Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Mon Aug 22 2016 .SYNOPSIS... High pressure will build eastward from the Ohio Valley today. The high will gradually shift eastward though the week ahead before a cold front crosses the area on Friday. High pressure behind that front will dominate through the weekend. && .NEAR TERM /THROUGH TONIGHT/... The primary cold front is offshore this morning, with high pressure located over the MS Valley. A secondary front/trough axis is located over northern PA, where light showers have been diminishing. Precipitation should not be a concern locally today though, as the high builds toward the Ohio Valley and upper level troughing exits New England. While highs won`t be that far from climo in the lower to mid 80s, the drop in humidity (dew points in upper 50s) will be noticeable. The center of the high will nearly be over the Mid-Atlantic by late tonight. This will mean rural sheltered areas will likely drop into the 50s, while the metros should remain in the mid 60s. One caveat is that that NAM keeps some clouds across the area which may hold temperatures up if realized. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Little sensible weather to talk about through the middle of the week as the surface high inches offshore and ridging builds aloft. Tuesday`s temperatures will be similar to Monday, while both the temperature and dew point will tick up on Wednesday as southerly flow develops -- but still relatively pleasant. Theta-e ridge will approach the mountains ahead of low pressure moving through the upper Great Lakes Wednesday afternoon or night, but dry air aloft supports a dry forecast for now, despite some light QPF model output. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Reasonably good agreement on long range guidance through the weekend. High pressure will be sliding east off the coast on Thursday. This will promote a warm and more humid southerly flow across our region. Next cold front will cross the region on Friday. Some advance showers and thunderstorms may affect the area as early as late Thursday but bulk of activity expected Friday. Guidance is not robust with this system and not expecting a great deal of rain at this time. High pressure then slides eastward from the northern Plains into northern New England on Saturday with slightly cooler and less humid weather. By Sunday the easterly flow will begin to bring more moisture back and with some insolation added in...we may start to see some afternoon diurnal showers or storms in the higher terrain. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... High pressure will dominate the weather through the middle of the week. A few NW wind gusts near 20 kt are possible after sunrise this morning. VFR cumulus can be expected during the afternoons. The NAM indicates a possible deck around FL050 tonight, but will withhold cig for now. Fog appears unlikely tonight with dry air remaining in place, but may become a concern Tuesday and Wednesday nights near MRB/CHO as dew points increase. Main concern Thursday into this weekend is scattered showers and thunderstorms possible late Thursday and Friday with the next cold front. && .MARINE... NW flow has been established behind a cold front. 20+ kt gusts have mainly been limited to the wider waters. Am hesitant to cancel the SCA though, as there could still be gusts after sunrise when mixing increases. Have also extended the SCA until 3 PM for the Bay south of Drum Pt and Tangier Sound based on latest hi-res guidance. Elsewhere, solid 15 kt gusts will be possible through afternoon before easing as high pressure builds. Flow will become onshore Tuesday and southerly Wednesday as high pressure moves east. At this time, winds are expected to remain less than 15 kt. Next front may bring some stronger SCA level winds late Thursday into Friday with cold advection behind it Friday night into Saturday. Odds are not high yet and will leave out of HWO for now. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until noon EDT today for ANZ530>533- 537>542. Small Craft Advisory until 3 PM EDT this afternoon for ANZ534- 543. Small Craft Advisory until 10 AM EDT this morning for ANZ535- 536. && $$ SYNOPSIS...RCM NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM is the U.S. government's official web portal to all federal, state and local government web resources and services.