Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 221420 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 1020 AM EDT Mon May 22 2017 .SYNOPSIS... A frontal boundary over the Carolinas will lift north as a warm front this morning as an area of low pressure tracks across the Mid Atlantic. This front will drop back into the Carolinas tonight, before lifting back north into the region once again Tuesday and Tuesday night as a potent low pressure system tracks along the boundary. Unsettled conditions continue Wednesday and Thursday as an upper level trough approaches from the west. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Current surface observations, radar imagery, and satellite imagery depict a compact low tracking newd from N-central NC into S-central VA. Areas of showers are primarily ahead of the low extending from S-central VA to the Nrn Delmarva. Periods of moderate to briefly heavy rain are possible from the Piedmont through the MD Ern Shore late this morning through midday due to the combination of decent forcing and pw values of +1-2 st dev. QPF of 0.5-0.75" is possible through this aftn. The primary forcing pushes offshore by late aftn, with some lingering showers/tstms possible with PoPs diminishing to 20-40%. Instability is limited (500-1000 J/kg of 0-1km MLCAPE) and 0-6km bulk shear is generally less than 25kt, so any threat of severe tstms is very minimal. Temperatures this morning are mainly in the low/mid 60s where pcpn is occurring, with low/mid 70s across SE VA/NE NC. Temperatures across the NW will rise once pcpn ends with highs today in the mid 70s to low 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... The front drops back into the Carolinas this evening/tonight with some drying aloft from the N as the shortwave aloft and surface low push offshore. PoPs drop below 15% across the N with some partial clearing possible (briefly), while mainly cloudy conditions continue S, with a 20-40% chc of showers. Lows range from the upper 50s to mid 60s. The flow aloft remains SW Tuesday, with another wave lifting newd across the Carolinas during the morning and the Mid- Atlantic during the aftn and evening, with deep layer moisture returning. Categorical PoPs overspread the entire area Tuesday after 12Z for much of the area (and after 15-18Z across the NE). 22/00z NAM/GFS/GEFS/ECMWF continue to show some differences in timing and location and strength of this wave of low pressure, but the general theme is for a potent system with deep anomalous moisture transport per strong H925-H700 southerly flow and PW values climbing to ~1.75" collocated with the favorable RRQ of a potent 120kt jet over the Northeast Conus. Will have "heavy rain" wording in the gridded forecast and will continue the mention of potential for heavy rain/possible flooding in the HWO. The current storm total QPF averages 2.00"-3.00" (bulk of this coming on Tue), and overall the 22/00Z models are into decent agreement with these amounts, though higher amounts are possible and areas of northeast NC near the coast could receive less overall with the main axis of best forcing a little to the NW of this region. The high temperature forecast for Tue shows generally low/mid 70s SE to the upper 60s/around 70 F central and mid 60s far NW. This shortwave/surface low push offshore Tuesday night, with latest models showing more significant drying aloft Tue night into midday Wed so have lowered PoPs during this period (though low levels remain saturated so it should stay mainly cloudy). Yet another wave approaching from the SW Wednesday aftn and will ramps PoPs back up to 60-70% W and 40% E after 18Z. Mostly cloudy to overcast with lows Tuesday night in the upper 50s to mid 60s, followed by highs Wednesday ranging through the 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The deep upper trough across the eastern U.S. will continue to affect the Middle Atlantic into Thursday as there are some indications that the trough may slow down and even become negatively tilted as it moves off the east coast Thursday into Friday. This should keep precipitable water values well above normal with an upper jet axis nearby. As such, have raised PoPs to likely across much of the area Wed night and maintained high chance PoPs on Thursday before the upper trough axis moves east Thu night. With weak high pressure building across the southeast and Middle Atlantic for Friday and Friday night, will maintain a dry and seasonable forecast with temperatures in the upper 70s/lower 80s. The upper trough finally moves northeast by Saturday, leaving more zonal flow across the region with building heights. The GFS and the Canadian suggest a weak upper disturbance moving through the area in W-NW flow later Saturday into Saturday Night, but the ECMWF keeps this further north as it builds heights across the area faster than the GFS/Canadian. With that being said, will Slight Chance of showers/storms Saturday Afternoon for much of the area with the exception of SE VA and NE NC. Better chances for showers and storms Sunday with better agreement from the models of another upper disturbance moving overhead. In general, temperatures will stay seasonable for this time of year with highs in the upper 70s and lower 80s with lows in the upper 50s to mid 60s. No major warmth is expected through at least next Sunday. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Numerous showers W and scattered showers east early this morning, with conditions IFR/LIFR at RIC and genly MVFR at PHF/ORF/ECG/SBY through this morning. Showers are expected to slowly track east through the region, becoming more widespread to the coast this aftn. MVFR conditions will become predominant with brief periods of IFR in heavier showers possible through later aftn. Tstms most likely for southeast VA and northeast NC from about 18Z-22Z. OUTLOOK...Precipitation will move out this evening as deeper moisture moves offshore, but potential for some IFR conditions mainly at SBY in patchy fog and low clouds. Rain redevelops from SW to NE Tuesday morning and overspreads all sites by 15-18Z with IFR/MVFR conditions likely. Degraded aviation conditions will be likely into Tue evening. Rain may become spotty for awhile Tue night through midday Wed, though the potential for lingering low clouds will still be present. Another slug of deeper moisture and showers/tstms possible Wed night along with a breezy S to SE flow. Dry weather not expected to return until late Thu/Fri. && .MARINE... Sfc high pressure off New England will continue to retreat to the NE today. Meanwhile, a cold front approaches from the west during the day and washes out over the local waters Tuesday morning. Potent low pressure rides NE along this boundary during Tuesday, crossing near/over the waters Tuesday aftn/eve. The low then pushes NE and away from the area Tuesday night. Southeast winds 10-15 kt early this morning will become SSE at similar speeds later this morning into the afternoon. A complicated wind pattern develops tonight and Tues with the frontal boundary washing out over the marine area. Winds will eventually turn to the NNE around 10 kt all waters tonight, except remaining southerly off the northern OBX thru daybreak Tues. ENE winds increase on Tues to 15-20 kt, but may become S-SW Tues aftn across the southern waters depending on the eventual track of the sfc low. Winds the turn to the SW and diminish to 10-15 kt all waters as the sfc low head NE. The wind forecast remains tricky on Tues as there are still some timing differences in the models. SCAs appear to be likely for a portion of the marine area but confidence is still low at this time to issue. Quieter marine weather expected for the end of the week as the flow becomes offshore behind the low. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LKB NEAR TERM...AJZ/LKB SHORT TERM...AJZ/LKB LONG TERM...MRD AVIATION...LKB/LSA MARINE...JDM

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