Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 240940 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 540 AM EDT Wed May 24 2017 .SYNOPSIS... Weak high pressure prevails over the area today. Unsettled conditions return this evening through Thursday as an upper level trough approaches from the west. Conditions improve on Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A shortwave trough will exit to the east of the area through sunrise and will take with it the last widespread batch of light rain currently seen on the radar. Some semblance of shortwave ridging develops over the Mid-Atlantic today due to the combination of the departing shortwave and a strong upper low digging across the mid-MS valley. Therefore, after the current light rain exits, will drop PoPs below 20% for most areas into the afternoon. Low clouds will struggle to erode despite some mid-level drying as the surface pressure gradient will be rather nebulous resulting in weak low-level flow. The best chc for any partial clearing will be across the MD Ern Shore. High temperatures will remain below average today given the onshore flow, ranging through the mid/upr 60s to low 70s, except mid/upr 70s across NE NC. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... The upper low digs into the Tennessee Valley with yet another shortwave trough lifting NNE across the Carolinas and Mid- Atlantic this evening through the early overnight hours. A secondary wave lifts NNE across the Blue Ridge late this evening through the overnight hours. PoPs quickly ramp up to categorical across the SW piedmont/NE NC early Wednesday evening and spreading NE into central/SE VA late evening through the early overnight hours, before shifting to the Ern Shore after midnight. Mid-level drying and subsidence will result in PoPs quickly diminishing from SW-NE late Wednesday night into early Thursday morning. There will be a chc of strong to severe thunderstorms mainly along/south of the VA-460 corridor tonight as 500mb flow strengthens to 40-50kt across far southern VA and NE NC and the presence of a surface warm front will result in a veering low-level wind field. SPC has upgraded our far southern counties into a slight risk where locally damaging winds and an isolated tornado may be possible if enough instability develops. Additional QPF tonight averages 0.30-0.60". The upper low finally begins to lift NE across the mountains Thursday. A strong shortwave trough will lift across the Mid- Atlantic during the afternoon/early evening. Once again PoPs increase, to ~60-70% from the Piedmont to central VA to the MD Ern Shore, with 40-50% far SE. 500mb flow of 45-55kt is expected along with modest instability. Therefore, a few stronger to marginally severe storms are possible. The main threat would be wind and hail as low-level shear is minimal but a decent cold pool aloft will exist. Additional QPF Thursday aftn/evening should average ~0.25" with locally higher amounts. High temperatures range from the mid 70s to around 80 after morning lows ranging through the 60s. The upper low continues to lift NE across PA/NY/New England late Thursday night into Friday. Drier conditions finally arrive as deep layered WNW flow develops over the region. Some lingering mid-level energy could result in some sct-bkn cu Friday aftn. Otherwise, drier and breezy with highs in the upper 70s to low 80s, after morning lows in the mid 50s to low 60s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Shortwave ridging builds over the Northeast Saturday as an upper level low tracks into the Great Lakes region. Weak area of surface high pressure slides off the Mid-Atlantic coast Saturday as a warm front lifts through the region. Weak perturbations in fast westerly flow aloft will result in low end chance POPs Saturday afternoon for showers and thunderstorms. Otherwise, warming trend continues with highs in the low to mid 80`s. The warm front locates/stalls over the northern Mid- Atlantic region Saturday night, resulting in continued chances for showers/thunderstorms over the northern local area as perturbations in the westerly flow track across the region. The upper low slowly pushes across the Great Lakes region Sunday with an associated cold front progged to reach the central Appalachians late Sunday. Pressure falls ahead of the approaching front will induce a lee side/thermal trough over the region and better chances for diurnally driven showers and thunderstorms. Highs Sunday generally in the mid 80`s. The cold front reaches the local area Monday, but is expected to stall over the region as subtropical high pressure strengthens off the Southeast coast. The weak front remains over the eastern local area through Tuesday, with chances for diurnally driven showers and thunderstorms. Highs Monday and Tuesday in the low to mid 80`s. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... Light rain will exit to the east thru 10z with relatively dry conditions on tap for much of the rest of today. Unfortunately, CIGS will improve very little if any through the day. Winds will be from the northeast and east this morning then veer to the southeast this afternoon at 10 knots or less. OUTLOOK...Additional rounds of showers and thunderstorms are expected Wednesday night into early Thursday morning and again late Thursday. Aviation conditions will likely be impacted through Thursday night. Dry weather returns Friday as weak high pressure builds over the region. Unsettled conditions return for the weekend when another frontal boundary affects the Mid Atlantic States. && .MARINE... Latest MSAS showing frontal boundary nearly stnry just south of the VA/NC line. Weak low pressure that moved along this boundary last evening now offshore. Still a challenging marine forecast given model projections versus the actual obs. Thus, will be making some adjustments to SCA headlines which will be based off of current obs. NE winds still gusting in places to around 20 kts so plan is cont the SCA headlines through 7 / 10 AM across the Ches Bay and adjacent coastal waters through the day for 4-5 foot seas. Seas expected to drop below 5 ft all areas by evening. Interesting to note the 180 degree change in wind direction due to the frontal position over ANZ656 (NE at Cape Henry / SW at Ches Light). The next in a series of low pressure systems lifts into the Ohio Valley tonight with a meso-low lifting along the Appalachians. Data suggests marginal SCA conditions possible tonight for a several hour period with this feature. Given medium confidence in a widespread SCA event and not wanting double headlines for separate events, will hold off on any second/third period headlines for now. SW flow increases Thursday as the low lifts north of the region, with speeds of 10-20 knots expected. Yet another marginal SCA event is possible Thursday night as the low tracks off the NE coast. && .TIDES/COASTAL FLOODING...
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A period of onshore flow and higher astro tides (moving toward a new moon) will result in elevated water levels through Friday. Several tidal sites reached action stage during last nights high tide cycle. Todays high tide cycle is forecasted to be the lower of the upcoming 2 cycles with some sites reaching action stage. However, tonights high tide cycle is a different story. Many sites are forecasted to approach if not reach minor flooding levels. Forecasted levels at both Ocean City, MD and Jamestown, VA are high enough to warrent an advisory attm. However, confidence at other sites along the Bay and coastal waters is not high enough for an advisory at this time so elected to hold off and let day shift evaluate the need for either a statement or advisory.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for MDZ024-025. NC...None. VA...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT Thursday for VAZ089-090-093. MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ634. Small Craft Advisory until 7 AM EDT this morning for ANZ630>632. Flood Watch from 10 AM this morning to 1 PM EDT this afternoon for ANZ670-672-674-676-678. Small Craft Advisory until 4 PM EDT this afternoon for ANZ652- 654. Small Craft Advisory until 1 PM EDT this afternoon for ANZ656- 658. Small Craft Advisory until 7 PM EDT this evening for ANZ650.
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&& $$ SYNOPSIS...JDM NEAR TERM...JDM SHORT TERM...AJZ/JDM LONG TERM...SAM AVIATION...JDM MARINE...MPR TIDES/COASTAL FLOODING...MPR

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