Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 230813 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 413 AM EDT FRI SEP 23 2016 .SYNOPSIS... Low pressure along with a weak frontal boundary will remain stalled along or just off the Carolina coast today. High pressure builds over the local area late today into Saturday morning. A backdoor cold front drops across the region during Saturday. The center of high pressure slides into southeast Canada during Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Sfc low pressure along a stationary frontal boundary remains along/just off the Carolina coast today. Meanwhile, weak high pressure remains in place across the local area with a cold front crossing the Northeast. The coastal boundary will remain an influence on SE portions of the FA today, and will therefore maintain slight chc to low chc pops 20-35% for scattered showers. Elsewhere, dry wx is expected today with morning stratus/patchy fog giving way to sunshine. Could be some breaks in the clouds across SE areas before dark. A bit warmer today with highs from the upr 70s/low 80s SE to the mid 80s N/W. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... Weak sfc high pressure remains over the area tonight but a backdoor cold front sags south overnight and reaches the northern FA toward daybreak. Meanwhile, the coastal boundary dissipates and slides farther offshore. Mainly clear and dry tonight with lows in the 60s to near 70. Patchy fog possible toward morning. The backdoor cold front will drop across the region during Sat with the center of sfc high pressure building into SE Canada by Sun morning. Will maintain dry wx Saturday, with generally a partly sunny sky. Highs from the upr 70s Eastern Shore to the mid 80s S/W. Models are keying on increased low level moisture and some weak isentropic lift in the wake of the backdoor front for Saturday night into Sunday. However, the depth of moisture is rather shallow favoring only low end pcpn chances for pockets of light rain/drizzle. For now will show slight chc pops across the Piedmont Saturday night and in areas west of the Bay on Sunday. Will have mostly cloudy/overcast skies for areas mainly west of the Bay during this same time, and partly to mostly clear skies for the Eastern Shore. Lows Saturday night from the mid 50s lower MD Eastern Shore to the 60s elsewhere. Highs Sunday only in the low to mid 70s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Medium range period characterized by continued large differences amongst the deterministic models and even within their member ensembles. Forecast period begins Sunday night with an amplified upper level ridge/trough pattern, with the ridge axis being centered from the OH/TN river valleys Into the central Gulf Coast. At the surface, cool air wedge will continue to ridge down across the local area from New England/QC. Have retained a slight chance for some light rain Sunday night in association with some weak overrunning moisture. Otherwise, remaining primarily dry albeit with increasing clouds once again Sunday night and Monday. Higher than average uncertainty remains for the remainder of the forecast period, although it does appear as if the models are trending toward a solution. The 00z/GFS and GEFS mean remain much stronger than the ECMWF with strong upper ridging and a potent (closed off) downstream trough over the upper midwest by later Mon/Tue. By contrast, the 00z/ECMWF and the 12z/Thu EPS before it confines blocking farther back (west) into the Canadian Rockies...with the downstream, more progressive upper trough quickly shoving through a strong cold front across the local area by mid to late week (as soon as Later Wed/Thu). The CMC remains the slowest solution wrt displacing the upper ridge off shore, and therefore is the warmest/driest solution. Taken at face value, the GFS solution would lead to more of a strong blocking pattern that would slow the eastward progression of upper ridge axis considerably, while the ECMWF would bring a quicker frontal passage and resultant cooler temps for the late week period. The good news is that the GFS has trended a bit toward the operational EC with respect to shifting the Sfc high offshore Tuesday into Wednesday...depicting a strong sfc cold frontal passage for the mid to latter portion of next week. Have made minimal changes to the going forecast for now until more definitive model consensus can be reached and ideally retained for a few cycles. For temps, Highs will start off cool, averaging in the low-mid 70s with early morning lows in the upper 50s to mid 60s Mon. Sfc high pressure becomes centered offshore by late Tue-Wed w/deeper moisture and a strong front to approach the area from the W. Pops remain a bit more broad-brushed in slight chc range 20% POP for now during this period. Highs will avg 75-80 F Tue/Wed with lows mainly in the 60-65 F range. Cooler by late in the week, with 00z MOS guidance advertising highs trending back into the low to mid 70s post-frontal by next weekend. Again, will stay close to the inherited forecast for now. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Abundant low level moisture and onshore flow are promoting widespread MVFR conditions this morning with some IFR cigs at KSBY/KECG. These conditions will be slow to improve thru the late morning. More favorable conditions are expected by midday today with VFR conditions and mainly dry weather across the area. OUTLOOK...A cold front sags south through the Mid Atlantic States during the weekend. There are some indications that low clouds and patchy light rain/drizzle could impact the TAF sites Sat night into Sunday. && .MARINE... Latest obs reflect diminishing NNE flow across the waters as pressure gradient has relaxed over the past 3-6 hours w/weakening low pressure lingering along the NC/SC coastline, even as high pressure slowly builds south. Have dropped SCA across the waters this morning, with seas finally subsiding a bit. Winds remain sub-SCA out of the NNE today, winds 10kt or less. Seas subside to 3-4 ft, 2-3 ft on the bay. Winds pick up a bit late tonight as a weak Cold front drops across the waters late tonight into Saturday, stalling just south of the waters Sat night and Sunday before sliding south into the Carolinas on Monday. CAA surge behind the front appears minimal. Wave energy kicks up on Saturday, courtesy of distant tropical Cyclone Karl Invof Bermuda. Resultant long period swell could well bring a period of SCA for hazardous seas over the coastal waters Saturday/Sat night, averaging 4-5 ft highest out by 20 nm marker. Wavewatch and NWPS both depict seas subsiding once again for Sunday through Sunday night. && .HYDROLOGY... The Cashie River at Windsor is still within major flood stage, which begins at 13 ft. The river is forecast to fall to around 12 ft by this evening (moderate flood stage) before steadily falling over the next several days...possibly dropping back below flood stage late Sunday. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...JDM NEAR TERM...JDM SHORT TERM...JDM LONG TERM...LKB/MAM AVIATION...JDM/LSA MARINE...LKB/MAM HYDROLOGY...

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