Area Forecast Discussion
Issued by NWS Wakefield, VA

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969 FXUS61 KAKQ 240120 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 920 PM EDT Sun Oct 23 2016 .SYNOPSIS... Low pressure tracks north of the region tonight, which drags a dry cold front through the area Monday. Canadian high pressure builds in from the northwest Monday night and remains across the region through the middle of the upcoming week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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The current surface analysis shows 1024mb high pressure centered over N FL/S GA. To the north, ~982mb low pressure was noted over se QB...with a second area of sfc low pressure over Lake Erie. The associated sfc cold front extended SW of this system back into Nrn Indiana and central Illinois to just north of KSTL at 01z. Aloft, GOES wv imagery continues to show potent troughing in place over Northern New England and se Canada, with a secondary trough diving across the Great Lakes. A 30-40kt LLJ associated with the Great Lakes trough and attendant surface low will push east across the northeast and northern Mid- Atlantic overnight. This feature will induce warm air advection across the local area through Monday morning ahead of the approaching front. Thus, despite a clear to mostly clear sky, look for early morning low temperatures to average ~10-15F warmer than those of last night, ranging from the upper 40s to low 50s.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... The trough and associated low pull offshore Monday with the trailing cold front pushing through the area during the aftn. The frontal passage will be dry and produce deep mixing, and caa will be delayed until Monday night with downslope flow. This will allow for slightly warmer temperatures Monday with highs ranging from from the low to mid 70s under a mostly sunny sky, with some sct aftn cu (mainly e). There should be enough mixing Monday night with caa to keep lows generally in the low/mid 40s (upper 40s se). However, the piedmont could decouple late, which will allow lows to fall into the upper 30s to around 40. Not expecting much more than patchy frost over the piedmont. Sunny and cooler on Tuesday as 850mb temperatures drop back to +4-6C with highs in the upper 50s ne to the low/mid 60s sw. The high continues to build in from the nnw Tuesday night. This appears to be the coldest night through midweek, with lows ranging from the mid/upper 30s n, to the low/mid 40s se. This will bring the potential for frost across wrn and nrn portions of the area. Some modest mid-level waa is expected to commence late Tuesday night, which could result in some clouds (mainly w). This will impact the potential for frost. Continued cool Wednesday under a partly to mostly sunny sky with highs in the upper 50s ne, to low 60s sw. There is the potential for slightly cooler temperatures if more clouds develop with mid-level waa. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... A series of northern stream disturbances will impact the region through the extended period. The first developing upper trough will drop over the Great Lakes Wednesday night and Thursday, pushing a cold front into the Mid Atlantic region Thursday afternoon and evening. Moisture return will be limited in west to southwest flow aloft, with precipitable waters progged around one inch. Best dynamics also expected to pass north of the region, but sufficient height falls and winds aloft will provide forcing for ascent along the cold front for chance to solid chance POPs south to north across the forecast area through Thursday night. Highs Thursday range from the low 60`s northwest to upper 60`s southeast under a partly cloudy to mostly cloudy sky. High pressure builds into the region Friday, with only a slight chance for precip lingering along the coast. Highs generally in the mid to upper 60`s. Confidence decreases thereafter as medium range guidance struggles to handle the evolution of the next northern stream disturbance. GFS is generally more progressive with the late week system, pushing it quickly offshore Friday night/Saturday. ECMWF suggests cyclonic flow will linger over the Northeast into Saturday. The main difference becomes the next trough that will impact the region late in the weekend into early next week. The associated cold front will impact the region late weekend into early next week. For now, will introduce only slight chances for precip Saturday night through Sunday night across the north to northeast forecast area. Saturday looks to be the warmest day with highs in the upper 60`s to around 70. Highs Sunday generally in the mid to upper 60`s. Mild overnights are forecast Thursday night through Saturday night, with lows generally in the mid/upper 40`s to low 50`s. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... High pressure over the Southeast states and low pressure in Canada north of Maine were controlling the weather over the Mid Atlantic States Sunday evening. A cold front extending from low pressure over southeast Michigan to the central Great Plains will cross the Mid Atlantic States during the day Monday. High pressure will then build into the region from central Canada and provide a reinforcement of Continental Polar air. Dry weather will prevail during the 00Z TAF period with the development of some mid level clouds possible during the day Monday across northern portions. Otherwise...a clear sky and unlimited visibility are expected. Southwest winds will become northwest behind the aforementioned cold front. OUTLOOK...Dry and VFR conditions can be expected through Wednesday. Fog will be possible Thursday morning as high pressure oves off the coast and moisture increases over the area. Another cold front crosses the area Thursday night bringing a chance of showers. Dry weather returns for Friday. && .MARINE... Latest surface analysis centers high pressure over the Gulf states and low pressure over southeast Canada. The resultant gradient over the local area has kept SCA conditions ongoing this afternoon in the Bay. Few westerly gusts to 25 knots observed this afternoon over the northern coastal waters, but the remaining coastal waters have diminished below 20-25 knots. Seas 2-3 feet. Gradient ramps back up again tonight with winds a few thousand feet aloft increasing to 30- 40 knots. While mixing will not be optimal thanks to warm air advection, still expect west to southwest winds of 15 to 25 knots. Gusts to 30 knots expected upper Bay and northern Coastal waters. Have included the Currituck Sound and lower James River. Solid 15 knots expected remaining river zones. Seas build back to 3-5 feet, upwards to 6 feet northern coastal waters out 20 nm. Waves 2-4 feet. Pressure gradient relaxes briefly Monday afternoon as a cold front approaches, and crosses the waters Monday afternoon. Expect another northwest surge late Monday through Monday night with a northwest wind of 15 to 25 knots. Seas 3-5 feet and waves 2-4 feet. High pressure builds in from the northwest Tuesday, with sub-SCA conditions expected through mid week. The next cold front pushes across the waters on Friday/Friday night. && .TIDES/COASTAL FLOODING... Strong west to southwest winds have resulted in negative tidal departures/blow out tides in the middle to lower Chesapeake Bay and the Atlantic coastline. Departures range from -0.7 to -1.2 feet. Low water conditions will be approached during tonight`s low tide cycles, with locations in the lower Bay and coastal regions possibly reaching low water conditions during low tide Monday morning. Will hold off on any advisories at this time and continue to watch the trends. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ630>632-634- 650-652-654-656-658. Small Craft Advisory until noon EDT Monday for ANZ633-638. && $$ SYNOPSIS...AJZ/LKB NEAR TERM...AJZ/MAM SHORT TERM...AJZ/LKB LONG TERM...SAM AVIATION...LSA MARINE...SAM TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.