Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210147 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 947 PM EDT Thu Oct 20 2016 .SYNOPSIS... A cold front will approach the area tonight before passing through Friday. An upper-level trough will pass through the area Saturday and high pressure will build into the region for Sunday. A reinforcing cold front will pass through the area Monday with high pressure returning for the middle portion of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Most of the region will be dry through tonight. Additional showers will approach the Potomac Highlands this evening, however, most activity will stay west of the region. Most of the rainfall will stay behind the front which will cross the region starting in the west early Friday morning. Main changes to the fcst next 24 hrs were to adjust temperatures for tonight and Fri. Used a 24-hr trend from the ECMWF to adjust minimum and maximum temperatures. This result in an upward trend overnight in the east and a downward/upward trend in the west/east respectively for tomorrow. High temps still likely to rise to the low 80s in the east in the morning before the rain arrives around midday. Falling temperatures will be the rule during the afternoon. Also raised PoPs for tomorrow and tomorrow night as strong upper level energy will move across the area providing strong forcing to generate light precip. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... The cold front will be cross the region Friday. Most of the precipitation will be on or behind the front as most of the forcing is behind the surface front. Rainfall amounts will range greatly across the region with amounts 1-1.5 inches across the Potomac Highlands to 0.25 inches across I-95/Chesapeake Bay region. Winds will increase behind the front with northwest gusts up to 20-30 mph by Fri afternoon. Temperatures will likely drop mainly west of the Blue Ridge during the day on Friday as CAA moves into the region. Temps on Friday will also greatly range from the 50s across the Allegheny Front to the low 70s across I-95/Southern MD. Rainfall will come to an end Friday afternoon/evening however showers will persist across the western slopes of the Allegheny Front. Rain showers may also turn to snow showers in this location into Saturday morning. No accumulation is expected. Gusty winds continue Saturday with gusts up to 35 mph. Elevations mainly above 1500 feet may see wind gusts up to 45 mph and a wind advisory is possible for Friday night into Saturday for higher elevations. Drying continues Saturday night as high pressure continues to move into Mid-Atlantic region. Temperatures in the 40s and 30s at higher elevations Sat night. && .LONG TERM /SUNDAY THROUGH THURSDAY/... High pressure centered over the Gulf states will build towards our region Sunday into Monday allowing for dry conditions. A cold front will move across our CWA on Monday with little moisture associated to it, so little to no precipitation expected... but it will drop temperatures slightly below normal. High pressure returns behind the front later on Monday through Wednesday and a warm front will approach Thursday increasing PoPs. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... VFR conditions expected through this evening. MVFR cigs expected early Friday morning as a cold front enters the region. -RA/MVFR cigs possible through Friday afternoon as the front crosses from west to east across the terminals. Gusty NW winds expected Friday night through Saturday night. Winds will peak Saturday morning and afternoon and 25-35 kts with gusts up to 40 kts possible at MRB/IAD/DCA/BWI/MTN. VFR conditions will continue for Sunday through Monday. VFR conditions expected Sunday into Wednesday with high pressure mainly dominating our weather conditions. Windy conditions expected Monday... and maybe some sub- VFR conditions on Monday with the passage of a weak front. && .MARINE... A cold front will approach the waters tonight into Friday morning before passing through Friday around midday. Southerly winds will continue ahead of the front. A Small Craft Advisory is in effect for most of the waters later this afternoon through Friday morning. Did leave out the Upper Tidal Potomac for now thinking that the stronger wind field aloft may hold off until after peak mixing. Gusty northwest winds will develop behind the boundary Friday afternoon. A Small Craft Advisory is in effect for all of the waters. More gusty winds are expected Friday night through Saturday night. A Small Craft Advisory will be needed and a Gale Warning may be needed for portions of the waters during this time. High pressure will build to the south of the water Sunday before another cold front passes through Monday. High pressure will build in for the middle portion of next week. A Small Craft Advisory may be needed for portions of the waters during this time. Small craft advisory conditions expected Sunday into Monday with windy conditions over our region. Winds should be diminishing on Monday night. No small craft advisory expected Tuesday into Wednesday. && .TIDES/COASTAL FLOODING... On southerly winds water levels are expected to reach minor coastal flood levels at Annapolis tonight. High tide is at close to 10 pm. Winds will turn to the northwest Friday afternoon bringing water levels down. && .CLIMATE... List of record daily warm temperatures for October 20th. Record daily high temperatures Site 10/20 DCA 86 (1969) BWI 87 (1969) IAD 83 (1969) *also occurred in previous years Record daily warm low temperatures Site 10/20 DCA 64 (1885)* BWI 65 (1910) IAD 59 (1993) *also occurred in previous years && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until midnight EDT tonight for MDZ014. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ530>534- 536>543. Small Craft Advisory from noon Friday to 6 AM EDT Saturday for ANZ535. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...HSK LONG TERM...IMR AVIATION...IMR/LFR MARINE...IMR/LFR TIDES/COASTAL FLOODING... CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.