Area Forecast Discussion
Issued by NWS Wakefield, VA

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777 FXUS61 KAKQ 200650 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 250 AM EDT WED JUL 20 2016 .SYNOPSIS... A cold front moves slowly south into the Carolinas by Wednesday where it will dissipate later in the week. High pressure builds over the Mid Atlantic States and then settles over the Southeast late in the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 9 pm update...Will be making some changes to near term grids based upon current conditions. Threat for severe weather has ended, and thunderstorms should either dissipate or be out of the cwa by midnight. Should be enough clearing overnight, with light winds, to allow some fog to form, at least in areas where more significant rainfall occurred. previous discussion...A weak cold front extended east to west across central Virginia Tuesday afternoon. A short wave trough over the upper Ohio Valley was deepening as it moves to the southeast. High pressure situated in Michigan was building to the southeast behind the aforementioned cold front. The Storm Prediction Center has a slight risk for severe thunderstorms covering most of our CWA except areas toward the coast. A severe thunderstorm watch is in effect for most of out Virginia counties except near the coast through 9 PM EDT. The main threat is for damaging winds with a minimal for large hail. Scattered thunderstorms were developing over the Piedmont Tuesday afternoon and are expected to increase to the southeast this evening. Steep lapse rates aided by a strong short wave trough along with various boundaries will contribute to the severe potential. CAPEs of 2 to 3 K J/Kg are indicated in portions of the CWA and especially northeast North Carolina. Shear and forcing is limited and the severe threat may remain unorganized. POPs due to thunderstorms will be likely in the I95 Corridor including Metro Richmond from 5 to 8 PM and then move southeast into Hampton Roads and most of northeast North Carolina after 8 PM. The area of thunderstorms will diminish or move out of the CWA shortly after Midnight. NAM12 suggests some upper level impulses and left over instability warranting low chance POPs for several hours behind the main area of thunderstorms. through the pre-dawn hours. Patchy fog is forecast during the predawn hours over inland portions of Virginia and North Carolina with most visbilities dropping to 1 to 3 miles with local areas possibly lowering below a mile. Visibilities improve by around 8 AM. Low temperatures are expected to be in the mid 60s to around 70 degrees Wednesday morning. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... Trough axis pushes offshore Wednesday as the upper level ridge amplifies over the nation`s mid section. Surface high pressure builds into New England and southward into our region. There is enough guidance to support chance POPs over far southeast Virginia and northeast North Carolina with slight chance POPs across eastern Virginia and the lower Eastern Shore. POPs decrease after 18z. Temperatures and dew points will be a bit lower making for a more comfortable day. Highs range from the mid to upper 80s. Northeast winds will keep areas near the coast closer to 80 degrees. Most locations will have a mainly clear sky Wednesday night. Lows range from the mid to upper 60s inland to lower 70s southeast. Some of the models suggest isolated precipitation Thursday through Friday but there`s not enough confidence to include any in the forecast. Surface high pressure slides offshore Thursday as the upper level ridge builds eastward. Plenty of sunshine will support highs in the upper 80`s to around 90. As we get toward Friday...Bermuda high pressure begins to dominate. Upper level ridging increases its influence over the area. This results in much higher temperatures. Lows Thursday night range from 70 to 75. High temperatures Friday are forecast to reach 90 to 95. Heat indices may reach just over 100 at some locations over inland Virginia east of Interstate 95. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Long term period will feature mainly dry conditions and above normal temps. For Friday night/Saturday, dry wx expected as surface high pressure stays off the se coast and a broad upper-level ridge slides east into the eastern Conus. Cannot rule out an aftn/eveng shra/tstm, but chance for rain is less than 20%. Very similar conditions for Sun with a weak thermal trough over the Mid Atlc and weak zonal flow aloft. Expect hi temps in the mid/upr 90s both days, and with dewpoints in the lo/mid 70s, aftn heat indices will reach near 105F (heat advsry criteria). Temps a bit lower for Mon/Tue...but still hot with highs in the 90s. Mainly climatological PoPs (20-30%) in the aftn/eveng. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... An area of showers/tstms to affect KSBY through 09Z, otherwise TAF sites will remain dry early this morning. Patchy fog/low cloud possible for a few hours early, mainly between 09-12Z this morning. Drier conditions with less shower/tstm development is anticipated today, only a few isolated showers/tstms possible from mid afternoon through early this evening/primarily along and near the coast. OUTLOOK...Dry weather and mainly VFR conditions are expected from tonight through Sat. Only flight restrictions would be from the chance for patchy fog from 06-12Z Thu morning. && .MARINE... No headlines necessary over the next several days as a weak frontal boundary drops south of the waters this morning with high pressure building in from the north later today. The high becomes centered off the mid-Atlantic/SE coast Thu-Fri as another weak front moves in from the NW Fri night and washes out across the area on Sat. Winds will become NE around 10 KT later this morning, and will shift to the E at 5-10 KT most areas this afternoon. Winds then transition to the E/SE Thu then S/SW Fri. The pressure gradient will increase a bit on Fri, so winds will avg around 15 KT fri afternoon/evening ahead of the front. Waves over the Bay will avg 1-2 ft, with seas over coastal waters 2-3 ft (3-4 ft Fri afternoon/evening). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...LSA NEAR TERM...LSA/WRS SHORT TERM...LSA LONG TERM...MAS AVIATION...LKB MARINE...LKB

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