Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250802 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 402 AM EDT Sat Mar 25 2017 .SYNOPSIS...
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High pressure over the western Atlantic will be in control today. A back door cold front will drop southwestward into the area later tonight and Sunday. The front will lift back to the north on Monday. Another cold front will drop back south across the region later Tuesday or Tuesday night. The front will stall to the south of our area through the rest of the week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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As of 3am, an approximate 1032mb surface high pressure is centered near Bermuda, 1006mb low pressure is centered over eastern Oklahoma, and 1034mb surface high pressure is centered over northern Ontario. The Canadian high pressure will shift southeast to New England through tonight. This will cause a backdoor cold front to cross the northern half of the CWA with the Bermuda high causing southerly flow south of the cold front. Today, very warm with temperatures 10 to 15 degrees above normal. Most uncertain area for MaxT today is the northern tier of counties where the southern section of an anafrontal zone will persist. Thicker clouds and chances for rain may keep temperatures in the mid 60s. Mid to upper 70s prevail south of the anafront.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
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Confidence in a backdoor front and subsequent onshore flow/cold air damming has increased, so temperatures were lowered below guidance consensus particularly around Baltimore where low 50s are currently expected. Also, patchy drizzle was added to the Sunday forecast generally Blue Ridge and east. A sharp gradient between warm southerly flow and cool easterly flow is expected over southern portions of the CWA. Subsequent shifts will need to focus on this for the MaxT forecast. Guidance shifts the CAD wedge north Sunday night. However, it is wise to hold onto an onshore flow and lower temperatures longer than guidance, so gradual improvement is given for Monday. Low pressure currently over Oklahoma will continue to drift northeast reaching the the Midwest tonight before dissipating over the Great Lakes under a northern stream ridge Sunday night. A second low currently along the California coast will reach the Midwest Monday night before reaching the eastern Great Lakes Tuesday (and also dissipating) per 00Z ECMWF/GFS. Continued moist southwesterly flow warrants high chance PoPs with slight chance for thunder for the LWX CWA Monday. Possibly a break in action, so Monday night was kept low at this time.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/...
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Guidance is not in great agreement regarding the weather systems in our region through the long term. However, most models agree that we will start out in the warm sector on Tuesday. Tuesday morning, the GFS has low pressure near Lake Erie, while the EC has the low furthe southwest over southern Indiana. GFS sends the low east across the St. Lawrence Valley and brings a cold front south in the evening, while the EC solution is slower and weaker with the low, with any frontal passage delayed until at least early Wednesday. This system will bring a threat of showers and thunderstorms with, with notable instablity progged across our region in the warm sector. By late Wednesday, both models have the front south of, with high pressure from Canada pushing cooler and drier air into the region. The remainder of the week appears to be in the cool sector north of the front. While Thursday starts out dry, by day`s end models bring another low pressure wave eastward into the region, with an increasing risk of rain by Thursday night and Friday. This system appears less likely to bring any thunder with it as current guidance generally keeps the warm sector away from us, resulting in a cool and rainy end of March.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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VFR under high pressure and southerly flow through today. Backdoor cold front shifts west across the DC metros tonight with onshore flow 10 to 15 knots through Sunday. Drizzle and IFR conds eventually develop and spread east to west late tonight through Sunday. Southwesterly flow from low pressure to the west/north Monday brings rain showers to the DC metros Monday. Thunderstorms are the main concern Tuesday. This concern will end at night and Wednesday looks VFR with some gusty NW winds likely behind a cold front.
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&& .MARINE...
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Southerly flow 10 to 15 knots today interrupted by a backdoor cold front tonight. Onshore flow expected Sunday into Monday before shifting south. Generally sub-SCA SWly flow prevails Monday. Thunderstorms are possible Tuesday. SCA possible behind a cold front Wednesday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ532>534-536-537-540>543.
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&& $$ SYNOPSIS...RCM NEAR TERM...BAJ SHORT TERM...BAJ LONG TERM...RCM AVIATION...BAJ/RCM MARINE...BAJ/RCM

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