Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 140229 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 929 PM EST Fri Jan 13 2017 .SYNOPSIS...
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A cold front will stall over the Carolinas overnight as high pressure builds east from the Great Lakes. The high will weaken over New England on Saturday, as low pressure lifts northeast through the mid Atlantic region. Another high pressure system will become centered from the Great Lakes to New England Saturday night through Monday as the frontal boundary remains nearly stationary across the southeast states.
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&& .NEAR TERM /THROUGH SATURDAY/...
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Sfc analysis late this evening indicates sfc cold front now south of the CWA and pushing into South Carolina with strong/1045mb sfc high pressure centered over the Great Lakes. N/NE low level flow prevails locally, with temperatures dropping through the 40s most locations. Clouds have begun to increase/thicken late this evening and the sky will become overcast all areas thru early Sat AM. Overnight, as the strong high pressure system continues to drift E from the Great Lakes to New England, a trough of low pressure lifts ENE from the TN Valley to the central Appalachians. 13/12Z guidance overall trended a bit warmer than last night`s 00Z runs (which makes sense given today`s temperatures). Expecting light overrunning precipitation, with GFS/NAM 295K surfaces spreading the overrunning moisture across the northwest half of the local area toward the Maryland Eastern Shore mainly after 06Z. Enough low level cold air arrives late (mainly below 900mb) to bring a chance of rain/freezing rain/sleet across the far northern forecast area (but have trended the forecast warmer and expect sfc temperatures to be above freezing as the precip begins (in most cases well above freezing). 850Mb temps expected to stay between +3 to +5C, except will fall to +1 to +2C across the MD eastern shore. Best chances for light rain to possibly transition to light freezing rain for a few hrs would be over the far N of the CWA, from Louisa to Caroline Co. and interior northern Neck counties from about 10-12Z. The warm nose aloft might be too shallow over the eastern shore for any freezing rain (thinking more sleet or a rain/sleet mix with temperatures staying above freezing there). From 12-15Z, as mid level warming aloft pushes a bit more to the NE, could see a brief period of light freezing rain mixed with sleet or plain rain over the MD eastern shore. Still appearing very marginal as sfc temperatures will likely have to column cool just to get down to 32 F (and if precip stays too light temperatures may remain above 32 F for the entire event). Also, ground and roads should be well above 32 F due to the warmth of the past few days. Therefore, confidence is not high due to borderline temperatures and onshore flow. Little, if any ice accumulation is expected (would be mainly for elevated surfaces if it were to occur). High pressure slides off the New England coast Saturday aftn as the frontal boundary stalls over the Southeast. The result will be ongoing northeast flow and wedge conditions. Maintained 60-80% POPS across the north and northeast half of the local area Saturday morning/early aftn tapering to low end chance across the southwest. Increased POPs for the Maryland Eastern Shore to categorical Saturday afternoon as a shortwave approaches from the west. Temperatures and low level thicknesses warm through the afternoon, with the p-type becoming all rain across the entire forecast area. Overall, forcing and moisture will be limited, resulting in only light QPF amounts (a tenth to a quarter of an inch north to a few hundredths south). Continue to undercut guidance due to cloud cover and northeast winds. Highs in the mid-upper 30`s north to low 40`s south.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Low pressure develops offshore the Mid- Atlantic coast Saturday night as shortwave energy digs over the Delmarva. Will linger 40-60% POPS along the coast Saturday evening as the moisture plume begins to push offshore and southward. Lows in the low 30`s north to upper 30`s south. Latest guidance has backed off on precip chances Sunday as the plume of moisture pushes south of the region. BUFR soundings indicate drying in the mid levels, but low level moisture will keep cloudy conditions in place through the day. A few breaks in the clouds expected across the northeast late Sunday. Will keep mention of slight chance to low end chance POPs for the Piedmont, but silent elsewhere. Highs in the low 40`s north to the upper 40s S. Lows in the 30s to around 40 F Sun night and mainly cloudy (except across the ern shore). By Mon, deep cutoff upper low begins to eject NE from west Texas to the southern central Plains as it become engulfed by the northern stream energy. Sfc low pressure moving from the southern Plains to the mid-MS valley will help lift a warm front through the region by late in the day. Still expecting mostly cloudy and cool conditions locally, with highs mainly in the 40s along with a 20-30% POP for light rain. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Above normal temps expected acrs the fcst area thru the extended period. At this time, will go with a blend of the ECMWF and GFS with respect to the timing/placement of fronts and the chcs for showers. Best chcs will be Wed/Wed night and again on Fri. Highs will range fm the mid 50s to mid 60s thru the period, with lows in the mid 30s to lower 40s Mon night, and ranging fm the lower 40s to lower 50s Tue night, Wed night, and Thu night. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... VFR conditions with mostly mid and high cloud ceilings continue to prevail across the region this evening. The cold front that moved through the region is over northern NC and nearly stationary. Arctic high pressure centered over the Great Lakes will push colder air into the Mid Atlantic region overnight. Some overrunning warm air from the west will move over this colder air late tonight into Sat and bring a chance of a wintry mix over portions of the Md Eastern Shore and Northern VA northward. Light rain is expected to occur over much of the remainder of the CWA. Cloud ceilings expected to lower to MVFR by Sat morning daybreak and to MVFR/IFR condition by the afternoon and evening. Vsby will likely stay 3 mi or better. The lower ceilings will linger in place into early Sunday and some light rain/drizzle will be possible into Sunday morning. Conditions will gradually improve Mon as the cold air erodes and southerly flow begins. Some clouds will linger but expect VFR conditions into Tue. && .MARINE... Will maintain SCAs for Ocean/Ches Bay/Currituck sound and Lower James River for this evening thru Sat morning, due to NNE surge as colder high pressure slides acrs the Great Lakes ewrd into New England. Expect speeds to pick up to 15 to 20 kt with gusts up to 25 kt this evening into the overnight. That sfc high will slide into the Atlc during Sat, but another sfc high will build fm the upper midwest ewrd into the northeast U.S. later Sat thru Sun night. This will maintain persistent NW thru NE winds acrs the waters into early Mon morning, altho speeds expected to be a few/several KT lower. Winds then turn to the S or SW and increase Tue thru Wed, as that high moves into the Atlc and a cold front approaches fm the west. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 11 AM EST Saturday for ANZ634-654- 656-658. Small Craft Advisory until 4 AM EST Saturday for ANZ632. Small Craft Advisory until 6 AM EST Saturday for ANZ633-650- 652. Small Craft Advisory until 10 PM EST this evening for ANZ630- 631. Small Craft Advisory until midnight EST tonight for ANZ638. && $$ SYNOPSIS...LKB NEAR TERM...JDM/LKB SHORT TERM...LKB/SAM LONG TERM...TMG AVIATION...JEF MARINE...TMG

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