Area Forecast Discussion
Issued by NWS Wakefield, VA

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368 FXUS61 KAKQ 181004 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 604 AM EDT Fri Aug 18 2017 .SYNOPSIS... A warm and humid air mass remains in place across the Mid- Atlantic states today on continued south flow. The next cold front will arrive late tonight and exit the region by Saturday morning. High pressure builds in for Saturday night through early next week. && .NEAR TERM /THROUGH TONIGHT/... A warm/muggy start to the day across the local area. Some SCT/BKN low stratus developing across the area attm, but little bit of mixing we do have has precluded more widespread fog development. Aloft, shortwave ridging remains in place over the local area. However, this will be short-lived...as an upper trough, and associated mid-level shortwave drops from the Great Lakes toward the northeast today into tonight. The associated surface cold front will drop across the Ohio Valley/interior northeast this afternoon, reaching our area tonight into early Saturday morning. For today, expect some pre-frontal showers to develop by late morning/early afternoon...however areal coverage should be quite low with these showers. More widespread showers and storms should occur along and just ahead of the front. PW values in the 2-2.5" range, increasing lift and increasingly diffluent flow aloft with time as the upper trough and sfc front approaches will allow for a period of moderate to heavy rainfall. Area of greatest concern is once again over the Northern Neck of Easter VA into the Lower MD Eastern Shore, where dynamics are most favorable for a period of heavy rainfall late this afternoon into this evening. Have held off with any flash flood headlines at this time, as Corfidi vectors do indicate decent storm movement with sct to numerous storms that develop this afternoon. However, this will obviously bear watching through the day. Have added heavy rain mention into grids and will highlight in HWO. Also, given strong heating and high PWs, a marginal risk for severe is in place across the local area, with the NE CWA also highlighted in a slight risk for severe. Once again, as noted above the best dynamics are along and NE of the local area into the northeast, with lesser deep layer shear likely portending to more of a pulse storm threat over much of the area. Also, timing of frontal passage in the evening/overnight will allow for a gradual but steady weakening trend with any storms. That said, Sig TOR/EHI values do indicate potential for isolated tornadoes across the Eastern Shore during the evening hours just ahead of the frontal passage. These parameters have been useful in previous events earlier this summer, and will therefore add a mention into the HWO for tonight. Lastly, temperatures will creep up slightly after stratus dissipates this morning. It will remain humid, with dewpoints creeping up slightly from the past few days into the low to mid 70s. In tandem with highs in the u80s/l90s, this will bring heat index values back into the low 100s. Have held off on heat headlines for now, as any exceedance of criteria would be quite brief. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... The front slowly pushes southeast early Saturday, and models have once again trended a bit faster with the frontal passage, allowing for a quicker end to showers Sat morning. A strong shortwave trough sweeps across the Mid-Atlantic States Saturday night, but it remains north of the area and with the low level moisture gone, not anticipating much except some mid level clouds. By Sunday, high pressure will be over the region with dry and seasonable weather in place. For temperatures, will continue to see near normal weather with highs in the upper 80s to around 90 each day and lows in the low to mid 70s each night except for Saturday night when the drier air will allow temps to drop into the upper 60s to low 70s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... 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 late Wed night. Conditions will become increasingly more humid with each passing day. Sfc features rather diffuse for Mon, however seabreeze boundaries with the presence of ample moisture will keep a slight chance for showers/storms in the forecast... primarily for the aftn/early evening. 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. Highs Mon-Wed generally upper 80s to lower 90s; low-mid 80s beaches. Lows Sun-Tue nights generally 70-75F. Lows Wed night mid-upper 60s NW to 70-75F SE. && .AVIATION /10Z FRIDAY THROUGH TUESDAY/... VFR conditions across the terminals this morning. A weak boundary will move north of the area later tonight into Friday morning. High-res models hint that a few showers are possible around daybreak along the coast near ORF, PHF and ECG, areal coverage should be low and as such will continue to keep out of TAF for now. Main story will be MVFR/IFR cigs and possible VSBY restrictions (mainly at RIC) after 09z. With the wind staying around 5 kt, still anticipate more of a lower stratus event vs. a low VSBY event at RIC. Elsewhere, it should remain VFR or MVFR with low probability of IFR expected. A cold front approaches the region today, with showers and thunderstorms developing and becoming more widespread Fri evening into Saturday. This will bring another chance for sub- VFR conditions in heavier showers. Confident enough to throw showers in at RIC/SBY, but will keep thunder mention out for now. Outlook: VFR conditions returns later Sat through the weekend as High pressure builds back into the region. Some early morning fog possible both Sunday and Monday mornings. && .MARINE... Latest sfc analysis shows weak high pressure offshore with a cold front over the OH Valley. This front will track east towards the Mid Atlc today, with southerly flow increasing ahead of the front as the pressure gradient increases. By this aftn/eveng before the fropa conditions will be close to SCA criteria over Bay due to ~15 kt sustained winds and northern cstl wtrs due to 4 ft seas. Not confident enough that SCA conditions will occur to issue headlines attm. The cold front drops into the wtrs tonight, with shras/tstms psbl and winds/waves/seas decreasing thereafter. For Sat, with the front weakening in the vicinity, expect winds aob 10 kt by the aftn with 1-2 ft waves over the Bay and 2-3 ft seas over cstl wtrs. Similar conditions into Sun with little change in the overall pattern. Sub-SCA conditions will continue into early next week with weak sfc high pressure in the area. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...MAM NEAR TERM...MAM SHORT TERM...ESS/MAM LONG TERM...BMD AVIATION...MAM/JAO MARINE...MAS

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