the low/mid 80s east to 75-80 west. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM EDT Saturday... Two main features in the forecast are the shallow trough sliding by to the north and Alberto. Refer to the latest NHC Advisories on Alberto for details and movement. The center of Alberto is forecasted to move over the eastern Gulf of Mexico Sunday night through Monday, and approach the northern Gulf Coast late Monday or Monday night. Alberto will continue to track northward into Tuesday night. This will keep the weather unsettled over the Appalachians with a warm and very moist airmass for the next several days. Sunday night into Monday may see some subsidence around the periphery of Alberto push in from the south along with slightly lower theta-e air. Scattered showers and thunderstorms are expected Sunday night and Monday with the highest pops across the southern half of the forecast area. Some of the rain may be heavy at times. Steering flow becomes very weak with little to move precipitation along and will have to watch for areas of prolonged persistent rainfall. Richer tropical moisture arrive Tuesday into Tuesday night as Alberto moves up the Mississippi valley and throwing waves of energy into our forecast area. Will continue to highlight the region for potential hydro issues in the HWO and wait for a more specific region to declare itself in time before considering any watches. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 300 PM EDT Saturday By mid to late week, remnants of the tropical system could bring tropical moisture and heavy rains to our region. Flooding potential will depend on the track of the system and how much rainfall is accumulated from the showers and thunderstorms earlier in the week. Alberto is expected to be in southern Tennessee Wednesday morning and lift northward towards the Ohio Valley Thursday morning. Thursday night into Friday, the low will open up and weaken as it moves northeast into the weekend. There is a continued threat for showers and thunderstorms into the end of the week. Urban and small stream flooding risk will be highest early in the week with river flooding possibly by the end of the week depending on actual rainfall totals. High temperatures will generally be around normal, climbing to above normal at the end of the week, with overnight lows remaining fairly mild mainly around 60 degrees to about 70 degrees. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 100 PM EDT Saturday... Widespread showers and storms will continue across the mountains and progress east across the rest of the region through the afternoon before tapering off this evening. This will lead to widespread sub-VFR cigs/vsbys over the west and deteriorating conditions over the east this afternoon. Localized LIFR along with mountain obscuration could also occur within the heavier bands espcly near the Blue Ridge. Expect showers to fade with loss of heating and passing of a mid level wave this evening. This likely to lead to sub-VFR in fog and low clouds given the widespread rainfall from earlier. Therefore including sub-VFR most spots excluding KROA with IFR or worse possible by daybreak on Sunday. .Extended Aviation Discussion... Wet pattern anticipated through the upcoming week with periods of at least diurnally driven sub-VFR conditions associated with deep convection. Moist low level southerly winds will also favor lower layers of cloudiness at night, especially along the spine of the Appalachians with potential for both MVFR Cigs and early morning MVFR visibilities from mist/haze. The tropical system over the Gulf of Mexico may begin to impact the region mid-week. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/PM NEAR TERM...JH SHORT TERM...KK LONG TERM...KK AVIATION...JH/PM

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