Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 191747 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 147 PM EDT TUE JUL 19 2016 .SYNOPSIS... A cold front moves slowly south across the Mid Atlantic States through Wednesday and then dissipates over the Carolinas later in the week. High pressure builds south into the area tonight and Wednesday. High pressure over the Southeast states becomes the dominant weather feature late in the week. && .NEAR TERM /THROUGH TONIGHT/... The weather map this morning had an east to west cold front oriented across Maryland to the Ohio Valley. High pressure was over the Great Lakes. In the upper levels...a weak zonal flow and some capping was holding off convection across the area. The cold front will be rather diffuse today and become better defined while moving south into North Carolina tonight and Wednesday morning as high pressure builds to the north of the region. An instability axis with mixed layer CAPEs over 2k develops over northeast North Carolina this afternoon. Dry air and weakening inversion should inhibit significant convection at that time. A short wave moving south from the Great Lakes will steepen lapse rates from north to south late this afternoon and this evening. Have highest POPs over the Piedmont by mid afternoon with likely POPs appearing across the Interstate 95 Corridor and in the 5 PM to 8 PM time frame and moving into southeast Virginia and northeast North Carolina after sunset. The Storm prediction Center has most of the area away from the coast in a slight risk for severe thunderstorms with the main threat being damaging winds. Strengthening lapse rates will be the primary contributor to expected instability. Abundant sunshine during the first half of the day will bring high temperatures to around 90 degrees inland and a few degrees cooler near the coast. Dew points have lowered a few degrees from yesterday`s values eliminating the potential for heat index issues. Convection shifts to the southeast and moving out of the area by shortly after Midnight. NAM12 suggests some upper level impulses and left over instability warranting low chance POPs through the pre-dawn hours. Low temperatures are expected to be around 70 degrees Wednesday morning. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... Trough axis pushes offshore Wednesday as the upper level ridge amplifies over the nation`s mid section. Surface high pressure builds into New England as the cold front washes out over the region. Expect enough forcing and moisture for a mention of slight chance to low end chance POP`s across the far southeast forecast area for diurnally driven showers and thunderstorms Wednesday. Weak flow may also result in seabreeze convection over the Eastern Shore to southeast Virginia. Otherwise, cooler, with highs in the mid 80`s under a mostly sunny to partly cloudy sky. High pressure settles over the Mid Atlantic region Wednesday night with dry conditions and a clear sky expected. Lows in the mid to upper 60`s inland to low 70`s near the coast. Surface high pressure slides offshore Thursday as the upper level ridge builds eastward. Dry conditions continue with highs in the upper 80`s. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Long term period will feature mainly dry conditions and above normal temps. For Thursday night/Friday, dry wx expected as surface high pressure slides just offshore and a broad upper- level ridge slides east into the eastern Conus. Temps max out in the lo-mid 90s. For the weekend, a thermal trough will hold in place over the Mid Atlc with weak w/nw flow aloft. Expect hi temps in the mid/upr 90s both days, and with dewpoints in the lo/mid 70s, afternoon heat indices will be near 105f (heat advsry criteria). 10-20% chances for rain Sat increase to 20-30% Sun. Continued hot into Mon (highs up to the mid 90s) with a 30% chance for rain as stronger mid- level energy approaches the region. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Mainly VFR conditions thus far this afternoon with sct-bkn ceilings developing between 4-5 kft. Convection was developing on the east side of the mountains and across the western piedmont moving southeast. Forcing from an upper level wave will support the development of more storms as the system progresses east. This would place showers and storms into RIC around 22z-01z. Have placed a tempo group in the RIC TAF. Storms will result in brief periods of IFR visbilities and gusty winds of 25-35 kt. For now it appears the best chances for showers and storms remains south of SBY, so have left mention out of the SBY TAF for now. The forcing pushes southeast to PHF and ORF from 23z-02z with showers and storms possible at both location along with brief periods of IFR visibilities and gusts winds similar to RIC. ECG will experience the storms a little later...mainly after 00z. Due to the upper level support the storms should be able to sustain themselves into northeast NC and may not weaken much with sunset. some lingering showers/tstms are possible over northeast NC after 06Z. In the wake of the showers there is the the potential for patchy fog and/or low clouds through 12Z/Wed with some IFR possible at all TAF sites. Confidence is low and have held off on putting IFR conditions in the TAFS, but IFR conditions are possible during the early morning hours Wednesday. OUTLOOK...Southern areas may see widely scattered to isolated afternoon tstms again Wednesday. Otherwise, mainly dry conditions are expected for the latter half of the week. && .MARINE... Current conditions now have winds that average around 5-10 Kt across the waters with the stronger winds now well off the coast as tstms have pushed farther offshore. Later today, a cold front weakens as it approaches from the nw, allowing NW winds to shift to the E/NE at only 5-10 Kt by this afternoon/evening. Lack of cold air advection and weak gradient winds will keep winds sub- SCA (to avg 10-15 KT) in the wake of the front on Wed. For Wed aftn/Thu...winds avg aob 10 kt with weak sfc hi pressure in the vicinity. Waves remain 1-2 ft with seas 2-3 ft. Winds increase to 10-20 Kt from the SSW Fri aftn/Fri night ahead of next frontal boundary. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...SAM/LSA NEAR TERM...SAM/LSA SHORT TERM...SAM LONG TERM...MAS AVIATION...JAO MARINE...LKB

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