Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 240222 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 1022 PM EDT Wed Aug 23 2017 .SYNOPSIS... A cold front drops south of the area tonight, stalling along the Southeast coast. Strong high pressure builds into the Northeast Thursday and Friday, and remains centered over the Northeast through early next week. Low pressure lifts offshore Monday into Tuesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Forecast updated to lower PoPs and temps for the overnight as the rain has come to an end over most areas, and some clearing has allowed temps to fall a fair bit. Previous discussion... Latest surface analysis places the cold front over northeast North Carolina. Scattered to numerous showers and thunderstorms have developed along and just behind the frontal boundary. A warm, humid, and unstable air mass exists across southeast Virginia and northeast North Carolina ahead of the area of showers and thunderstorms. RAP/SPC analysis indicates mixed- layer CAPE values of 1500-2500 J/kg, where temperatures are still in the mid to upper 80`s with dewpoints in the mid to upper 70`s. Shear remains marginal, around 25-30 knots, which is enough for at least some organization and stronger storms. Main threat remains locally damaging winds. Another concern will be along the coast as the front slows and better upper level support arrives. Impressive omega along the front with precipitable waters in excess of 2 inches and MBE vectors at or below 10 knots will result in locally heavy rainfall. Flash flood guidance across the southeast is around 2-3 inches, but given the overall progressive nature of the system, do not anticipate widespread impacts from flooding. Headlines are not anticipated. Flow becomes north to northeast behind the front, as drier air starts to spread into the area from the northwest later this afternoon into tonight. Guidance indicates some linger moisture over the Piedmont into central Virginia behind the front as another area of convergence could result in additional showers into this evening. Have increased cloud cover inland late today through this evening and lingered chance PoPs inland through the evening hours. Showers/thunderstorms diminish along the coast through the evening as instability wanes and the shortwave pushes offshore. Low tonight generally in the low to mid 60`s northwest to low 70`s southeast. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Potent shortwave digs over the Great Lakes into the Ohio Valley Thursday as the old cold front settles along the Southeast coast. Height falls ahead of the shortwave will induce waves of low pressure along the front, keeping low chance PoPs across southeast Virginia and northeast North Carolina. North to northeast flow will keep sky conditions generally mostly cloudy along the coast to partly cloudy inland. Cooler and less humid, with highs in the low to mid 80`s. Trough axis slides north of the region Thursday night, along with the deepest moisture and best chances for measurable precip. Have trended toward warmer guidance Thursday night due to likelihood of cloud cover. Lows in the low to mid 60`s. Upper 60`s near the coast. Onshore flow persists Friday, as model soundings indicate lingering low level moisture. Perturbations in the fast west to northwest flow along with convergence near the coast will result in a slight chance PoP Friday afternoon. Some modest instability is indicated, but will keep only shower wording due to stable onshore flow. Sky again averages partly cloudy to mostly cloudy. Highs in the low 80`s. Partly cloudy to cloudy Friday night as high pressure builds north of the region. Lows generally in the low to mid 60`s. Some locales in the Piedmont forecast to drop into the upper 50`s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... High pressure builds from the Great Lakes across the Saint Lawrence Valley and into New England Friday through Sunday bringing mild and mainly dry conditions. Highs Friday through Sunday will generally be in the upper 70s to low 80s with lows in the upper 50s to low 60s, and mid/upper 60s at the coast. Low pressure (potentially tropical) eventually develops along a stalled frontal boundary off the Carolina Coast early next week. This could potentially bring some moisture into the region in the Monday- Wednesday timeframe, but PoPs are only 20-30% at this time. Expect a modestly strong ENE wind along the coast with strong high pressure N of the region and developing low pressure off the Carolina Coast. High temperatures Monday through Wednesday remain in the upper 70s to low 80s, with lows ranging through the 60s. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... A cold front continues to push through the region and is along the VA/NC border at 00Z. Scattered showers still linger along and ahead of the front as well as behind the surface boundary. Ceiling and visibilities are mostly VFR across the region although some tempo MVFR conditions will occur with any precipitation. Most of the tstms have now moved well south into NC. The front with linger along the coast tonight, with chances for showers along the coast. MVFR ceilings are possible across southern Virginia and northeast North Carolina tonight for a brief period but overall expect generally VFR conditions with ceilings ~3500 to 5000 ft. Wind becomes north to northeast behind the front, generally at or below 10 knots. High pressure builds in from the northwest on Thursday as the front stalls along the Southeast coast. An uptick in northeast winds is anticipated Thursday morning with a surge of cold advection, but winds diminish mid to late morning. Flow also results in broken to overcast skies near the coast Thursday with lingering chances for showers across the far southeast. High pressure slowly builds north of the region through Saturday, with periods of clouds due to onshore flow. Winds remain northeast. && .MARINE... A cold front will push across the Mid-Atlantic coast late this aftn and evening bringing numerous showers/tstms. The wind will generally become NE 10 to 15kt behind the front. However, some locally stronger wind is expected along with and in the wake of tstms. Later tonight, high pressure will build in from the NNW and this will result in a shallow CAA surge late tonight into Thursday morning, which should produce a ~6hr period of low-end SCA conditions in the Bay/lower James. Expect a NE wind to increase to 15-20kt in these locations. The duration of the wind is not expected to be long enough to build seas to 5ft in the ocean. SCA flags have been raised for the Bay/Lower James for late tonight into Thursday morning. The wind should diminish and remain NE later Thursday aftn into Friday as high pressure builds into the region. Seas should subside from 3-4ft to 2-3ft, with 1-2ft waves in the Bay. Onshore (ENE) flow should continue through the weekend as strong high pressure builds N of the region across New England. The wind should remain elevated Saturday, 10-15kt/15-20kt ocean, and then increase more significantly Sunday into Monday as low pressure develops along a stalled frontal boundary to our S and then gradually lifts nwd. The wind increases to 15-20kt/20-25kt ocean (potentially 25-30kt S of Cape Charles). Seas initially build to 3- 5ft Saturday, then 5-7ft Sunday, and potentially 6-10ft by Monday. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 PM EDT Thursday for ANZ632-634. Small Craft Advisory from 4 AM to 1 PM EDT Thursday for ANZ638. Small Craft Advisory until 10 AM EDT Thursday for ANZ630-631. && $$ SYNOPSIS...SAM/TMG NEAR TERM...MAS/SAM SHORT TERM...LKB/SAM LONG TERM...AJZ AVIATION...SAM/JEF MARINE...AJZ

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