Area Forecast Discussion
Issued by NWS Sterling, VA

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661 FXUS61 KLWX 201432 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1032 AM EDT Sat Aug 20 2016 .SYNOPSIS... Weak high pressure will drift offshore today. A cold front will move through the area Sunday afternoon. High pressure then builds over the area into Tuesday before persisting offshore through the rest of the week. && .NEAR TERM /THROUGH SUNDAY/... As of 10am...1030mb surface high is along the Mid-Atlantic coast. An east wind this morning will shift south through the rest of the day. Dewpoints are around 70F, but subsidence will suppress cu and thunderstorm development east of the Blue Ridge. A few isolated showers t-storms possible along and west of the Blue Ridge this afternoon with peak heating and marginal moisture dissipating in the early evening. Otherwise, very warm with temperatures to around 90F. Deeper moisture begins to overspread the area late tonight and early Sun morning as deep layered flow becomes from the SW. Sct showers are possible by daybreak, but most of the activity is likely to hold off until after 12z. PWs rise over 2 inches and showers become more widespread as convergence increases along approaching cdfnt. Threat for heavy rainfall and flash flooding still exists mainly over northeast MD due to very high PWATs close to 200% of normal. However, threat will be mitigated by fast storm motion of 20-25 kt. Latest WPC PQPF guidance is showing 10-40% chance of exceeding 0.5 inches in 6-hrs which could be enough for some flooding in highly vulnerable area of Baltimore. There will also be a threat of 30-50 mph wind gusts with the t-storms given fast storm motion, moderate instability and marginal shear. Special marine warnings are likely to be required. SPC Day 2 Otlk has area under marginal risk and this looks very reasonable. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Cdfnt clears the area early Sun evening with showers ending quickly. High pressure then builds through the first half of next week with temps cooling down to the low and mid 80s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Surface high pressure will be centered over the Mid-Atlantic on Tuesday. The seasonably pleasant weather will continue with slightly below normal temperatures and dew points remaining in the 50s. The high will move offshore on Wednesday and Thursday as heights build aloft. This will lead to a gradual warming trend as well as slightly more humid conditions. There may be enough moisture return into the western mountains on Thursday for a few showers and storms to develop. Computer guidance is in fairly good agreement of a cold front approaching Friday, which will bring the next notable chance of showers and storms. However, the front will be slowing, and there will be minimal upper level forcing, so it does not appear like a widespread rain threat at this time. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... VFR prevails across the area into late tonight. Isolated afternoon t-storms possible invof KMRB and KCHO. Cdfnt to move through the terminals late Sun with showers and sct t-storms with gusty winds and heavy rainfall with possible brief IFR conditions. No significant weather expected through mid-week under high pressure. && .MARINE... East wind less than 10 kt with high pressure along the Mid- Atlantic coast this morning will shift south through the day. Small craft advisory conditions possible late Sun night through Mon as cdfnt moves through the waters and winds strengthen. Also, t-storms Sun afternoon may be capable of producing strong wind gusts and may require SMWs. Northerly winds may continue up to 15 kt early Tuesday, but will become light and variable as high pressure moves overhead late Tuesday into Wednesday. Light southerly flow will develop by Thursday as the high moves offshore. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BAJ/LFR NEAR TERM...BAJ/LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...BAJ/ADS/LFR MARINE...BAJ/ADS/LFR is the U.S. government's official web portal to all federal, state and local government web resources and services.