Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
651 FXUS61 KLWX 100120 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 920 PM EDT Thu May 9 2024 .SYNOPSIS... Showers and thunderstorms will continue through Friday as a slow moving front pushes southeast across the region. Precipitation chances slowly decrease behind the front going into the weekend with cooler temperatures and high pressure nearing the area. Shower and thunderstorm chances along with warmer temperatures return by the middle of next week as high pressure pushes offshore. && .NEAR TERM /THROUGH FRIDAY/... The radar as of 9pm Thursday is showing widely scattered rain showers along the Mason-Dixon line near Northeast Maryland, a few patches of rain showers near and southeast of Washington D.C., scattered showers in parts of northeastern West Virginia, and a broad band of heavier showers and embedded strong thunderstorms extending from the northern West Virginia Panhandle to western Maryland. The more intense thunderstorms along this broad band have been producing occasional lightning and very heavy rainfall. As a matter of fact, dual-pol radar indicates rain rates of 1 to 1.5 inches per hour with more on the way over the next couple of hours. A Flash Flood Warning has been issued and is currently in effect for northwestern parts of Garrett County in western Maryland until 1145pm. Additional heavy showers and thunderstorms could prompt additional flood or flash flood warnings over the next few hours. So be aware across western and central Maryland, northeastern West Virginia, and into far northwestern parts of Virginia. Lows tonight will be cooler with temperatures dropping into the 50s. A low pressure system over north- central West Virginia will move east overnight and during the day Friday. A stalled front to our south will slowly move northward as a warm front overnight and Friday morning. The warm front may only make its way into northern Virginia before it is shunted eastward with the low pressure system and its trailing cold front later Friday. The combination of the stalled front, the low pressure system and the cold front will make for an unsettled prolonged period from late this evening right into Friday evening. An upper level trough will pivot over the region behind the surface low pressure system on Friday. This upper trough will aid in additional development of showers and thunderstorms. In the wake of a cold front late Friday into Friday evening, temperatures will be noticeably cooler with high temperatures in the 50s and 60s for most. Those in the southernmost portions of the area will see high temperatures in the low to mid 70s where cloud cover will be less. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... Precipitation chances decrease gradually overnight Friday with low temperatures in the 40s to low 50. Saturday will begin dry with dry air aloft inhibiting any precipitation chances. A low pressure system approaching from the Great Lakes will bring increasing shower and thunderstorm chances Saturday afternoon. Temperatures will be in the 60s for most of the area. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Longwave troughing/upper level trough axis will swing offshore Sunday afternoon as mid and upper level ridging build back into the region. Some showers and isolated thunderstorms will be possible Sunday morning into Sunday afternoon especially north of I-66/US-50 where better forcing with the departing trough axis can be found. Areas further south will likely stay dry with surface high pressure building eastward from the Ohio River Valley into the central Appalachians region. Severe weather will not be concern although any showers or thunderstorms that due form could put down a brief downpour along with small hail. Monday looks to be our driest day of the next 7 days as 500 mb heights rise with surface high pressure sitting just to the south of the region. This will yield a nice late Spring day with highs in the mid to upper 70s underneath partly cloudy skies. Unfortunately, the dry time will be brief as an upper trough develops in the lee of the Rockies, and deepens as it tracks into the south central US and Gulf Coast states during the middle part of workweek. Meanwhile, high pressure will shift off the VA/NC coast Tuesday into Wednesday allowing for south to southeasterly return flow to ensue. This will allow Atlantic and eventually Gulf of Mexico moisture to increase across the region yielding daily isolated to scattered chances for showers and thunderstorms. Uncertainty remains in the placement and timing of the heaviest precipitation with a focus mid to late week (Wednesday and Thursday). This is due largely in part to a warm frontal boundary that will be lifting northward into the region. As for severe weather, it cannot be ruled out, but overall predictability remains too low at this point to pick a given day out. CSU learning machine and CIPS probabilities point toward the Wednesday and Thursday timeframe given the front lifting and added moisture lifting into the area. Highs will continue to be in the low to mid 70s for areas east of the Allegheny Front (60s). Lows will drop down mostly in the 60s during the middle part of the week. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... MVFR conditions over the northeastern Maryland terminals, while VFR conditions and some rain showers around are near DCA and IAD. Expect IFR conditions at all terminals overnight. Showers and thunderstorms could impact all terminals with focused attention to the broad band of heavy showers and thunderstorms approaching MRB in the next hour to hour and a half. Gusty winds are possible with thunderstorms The best chances for showers and thunderstorms is the remainder of this evening into the overnight. Thunderstorm chances should decrease shortly after midnight. IFR conditions continue Friday as precipitation chances linger. Conditions improve to VFR on Saturday. Winds shift to northeasterly tomorrow before becoming southerly on Saturday. SCA level winds return SUnday in the wake of a shortwave trough pushing offshore and high pressure building to the south. SCA conditions will likely continue Monday, Tuesday, and Wednesday as low pressure approaches from the south and high pressure pushes offshore. && .MARINE... Easterly winds have increased some since late this afternoon. There are occasional gusts of SCA in scattered areas of the Bay and Potomac River. A SCA will be issued for this evening into early overnight. Winds diminish early Friday morning. Winds remain out of the northeast on Friday, while blowing right at or just below SCA criteria in the afternoon. Rain showers and thunderstorms could impact the waters overnight and Friday, mainly in the afternoon. Winds shift to northerly Friday night before shifting to southerly for the weekend. SCA level winds return SUnday in the wake of a shortwave trough pushing offshore and high pressure building to the south. SCA conditions will likely continue Monday, Tuesday, and Wednesday as low pressure approaches from the south and high pressure pushes offshore. && .TIDES/COASTAL FLOODING... The increase in easterly winds over the Bay could allow for sensitive areas like Annapolis, Straits Point and SW Washington DC waterfront to reach minor stage late overnight into early Friday. Levels should drop well off by Sunday when offshore northwest flow kicks in across the area. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...AVS/KLW SHORT TERM...AVS LONG TERM...EST AVIATION...KLW/EST MARINE...KLW/EST TIDES/COASTAL FLOODING...KLW