Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 171939 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 239 PM EST Fri Nov 17 2017 .SYNOPSIS...
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High pressure traverses the area through tonight. The high slides offshore Saturday with a cold front approaching the region from the west late. The cold front moves across the area late Saturday night into Sunday morning, producing scattered showers.
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&& .NEAR TERM /THROUGH TONIGHT/...
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1023mb high pressure is centered directly over the local area this afternoon. Other than some passing high clouds, benign wx is on tap through tonight with the high gradually sliding SE and offshore by daybreak Sat. Chilly tonight with lows from near 30/low 30s inland and interior Eastern Shore to around 40 at the immediate coast.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY/...
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Turning milder again on Saturday due to return flow around the offshore high. Increasing pressure gradient due to advancing Midwest cold front will allow for breezy conditions/late morning into the afternoon with gusts of 25 to 35 mph (highest immediate coast and Eastern Shore). Compressional warming out ahead of the approaching cold front will drive maxima well into the 60s...to around 70 across SE VA/NE NC, with low to mid 60s across northern zones. Quick dewpoint surge with warm front lifting across the area Sat aftn/night. Low level S-SW flow quickly increasing PW values into the 1"-1.25" range after 00z/Sun. A brief window for showers coincident with narrow axis of low-level convergence/forcing ahead of the frontal passage late Sat evening (west) into early Sunday morning (east of I-95) will require likely PoPs (60-70%) most areas Sat night, mainly west of RIC metro before 4am, then reaching the coast before sunrise Sun morning. Convective parameters remain weak with the fropa, owing to the timing and the progressive nature of the system. Therefore, will keep thunder mention out of the forecast. Lows Saturday night from the mid 40s Piedmont to the mid 50s coast. Some concern for gusty winds with and in the immediate wake of the frontal passage. Gusts to 30-40 mph (higher possible MD counties and northern neck) possible late Sat night and Sunday morning. Cold front pushes offshore early Sunday. After some lingering clouds east (morning shower possible over coastal areas), subsidence behind the front should result in a mostly sunny sky. Winds diminish late afternoon as the gradient slackens. Cooler with highs in the 50s...to near 60 SE coast. Cool sfc high pressure centered over the TN Valley Sunday night will expand eastward into the mid-Atlantic on Monday. We can expect a clear sky and below normal temperatures. Lows Sunday night in the mid/upr 20s Piedmont to the mid/upr 30s coast. Highs Monday in the upr 40s to low 50s.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... High pressure is expected to build into the region Monday before moving offshore during the day on Tuesday. Cold air aloft and a northwest flow will lead to a chilly day on Monday with highs struggling to climb out of the upper 40s. Lows on Monday night will dip down into the lower 30s away from the coast and upper 30s to near 40 at the coast. Temperatures warm on Tuesday due to southerly flow on the backside of the high. Highs on Tuesday will range from the upper 50s to the lower 60s. A dry cold front is expected to drop into the region late Tuesday night. High pressure builds back into the region Wednesday through Thursday which will allow for continued cool but dry conditions. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... High pressure over the area this afternoon will gradually slide east to a position off the coast by midday Saturday. During this time, VFR conditions will continue despite some high clouds. Clouds increase late Saturday, then thicken/lower ahead of the next cold front to approach the region Saturday night. That front crosses the local area early Sunday morning, a brief period of sub-VFR cigs and rain showers are possible with the frontal passage late Saturday night into Sunday morning, clearing Sunday morning as cool high pressure builds back into the region, bringing a return to VFR conditions. A gusty NW wind is expected immediately behind the front on Sunday morning/aftn. High pressure gradually slides off the Southeast coast Monday and Tuesday with VFR conditions prevailing. && .MARINE...
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Quick moving weather systems will lead to some rapidly changing conditions over the next 24-48 hrs. Sfc high moves offshore tonight shifting winds from the N aob 10 kt this evening to the SW after midnight. SCA`s for seas early this evening will end as seas subside to 2-4 ft. Pressure gradient quickly increases as a warm front pushes north across the region Sat. S-SW winds quickly ramp up into SCA levels by the afternoon with gusts to 30 kts over most areas. Data suggests offshore gusts to 35 kts possible across the coastal waters but not until after 00Z Sun. Even the "old" Boston technique suggests best mixing not until after fropa Sunday morning. Sharp pressure rises behind it will combine with strong CAA to produce widespread high end SCA`s to low end gales across the waters Sun. Issue with this forecast package is one of confidence given the NNW winds behind the front should be stronger than the SSW winds ahead of it. Thus, decided to go with a gale watch for the coastal waters Sat night into Sunday. Left strong SCA`s over the bay/sound and rivers for now. This way it gives later shifts the flexibility to upgrade to a warning or keep strong SCAs. Ended the headlines at end of 4th period per local policy, although SCA`s will likely be needed early Monday.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ650- 652-654-656-658. && $$ SYNOPSIS...JDM/MAM NEAR TERM...JDM SHORT TERM...JDM/MAM LONG TERM...AJB AVIATION...JDM/MAM MARINE...MPR

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