Area Forecast Discussion
Issued by NWS Wakefield, VA

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799 FXUS61 KAKQ 231933 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 333 PM EDT Thu May 23 2019 .SYNOPSIS... High pressure settles off the Southeast coast through tonight as low pressure passes north of the region. This area of low pressure drags a weak cold front through the area late tonight. High pressure builds in from the northwest Friday and then passes over the region Saturday, and then shifts off the Southeast coast Sunday and Memorial Day. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 340 PM EDT Thursday... Severe T-Storm Watch 219 in effect for northern tier of counties along and north of I-64 through 00z/8pm EDT. Shortwave trough evident on early aftn IR/VIS satellite sliding across the upper Great Lakes this aftn, and has allowed a narrow line of convection to re-develop across northern VA/SE PA. Best forcing/kinematics for strong to severe tstms remains just to the north W/Central MD to SE PA/S NJ later this aftn in a zone of 40-50kt 500mb flow and 35-45kt 700mb flow. WW219 now in effect for far northern tier of counties. MLCAPE on the order of 1000-1500 J/kg over this area, with CU just beginning to develop as convective temperatures just being reached over the past hour or so. Any tstms that do reach the area will be capable of locally damaging wind gusts and (secondarily) large hail. PoPs are mainly 20-30% from about 20z/4p- 04z/Midnight. Gradual clearing tonight as drier air arrives late tonight in association w/a weak cold front dropping across the area. A few showers may occur coinciding with the frontal passage. Otherwise, becoming mostly clear late w/early morning low temperatures late tonight range from the upper 60s to low 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/... As of 340 PM EDT Thursday... No major changes to forecast rationale for the near term period, with weak high pressure building in from the north behind the front for Friday. Still rather warm, but a bit drier across the area, as high temperatures range from the low 80s over the Ern Shore (upper 70s immediate Atlantic coast), to the upper 80s/low 90s in downsloping deep layer NW flow. Aftn dewpoints drop into the low/mid 50s. Could have some aftn Cu/Stratocu in association with a weak disturbance. However, warm/dry soundings should preclude any pcpn Fri/Saturday. Latest numerical guidance depicts somewhat of a reprieve from the anomalous heat Saturday, as high pressure passes across the region resulting in E-SE low-level flow along the coast, and SE-S flow farther inland. Forecast highs Saturday range from the low/mid 70s E (cooler along the immediate Atlantic coast of the Ern Shore) to the low/mid 80s farther inland, after morning lows in the upper 50s to mid 60s. By Saturday evening, there is a slight chc of showers/tstms drifting off the higher terrain into the Piedmont. Heat is back on for Sunday...which has the potential to be the hottest day of the Spring thus far across our region. Surface high pressure slides well off the Southeast coast as low pressure moves into the Ern Great Lakes. This will result in W-SW low-level flow, which will help boost high temperatures into the low/mid 90s inland, with upper 80s over the Ern Shore, and even mid 80s at the immediate Atlantic coast. Lows Sunday morning range from the mid 60s to around 70F. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 230 PM EDT Thursday... Summerlike/temperatures remaining above normal through the extended forecast period. An upper level anticyclone remains centered along the Gulf Coast early next week before expanding eastward into the western Atlantic by midweek. Our region will be under the influence of W-NW flow aloft thru Tuesday, then SW flow aloft Wed-Thu. A weak frontal boundary crosses the area Sun night and Monday, but with only isolated showers/tstms possible Sun night. The boundary lifts back NE quickly early Tues with little if any forcing for convection leftover by afternoon under the influence of SSW flow at the sfc and rising H5 heights. Other than a late-day tstm possibility near the Piedmont trough, Wednesday looks dry also. Wednesday also looks to be the hottest day next week as H85 temps rise to 20-22C with deep- layered SW flow ahead of the next potential cold front by next Thursday. Lows through the period in the 60s to low 70s, except some mid 70s possible Wed night. Highs Mon in the 80s over the lower Ern Shore to the low 90s inland. Highs Tue from the mid-upr 80s over the Ern Shore to the low 90s inland. Forecast highs on Wed are in the upper 80s to low 90s lower Ern Shore to the low-mid 90s inland. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 155 PM EDT Thursday... High pressure is centered off the coastal Carolinas/lower Mid- Atlantic coast this aftn. Vis radar imagery showing some SCT-BKN stratus S-SW of KRIC this aftn, which should continue to dissipate and move offshore over the next few hours. Main operational issue is with MCV sliding from the nrn/central Appalachians toward the Mid-Atlantic this aftn. SCT CU are expected to develop by mid to late aftn, with increasing rain chances after 20z as convective line approaches this aftn. A 20-30% chc of showers/tstms (primarily from RIC- SBY and N) after 22z/6pm and continuing through 04z/midnight EDT Friday as a trough pushes across the region in NW flow aloft. Tstms could produce locally stronger wind gusts along with reduced vsby in brief heavy rain. Have maintained a tempo group at SBY...but low areal coverage at RIC and pts south/southeast will continue to preclude mention in the remaining TAFs for now. Outlook: Mainly dry conditions are expected Friday through the Memorial Day Weekend, as weak high pressure prevails over the region. There is a low probability of ISO showers/tstms Sunday evening along and N of a line from RIC-SBY. && .MARINE... As of 300 PM EDT Thursday... SCA is up from 7pm Thurs to 7am Fri for our northern ocean zones. Winds this afternoon will continue to be 15-20kt (gust up to 25 kt) for the Ches Bay and northern Atlantic zones (lasting into tonight for ocean). Waves in the bay will be 2-3 ft and decreasing tonight. For the Atlantic zones off the Eastern Shore, seas will build into this evening up to 5 ft (warranting SCA). High pressure will move in overnight and winds and seas will decrease. Friday afternoon there will be a surge of wind NW 15-20 kt across the northern zones as a low deepens off the southern New England coast. A series of high pressures will be moving into the area through the holiday weekend and into next weekend. There will be periods of stronger southerly winds (around 15 kt) through the extend forecast. However, it looks like winds and seas will stay below SCA criteria through Monday. && .CLIMATE... * Avg Date of 1st 90F (1981-2010 Climatology): * Site Avg 2019 Value * Richmond: May 13th (Sun 5/19) * Norfolk: May 16th (Sun 5/19) * Salisbury: May 27th (none so far) * Eliz City: May 18th (Sat 5/18) * Number of Days of 90F+ in May: * Site Avg Most * Richmond: 2 days 11 days (1962) * Norfolk: 2 days 13 days (1880) * Salisbury: 1 day 7 days (1991) * Eliz City: 2 days 9 days (1944 & 1941) && .EQUIPMENT... As of 320 PM EDT Thursday... KAKQ 88D radar is back online. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 7 PM this evening to 7 AM EDT Friday for ANZ650-652. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...AJZ/MAM LONG TERM...ERI AVIATION...AJZ/MAM MARINE...CP CLIMATE... 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