Area Forecast Discussion
Issued by NWS Wakefield, VA

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486 FXUS61 KAKQ 242121 AFDAKQ Area Forecast Discussion National Weather Service WAKEFIELD VA 421 PM EST Fri Feb 24 2017 .SYNOPSIS...
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A cold front tracks across the Ohio Valley tonight as low pressure persists off the Southeast Coast. The front crosses the local area Saturday afternoon and evening. High pressure and more seasonal conditions return for Sunday and Monday.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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A potent sfc low entering Michigan late this aftn will continue to intensify/deep overnight as it tracks NNE into Canada. The associated sfc cold front is expected to cross the Ohio Valley and become located over the wrn Appalachians by morning. Conditions for the Mid Atlantic Region tonight will be warm and calm with lows generally in the mid 50s (lower 50s Atlantic/Ches Bay beaches north of the York River). Patchy ground fog may be possible again closer to daybreak. Confidence not high enough to add into forecast attm.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
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Potent sfc low now in Canada (just NE of Lake Huron by daybreak) will continue to track NNE to the east of Hudson Bay by Saturday evening. As the strong mid-level shortwave feeds into this system, models are trending twd a more longitudinal tilt to the upper level features which would likely slow the arrival of the cold front (into the local area) until mid aftn. The main caveat working against this will be the strong, unidirectional westerly flow throughout the atmospheric column and the much colder air behind the front that could actually accelerate the front through the region. With the best dynamics located farther north, am leaning twd the slower timing. If fog develops around daybreak, this could effectively prime the atmosphere to support airmass thunderstorms ahead of the cold front in the aftn due to more low-level moisture present than models are really showing. In addition, breezy S-SW winds gusting to 25 mph and ample warm air advection ahead of the front will warm daytime temps into the mid 70s NW to upper 70s (maybe 80?) SE. We may flirt with a few record highs. Please see Climate Section below for more information. The aforementioned unidirectional wind shear will also be a huge proponent in the development of strong, gusty winds with any thunderstorms that develop as well as the formation of line segment type convection. SPC has the area within Marginal Risk for isolated severe storms. Since best dynamics/instability remain across the nrn half of the CWA, will maintain the thunderstorm wind threat in the HWO and add in the rest of the VA counties. Once the front exits the area Saturday evening, winds veer to the NW and remain breezy overnight (especially at the immediate coast) as much colder air rushes into the region. Temperatures will be more seasonal with lows in the low-mid 30s NW to the upper 30s/around 40F SE. Sfc high pressure builds across the Southeast States Sunday, up along the SE VA coast Sunday night, and then moving well off the Mid Atlantic Coast on Monday. Conditions will be dry and more seasonal on Sunday with mostly sunny skies and breezy west winds. Highs in the lower 50s (mid-upper 40s Nrn Neck and MD/VA Eastern Shore). Winds decouple Sunday night with light south winds but the area remains somewhat wedged in the cooler airmass. Lows generally 31-35F inland (upper 30s to around 40 immediate coast). Clouds increase late Sunday night into Monday as the sfc high moves offshore and shortwave moisture/energy begins streaming into the region from the southwest. Forecast remains dry with temperatures generally warming into the lower 60s (upper 50s far nrn counties and MD/VA Eastern Shore).
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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A couple of opportunities for much-needed-rain are showing up in the medium range model guidance for next week. The first such opportunity is Monday night into Tuesday as a disturbance lifts NE across the region in the mid/upr levels. Will carry solid chc pops (40-50%) during this time with models in decent agreement. There is a brief reprieve Tuesday night before the next system is expected to impact the region during Wednesday. Subtle timing differences exist between the GFS and ECMWF with regards to timing of the onset of pcpn. However, agreement is good enough in the models at this point for solid chc pops (~40%). Drier weather looks to return late next week with high pressure attempting to rebound. Highs will remain unseasonably warm Tues/Wed from the mid 60s to the mid/upr 70s (warmest Wed). Trending cooler next Thursday/Friday with highs returning to the mid 50s to low 60s and lows in the 30s.
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&& .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
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Mainly VFR conditions are expected to continue this afternoon and through the first half of the night for all TAF sites. Surface high pressure is in control allowing for continued dry conditions across the region. Scattered cumulus have developed once again this afternoon with the heating of the day, bases are generally around 3000 to 4000 feet. Any cumulus will begin dissipate around sunset leading to mainly clear skies for the first half of tonight. Winds will remain light this afternoon, 5-10 knots, out of the S/SE. Patchy fog and low stratus will be possible Saturday morning, mainly after 08Z. Confidence is still low on fog coverage, so left VFR visibilities at all TAF sites besides PHF. Added MVFR ceilings at all TAF sites tomorrow morning to account for the possibility of low stratus. Model guidance has even hinted at the potential for IFR ceilings tomorrow morning. Showers and thunderstorms are expected to develop with a cold front Saturday afternoon into early evening. Outlook: Dry/VFR conditions return for Sunday as surface high pressure builds into the region. Winds will be gusty out of the WNW at times on Sunday, especially near the coast. Sub-VFR conditions will once again be possible late Monday and into Tuesday as a low pressure system approaches from the west.
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&& .MARINE...
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High pressure will move further off the Mid-Atlantic coast tonight as low pressure lifts NE well off the Carolina coast. A cold front will push from the Ohio Valley tonight and ewd across the mountains Saturday. A SSE wind will remain aob 15kt through tonight, and may increase a few kt Saturday due to a tightening pressure gradient, but should still remain sub-SCA, although locally stronger gusts are possible with tstms Saturday aftn/early evening. Seas are currently running 4-5 ft off the NC OBX, and will increase to 4-5ft all ocean zones tonight into Saturday as long period swell arrives from the low offshore. Waves in the Bay will average 1-2ft. The cold front will cross the coast Saturday eve/night followed by modest CAA and strong pressure rises. NW winds will average 15-25kt with gusts to 30kt and 4-6ft seas/3-4ft waves thru midday Sunday. SCA flags have been hoisted this afternoon for the Bay, Sound and Rivers. SCA flags will remain in effect for the coastal waters now thru midday Sunday to account for both events. The wind diminishes Sunday afternoon as high pressure builds into the region. High pressure quickly pushes offshore Sunday night into Monday with the wind becoming S.
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&& .CLIMATE...
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Feb 2017 is shaping up to rank among the warmest on record given continued warmth over the next week. Daily record highs are listed below for today and Sat, with the top 3 warmest February`s on record listed below that. Expecting RIC, ORF to be the 2nd warmest and ECG to be at least into the top 3 warmest. SBY looks on track to be 4th or 5th warmest. Daily Record Highs for Saturday 2/25: 2/25 ---------- RIC 83 in 1930 ORF 81 in 1930 SBY 80 in 1930 ECG 77 in 1985 Warmest February`s on record (average temps): * RIC: (most likely finish for 2017: 2nd warmest) 1) 49.9 (1890) 2) 48.5 (1976) 3) 48.1 (1884) * ORF: (most likely finish for 2017: 2nd warmest) 1) 52.4 (1890) 2) 50.5 (1909) 3) 50.1 (1990) * SBY: (most likely finish for 2017: 4th warmest) 1) 46.1 (1976) 2) 45.8 (1984) 3) 45.7 (1925) * ECG: (most likely finish for 2017: 3rd warmest) 1) 52.1 (1990) 2) 51.8 (1939) 3) 50.3 (1976)
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 6 PM Saturday to 4 AM EST Sunday for ANZ635>638. Small Craft Advisory from 6 PM Saturday to 6 AM EST Sunday for ANZ630>634. Small Craft Advisory until noon EST Sunday for ANZ650-652-654- 656-658.
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&& $$ SYNOPSIS...BMD NEAR TERM...BMD SHORT TERM...BMD LONG TERM...JDM AVIATION...AJB MARINE...JDM CLIMATE...AKQ

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