Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 280802 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 402 AM EDT Sun May 28 2017 .SYNOPSIS...A surface trof will move across the area tonight followed by a weak cold front Monday afternoon. Upper level low pressure will linger north of the Great Lakes Monday night through the remainder of the week with persistent weak high pressure over the Mid-Atlantic. && .NEAR TERM /THROUGH TONIGHT/...Dense fog has formed across the northern part of the fcst area with many sites reporting less than a quarter mile visibility. For today, weak sfc front/trof will get hung up across the area today and this evening with models indicating decent sfc convergence across the nrn part of the fcst area. A shortwave- trough will move across the area this evening and help trigger numerous to widespread showers and t-storms. Overall, trend in the models and ensembles the past 24 hrs is for weaker sfc convergence and less QPF than yesterday. Despite this, there is still some concern for flash flooding mainly across the far northwest part of the fcst area where sfc convergence/lift will be strongest and a plume of 1.5+ inches of PW will advect in. 1-2 inch hourly rain rates can be expected with heaviest showers. Isolated instances of flash flooding are possible mainly across Allegany, Mineral, and Grant counties. Think severe threat will be more limited due to plenty of cloud cover and weak instability below 1000 J/kg. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...Things will calm down somewhat as drier air filters in on westerly flow, but it won`t be completely dry. Still risk of showers/t-storms Tue afternoon as a weak cdfnt moves through. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The upper level pattern for the middle and end of the week will feature a closed low drifting across eastern Canada. While increasing model spread of this feature late in the week lends some uncertainty, there is some signal in the noise. On Wednesday, a weak cold front will be drifting south of the area. There are some indications this front could waver, resulting in lingering chances of showers, but eventually high pressure building from the west should lead to higher probabilities of dry conditions. Thursday has the highest probability of being dry this week. Return flow will begin on Friday, although forcing/instability aren`t that notable. A cold front will be sinking southward next weekend, although progress will be slow since it will be parallel to the upper flow. Thus an unsettled period appears probable, but timing is uncertain. Temperatures will settle close to normal behind the front on Wednesday and Thursday, then warm back up (highs in the 80s) ahead of the next front on Friday and Saturday. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/...LIFR conditions through 12Z today at KCHO and KMRB due to dense fog. Then, showers and t-storms this afternoon and evening with brief MVFR/IFR cigs in t-storms with heavy rain. Overall Wednesday should be VFR, but there is a small chance of showers as a front sags south of the area. Winds could also gust around 20 kt. VFR conditions are expected Thursday as high pressure builds in from the west. && .MARINE...Winds should remain below SCA through the first half of the week, but higher winds and waves can be expected near thunderstorms. Depending on the position of a cold front, winds could near SCA levels on Wednesday but confidence is low. Lighter winds are expected on Thursday as high pressure builds in from the west. && .TIDES/COASTAL FLOODING...Water anomalies will continue to rise through 12Z Mon with minor coastal flooding expected at many of the coastal sites. Winds turn westerly on Mon, but they will be generally light and may not be able to lower anomalies that much. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory from 8 AM this morning to 2 PM EDT this afternoon for DCZ001. MD...Dense Fog Advisory until 7 AM EDT this morning for MDZ003>005- 501-502. Coastal Flood Advisory until 10 AM EDT this morning for MDZ014. Coastal Flood Advisory until 8 PM EDT this evening for MDZ017. VA...Dense Fog Advisory until 8 AM EDT this morning for VAZ028-031. Coastal Flood Advisory from 8 AM this morning to 2 PM EDT this afternoon for VAZ054. WV...Dense Fog Advisory until 8 AM EDT this morning for WVZ053. Dense Fog Advisory until 7 AM EDT this morning for WVZ050>052- 504. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...ADS/LFR MARINE...ADS/LFR TIDES/COASTAL FLOODING...LFR

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