Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 292100 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 400 PM EST Sun Nov 29 2020 .SYNOPSIS... High pressure slides off the Mid-Atlantic coast this evening. A strong storm system will affect the region late tonight into Monday afternoon. High pressure builds back in from the southwest late Tuesday through Wednesday. && .NEAR TERM /THROUGH MONDAY/... As of 355 PM EST Sunday... ...Overview... Only minor changes needed to the going forecast, with the local area still on track for a period of active weather tonight and tomorrow. Latest upper air analysis reveals a broad upper level trough diving south across the northern plains/northern MS Valley. Meanwhile, to the west, an upper level low continues to slide east across the Red River Valley into the Texarkana region. Sfc low pressure was noted over the central Gulf coast, with a wavy stationary front draped E-NE across the Florida panhandle. A broad swath of light to moderate overrunning precipitation Previously referenced sfc reflection lifts N-NE across the mid- south tonight, then along the spine of the Appalachians overnight into midday Mon, before reaching western PA and NY Mon aftn & early evening. First slug of overrunning showers lift SW-NE across the area after 7pm tonight, and rain chances steadily increase across the area this evening. The warm front lifts across the area after midnight tonight through Monday morning. Temps initially falling off tonight become steady or slowly rise overnight, with PW also ticking up overnight on steadily increasing S-SW flow. Rain will be moderate to locally heavy at times overnight, but begins to taper off before sunrise Mon, as a mid- level dry slot pushes in from the S-SW. ...Severe Potential/Gusty Winds... Conditional threat for strong to locally severe storms continues. Primary threat will come from low-topped showers and embedded elevated T-storms. Deep-layer shear values ramp up to 50-70 kts late tonight and Mon morning, as well as a strong LLJ nosing in late tonight and early Monday morning with the area in the warm sector preceding the sfc cold front. As is typically the case, instability will be a limiting factor. That said, given T/Td warming quickly into mid to upper 60s in the warm sector, expect at least 500-1000 J/kg of MLCape over our SE coastal counties. The greatest threat seemingly remains along/east of US-13 over the coastal plain after sunrise Monday morning. SPC has continued a Slight Risk over this area for Monday, with a Marginal Risk for the remainder of the local area. Storm mode favors quick-moving multicells/bowing segments producing strong to locally severe wind gusts and perhaps a discrete cell or two given favorable kinematics. This also brings up large, curved hodographs that portend potential for a tornado or two over this same portion of eastern Tidewater for the mid to late morning into Monday afternoon. Outside of the eastern Tidewater area, cool air wedge gradually breaks down late tonight/early Monday morning. Overrunning light to moderate rain pushes in tonight, with some patchy fog likely ahead of the warm front. A narrow, well-forced line of showers preceding the front will likely bring a quick surge of winds across the piedmont and Richmond metro area by late morning/early afternoon, pushing across the northern neck and eastern shore by mid afternoon. Wind gusts of 25-35 MPH (inland) and 35-45 mph (coastal areas) are expected post-frontal. A Wind Advisory has been issued for the lower eastern shore counties for Monday. Coastal portions west of the Ches Bay from Northumberland County, VA down to Currituck NC are close to criteria and will bear watching for potential extensions to the Wind Advisory. However for now, local wind probs are most supportive of 50+mph gusts on the eastern shore, so will confine there. Will continue HWO mention for the gusty winds and severe potential. ...Heavy Rainfall... As far as QPF goes, storm total QPF amounts look to avg 1.00 to 2.00" (most of it prior to Mon aftn with a few rounds of overrunning rains. Locally higher amounts will be possible given convective elements ahead of the front during the day Mon. However, no significant concern for flash flooding given expected very progressive convection late tonight and tomorrow. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 345 PM EST Sunday... Sfc low lingers across the eastern Great Lakes as it occludes Monday night. The attendant cold front slides through the remainder of the area early Monday evening then offshore, with a reinforcing shot of cool air coming with the parent upper trough crossing after midnight Monday into Tuesday. Therefore, clearing conditions across the area Monday night will yield another-lived increase in clouds late Mon night/early Tue morning. Some scattered showers will also be possible during this period, though QPF would be on the order of a few hundredths at the most. Lows Mon night in the mid 30s to low 40s. Otherwise, cool (albeit quickly modifying) Canadian airmass overspreads the region, bringing a few dry days through midweek. Subsidence on the back side of the departing trough should bring quick clearing later Tuesday morning into Tue night. Despite plenty of sunshine, thickness tools only yielding highs in the low to mid 40s. Downslope drying will help negate that to a small degree, but continued breezy and cooler any way you cut it. Highs Tue in the mid to upper 40s, to ~50F along the coast. Becoming clear to mostly clear and cold Tue night with winds finally laying down and allowing lows to plummet into the upper 20s to mid 30s. High pressure builds across the southeast Wednesday, with temperatures moderating slightly into the upper 40s to low 50s, under a sunny to mostly sunny sky. Cold once again Wed night with lows in the 20s inland to near 30 at the coast. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 210 PM EST Sunday... Medium range period begins cool and dry, with 1028+mb sfc high pressure over the area on Thursday, before it slides offshore into Friday. Temperatures will be near or just below climo normal, with highs in the 50s. Not quite as cold Thu night in developing return flow with early morning lows in the mid 30s to low 40s. Pattern transitions to a more active period late in the week into next weekend, ahead of another developing potent mid/upper level trough diving across the Canadian Prairies into the High Plains Wed night/Thursday, which both deterministic runs and the member ensembles evolve into a positively- tilted upper trough by Friday night. However, the synoptic/sensible wx details are a bit more in the air. Given the positively-tilted trough, have favored the weaker/more progressive NAEFS/GEFS solution for now...which would bring another round of overrunning precip Friday into Saturday. Have maintained a slight to low-end chance PoP at this time during this period. Cold front should cross behind these showers, with drier conditions settling in for the latter half of the weekend into early next week. Temperatures start off cool, but moderate back toward/above climo by the end of the period ahead of the next approaching cold front. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... As of 1235 PM EST Sunday... VFR conditions expected to continue through the daylight hours today into the first part of tonight. High/mid clouds will be on the increase this afternoon and evening as a potent storm system approaches the region from the SW. Mainly SE winds this afternoon and evening at around 5 to 10 knots. Conditions deteriorate later tonight into Monday morning as the storm system lifts along the Appalachian mountains. Rain showers and low ceilings overspread the region from the SW generally after 03z. MVFR ceilings are expected at all TAF sites later tonight with IFR conditions possible at RIC and SBY by Monday morning. Heavier rain showers will also have the potential to restrict visbilities at times. Finally, there will be a threat of thunderstorms, especially ECG/ORF, after sunrise into Monday afternoon that will have the potential to produce strong wind gusts. S to SW Winds increase through tonight into tomorrow morning with gusts to 30 knots+ possible at times, especially near/along the coast. Conditions gradually improve later Monday afternoon into Monday evening. Outlook: Clearing out back to VFR, as pcpn ends late Mon aftn into Mon night, though remaining breezy to windy through Mon evening. Another brief period of sub-VFR conditions are possible early Tue, as the upper low slides across the region. Clearing out again and remaining breezy on Tue, with VFR conditions likely Tue through Thu. && .MARINE... As of 355 PM EST Sunday... High pressure moves offshore this evening ahead of a strengthening low pressure system currently in the Deep South which will affect the local waters tonight into tomorrow. Winds are currently SE around 5 to 10 kt and will increase to 10 to 15 kt early tonight. Seas remain ~2ft and then build to 2-3ft this evening, while waves in the Bay are around 1 foot (1 to 2 feet near the mouth of the bay) and will build to 1-2 ft this evening. The aforementioned area of low pressure deepens as it races northeastward along the Blue Ridge later tonight into tomorrow morning, and then into PA/NY by tomorrow afternoon, with the associated cold front nearing the Mid-Atlantic coast by late tomorrow afternoon/evening. Strong pressure falls on the order of -12 to -15mb/6hr are expected in the 06z-12z and 09z-15z timeframe late tonight into tomorrow morning. This will combine with a 55-65kt SSE LLJ bringing the potential for a 3-6hr period of gale conditions in a SSE wind primarily late tonight into tomorrow morning. Seas build to 7-12ft tomorrow, with 3-5ft waves in the Bay, and potentially up to 6ft in the southern Bay. Gale warnings go into effect for the ocean, Ches Bay, lower James, and Currituck Sound tonight. The gale flags for the Bay and ocean S of Parramore Is. are in effect from 2 am to 1 pm Mon, 5 am to 4 pm Mon N of Parramore Is., and from 2 am to 10 am Mon for the Sound and lower James. SCA flags have been raised for the remaining river zones from 2 am to 7 pm Mon. The wind becomes SW 20-25kt by early Monday aftn, then 15-20kt later in the aftn. The cold front will push across the coast tomorrow night, with a CAA surge beginning early Tuesday morning and continuing into Tuesday night, with a WSW wind of 15-25kt. SCA conditions are likely to linger into at least Wednesday morning due to a combination of elevated seas and winds. The wind gradually subside to 10-15kt Wednesday into Thursday as high pressure settles in vicinity of the Southeast coast. Seas/waves will continue to subside during this time-period. && .TIDES/COASTAL FLOODING... As of 355 PM EST Sunday... A strong area of low pressure is progged to track along the spine of the Appalachians late tonight into Monday with a cold front crossing the area Monday evening into the first part of Monday night. A strong SE-S wind is expected overnight into Monday aftn. This will cause tidal anomalies to increase, especially across the mid/upper Chesapeake Bay (and perhaps the Atlantic coast of VA). While astronomical tides are not that high, nuisance to perhaps minor tidal flooding is possible across these areas during high tide cycle Monday afternoon with tidal departures on the order of 1.3-1.5ft above astronomical. Lingering nuisance tidal flooding is possible across the Bay side of the MD Ern Shore Tuesday as winds turn to the SW following the cold front. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Wind Advisory from 6 AM to 6 PM EST Monday for MDZ021>025. NC...None. VA...Wind Advisory from 6 AM to 6 PM EST Monday for VAZ099-100. MARINE...Small Craft Advisory from 2 AM to 7 PM EST Monday for ANZ635>637. Gale Warning from 2 AM to 1 PM EST Monday for ANZ630>632-634- 654-656-658. Gale Warning from 2 AM to 10 AM EST Monday for ANZ633-638. Gale Warning from 5 AM to 4 PM EST Monday for ANZ650-652. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...MAM/TMG LONG TERM...ERI/MAM AVIATION...AJB MARINE...AJZ/RMM TIDES/COASTAL FLOODING...

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