Area Forecast Discussion
Issued by NWS Wakefield, VA

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358 FXUS61 KAKQ 261743 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 143 PM EDT Wed Jul 26 2017 .SYNOPSIS... High pressure builds over the Northeast today, sliding offshore tonight. The next low pressure system affects the region late Thursday through Friday night. High pressure builds into the region through the weekend. && .NEAR TERM /THROUGH TONIGHT/... Latest water vapor imagery and RAP analysis depicts a shortwave tracking across the Delmarva. Thermal soundings indicate some modest instability in the low levels from the Northern Neck to the Maryland Eastern Shore, in tandem with low level moisture trapped beneath a strong subsidence inversion. The result is ongoing scattered showers across the Northern Neck to the Maryland Eastern Shore. Will keep scattered wording in the forecast through early afternoon before the shortwave slides offshore. The remainder of the forecast area remains dry as surface high pressure over the Northeast ridges southward over the region. Onshore flow over the region will serve as a pleasant, albeit brief reprieve. Highs today in the upper 70`s to around 80 on the lower Eastern Shore to the low to mid 80`s west of the Bay. Cooler along the immediate coast due to onshore flow. Weak shortwave tracks across the region this afternoon, resulting in a partly cloudy sky inland to mostly cloudy northeast. Will keep mention of isolated showers from the Northern Neck to the Maryland Eastern Shore, but overall dry conditions expected. Dewpoints begin to creep back up tonight as the surface high pushes offshore and return flow re-establishing itself. Still mild and generally comfortable, but some patchy stratus/ground fog possible late. Lows ranging through the 60s to near 70 under a partly cloudy sky. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... Attention then turns Thu to an approaching potent mid-level shortwave trough and its associated sfc low, which will bring increasing rain chances to the local area late Thursday through Friday. Model timing has slowed with 00z/26 model suite, and have accordingly backed off w/timing of likely pops until later Thu night into Friday. Expect dry wx is expected for much of Thu, with PoPs increasing late in the day to 30-40% over the far northern tier of the CWA into Thu evening, as the lead shortwave aloft crosses along prefrontal sfc trough just north of the local area. Shearing shortwave drops across the area overnight Thu into Friday morning, and have therefore lingered T-storm mention through the night Thu. After a brief lull Friday morning behind the lead wave, chances of rain ramp up into high end chance to likely PoPs everywhere on Friday aftn into the evening as the main sfc low/cold front crosses the local area. SPC has a convective slight risk for Thu, with the main threat being damaging wind gusts. Given slower timing, have pushed timing back into Thu night/early Friday morning. Some stronger storms possible even into the early overnight hours over the northeastern third of the area with the area still in the warm sector, and strong deep layer shear (30-40 KT, mainly N) present coincident with the passing of the shortwave energy aloft. Heavy rain is also psbl with weak steering flow, dewpoints back in the low to mid 70s, and high PW values AOA 2" Thu night into Friday morning. Will continue to include mention in the HWO. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Potent shortwave progged to dig into the Mid-Atlantic region Friday night into Saturday, before de-amplifying and pushing offshore Saturday. An associated cold front pushes offshore Saturday morning. Have kept high end chance POPs central Virginia to the coast Friday night as the front pushes across the region. Low pressure forecast to develop along the frontal boundary as the strongest height falls spread across the region. The low lifts along the Northeast coast Saturday as the front stalls along the Southeast coast. Lingering mid-level moisture and the shortwave pushing across the region will keep slight chance to chance POPs Saturday afternoon. Cooler behind the front, with highs generally in the mid 80`s. An upper level trough remains over the eastern US through early next week, as a ridge of high pressure remains entrenched over the western Atlantic. High pressure slowly builds in from the Midwest Sunday and Monday as the front stalls along the Southeast coast. The GFS keeps the moisture farther offshore, but the ECMWF hugs the coast, developing a wave of low pressure off the Carolina coast. Have kept slight chance to low end chance POPs across the far southeast forecast area Sunday and Monday. Highs Sunday and Monday generally in the mid 80`s. Medium range guidance indicates the subtropical high over the western Atlantic may retrograde slightly Tuesday, which could push the coastal front inland. Have introduced low end POPs Tuesday as a result. Warmer, with highs in the mid to upper 80`s, but still relatively comfortable this time of year with dewpoints in the low to mid 60`s. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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VFR conditions through the 18z TAF period with areas of cu sct- bkn035 will persist through the afternoon giving way to more sct040 to sct070 this evening. Flow remaivs E to SE across the region and conditions VFR overnight into Thursday. Primarily VFR conditions expected through Thursday. A cold front approaches the area late Thursday into Friday bringing the threat for periodic flight restrictions in showers and thunderstorms Thursday night and Fri. Showers and thunderstorms may linger into Saturday, but drier conditions arrive for the second half of the weekend.
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&& .MARINE... High pressure will reside over the area today into tonight, and onshore winds will persist aob 10kt. High pressure slides offshore on Thu as a cold front approaches the mts, and winds become more SSE aob 15kt. Conditions generally dry Wed through Thu with high pressure over the waters. The cold front approaches the waters Thu night and is expected to slowly cross the waters Fri/Fri night. SW winds aob 15kt (15-20kt ocean) should be anticipated Thu night/Fri with wind speeds increasing 5-10kt along the front Fri night as the pressure gradient tightens. Winds switch to the north behind the cold front Sat morning as the pressure gradient remains tightened and a decent amount of colder air surges over the waters. Low-end SCA conditions may be possible from Sat morning through Sat evening before wind speeds diminish. Seas average 2-3ft Wed-Fri night all waters; 3-4ft north at times...increasing to 3-4ft Sat. Waves generally 1-2ft (2-3ft possible Thu night)...increasing to 3-4ft Sat into Sat evening. High pressure prevails Sat night into Sun. Winds N aob 15kt Sun/Sun night. Seas 3-5ft Sat night; 2-4ft Sun/Sun night. Waves 2-3ft Sun morning...subsiding to 1-2ft Sun aftn into Sun night. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAM/SAM NEAR TERM...MAM/SAM SHORT TERM...MAM LONG TERM...SAM AVIATION...MAM/JAO MARINE...BMD

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