Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 181750 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 150 PM EDT Thu May 18 2017 .SYNOPSIS... High pressure remains anchored off the Mid Atlantic Coast through Friday. A frontal boundary moves south across the local area Friday night and then stalls over the Carolinas on Saturday. This front will lift back north as a warm front on Sunday. && .NEAR TERM /THROUGH TONIGHT/... Sfc high pressure remains settled over the wrn Atlantic today with mid-upper level ridging shifting just east of the Mid Atlantic coastline. Remnant moisture from an upper low that crossed the Plains yesterday and moved into the Upper Midwest overnight is crossing the area with sct-bkn cirrus passing overhead. The high clouds are expected to continue breaking up and scour out shortly after sunrise. Another warm and muggy day ahead with little change to the overall airmass. Dewpoints in the lower 60s today with highs peaking in the upper 80s to lower 90s (low- mid 80s Atlantic beaches of the MD/VA Eastern Shore). Breezy SW winds develop by mid to late morning with speeds of 10-15 mph and gusts of 20-25 mph this aftn. Winds decouple slightly overnight tonight as a lee trough develops ahead of a cold front dropping down from the north and the sfc pressure gradient remains tightened. This will keep the environment well-mixed overnight as another round of high clouds streams into the area from the W-NW. These conditions will result in warm overnight lows in the upper 60s to lower 70s (similar to what is being experienced this morning). && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Lee trough continues to tighten up on Friday as the cold front advances on the region from the north. Warm and muggy conditions will persist through the day. Although highs should generally peak in the upper 80s, dewpoints will be warmer (in the mid 60s). Showers may be ongoing over the mountains in the morning, however light steering winds and downslope drying effects from already breezy SW winds should keep them from impacting far wrn counties to start the day. This will change by the aftn as showers/thunderstorms are anticipated to develop along/west of the lee trough axis, which extends from roughly the Delmarva to the far SW VA panhandle. Pwats increase to around 1.50 inches and periods of moderate to heavy rainfall should be anticipated. In addition, the primary threat with any strong storms that develop will mainly be wind (based on drier air present in model soundings), however isolated hail cannot fully be ruled out. Showers/storms move west to east into the evening and then get shunted southward as the cold front finally pushes through the area. Lows in the 60s Friday night. The cold front stalls near the VA/NC border Saturday and showers will taper off from north to south through the day. Cold air advection not that impressive behind the front, however the combination of clouds, evaporational cooling from recent rains, and decent onshore winds over the cooler waters (15-20 mph with gusts to 25-30 mph immediate coast) should hamper daytime heating. Expect highs in the mid-upper 70s inland and in the 60s closer to the coast. The stalled frontal boundary washes out into a warm front Saturday night. Although wind speeds at the coast are expected to diminish after midnight, return flow along the boundary could pull enough moisture over the warm front and allow isolated light rain showers to develop overnight. Lows in the upper 50s north to lower 60s south (mid 50s possible MD Lower Eastern Shore). && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Unsettled pattern setting up next week. Frontal boundary stalls across the Carolinas Sat night before lifting back north as a warm front Sun. Tsctns show enough moisture to keep skies mostly cldy until the warm fronts lifts north. Not much of a trigger to produce pcpn Sat night into early Sun so kept it dry for now but would can`t rule out some drizzle given a persistent onshore flow. Low confidence in this so left out of grids for now. Lows in the mid 50s north to lwr 60s south. Area becomes warm sectored Sun afternoon. Not much of a trigger seen, but did keep slght chc pops after 18Z due to daytime heating of the moist airmass. Highs in the 75-80 west of the Bay, low-mid 70s Eastern Shore. Cold front approaches from the west late Sun night. Evening pops diminish but then increase across the Piedmont late. Lows in the low to mid 60s. Both GFS/ECMWF agree low pressure accompanies a strong cold front as it crosses the area Monday afternoon and night. Abundant moisture with this feature to produce likely pops. Given a late day timing and forecasted instability, some strong storms possible along with heavy downpours if enough heating can occur. Highs in the upr 70s to lwr 80s. Likely/high chc pops Mon evening taper off to chc after midnight. Lows in the upr 50s to mid 60s. A brief break in the pcpn Tues as the GFS pushes the system and associated moisture offshore and temporarily dries it out while the ECMWF stalls the system keeping unsettled conditions across the region. Will keep it mstly cldy with chc pops at this time. Highs Tue in the mid to upr 70s. Lows in the upr 50s to lwr 60s. Another potent system and trailing cold front progged to cross the area Wed. Chc pops with his for now. Highs Wed 75-80. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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VFR through the 18Z TAF period. Aside from some scattered high clouds this aftn, expect SW winds gusting up to 20-25 kt with sfc high pres centered offshore. Similar conditions into Fri, as a cold front approches from the north late in the day. There is a chance of showers and thunderstorms late in the day, with MVFR/IFR psbl with the pcpn. Onshore flow and lower cigs psbl then into Sat and Sun, with a better chance of pcpn into early next week.
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&& .MARINE... Latest sfc analysis shows sfc high pressure centered well off the southeast coast with strong low pressure over the Upper Midwest. SW winds to avg 10-15 kt today with waves 1-2 ft and coastal seas building to 3-4 ft N and 2-3 ft S. The gradient tightens up in advance of an approaching cold front tonight, and high res model data suggests the potential for marginal SCA conditions in the Bay from about 04-10Z/Fri. Wavewatch depicts seas to around 5 ft at the far outer 20 NM portion of the northern coastal waters while NWPS generally keeps the 5 ft seas offshore of 20 NM. Given that both of these scenarios will be marginal and and overall expect conditions to be sub-SCA, will not issue any late 2nd period headlines and allow day shift to determine if they`ll be needed. Otherwise, the gradient weakens on Friday and other than locally higher winds associated with convection late Fri/Fri evening, conditions will be sub-SCA. Models continue to show a more significant surge of colder air as high pressure builds N of the area on Sat. SCA conditions appear likely for much of the area on Sat, and have generally gone a little stronger with the winds than what a blend of models would yield. Seas build to 4-5 ft on avg and waves in the lower Bay will avg 3-4 ft. The event is fairly short in duration, with winds diminishing by Sat evening as high pressure builds a little farther south and easterly winds diminish to 10-15 kt. Seas on Sun avg 3-4 ft. Winds shift to the SSE later Sun into Mon. && .CLIMATE... There were two locations that had record high temperatures on Wednesday, May 17. Norfolk had a high of 94 degrees, which exceeded the previous record of 93 degrees in 1941. Salisbury had a high of 91 degrees; surpassing the reading of 90 degrees on this date in 1944. Here are the record highs for Thursday, May 18: Record Location High Year -------- ------ ---- Richmond 95 1962 Norfolk 95 1877 Salisbury 96 1911 Elizabeth City 93 1987 && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...ALB/BMD NEAR TERM...BMD SHORT TERM...BMD LONG TERM...MPR AVIATION...MAS MARINE...LKB CLIMATE...

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