Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 222005 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 405 PM EDT Mon May 22 2017 .SYNOPSIS...
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Low pressure will track off the Mid Atlantic coast this evening with a frontal boundary dropping into the Carolinas. This front will lift back north into the region late tonight into 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.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Current surface observations, radar imagery, and satellite imagery depict a compact low tracking newd across the Peninsula. Periods of moderate to heavy rain are possible across the Tidewater and Ern Shore late this aftn through early evening as this system pushes through due to the combination of decent forcing and pw values of +1-2 st dev. QPF of 0.5-1.00" is possible through this evening, with some locally higher amounts. Instability has climbed to 1000-2000 J/kg, but 0-6km bulk shear is generally less than 25kt, so any severe threat has bee localized, and should end by 5 pm along coastal SE VA/NE NC. Temperatures this aftn are mainly in the low/mid 70s, with low/mid 80s across NE NC. The front associated with the low drop back into the Carolinas this evening with some drying aloft as the shortwave aloft and surface low push offshore. PoPs drop below 15% across the N with some partial clearing possible, while mostly cloudy conditions continue S. A chc of rain returns across srn VA/interior NE NC overnight as moisture from the WSW begins to increase along the frontal boundary. Likely to categorical PoPs arrive for the SW corner of the area by daybreak Tuesday. Lows range from the upper 50s to mid 60s.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
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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. Categorical PoPs overspread the entire area Tuesday after 12Z for much of the area (and after 15-18Z across the NE). 22/12z NAM/GFS/GEFS/ECMWF/CMC 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 120-130kt jet over the Northeast Conus. The threat for heavy rain and possible flooding will continue to be mentioned in the HWO, and have opted against a flood watch at this time as 6hr FFG is generally 4-6" across much of the area, with some values of 3-4" across the Piedmont and MD Ern Shore. QPF through 00z Wednesday averages 1-3" across the region, and higher amounts are possible. Storm total QPF through Thursday ranges from 1.5-3.5" (tonight through Thursday) The axis of heaviest rain per 12z model consensus is generally in the I- 85/US 360 corridor. The current high temperature forecast 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 evening. However, 22/12z NAM/ECMWF depict a secondary wave lifting across the srn half of the are 00-06z Wednesday, so have bumped PoPs up to 40-70% S to account for this. Yet another wave approaches from the SW Wednesday aftn as an upper low approaches from the W. This wave tracks across the region Wednesday evening through the early overnight hours bringing another round of likely PoPs along with a chc of embedded thunderstorms. Current 12z guidance suggests the best instability remains offshore. However, the potential for some strong to severe storms will need to be monitored with 500mb height falls and strengthening/veering flow at the 500mb level. Unsettled conditions continue into Thursday with chc to likely PoPs continuing along with a chc of thunder. Mostly cloudy to overcast Tuesday night through Thursday with lows Tuesday night/Wednesday night in the upper 50s to mid 60s, followed by highs Wednesday/Thursday ranging through the 70s.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... 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 /20Z MONDAY THROUGH SATURDAY/... Widespread IFR currently from RIC to SBY in a rain shield. Meanwhile, over extreme SE VA and NE NC, a line of thunderstorms have developed. These will reach ORF and ECG around 20z with gusty winds and IFR conditions possible. This first batch of rain will move through this afternoon, with conditions improving MVFR or even VFR by late this afternoon before the next batch of moderate rain moves into the area late tonight into Tuesday mornign. Expect widespread IFR to redevelop later tonight and continue through Tuesday morning. Could even see some brief LIFR especially at SBY later tonight if fog develops, but will not include in the terminal at this time. OUTLOOK...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...AJZ/LKB NEAR TERM...AJZ SHORT TERM...AJZ/LKB LONG TERM...MRD AVIATION...MRD MARINE...JDM

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