Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 222309 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 709 PM EDT Tue Aug 22 2017 .SYNOPSIS... High pressure remains centered off the Mid Atlantic coast through tonight as a cold front begins to approach from the west. The front crosses the area late Wednesday afternoon through Wednesday night, with strong high pressure building north of the area from Thursday into the upcoming weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Latest surface analysis centers high pressure over the western Atlantic, with a lee/thermal trough over the Piedmont. Isolated to widely scattered showers and thunderstorms have spread into interior portions of northeast North Carolina, but the overall trend is for the activity is to dissipate as it moves northeast. Activity will dissipate this evening as instability wanes. Warm/humid tonight with little chance for any rain under a SW wind of 10 mph. Lows mainly in the mid to upper 70s. Clouds increase across the north ahead of the approaching cold front and lead shortwave. Have introduced a slight chance PoP for the Maryland Eastern Shore late tonight, but best chances for measurable precipitation remain north and west of the local area. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... Models in good agreement with dropping the cold front into the local area Wednesday morning, then pushing the front across the area through Wednesday afternoon. Shearing vort lobe progged to ride along the front as winds increase aloft. The added forcing along the boundary along a narrow ribbon of high precipitable waters will result in scattered to numerous showers and thunderstorms Wednesday afternoon. Downslope flow from 1-3km will limit the coverage over the Piedmont, but hi-res and course resolution guidance indicates that the activity should become more organized central Virginia eastward as it interacts a moderately unstable air mass (mixed-layer CAPE values 500-1500 J/kg) and marginal shear (25-30 knots). Dry mid levels and an inverted V sounding indicate the main threat will be damaging winds and frequent lightning. SPC maintains a marginal risk for severe weather across the southeast half of the local area. Heavy rainfall is also possible as the cold front slows as it reaches southeast Virginia and northeast North Carolina Wednesday afternoon. Precipitable water values progged around 2 to 2.25 inches. Westerly flow in the mid levels indicates that the motion should prevent widespread heavy rainfall, but some areas could see periods of heavy rainfall. No headlines planned at this time. Flow becomes north to northeast behind the front, as dry air spreads into the area from the northwest. The front and upper wave push offshore Wednesday evening. Guidance indicates a wave of low pressure develops along the front over the Carolinas, keeping rain chances in northeast North Carolina and far southeast Virginia through Wednesday night. Highs Wednesday range from the mid 80`s northwest to around 90 southeast. Lows Wednesday night in the low to mid 60`s inland to the low 70`s near the coast. High pressure builds in from the northwest Thursday as the front stalls along the Southeast coast. Will keep low chance PoPs across northeast North Carolina Thursday nearest the front and deepest moisture. Otherwise, dry, cooler and less humid conditions expected. Highs Thursday forecast in the low to mid 80`s under a partly cloudy sky. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Cooler and drier for the late week period courtesy of building longwave upper level trough over the eastern United States. Meanwhile, broad 1024+ mb surface high pressure builds south over the interior northeast from Great Lakes Thursday and Friday, eventually setting up over New England and ridging down the east coast over the weekend into early next week. Forecast remains mostly dry, although a few showers possible along the coast in persistent onshore flow. Medium range guidance in relatively good agreement with developing a tropical system along and offshore of the southeast coast along the old frontal boundary early next week. Kept weekend dry, with low rain chances along the SE coast by Monday. Looking ahead, rain chances look to improve into the middle of next week, with moisture from the remnants of Harvey looming to the SW. For temperatures, high temperatures Fri-Mon will be at or just slightly below normal through the period, mainly in the upper 70s to low 80s. Early morning lows in the 50s inland to mid 60s along the coast. && .AVIATION /23Z TUESDAY THROUGH SUNDAY/...
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VFR and dry conditions continue at the 00Z TAF period with high pressure just offshore. Skies are mostly clear with a few cu that are generally dissipating. South to southwest winds 10-15 knots will prevail through the overnight. A cold front approaches the region late tonight into Wed afternoon and evening. Flight restrictions will be possible with the front later on Wednesday...mainly in the late afternoon into Wednesday night from showers and thunderstorms. The front should exit the coast early Thursday morning with lingering showers possible across far SE VA/NE NC. Conditions are anticipated to improve Thursday afternoon into Friday as the front shifts farther southeast and high pressure builds north of the region. Breezy NE winds expected near the coast Thursday and Friday.
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&& .MARINE... A cold front will approach the waters from the northwest tonight, crossing the area Wednesday through Wednesday night. Winds will increase tonight ahead of the cold front with SSW winds of 15 to 20 knots possible across both the bay and ocean. A few wind gusts of 25 knots will also be possible across the northern ocean and bay zones. As a result, went ahead and issued a Small Craft Advisory for the Chesapeake Bay tonight into early Wednesday morning. Waves will build to 2 to 3 feet in the bay and seas will build to 3 to 5 feet in the northern zones. Winds shift to the N/NE 10 to 15 knots behind the front by Wednesday afternoon through early Thursday morning. Strong high pressure builds north of the region Thursday and into the weekend. Expect wind speeds of 10 to 15 knots with a few occasional gusts to 20 knots, particularly early Thursday morning as the gradient tightens. Waves will be 1 to 3 feet and seas will be 2 to 4 feet. Onshore (E-NE) flow for the late week period as high pressure builds NNW of the local area. Winds remain elevated 10 to 15, occasional gusts to ~20 kt through the late week period as a couple of waves move across the stalled front to the south across the Carolinas. Seas remain choppy for the late week period into the weekend with the persistent onshore flow, remaining 2-4 ft northern waters...4- 5ft southern waters. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 10 PM this evening to 6 AM EDT Wednesday for ANZ630>632-634-650-652. && $$ SYNOPSIS...LKB NEAR TERM...LKB/SAM SHORT TERM...LKB/SAM LONG TERM...MAM AVIATION...SAM/JEF MARINE...MAM

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