Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 211818 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 118 PM EST Sat Jan 21 2017 .SYNOPSIS... High pressure over the area this morning will weaken and slide offshore later today as a frontal boundary stays just off to the south. Low pressure over the nations mid section will intensify as it slowly tracks east across the Mid Atlantic region Sunday and Monday. The intense low will move off the New England coast Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Per current conditions, added patchy fog for the next few hrs across the fa although vsbys are quickly improving in some areas. Local cams still showing low vsbys over the water so maintained 1NM vsby with fog per marine dense fog advisory criteria. Went ahead and lowered temps a few degrees (more in line with the LAV numbers). Also slowed down the onset of pcpn across the sw as the latest high res data doesn`t show much until btwn 21Z-00Z. PVS DSCN: Best timing for the approaching slug of moisture and forcing will be this eveng across the area, and have increase PoPs to likely-categorical southern half of area, with chance PoPs remainder of area. With a break in the pcpn overnight and light winds, could see another round of patchy DZ/FG so added this to the forecast as well, through mid morning Sunday. Lows tonight range from the mid 40s NE to lwr 50s SW. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... Tricky forecast continues for the short term period. Following any morning DZ/FG Sun, PoPs quickly ramp up through the day Sun as strong sfc low pressure and shortwave energy aloft approach from the west. Increasing PW`s will result in moderate to locally heavy rainfall. Likely-categorical PoPs. Warm frontal boundary progged to drift north to near the NC-VA border so will have chc thunder across southern half of fa during the afternoon with decent shear as well. High temps upr 50s north to mid 60s south, but temps could easily end up higher or lower. Models continue to have trouble with the stacked upr-level low progged to slowly cross the region late Sunday night and Monday. Categorical pops for shwrs Sunday night. Lows upr 40s/mid 50s. At some point in time, a triple point low is forecasted to cross Virginia. Current timing is Monday afternoon which will continue to produce widespread shwrs across the north with a dry slot potentially cutting off pcpn across parts of the area Monday afternoon. However, enough instability is noted to keep thunder mentioned across the SE in the warm sector. Highs mid 50s to lwr 60s. QPF through Monday should average one to two inches with locally higher amounts possible. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
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Overall, the models are in good agreement in the extended period with only a few minor differences on the timing of the frontal passage on Wed night into Thursday. But those differences are minor and the 12z GFS has moved closer to the 00z ECMWF. In the wake of the storm that will move through by Tuesday, a shortwave ridge builds in Tues night into Wednesday. This will allow for W to SW flow and should be a mild dry period. However, the upper level pattern will begin to flip with a broad trough developing over the eastern half of the country for the second half of the week. This trough will enter the region Wed night into Thursday as a sfc cold front slides into the area. This front will be lacking moisture so have limited the pops to slight chance to chance range. The best opportunity for rain looks to be in the southeastern part of the area where a little additional Atlantic moisture may be available. The timing on the front is still a little up in the air. The ECMWF moves the boundary through more quickly, while the GFS develops a wave and is slower. But the trend has been toward the ECMWF timing so focused the highest chance on Thursday. Will also need to watch the timing on the cold air arrival as well as this could impact the pcpn type, but for now don`t think the cold air will arrive until after any pcpn is gone. For Thursday night into Saturday, the region will be dominated by strong NW flow which will drop temperatures back down into the 40s for highs and lows in the upper 20s to low 30s. Have kept the fcst dry too, but will have to monitor shortwaves rotating through the upper trough as with this polar airmass, if one of these waves amplifies a bit, some snow showers would not be out of the realm of possibility.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Widespread IFR ceilings expected to persist through the entire TAF period. with no mixing and the warm front well to south expect IFR ceilings to persist through the afternoon and overnight. A weak area of low pressure will move acrs NC and SE VA later tngt thru Sun. This will bring a decent wave of rain to spread from SW to NE across the entire region from 01z to 12Z. Also expect some LLWS in areas across SE VA and NE NC overnight. OUTLOOK...Periods of rain, moderate to heavy at times, Sunday through Monday, will be accompanied by IFR conditions. As low pressure moves off to the northeast...dry weather and a clearing sky is indicated for Tuesday and Wednesday. && .MARINE...
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Weak high pressure right over the marine area will slide out into the Atlantic this evening. winds will remain S to SE this afternoon around 5 kt or less. an approaching low will turn winds to the E or SE acrs most of the waters, except SW or S ovr the NC waters during this time with speeds 5 to 15 kt. Waves 1 to 2 ft and seas 2 to 4 ft. Then Sun night into Tue morning, stronger low pressure will move fm ern TN/wrn NC and SC east- northeast acrs the CWA to just off the srn New England coast. This will result in stronger E, SE and S winds over the waters (10-20 kt with gusts to around 30 kt) Sun night thru most of Mon, with the strongest ESE winds affecting the two nrn coastal waters. SCA conditions will be likely there esply late Sun night thru Mon. SCA may be needed acrs the remainder of the coastal waters as seas could reach at least 5 ft out toward 20 NM. Seas may build to 6 to 9 ft ovr the two nrn coastal waters. Winds become NW all waters on Tue with SCA conditions probable, esply for the coastal waters. Seas 4-6 ft.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Dense Fog Advisory until 5 PM EST this afternoon for ANZ630>638-650-652-654-656-658. && $$ SYNOPSIS...MAS NEAR TERM...MAS/MPR SHORT TERM...MAS/MPR LONG TERM...ESS AVIATION...MAS/JAO MARINE...TMG

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