Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 201958 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 358 PM EDT Fri Oct 20 2017 .SYNOPSIS... High pressure remains over the Mid Atlantic region through the weekend...with temperatures gradually warming. The next cold front is expected to impact the region Monday night and Tuesday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Sfc high pressure centered over the Ohio Valley is providing another sunny and pleasantly warm late October day. As we head into this evening, the sky remains clear with comfortable temperatures. Clear and seasonable tonight, except patchy/areas of fog late. Lows from 45-50F inland...to the low/mid 50s at the immediate coast. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... High pressure sfc-aloft remains anchored invof FA through Sat...then slowly shifts off the coast Sat night-Sun. Other than possible patchy/areas of FG Sat night...dry-continued seasonably warm wx expected Sat-Sun. Highs Sat in the mid/upr 70s...low 70s right at the coast. A few more clouds possible by Sun afternoon as the low level flow becomes more SE ahead of the next cold front (which will be entering the OH-TN valleys late)- so may become partly sunny vs mostly sunny. Lows Sat night in the upr 40s to low 50s inland to the mid/upr 50s at the coast. Highs Sun ranging through the 70s. By Monday, low pressure deepens over the Deep South/lower MS Valley while a strong upper ridge remains in place along/just off the East Coast. ECMWF and GFS showing some subtle timing differences with respect to how quickly the precip from the southern low is able to spread east into the Mid-Atlantic. Based on 12z suite of models, have trended precip arrival a bit slower on Monday, favoring just slight chc PoPs (~20%) across the Piedmont toward evening. Clouds will be on the increase from west to east Monday. Highs again the the mid/upr 70s, after morning lows in the 50s to low 60s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Still a lot of uncertainty as to how next weeks system plays out as models offer up different timing and moisture field solutions. What is agreed upon is that a full latitude trof will move across the region Tue, what is yet to be determined is the scope and track of several s/w`s embedded in the trof and timing of a cold frontal passage across the area. GFS slower/much wetter as copious amounts of GOM moisture gets transported north ahead of the front. ECMWF faster/drier with the fropa with a dry slot cutting the pcpn off. Decent low level jet and theta-e advection progged ahead of the front for at least some instability to develop. Went ahead and bumped up pops to between 70-80% late Mon night and Tue with pcpn ending west to east Tue night as the deepest moisture pushes offshore. Added moderate rain and slight chc thunder for Tue for now. Later shifts can adjust as needed. Warm and humid Mon nite with lows in the 60s. Breezy Tue with highs 70-75. Cooler Tue nite with lows in the upr 40s west to upr 50s along the coast. Slight chc pops Wed as upr level energy lingers. Cool with highs in the low to mid 60s. The upr level low lifts NE Thu allowing high pressure to build across the southeast. Dry Thurs and Fri. Highs Thurs in the low to mid 60s. Lows in the 40s. Highs Fri 65-70. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... Sfc high pressure remains invof of the area through midday Sat. Potential for patchy FG by late tonight/early Sat morning under light winds, especially KECG/KSBY/KPHF. Sfc high pressure slides farther offshore Sun...w/ a cold front expected to push across the local area late Mon night through Tue (resulting in at least periodic sub-VFR conditions in RA/lowering CIGs likely. && .MARINE... A weak sfc cold front has pushed off the New England coast, and winds over the local area have shifted to the N to NE at around 10 kt. Bay waves are 1-2 ft with coastal seas of 2-3 ft on avg. Tonight, a broad area of sfc high pressure over the region will allow for generally benign conditions over the waters and waves in the Bay and rivers should be 1 foot or less except for 1-2 ft at the mouth of the Bay with coastal seas of 2 to 3 feet. Light ENE flow will prevail on Sat, shifting to the ESE on Sunday, with favorable boating conditions as wind speed will mainly avg 5-10 kt. The next chance for significant weather over the waters does not come until early next week as a strong cold front approaches from the west on Monday and slowly crosses the waters on Tuesday. The pressure gradient will lead to increasing southerly flow ahead of the front later Monday into Tuesday, shifting to the WNW behind the front Tuesday night into Wednesday. Small Craft Advisories will likely be needed for most or all of the area Mon night/tue as the pressure gradient should be strong enough for winds of 15-25 kt with higher gusts. Coastal seas build to 6-9 ft with waves of 3-5 ft in the Bay likely. A fair amount of uncertainty remains Tue night/Wed regarding how strong the pressure gradient will be as the models tend to keep the cold air and strong winds off to our NW over the Great Lakes until Thu. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...JDM NEAR TERM...JDM SHORT TERM...JDM LONG TERM...MPR AVIATION...ALB/JDM MARINE...LKB

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