Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 182024 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 424 PM EDT Fri Aug 18 2017 .SYNOPSIS... A warm and humid air mass remains in place across the Mid- Atlantic states this evening, but a cold front will arrive late tonight and exit the region by Saturday afternoon. High pressure builds in for Saturday night through early next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Hot and humid air mass is place across the region this afternoon with many locations seeing heat indices in the 105 - 110 range and a few higher than that. A cold front, that stretches from Central PA southward into the mountains of Eastern West Virginia and Western North Carolina, will slowly push eastward tonight and is expected to generate some showers and storms. Some of the high resolution models blow up a very solid line of convection along with the 12z NAM. The 12z GFS and ECMWF are less bullish and have a more scattered to broken line of convection. For now have increase pops a touch across northern portions of the CWA where the lift is more organized and keep pops slightly slower further to the south. There is a svr tstorm watch until 01z in effect for the MD portion of the Delmarva. This is closer to the better forcing and wind damage would be the biggest threat from these storms as the directional shear is weak and the wind flow aloft is only around 15 to 30 kts. The other hazard is the potential for very heavy rain as precipitable water values are over 2". The front will slowly push sewd overnight and should be over the VA Tidewater and NE NC by 12z Saturday. The threat for heavy rain will continue through about 6z when the forcing really weakens and the front sags toward Southern and Southeastern VA and the axis of higher moisture gets pushed off the coast. So expect to see the chances for rain gradually diminish during the overnight hours. For temperatures, another warm muggy night can be expected this evening with most areas remaining in the mid to upper 70s && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... The models are still struggling on how much push is there to get the front through the region on Saturday. With a strong shortwave trough digging through the Ohio Valley, it makes sense that the front will temporarily stall waiting for the shortwave trough to move past. This should allow the front to finally get south of the area and off the coast by Saturday evening. So have kept a low chance for showers and afternoon storms over NE Nc and the Tidewater area on Saturday. High pressure builds into the area on Saturday night into Sunday and lingers through Monday. Temperatures will be a couple degrees cooler, but the humidity will be much less making for more comfortable conditions. For temperatures, highs on Saturday will still be in the upper 80s to the lower 90s and that will continue on Sunday and Monday. But overnight lows Saturday night and Sunday night will be cooler with readings in the upper 60s nw to low to mid 70s se. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Sfc high pressure builds north of the area with stacked high pressure residing off the Southeast Coast through Mon night. A thermal trough develops in the lee of the Appalachians for Tue/Tue night, and then a cold front is expected to track through the area on Wed...exiting the coast Thu morning. Conditions will become increasingly more humid ahead of the front. Thunderstorm activity expected to become widely scattered Tue as convection develops invof lee trough. The frontal passage Wed/Wed night will provide a better focus for more organized thunderstorms to occur. Lingering showers/storms possible far SE VA/NE NC on Thu. Otherwise, cool Canadian high pressure builds across the Midwest with dry conditions anticipated for the Mid Atlantic Region Thu night-Fri night. Highs Tue-Wed generally upper 80s to lower 90s; low-mid 80s beaches. Highs Thu/Fri low-mid 80s; mid-upper 70s beaches. Lows Mon-Tue nights generally 70-75F. Lows Wed night mid-upper 60s NW to 70-75F SE. Lows Thu/Fri nights around 60F NW to around 70F SE. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... Early morning stratus has burned off with cu developing across much of the region at 18Z. Developing showers/tstms SE of KORF should move offshore before 1830Z, but have included VCSH there in the 18Z-19Z time frame. Radar suggests tstms SE of KECG will remain far enough SE of the terminal to not be an issue, but will continue to closely monitor. A cold front approaching the region this afternoon/evening will initiate shower/tstm development W/NW of the area by 21Z, then moving E/ESE into the region through 03Z. The potential for MVFR/IFR conditions exists as tstms will produce heavy rainfall, but uncertainty of exact timing precludes adding too much specificity to the 18Z TAFs. Have added VCTS to KPHF/KORF since hi-res model guidance suggests decent tstm potential both terminals after 01Z. Expect precipitation to wane after 08Z, leaving generally VFR conditions for the remainder of the TAF period. Outlook: VFR conditions returns later Saturday through the weekend as high pressure builds back into the region. Some early morning fog possible both Sunday and Monday mornings. && .MARINE... A cold front approaches the region through this evening with isolated to scattered thunderstorms developing along a weak boundary along the Mid Atlantic Coast. Winds generally south 10-15kt the rest of today with locally higher gusts of 20-30kt possible in thunderstorms. The front crosses the waters late tonight with more widespread and organized thunderstorms anticipated. Strong wind gusts above 30kt, heavy rainfall, and frequent lightning will be the primary impacts. Seas 2-3ft build to 3-4ft this evening and during the frontal passage later tonight...subsiding closer to daybreak Sat morning. Waves will average 1-3ft through tonight. Synoptic SCA conditions still not anticipated tonight except with the thunderstorms associated with the front. If any headlines are necessary, they can be handled with short- fused MWS or SMW products. Winds light and variable aob 10kt by mid-morning Sat through Sun as the front stalls near the Mid Atlantic Coast. Winds become more onshore Sun night into Mon as the front sags well south of the area. Seas subsiding from 2-3ft Sat aftn to 2ft by late Sat night through most of Tuesday. South winds Tue/Tue night as a thermal trough develops inland with seas building to 2-3ft Tue/3-4ft Tue night. Winds SW around 15kt Bay/ocean Tue night/Wed as the next cold front is expected to cross the region. Seas/waves average 2-3ft. Winds N-NE aob 15kt behind front Thu/Fri. Seas 2-3ft/waves 1-2ft. && .TIDES/COASTAL FLOODING...
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Minor coastal flooding is expected for areas adjacent to Ches Bay invof Bishops Head late this evening. Water levels should reach 3.5ft around high tide, which occurs at 1136 PM this evening. Cambridge is expected to reach 3.1ft, thus remaining below minor flooding thresholds.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT Saturday for MDZ021>023. NC...Heat Advisory until 8 PM EDT this evening for NCZ013>017- 030>032. VA...Heat Advisory until 8 PM EDT this evening for VAZ084-089-090- 093-095>098-523>525. MARINE...None. && $$ SYNOPSIS...ESS NEAR TERM...ESS SHORT TERM...ESS LONG TERM...BMD AVIATION...MAM/WRS MARINE...BMD TIDES/COASTAL FLOODING...BMD is the U.S. government's official web portal to all federal, state and local government web resources and services.