Area Forecast Discussion
Issued by NWS Sterling, VA

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670 FXUS61 KLWX 250804 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 404 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/... Low pressure is located over IN/OH this morning while an associated cold front moves across the Appalachians. A warm front stretches east-west across southern VA this morning. Rainfall has been spreading northward across the Mid-Atlantic states overnight as southerly flow transports moistures from the Gulf and Atlantic. Stable conditions are across the Mid-Atlantic region, north of the warm front and overrunning will continue with easterly flow in place at the sfc. The cold front and warm front will pivot northeastward today and low pressure will transition to the Mid-Atlantic states. This will push most of the moisture/steady rain off the east coast this morning and a brief dry period is expected. As the low moves overhead and the warm sector moves northward into the region, showers and thunderstorms are expected to form early this afternoon. The best shear profiles will likely be this morning while the best instability will be this afternoon. As showers and thunderstorms develop this afternoon some thunderstorms may become strong to severe with the best chance early this afternoon where shear and instability will be co-located. Activity will move east-northeast today. There is uncertainty as to how far north the warm sector gets today and places near the Mason Dixon line may not see the chance for thunderstorms until late this afternoon and by then they should be sub-severe. Best chance for strong to severe storms will be east of the Blue Ridge Mtns and south of I-66/MD-50 today. Gusty winds and hail are the main threats today. 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. Uncertainity 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 /08Z THURSDAY THROUGH MONDAY/... Easterly flow continues this morning with gusts around 16-20kts. IFR/LIFR conditions expected this morning as steady rain continues across the region. RA will become isolated to scattered after sunrise however IFR cigs will continue through most of the morning. Terminals will improve today mainly from south to north. CHO will likely become MVFR/VFR this morning and MRB/BWI not until around noon. SHRA/VCTS are expected this afternoon. 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 afternoonn as cdfnt moves through the area with heavy rainfall again the primary threat. && .MARINE... An onshore flow will strengthen ahead of low pressure tonight. A Small Craft Advisory is in effect for the waters. Low pressure will move overhead today and the gradient may weaken a bit. However...low pressure and its associated cold front will move away from 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 today`s high tide cycle and a coastal flood watch may become necessary for Straits Point for tonight`s high tide. A blend of latest ESTOFS and ETSS yields a -0.1 ft surge compared to this morning`s high tide which resulted in moderate coastal flooding. Tonight`s high tide will be very close to moderate. Straight ETSS suggests more westerly flow and negative anomalies preventing from reaching moderate. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 11 AM EDT this morning 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- 017. Coastal Flood Advisory until 10 AM EDT this morning for MDZ011. VA...Coastal Flood Advisory until 6 PM EDT this evening for VAZ057. Coastal Flood Advisory until 11 AM EDT this morning for VAZ054. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ532>534-537- 540>543. Small Craft Advisory until 9 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. Small Craft Advisory until 6 AM EDT early this morning for ANZ535-536. && $$ SYNOPSIS...LFR NEAR TERM...HSK SHORT TERM...HSK LONG TERM...LFR AVIATION...HSK/LFR MARINE...HSK/LFR TIDES/COASTAL FLOODING...LFR is the U.S. government's official web portal to all federal, state and local government web resources and services.