Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 240803 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 403 AM EDT SAT SEP 24 2016 .SYNOPSIS... A backdoor cold front drops south across the region Today. High pressure tracks across Southeast Canada early next week. A second, stronger cold front will cross the region later Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Latest analysis features strong 1026+mb high pressure over Ontario into the Upper Great Lakes. Subjective wx analysis places weak cool frontal boundary from Southern New Jersey back into the Mason-Dixon line and the lower Ohio Valley early this morning. Meanwhile, weak ~1018mb high pressure is in place across the region. Aloft, prominent upper level ridging remains in place, centered across the mid-south and Mississippi River Valley. this is keeping PW values suppressed in the 1-1.25" range across the region per early morning Blended TPW sat product. Have noted some areas of ground fog, dense in spots along the southern tier of the forecast area. Will likely have to handle with a round of targeted statements this morning, but otherwise expect fog and any lingering stratus to get mixed out quickly after sunrise this morning. After fog scours out, expect a partly to mostly sunny start, with clouds quickly increasing across the northern tier of counties from Late Morning through the aftn as the front drops across the area. Winds shift to the N-NE during this timeframe. High-res models resolute in showing an area of rather shallow lift along the front as it drops across the southern half of the area from late aftn through about midnight. Have accordingly kept the forecast dry through the day, introducing some sct showers tonight, mainly across the piedmont and I-85 corridor. QPF will be minimal with still relatively dry air aloft. and only weak isentropic lift. Thickness tools and Conshort/HRRR basically identical wrt temps, producing highs in the mid to upr 70s eastern shore...low to mid 80s RIC metro...and mid to upper 80s far SW zones. Front drops south of the area late tonight, with sct showers along the boundary likely lingering into the morning hours. Clouds will be on the increase post-frontal, especially inland with post frontal nne flow as high pressure ridges down and cool air wedge begins to set up. Accordingly beefed up sky cover tonight and into Sunday. Lows Sat night in the mid 50s north to mid 60s south. && .SHORT TERM /SUNDAY THROUGH MONDAY/... Front continues to push south into the Carolinas Sunday in response to high pressure sliding across Southeast Canada. This high extends south across the Mid Atlantic Region Sunday and Sunday night. Latest data continues to focus on increasing low level moisture and weak isentropic lift Sunday and Sunday night. The depth of moisture remains rather shallow...favoring only low end pcpn chances for pockets of light rain or drizzle mainly along and west of the I-95 corridor. Kept slight chc pops (stratiform rain rather than showers) across the Piedmont. The onshore flow results in mostly cloudy/overcast skies for areas mainly west of the Bay during this same time and partly cloudy for the Eastern Shore. Highs Sun 70-75. Lows Sun night in the mid 50s to lwr 60s. If it clears early enough...SBY could drop to near 50 by 12Z Mon. High pressure moves north of New England Monday with the next front approaching from the west during the afternoon. Slight chc showers across the Piedmont ahead of the front. Onshore flow and clouds keeps it cool with highs in the low to mid 70s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Medium range period has become somewhat clearer with the latest 12Z model suite trending further into at least modest agreement. There are still significant timing differences that exist regarding a cold frontal passage Tue into early Wed followed by a large area of High pressure building into the local area from the west as an upper level trough becomes centered over eastern Canada and the NE CONUS/New England Tue/Tue night, then shifts off the E coast by Thu. Have raised POPS Tue/Tue night to 30-40% with the front, along with a chc for tstms Tue aftn/evening. Beyond that, will linger 20-30% POPS mainly along the coast Wed in case the front trends slower, with mainly dry conditions expected Wed night through Fri. Temperatures will avg close to seasonal averages, with highs Tue ranging from the mid 70s NW to around 80 F S/SE (where more sun may occur ahead of the front). Highs Wed-Fri generally in the 70s with lows in the 50s, except in the 60s SE. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... Mostly clear skies this morning as weak high pressure slides over the area. Given light winds and still wet grounds, noting areas of low Stratus/fog across the SE coastal plain, impacting KECG, and eventually KSBY and KPHF after 08z. Expected low clouds/fog will scour out quickly after sunrise this morning, improving quickly from LIFR/IFR at ECG to MVFR/VFR after 14z. Thereafter, primarily VFR conditions expected. A backdoor cold front drops across the area through the day Saturday...primarily spreading widespread high clouds across the area during the day. Given the abundant/recent rainfall from the past several days and persistent onshore/ne winds, expect SCT cumulus to develop during the aftn...especially near coastal sites. KSBY will likely experience MVFR cigs given frontal timing, and Hi-res models continue to support VFR farther inland. Could see some Sct showers west of KRIC after 21z this aftn, but minimal support for pcpn at terminals with plenty of dry air in place aloft. The front pushes south of Albemarle Sound after midnight Saturday night with stronger central high pressure sliding across Southeast Canada and building down into the Mid Atlantic Region through Sunday night before sliding off the New England coast early next week. Areas of fog and some low stratus expected once again across the southern terminals late Tonight into early Sunday morning. Outlook... Cigs trend back toward VFR for most locales along the coast as cool air wedge sets up across the piedmont. Lingering low clouds/light rain possible at KRIC and west. && .MARINE... Latest obs continue to depict diminishing NE flow across the waters, generally 5-10 KT. Seas avg 3-4 ft with 10-12 second dominant periods and wave in the Bay are 1-2 ft. Trends are slower with the approaching cold front from the N later tonight into Sat, now the winds tonight will avg 5-10 Kt or less and gradually shifting to the SSW after midnight. On Sat, front progged to push through the waters from N to S, pushing into NC by late afternoon. Did not raise SCA headlines as winds should stay below thresholds, but there will probably be about a 3 hr period with occasional gusts to 20 KT. Waves in the Bay should build to 2-3 ft by late morning/early aftn and to 2 ft in the rivers so still not ideal boating conditions even without headlines (may need to issue an MWS). For the coastal waters, distant tropical Cyclone Karl Invof Bermuda looks to aid in seas building to 4-5 ft. Trends in wavewatch are slower and slightly weaker however, so did not issue SCA headlines as this is marginal and will be late 2nd period (will allow next shift to determine if seas ever do reach a widespread 5 ft). Wavewatch and NWPS both depict seas subsiding once again for Sunday through Sunday night. Next cold front approaching from the NW will shift winds back to the SE on Mon and increase from the S Mon night/Tue. Still some models differences/uncertainties but could see marginal SCA conditions in the Bay Mon night/Tue and probably will have SCA conditions behind the front sometime midweek as significantly cooler airmass and strong high pressure builds in from the NW. && .HYDROLOGY... The Cashie River at Windsor continues to fall but remains in the moderate flood range. The river is forecast to slowly fall below flood stage late Sunday night. See FLSAKQ for details. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...MPR/MAM LONG TERM...LKB AVIATION...MAM MARINE...LKB HYDROLOGY... is the U.S. government's official web portal to all federal, state and local government web resources and services.