Area Forecast Discussion
Issued by NWS Sterling, VA

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158 FXUS61 KLWX 281846 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 246 PM EDT Fri Apr 28 2017 .SYNOPSIS... High pressure will slide off the southeast coast Saturday. A cold front will move over Pennsylvania Saturday before lifting back northward Sunday. A stronger cold front will move through the region Monday. Canadian high pressure will build over the area during midweek. && .NEAR TERM /TONIGHT/... Sunny skies for the remainder of the afternoon, and continued mostly clear this evening. Clouds will increase after midnight ahead of a warm front moving into OH. Almost all models keep the deep moisture to our north, but the HRRR has consistently been painting a picture of convection moving east of the mountains around midnight...moving through the Bay between 3-4 am. My confidence level on that occurring is not good, but given its consistency I feel I have to keep a mention of isolated thunderstorms across the northern part of the forecast area. Lows primarily in the 60s, but the cities may not drop below 70. This has never happened before in DC - record high min is 69 set in 1896. The year 1896 holds the record high min for Baltimore for five consecutive nights in April. They did only drop to 70 on April 19, 1896. See climate section for more information. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... "Hot" will be the operative word for Saturday as high pressure moves off the southeast coast and pumps warm air into the Mid Atlantic. Again, see the climate section below for high temperature records - these will definitely be in jeopardy. Heat indices will be in the low/mid 90s in the I-95 corridor, nowhere near heat advisory levels but notable for April. Continued warm temperatures Saturday night/Sunday. There is not any real trigger for organized convection approaching, but this is somewhat of a summertime pattern. Hence it is not out of line to see orographically driven storms develop Sunday afternoon. The best thunderstorm chances hold off until Monday. && .LONG TERM /MONDAY THROUGH FRIDAY/... A cold front over the eastern Ohio Valley early Monday will move across the region Monday into Monday night. Showers and thunderstorms, some strong, will develop ahead of and along the cold front Monday afternoon and evening. Temperatures will be about 15 degrees above normal. Weak high pressure will build in behind the cold front Tuesday. A gusty westerly breeze will usher in drier air. Temperatures will not be as warm as Monday, but could still be 5 to 10 degrees above normal. As the high moves east, a secondary cold front will move across the region from the northwest Tuesday night. This front should be a dry front. The front could sag into the Carolinas Tuesday night before starting to move northward as a warm front on Wednesday. A low pressure system is expected to develop along the western end of the warm front over the Lower Mississippi Valley Wednesday night and early Thursday. We introduce a slight chance of showers or a rumble of thunder Wednesday night with a higher chance to likelihood of encountering showers and thunderstorm Thursday through early Friday. At the tail-end of an associated cold front with the storm system, another storm system could develop and deepen over the interior Southeast U.S. Friday and Friday night. The chance of showers and thunderstorms will linger during the period. Temperatures will also be closer to normal Friday and Friday night. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... VFR conditions tonight through Sunday night. A few showers/ thunderstorms will be possible overnight with MRB being the main consideration. Ifr to lifr conditions possible Monday and Monday night. Vfr conditions Tuesday and Tuesday night. Winds south-southwest 10 to 15 knots Monday, becoming southwest around 10 knots Monday night, then west-southwest 10 to 15 knots Tuesday, and west 5 to 10 knots Tuesday night. && .MARINE... Winds below SCA values tonight through Saturday night. Isolated showers/thunderstoms will be possible on the northern part of the Bay after midnight tonight and on all of the waters Sunday. Small craft advisories likely Monday. Small craft advisories possible Monday night and Tuesday. No marine hazards Tuesday night. Winds south 10 to 20 knots gusts 25 knots Monday, becoming southwest 10 knots Monday night, then west-southwest 10 to 15 knots Tuesday, and west 10 knots Tuesday night. && .TIDES/COASTAL FLOODING... Tidal anamolies are expected to decrease slightly over the next several days as wind flow decreases. However, return of southerly flow later today into the weekend will keep anamolies elevated. && .CLIMATE... Record highs/warm lows through the weekend: Washington DC... Saturday 29 April...91 (in 1974)/68 (in 1956) Sunday 30 April...92 (in 1942)/67 (in 1983) BWI Airport... Saturday 29 April...91 (in 1974)/67 (in 1956) Sunday 30 April...92 (in 1910)/63 (in 1983) Dulles Airport.. Saturday 29 April...87 (in 1996)/62 (in 1996) Sunday 30 April...86 (in 2007)/64 (in 1983) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ PRODUCTS...WOODY!/KLW

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