Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 251436 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1036 AM EDT Thu May 25 2017 .SYNOPSIS... Low pressure and associated cold front will move through the area late today. Weak high pressure will return to the area Friday night and Saturday. A warm front will stall over the region Saturday night. A stronger cold front will cross the region late Sunday night. && .NEAR TERM /THROUGH FRIDAY/.. Vertically stacked low pressure will move through the Ohio Valley today. An occluded front associated with the low will move into our area...and surface low pressure will develop along that boundary overhead. Latest guidance shows a theta e ridge along and ahead of the occluded boundary. Modified KLWX sounding shows close to 1000 J/KG of MLCAPE this afternoon along and ahead of the occluded boundary. The upper-level low to our west will be building overhead later this afternoon into this evening. Popup showers and thunderstorms are expected over the area. Shear profiles will be weakening during peak heating this afternoon...but they should still be strong enough to elevate the threat for severe thunderstorms mainly for locations near and to the north of the occluded boundary. Those areas appear to extend from eastern West Virginia across northern Virginia toward the Washington and Baltimore Metropolitan areas. Locally damaging winds and large hail are the primary concerns. Low clouds still have to dissipate by early this afternoon for the severe threat to be elevated. Current thinking is that the marine layer is shallow enough this morning for the clouds to mix out...but will have to monitor satellite trends closely. Due to recent rainfall...any heavy rainfall from thunderstorms does pose a threat for localized flash flooding. However...it appears that any threat would be localized so confidence is too low for a watch at this time. Low pressure will move to the north this evening and convection will come to an end. A closed upper low will move overhead this evening and the chance for showers will persist overnight. Remnants from the upper low will persist across the region Friday however the sun should peak out of the clouds by afternoon. The chance for showers will persist across the Highlands through Friday afternoon. Temps will range from the L70s across the Highlands to the U70s across the low-lying areas Friday. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/... High pressure will briefly move into the Mid-Atlantic region Fri night-Sat morning. A warm front is expected to approach the region during this time and clouds will increase from west to east through Sat morning. The front will settle across the region by Sat night and showers will return to the region by this time. Uncertainty exists regarding onset of showers Saturday. At this time...showers will likely move into the region from west to east through the afternoon. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A warm front will stall over the region Saturday night and will serve as focus for showers and t-storms. Latest Euro shows a strong signal for a t-storm complex to roll through the region late Sat into Sat evening. Given stationary nature of front and potential for training convection, heavy rainfall and possible flash flooding appear the biggest threat. Exact timing with convection as it is typically remains far from certain, but guidance suggest Sat afternoon and evening will be the best chance for active wx. A stronger cdfnt will move through Sun night with more showers and t-storms Sun afternoon and evening. Given lack of strong instability, heavy rainfall appears the biggest threat. Quieter and drier weather returns for next week as low pressure exits the region and westerly flow establishes. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Low clouds will gradually lift into early this afternoon. Popup showers and thunderstorms are expected this afternoon into this evening. Some TS may produce hail and gusty winds. Activity moves to the north tonight and VFR conditions tonight through Saturday. Possible complex of t-storms will roll through the area Sat evening with heavy rainfall the primary threat. Then, more t-storms Sunday afternoon as cdfnt moves through the area with heavy rainfall again the primary threat. && .MARINE... Low pressure has moved overhead this morning. A Small Craft Advisory remains in effect for middle portions of the Bay and the lower tidal Potomac River through tonight. A cold front will pass through the waters tonight. W-NW winds expected on the waters Friday and a Small Craft Advisory is in effect for all waters Friday. The Advisory may be needed into Friday night. Dry conditions early on Saturday before periods of showers and thunderstorms move through Saturday night into Monday as front stalls and moves across our region. Winds will be below the SCA threshold Saturday into Monday. Gradient winds should remain below SCA away from convection. Mariners should remain alert to possible issuance of SMW`s as t-storms are forecasted. && .TIDES/COASTAL FLOODING... Combination of high astronomical tides due to a new moon and onshore flow will result in minor coastal flooding possibly moderate flooding at Straits Point today and tonight. Advisories have been extended through late this afternoon and evenings tide cycle and a coastal flood watch is in effect for Straits Point for late tonights high tide. Straight ETSS suggests more westerly flow and negative anomalies preventing most other areas from reaching moderate. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 11 PM EDT this evening for DCZ001. MD...Coastal Flood Advisory until 8 PM EDT this evening for MDZ014- 018. Coastal Flood Advisory until 6 PM EDT this evening for MDZ016. Coastal Flood Watch late tonight for MDZ017. Coastal Flood Advisory until 2 AM EDT Friday for MDZ017. Coastal Flood Advisory until noon EDT today for MDZ508. VA...Coastal Flood Advisory until 6 PM EDT this evening for VAZ057. Coastal Flood Advisory until 11 PM EDT this evening for VAZ054. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ532>534-537- 540>543. Small Craft Advisory until 11 AM EDT this morning for ANZ530- 531-538-539. Small Craft Advisory from 6 AM to 6 PM EDT Friday for ANZ530- 531-535-536-538-539. && $$ SYNOPSIS...LFR NEAR TERM...BJL/HSK SHORT TERM...HSK LONG TERM...LFR AVIATION...BJL/HSK/LFR MARINE...BJL/HSK/LFR TIDES/COASTAL FLOODING...LFR/BJL

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