Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 211759 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 159 PM EDT Fri Oct 21 2016 .SYNOPSIS... A cold front will mainly cross the area this afternoon into early this evening. Breezy northwest winds will develop later tonight and continue through Saturday. Otherwise, cool and more seasonable conditions will persist tonight through next week. && .NEAR TERM /THROUGH TONIGHT/... A vigorous upper trough digs over the Ohio Valley today and effectively slows the ewd progression of the approaching sfc low/cold front expected to cross the area today. Have delayed the onset of precip in wrn portions of the area until later this morning/early aftn once isentropic lift begins to enhance precip generation along the frontal boundary. Although ample vertical and directional shear is present across the region today, cross sections continue to show a lack of lift/omega aloft (much less through the hail growth zone) with a 100kt jet streak still located well behind the cold front. Therefore no mention of thunder remains based on latest model analysis. Despite the slower start to precip, expect rainfall to increase from west to east through this aftn/early evening. Overall storm total precip values totals will be rather light... still ranging from 0.10-0.30 inches (highest amounts across the north where the better dynamics are located closer to the parent low). Rain comes to an end tonight within an hour or two of the frontal passage as a cold Canadian high builds into the region behind the front. Meanwhile, a coastal low NNE of the Bahamas (possibly becoming a tropical cyclone) slowly tracks northward...staying well offshore. The interaction of the passing cold front with the coastal low (they are expected to merge tonight) and the incoming cold Canadian high pressure will significantly tighten the sfc pressure gradient beginning this aftn. Strong W-NW winds will develop quickly this evening... mainly due to the strong upper trough swinging through the area (accompanied by a 100kt jet streak) and strong cold air advection occurring as well. Winds will be highest along the coastal areas of Ches Bay and the Atlantic Ocean where sustained winds will average 20-25 mph with gusts of 30-35 mph. Gusts may be as high as 40 mph along coastal areas of the Nrn Neck and MD/VA Eastern Shore. Will highlight these areas within the HWO. Farther inland, gusts will average 20-25 mph. Temperatures will be at to about 5-7 degrees above seasonal normals with highs in the mid-upper 70s (low-mid 70s beaches). Once cold air advection processes commence tonight, temps will plummet to more seasonal values with lows in the mid-upper 40s (around 50 degrees far sern coastal areas). Thankfully, the well-mixed environment tonight will keep lows from dropping to their fullest potential. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Strong upper trough swings into the region on Saturday and exits the region Saturday night. A tight sfc pressure gradient, strong cold air advection, and strong jet streak nosing through the area on the back side of the upper trough (100-120kt) will all contribute to the following conditions for Saturday: 1. Strong W-NW winds persisting through Saturday. Sustained winds across the area will average 20-25 mph. At the coast, expect wind gusts of 30-40 mph. Farther inland, gusts will average 25-30 mph. 2. Much cooler temperatures that will run 5-10 degrees below normal. Expect highs in the lower 60s. And near normal lows Saturday night in the low-mid 40s (45-50 possible at far SE VA/NE NC beaches). 3. Dry weather conditions under mostly clear skies. For Sunday...dry and sunny conditions will continue as west winds start to slacken. Gusts should average 25-30 mph at the immediate coast. High temperatures slowly rebound into the mid 60s as westerly/zonal flow develops aloft. Sfc winds become more southwest Sunday night, which will contribute to warmer overnight lows ahead of an Alberta Clipper type system approaching the region. Expect lows around 50 degrees. && .LONG TERM /MONDAY THROUGH THURSDAY/... High pressure settles across the sern states Sat night and Sun as intense low pressure moves into eastern Canada. Dry with slowly diminishing winds Sat nite. Lows in the low to mid 40s except upr 40s to lwr 50s sern coastal areas. Highs Sun in the mid 60s. Lows in the upr 40s to lwr 50s. Next cold front crosses the region Monday. No significant moisture noted so expect a dry fropa. CAA lags so expect a milder day with highs in the upr 60s to lwr 70s. Lows in the 40s except lwr 50s sern coastal areas. Canadian high pressure builds across the area for the mid week period. Remaining cool and dry. Highs Tue 60-65. Lows in the 40s to lwr 50s sern coastal areas. Highs Wed in the 60s. Lows in the mid 40s to lwr 50s. Low pressure progged to move from the nations mid section Wed to the Gt Lakes region Thurs. Limited moisture returns in advance of the approaching warm front. Added slight chc pops Thu across the northern half of fa with this feature. Highs 65-70. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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A cold front is approaching from the west this afternoon and is located over the VA piedmont as of 18z. A broken line of shra has developed ahead of the boundary, and could clip RIC through 19z. Otherwise, the front will push across the region this afternoon into early evening. Shra are expected to increase in coverage behind the front as additional energy arrives from the sw later this afternoon and evening. The onset of -shra will likely occur after 22z for SBY/PHF/ORF/ECG. Overall, pcpn is not expected to produce much of a vsby restriction, with the exception of only very brief restrictions in the leading line of shra. Cigs are expected to drop to mvfr in the wake of the boundary and could briefly drop to ifr at SBY later this evening. Drier air gradually arrives from the west later tonight through midday Saturday with cigs lifting from w-e then scattering through 18z Saturday. A nw wind will increase to 15-20kt late tonight into Saturday, with gusts up to 25-30kt, and locally up to 35kt at SBY. High pressure builds across the Southeast Saturday night into Sunday. A (dry) cold front sweeps across the area Monday, with high pressure returning Tuesday and Wednesday.
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&& .MARINE... Generally benign conditions early this morning with winds of 10 KT or less and seas 2-3 ft/ waves 1-2 ft or less. Significant changes are coming later today and tonight however, and all zones remain either in Gale or SCA headlines. As noted by last shift, the real CAA surge is not expected to arrive until later tonight into Sat morning. Given rather sharp pressure rises behind the front, 925-950 MB winds between 35-40 kt, falling H85 temps and water temps arnd 70 F, confidence remains high that enough mixing occurs to support Gales for the Bay and coastal waters, with strong SCA`s and frequent gusts a little over 30 KT for the Rivers and Currituck Sound. Strongest gusts up to 40 KTS looks to be across the northern waters with gusts to 35 KT across the south. Probably a secondary surge/increase in mixing Sat evening and with this in mind have extended the Gale Warning for the coastal waters N of Parramore Island until 10 pm Sat. As the event unfolds, may need to extend portions of the Bay into Sat aftn as well but in general the strongest winds look to occur from midnight-noon Sat so left them as is for now. The offshore NW flow will keep seas from building to much higher than 5-7 ft most areas (highest out 20 NM offshore). Bay waves build to 4-5 ft. Winds remain elevated on Sunday but should diminish to some extent and avg 15-20 KT. The next front crosses the area Mon. Appears another surge (albeit much weaker) will likely require SCA headlines late Monday or Monday night. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 6 PM this evening to 4 AM EDT Sunday for ANZ633-635>638. Gale Warning from 8 PM this evening to 4 PM EDT Saturday for ANZ630>632-634-654-656-658. Gale Warning from 8 PM this evening to 2 AM EDT Sunday for ANZ650-652.
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&& $$ SYNOPSIS...BMD NEAR TERM...BMD/MAS SHORT TERM...BMD LONG TERM...MPR AVIATION...AJZ MARINE...LKB is the U.S. government's official web portal to all federal, state and local government web resources and services.