Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
735 FXUS61 KLWX 220022 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 822 PM EDT Mon Jul 21 2025 .SYNOPSIS... Lower rain chances and lower humidity are expected through the middle of the week as a strong area of Canadian high pressure builds to the north. A return to more summertime conditions is expected by late this week. && .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/... Any residual shower activity south of I-64 and east of I-81 will gradually come to an end before sunset. Severe and hydro threats will continue to remain low given marginal CAPE, shear, and PWATS in the area. This activity is in association with a cold frontal boundary that continues to sag south across southwest and southeast Virginia. Further north of I-64, dry air advection (PWATS on the 00z sounding this evening at KIAD down to 0.84" with mid level RH at 17 percent) has taken hold with dewpoints falling into the mid to upper 50s and low 60s. SOme valley locations (i.e Mill Gap/Mustoe, VA, Bayard, WV, and Bittinger, MD could see lows in the upper 40s and low 50s). Expect this trend to continue across the entirety of the area tonight which is a much needed reprieve from the oppressive humidity as of late. Skies will also continue clear from north to south with overnight lows in the upper 50s and low to mid 60s. Urban areas will be a touch warmer with lows just under 70 degrees. Some valley fog is possible near the Alleghenies/Appalachians and down across central VA with the showers earlier this evening. Overall dry air advection should mute this threat for most locations overnight into early Tuesday morning. && .SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Canadian high pressure will dominate across the region through mid week. Dry and seasonable conditions prevail. Highs will be in the 80s each day with overnight lows in the 60s. Northeast to east winds on Tuesday shift to southeast on Wednesday as the high slides offshore. Mid-level ridging starts to build into the area from the west on Wednesday, but we won`t see any significant temperature increases until late in the week. && .LONG TERM /THURSDAY THROUGH MONDAY/... Upper level ridge over the Mid South will crest over the area Thursday evening resulting in high heat. By the end of the week, surface high pressure shifts offshore allowing southerly winds to develop and drive higher dewpoints into the area. Expect heat indices Fri and Sat to be at or near heat advisory criteria. By Saturday, the ridge pattern breaks down allowing thunderstorm chances to increase markedly, particularly Saturday. A weak front may approach the area Sunday bringing some relief to the heat and humidity. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... VFR conditions will continue to prevail across the terminals this evening and right on through the middle of the workweek. The cold front of yesterday has since sagged into southwest VA with just a few residual showers south of KCHO and east of KLYH. These showers will quickly come to an end after sunset. With lingering low level moisture nearby, went ahead and added a little fog at KCHO between 08-12z/4-8am Tuesday. Vsbys may drop as low as 2 to 4 miles before quickly improving after daybreak. Elsewhere, fog will remain limited as ample dry air advection overspreads the region. Winds will remain light out of the north tonight before turning to the east and northeast Tuesday. Southeasterly winds at less than 10 kts return Wednesday as high pressure to the north slides offshore. No significant weather is expected Thursday other than the heat and humidity. Temporary reductions look to return to the terminals during the afternoon and evening hours Friday into the weekend due to thunderstorms. This is in association with several pieces of energy ahead of a weak front that looks to cross SUnday into early next week. && .MARINE... Light north to northeast winds are expected to continue through Tuesday morning as high pressure sits north of the waters. Winds will slowly chance to the east Tuesday afternoon before switching to the southeast Wednesday at less than 15kts. There still remains a brief window for SCA conditions for an 1 to 3 hours due to northerly channeling. Highest condfidence (albeit low) would be over northern and middle portions of the bay. A Marine Weather Statement may be needed to encompass this threat as it evolves. SCA conditions are possible Thursday through Fri night, particularly at night due to channeling. SMWs may be needed during the afternoon and evening hours this weekend as thunderstorm chances increase across the region. && .TIDES/COASTAL FLOODING... By the middle of the week, water levels are expected to rise again on strengthening southeast winds. Snapback tide could push water levels into minor flood stage at some sensitive locations (mainly Annapolis) by the middle of the week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...EST SHORT TERM...DHOF/KRR LONG TERM...CJL AVIATION...DHOF/CJL/EST MARINE...DHOF/CJL/EST TIDES/COASTAL FLOODING...KRR