Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 230842 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 342 AM EST Tue Jan 23 2018 .SYNOPSIS... A trough crosses the region this morning...with the cold front lagging behind and moving through the region by late afternoon. The front pushes well off the coast tonight. High pressure becomes centered over the south central states Wednesday and builds east into the local area by Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Sfc lo pres found invof north central MI attm will be tracking ENE into SE Canada today. Its accompanying cold front was the approaching the mtns attm...and will be crossing the FA midday- afternoon. Moisture continuing to increase ahead of the FA along the E coast on S winds (becoming gusty). Area of SHRAs now moving through west central NC and SW VA will be spreading into at least wrn/central portions of the FA before sunrise. Maintaining hi PoPs (60-90%) this morning as cold front enters/begins to cross (wrn/central portions of) the FA. Will have widespread SHRAs w/ possible ISOLD tstms (despite minimal instability/CAPE). Model SHERB values are from +1 to +1.5 between 12-18Z/23...though this parameter does have some limitations and the synoptic pattern (sfc low into Great Lakes)/composites (lack of a sharp-digging upper level system just W of the immediate region/dissimilar upper level jet structure) do not portray a high prob for tstms/strong-severe threat for the local area (substantially different from event earlier this month (eve of the 12th)). SPC maintains a marginal risk for severe...and if a distinct line or some discrete cells do develop Tue morning...they will need to be monitored closely (given strength of low level SSW jet). Will maintain mention in HWO. Models remain in good general agreement wrt timing and point to PoPs tapering off W-E quickly by aftn...w/ pcpn moving out of the entire area by 21Z/23-00Z/24. VRB clouds-partly sunny by afternoon...deep mixing and a downslope SW flow...highs will be 70-75F across much of central/SE VA and NE NC...w/ 65-70F on the eastern shore and over the W/NW sections of the FA (record highs noted in CLIMATE section below). && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... Dry cooler tonight/Wed w/ lows mainly in the 30s (around 40 F SE). Mostly sunny with highs Wed u40s on the ern shore to 50-55 F elsewhere. Partly cloudy as an upper trough swings through Wed night with lows in the u20s-l30s. Mostly sunny and seasonable Thu w/ highs from the l40s NE to around 50 F south central VA. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Overall pattern continues to show the long term period beginning with a shortwave ridge building eastward from the Mississippi Valley into the Southeastern US and Mid-Atlantic states on Friday into Saturday. This is followed by a full latitude trough that moves in on Sunday into Monday. But today, the timing between the models and strength of the cold front crossing the area is different with the 12z GFS slower and weaker while the 12z ECMWF is slower, stronger and would provide more rain for the region. The ECMWF right now has better run to run continuity than the GFS as the 6z GFS was slower and wetter than the 12z run. So for now have leaned a little more toward the slower ECMWF for that part of the forecast. On Thursday night through Friday, high pressure will be in control of the regions weather with the high overhead expect to see a very cool night with good radiational cooling, lows in the m20s-l30s. Temperatures will begin to warm again on Friday as warm advection begins with sw flow, expect highs in the u40s to u50s. Mex guidance is a bit warmer and began to trend that direction raising highs a few degrees above the other guidance. The SW flow continues on Fri night with more dry weather and maybe a few more clouds. Temperatures in the mid to upper 30s are expected. For Saturday through Sunday night, this is where the most interesting portion of the extended lies as the quicker GFS has the moisture and front approaching the area by late Sat afternoon, which is about 6 to 12 hours faster than the 6z GFS or ECMWF. At this range, did raise pops a touch, but kept the forecast dry on Sat with temperatures getting back into the U50s to l60s. But beginning Sat night did start to raise pops up to high chance values. Some guidance suggest pops in the likely range are possible now, but with timing issues and also the questionable forcing have capped pops at 50% from Late Sat night through Sunday with a slow clearing of the pops in Sunday evening. Sunday looks like the most probably period for rain and the ECMWF would indicate a beneficial rain, which would be good for the drought areas, but at this range models have been showing these types of events for the last few weeks, but the plentiful rain has been materializing. Have kept temps mild on Sat night and Sunday with lows in the 40s and highs still in the 60s. The front should clear the area Sunday night with NW and high pressure building in on Monday. The strength of the developing upper trough will determine how strong the low over New England gets Sunday night and this will impact temps on Monday. The ECMWF would suggest temperatures cooler than the currently forecast in the upper 40s to mid 50s on Monday. But for now will not bit completely on the ECMWF. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Lowering CIGS (to IFR/low end MVFR) through the early morning period as moisture continues to increase on deep layered S winds. A cold front is approaching from the W attm...and will push across the FA this morning...then off the coast this afternoon/eve. The front will be accompanied by SHRAs. Instability with the front will also bring a lo prob for ISOLD tstms through midday/early afternoon. Clearing/improving conditions expected during the afternoon/eve. Sfc hi pres builds into the local area from the SW through Thu. && .MARINE...
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A tightening pres gradient ahead of an approaching cold front will increase winds to 15 to 25 kt from the S-SW this morning. These winds will persist thru midday/early aftn becoming rather gusty by mid morning. Seas on the coastal waters building to 4-6 FT; waves 3-4 ft on the Bay rather quickly in response to the SW winds. SCAs remain in effect for all waters today. With the primary surface low so far displaced to the north it will be hard to get Gales with warm S-SW winds over cold water this time of year, but did keep mention of a few gusts to 35 kt for our northern coastal waters. Once the front clears the area late this afternoon/evening, winds will shift to the west 15 kt tonight/Wed and then northwest on Thursday. Waves/seas subside to 2-3 ft. There is another surge of cold air Wed night into early Thu which will maintain the NW winds of 15 kt with some higher gusts. Waves and seas may increase by a foot to 2 to 4 ft with this surge Thu. Conditions improve by Friday as high pressure builds into the area.
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&& .CLIMATE... Record high temperatures today. Tuesday RIC 76/1974 ORF 76/1999 SBY 73/1999 ECG 76/1937 && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ630>638. Small Craft Advisory until midnight EST tonight for ANZ650-652- 654. Small Craft Advisory until 10 PM EST this evening for ANZ656- 658. && $$ SYNOPSIS...AJZ/LKB NEAR TERM...ALB/LKB SHORT TERM...ALB/LKB LONG TERM...ESS AVIATION...ALB MARINE...MAS CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.