Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
742 FXUS61 KLWX 081432 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 1032 AM EDT Wed May 8 2024 .SYNOPSIS... Showers and thunderstorm chances continue through Thursday with multiple waves moving through the Mid-Atlantic. A strong cold front will bring increased chances for severe and flooding impacts Thursday into early Friday. Precipitation chances decrease behind the front going into the weekend with cooler temperatures and high pressure nearing the Mid-Atlantic. && .NEAR TERM /THROUGH TONIGHT/... Cloud cover from remnant MCS from overnight continues to show signs of dissipation with clearing expected to occur across northern areas. Guidance indicate increasing subsidence later today with 925 and 850 mb dewpoints forecast to come down significantly during the afternoon and evening on stregnthening westerly flow. Any threat for thunderstorms appears to be along and south of I-64 in central VA. By tonight, clouds will increase from the west ahead of the approaching cold front moving in from the Ohio Valley. Rain chances will increase from west to east, especially after midnight, and continue through the night and into Thursday morning. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Increasing showers and isolated thunderstorms will continue Thursday morning ahead of the cold front passage. Expect overall QPF to be 0.50 to 1" with localized higher amounts, especially in heavier downpours and thunderstorms. Isolated instances of flooding will be possible, given the anomalously high PWATs coupled with antecedent moist conditions over the last week, especially across areas along and west of the Blue Ridge Mountains. A fairly sharp instability gradient may develop east of the Blue Ridge just ahead of the cold front Thursday afternoon. There is some uncertainty with this given any earlier convection/cloud debris from early convection late tonight into early Thursday. Should there be a lull with increasing breaks in the clouds, then some thunderstorms may develop and become strong to even severe. Main hazards will be damaging winds along with large hail of 1 inch diameter or greater as a result of steeper lapse rates. The best chances for thunderstorms will likely be across the VA Piedmont into southern MD. Afternoon highs will be in the upper 60s to low 70s across the MD/PA border, with low 80s further south across central VA. Showers and isolated thunderstorms will linger early Friday, with showers continuing throughout much of the day as a result of the departing low pressure system off to the north. Cannot rule out an isolated thunderstorm Friday afternoon. Highs will cooler as a result of northwest flow, with mid to upper 60s across most areas with even mid 50s across the Allegheny Front. NW winds will be gusting 20 to 25 knots during the afternoon on Friday, with higher gusts possible along the ridges. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Longwave troughing will remain in place across the eastern US this weekend. On Saturday we`ll start the day off between one shortwave departing offshore, and another digging down the backside of the longwave trough into the Ohio Valley. The latter shortwave will pass overhead Saturday night into the day Sunday. Conditions should start off mostly sunny on Saturday within the subsidence behind the departing shortwave. Clouds and eventually showers will be on the increase as we progress through the afternoon as large scale ascent ahead of the next shortwave starts to overspread the area. Chances for showers will continue through Saturday night and into the day Sunday as the upper trough axis moves overhead. High temperatures this weekend are forecast to reach into the upper 60s and lower 70s, while low temperatures will generally be in the 40s to lower 50s. Upper troughing will progress off to our east early next week, allowing heights to start rising aloft. Such a pattern will lead to drier conditions and a warming trend in temperatures. Highs are expected to reach into the low-mid 70s on Monday, and into the mid- upper 70s on Tuesday. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... Just high clouds today with a slight chance of a thunderstorm mainly at KCHO. Widespread showers and thunderstorms are likely Thursday, with some strong to severe storms possible for the afternoon and evening hours. Best chances for this to occur would be across the I-95 corridor terminals. VFR conditions are likely outside of the thunderstorm activity. These conditions will likely continue into Friday with gusting NW winds 20 to 25 knots throughout the day. Prevailing VFR conditions are expected at the terminals this weekend, but passing showers could lead to temporary drops to sub- VFR either day. Winds are forecast to be out of west to southwest on Saturday, and then out of the northwest on Sunday. && .MARINE... Westerly winds may near SCA criteria this afternoon, especially across the northern bay and upper tidal Potomac. There are still uncertainties with this but will continue to monitor the trends for any needed issuances. Cannot rule out an SMW across the southern water especially this afternoon with any strong thunderstorms that cross the waters but confidence is low in this occurring. SCAs are possible Thursday and Friday as a result of southerly channeling. SMWs will be possible Thursday afternoon ahead of a cold front passage bringing heavy showers and thunderstorms over the waters. Winds may near low-end SCA values in west to southwesterly flow on Saturday, and then again in northwesterly flow on Sunday. && .TIDES/COASTAL FLOODING... Water levels remain elevated in southerly flow this morning. Coastal Flood Advisories are in effect for the ongoing tide cycle at Annapolis, Straits Point, and DC. Westerly winds should allow water levels to decrease this afternoon. Winds turn southerly again late tonight into tomorrow morning, which could lead to additional Minor flooding at the most sensitive sites. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 11 AM EDT this morning for DCZ001. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>532-535-536-538>540. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...ADM LONG TERM...KJP AVIATION...LFR/KJP MARINE...LFR/KJP TIDES/COASTAL FLOODING...