Area Forecast Discussion
Issued by NWS Sterling, VA

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923 FXUS61 KLWX 061924 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 224 PM EST Wed Dec 6 2017 .SYNOPSIS...Surface ridge will remain in place through Friday. Low pressure will pass to the east Friday night, then another low pressure will cross the region Saturday night. High pressure will then return Sunday into Monday. && .NEAR TERM /THROUGH THURSDAY NIGHT/...Quiet but chilly next 24-36 hrs under surface ridge. Jet stream cirrus will stream overhead next svrl days keeping skies generally cloudy. This will inhibit radiational cooling and prevent temps at night from falling too much. Lows generally in the 30s with highs in the mid 40s. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...Low pressure will develop offshore along a stationary front Friday night before moving well out to sea Saturday. Guidance have remained generally inconsistent on how far northwest precip shield gets, but latest guidance suggest that southern MD should see some precip Fri afternoon and night. If precip were to begin Fri, it would probably start as rain in southern MD then mix and change to snow Fri afternoon and evening. There is potential for some light snow accumulations across the southern half of St. Marys county mainly Fri night into early Sat. There is still some uncertainty on how far NW precip shield gets, so some adjustments to PoP, QPF and snow totals may be required. Dry low levels below 850 mb could also result in precip evaporating before reaching the ground especially in northwest St. Marys, northern Calvert and Charles counties and points northwest. An inch or two of snow appears the most likely scenario across the southern half of St. Marys county with a trace or nothing northwest of there. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... We may have ongoing light precipitation across portions of the region Saturday morning as the coastal wave moves northeastward. Uncertainty remains high along the western flank of the precip shield, but greatest chances of accumulating snow will be across southern and eastern Maryland. At the same time, a potent upper level trough and strong cold front will be digging through the Midwest during the day, and will cross the region Saturday night. This has the potential to bring a period of snow showers and possibly some squalls late Saturday and Saturday night, lingering into Sunday morning across the upslope regions along the Allegheny Front. Behind the front, blustery and cold conditions are expected for Sunday. The next fast moving upper level feature and re-enforcing cold front will move towards the east coast late Monday into Tuesday with chances for some precipitation, followed by cold and blustery conditions Wednesday. Temperatures throughout the period will be below normal, possibly significantly below, especially Sunday and Wednesday. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... VFR conditions through Fri night. Any precip aloft Fri night is not likely to cause any flight restrictions. Potential for sub-VFR conditions in light precipitation Saturday morning, with greatest risk at BWI/MTN/DCA. Additional periods of sub-VFR conditions are possible in snow showers or possibly squalls Saturday evening and Saturday night. VFR is expected Sunday into Monday, with gusty northwest winds expected Sunday. && .MARINE...Winds have diminished for the time being but are expected to pick up a bit late tonight across the southern waters. Have modified SCA to just include the southern waters. Winds may strengthen again some Fri night and reach SCA. For now, will hold off on issuing any SCA given it appears a borderline event. Sub-SCA conditions expected Saturday, but winds will increase Saturday night and Sunday associated with a strong frontal system, and Small Craft Advisory conditions are likely. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 10 AM EST Thursday for ANZ533-534-537-541-543. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...MM AVIATION...MM/LFR MARINE...MM/LFR is the U.S. government's official web portal to all federal, state and local government web resources and services.