Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 230623 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 123 AM EST Tue Jan 23 2018 .SYNOPSIS... High pressure slides farther off the coast tonight. A trough crosses the region Tuesday morning, with the cold front lagging behind and pushing through the region by late afternoon, before pushing well off the coast by Tuesday night. High pressure becomes centered over the south central states Wednesday and builds east into the local area by Thursday. && .NEAR TERM /THROUGH TODAY/... Latest analysis places a potent upper low over the Midwest, with a double surface low ~998 and 999mb one beneath the upper system over SE IA and the other near Lake Michigan. Meanwhile, sfc high pressure is pushing well off the mid-Atlantic. Temperatures this evening are mainly in the 50s for most of the CWA with the exception the Ern Shore where temperatures are in the mid 40s to around 50F. Fairly thick cirrus shield remains in place for the most part, with some low and mid clouds arriving from the SW. Very mild overnight with temperatures staying in the 50s just about everywhere (mid/upper 40s coastal eastern shore, but these values should rise overnight). Becoming cloudy overnight with increasing rain chances after 06Z mainly over the Piedmont, and will overspread likely PoPs to the I-95 corridor between 09-12Z. Enough mid level instability will move in late to include mention of isolated tstms late west of I-95, though at this point these will be elevated. High rain chances (60-90%) prevail Tue morning as main sfc low pressure becomes occluded over Michigan and significant pressure falls and a meso-low develop along the central Appalachians by around 12Z. The strength of this feature will likely have a significant affect on QPF and the potential for some embedded convection in the morning in a high shear/minimal CAPE environment. Latest GFS/NAM SHERB values are from +1 to +1.5 between 12-18Z, though this parameter does have some limitations and the synoptic pattern (sfc low into Great Lakes), does not typically favor a lot of tstms/severe threat for the AKQ CWA. However, with significant shear and some instability aloft (H7-H5 lapse rates of 6.5C/km) can`t rule out isolated strong tstms mainly from 12-15Z west of i-95 and 15-18Z farther east. SPC has most of the CWA in 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. The current pattern with convection across the deep south and Gulf of Mexico could be a hint that a split in the precip shield is likely (and thus most areas should expect only around 0.25" or less of total QPF except for locally higher amounts in tstms and over the far N). Models remain in good general agreement wrt timing and should see PoPs taper off W-E quickly by aftn...w/ pcpn moving out of the entire area by 21Z/Tue to 00Z/Wed. With partial aftn sunshine, deep mixing, and a downslope flow highs Tue will be breezy and unseasonably warm, possibly close to record highs. Current forecast is for highs 70-75 F across much of central/SE VA and NE NC, with 65-70 F on the eastern shore and over the W/NW sections of the CWA. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... Dry cooler Tue night/Wed w/ lows mainly in the 30s (around 40 F SE). Mostly sunny with highs Wed upper 40s N and on the ern shore to 50-55 F elsewhere. Partly cloudy as an upper trough swings through Wed night with lows in the upper 20s to lower 30s. Mostly sunny cooler/seasonable Thu with highs from the lower 40s 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 mid 50s. 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 /06Z TUESDAY THROUGH SATURDAY/...
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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.
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&& .MARINE... High pressure over the waters is shifting east and offshore this evening as low pressure moves into the Great lakes. A tightening pres gradient ahead of the approaching cold front tonight will increase winds to 15 to 25 kt from the S-SW prior to daybreak Tues. These winds will persist thru midday/early aftn Tue 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 overnight into Tuesday. 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 30 to 35 kt for our northern coastal waters. Once the front clears the area Tues afternoon, winds will shift to the west 15 kt Tues night/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 weak high pressure builds into the area. && .CLIMATE... Record high temperatures today and Tuesday. Today Tuesday RIC 75/1906 76/1974 ORF 77/1937 76/1999 SBY 72/1927 73/1999 ECG 79/1937 76/1937 && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ630>632-634>638. Small Craft Advisory from 6 AM this morning to 6 PM EST this evening for ANZ633. Small Craft Advisory until midnight EST tonight for ANZ650-652- 654. Small Craft Advisory from 6 AM this morning to 10 PM EST this evening for ANZ656-658.
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&& $$ SYNOPSIS...AJZ/LKB NEAR TERM...AJZ/LKB SHORT TERM...ALB/LKB LONG TERM...ESS AVIATION...ALB MARINE...JDM CLIMATE...

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