Area Forecast Discussion
Issued by NWS Wakefield, VA

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599 FXUS61 KAKQ 271957 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 357 PM EDT MON JUN 27 2016 .SYNOPSIS... A cold front slowly approaches from the west tonight. The front will move across the region Tuesday and Tuesday night. Weak high pressure builds in from the north Wednesday and Thursday as the front stalls across the Carolinas. The next cold front approaches the region late in the work week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Latest mesoscale analysis depicts a stable air mass over the region. Aloft, a ridge axis remains over the region with a warm layer observed on thermal profiles above 850mb. Upstream showers and thunderstorms over the higher terrain are having a difficult time moving off the mountains into the Piedmont. Expect this trend to continue through the afternoon as very little instability is observed, even with a moist boundary layer.However,expect to see an increase in mid level clouds from the west as the next system approaches. For tonight, a moist air mass west of the mountains will surge into the area overnight as the ridge axis pushes offshore. Precipitable waters will rapidly climb to 2.00+ inches. A cold front drops into the Ohio Valley, with pressure falls along the lee side of the mountains sharpening the thermal trough. Although better low level forcing is expected in an increasingly moist air mass, warm air aloft, a lack of appreciable forcing, and very little deep layer shear will be limiting factors. Hi-res (convective allowing models) guidance has had the same idea the past few runs with dissipating showers/thunderstorms as they track into the Piedmont/central Virginia overnight. More course resolution guidance pushes showers through the stable air all the way to the coast. Will maintain likely POPs over the far western Piedmont, but have followed hi-res trends and have lowered POP`s overnight over central and eastern Virginia. Expect only scattered showers with isolated thunder. Based on the anomalously moist air mass and lack of storm motion, locally heavy rainfall is possible under storms that do develop/move off the higher terrain. With the trend away from overnight convection, have lowered temperatures a few degrees. Lows forecast generally in upper 60`s to near 70 under a mostly cloudy sky. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/... Upper level trough digs into New England Tuesday with an attendant cold front approaching from the northwest. Lead shortwave energy progged to lift into the area Tuesday morning, with general model consensus developing showers along the lee/thermal trough from the Piedmont into central Virginia. Latest SREF guidance depicts an anomalously moist air mass over the region, with precipitable waters progged over 2 inches ahead of the surface trough (+2 standard deviations). Instability will be limited in the morning, but will keep mention of chance thunder. Theta-e advection and temperatures warming into the low to mid 80`s will result in a marginally unstable air mass Tuesday afternoon with thunder becoming more widespread. However, with the strongest height falls north of the region, only expect deep layer shear or 20 to 30 knots. Organized convection is not expected. Likely POPs will be maintained generally along and east of Interstate 95. The main threat will be locally heavy rainfall due to the moist air mass and relatively weak flow. Upper trough tracks over New England Tuesday night, pushing the cold front through the local area. Height falls will result in cyclogenesis just off the Northeast coast Tuesday night. As the low wraps up, lingering mid level moisture across the northeast forecast area in concert with strengthening forcing for ascent is expected to produce scattered showers Tuesday evening. Best chances will be from the Northern Neck to the Eastern Shore. Drying late Tuesday night with a clearing sky inland. Partly cloudy near the coast. Lows range from the mid to upper 60`s. Broad, upper level trough pushes across the region Wednesday. The frontal boundary expected to stall in the vicinity of northeast North Carolina as high pressure builds in from the northwest. Departing 70+ knot upper jet and enough lingering mid level moisture (precipitable waters drop below 1.5 inches) should be enough for scattered diurnally driven showers and thunderstorms. Highs generally in the mid 80`s under a partly cloudy sky. Best chances for measurable precipitation will be south of the Albemarle Sound Wednesday night, but will keep mention of slight chance showers. Lows generally in the low to mid 60`s. Surface high pressure centers along the Mid-Atlantic coast Thursday as the next upper level shortwave approaches from the west. Low pressure progged to develop over the Southeast states with an inverted trough extending northward over the central Appalachians. Upslope flow and the approaching wave will result in showers and thunderstorms over the higher terrain. Expect much of the forecast area to remain dry, but will mention a slight chance POP for showers coming off the higher terrain Thursday afternoon. Otherwise, near seasonal temps again with highs forecast in the mid 80`s. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Active northern stream upper trough will remain the dominant wx feature through the medium range period. Resultant W-NW flow will continue for the late week/Holiday weekend period. Meanwhile, at the surface, a rather stagnant pattern looks to set up with weak front/sfc trough dropping into the area and lingering over the local area. Warm, moist airmass (PW AOA 2" from Friday night through the weekend) in tandem with the boundary and numerous disturbances riding across the area in WNW flow aloft will bring a solid chance for mainly diurnally driven showers and tstms. Have continued solid chance pops each day during this period. Stronger front crosses the area by later Sunday into Monday. For temps, pattern favors temperatures hovering right around climo normal...with highs in the mid to upper 80s. Early morning lows generally in the 60s. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... VFR conditions are expected through this evening at all sites. Showers and thunderstorms over the mountains will attempt to move into the region tonight, however it is unclear how widespread they will become. If nothing else, ceilings will lower overnight at all sites and may become MVFR late tonight into Tuesday. There are chances for thunderstorms late tonight, but confidence is not high enough to include in any terminal at this time. Best chance for thunder would be at RIC. Continued MVFR or lower end VFR on Tuesday. OUTLOOK...Chances for thunderstorms will continue Tuesday afternoon into Wednesday as the front moves slowly through the area. This front remains just south of the area through Friday, and with that a chance for showers and storms, especially at ORF and ECG. && .MARINE... Latest obs reflect sub-sca E-SE flow across the waters this aftn. 1024+mb sfc High remains centered off the New England and northern Mid-Atlantic coast, while a cold front continues to slowly slide across the Ohio valley. Sfc high will continue to slowly drift east through tonight as a pre- frontal trough approaches from the WNW. As noted in the near term above, near-term CAMS becoming a bit less bullish on convection...and are anticipating a bit more in the way of clearing/cooling over the area later tonight. This, in tandem with tightening pressure gradient w/pre-frontal trough building in will likely result in at least a few hours of low end SCA winds in the Ches Bay, and have accordingly hoisted SCA for tonight. Winds will lessen a bit and become SSW as the high moves farther offshore and the trough moves in Tuesday morning. SSW flow 10 to 15 kt continues Tue into Tue ngt, as the (weak) cool front approaches from the WNW. The front and accompanying wind shift to the N-NE wind drops through the waters Wed morning into Wed aftn with high pressure pushing into the Great Lakes and OH Valley. This will maintain a NE to E flow later Wed and Thu. Weak front/sfc trough will meander over/just south of the area for the late week period, and will serve as the focus for late day convection over the area late in the week and through the weekend. && .CLIMATE... Chances to add to an already wet month mainly tonight and Tue. June has been another wet month at Richmond, the monthly total rainfall through the 24th stands at 6.92" and already makes this the 9th wettest June on record (2004 is wettest June with 9.93"). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ630>632-634. && $$ SYNOPSIS...LKB/SAM NEAR TERM...LKB/SAM SHORT TERM...LKB/SAM LONG TERM...MAM AVIATION...MRD MARINE...MAM CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.