Area Forecast Discussion
Issued by NWS Sterling, VA

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674 FXUS61 KLWX 211842 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 242 PM EDT Tue Mar 21 2017 .SYNOPSIS... A strong cold front will cross the area tonight into early Wednesday. High pressure will return Wednesday afternoon through Thursday night. A warm front will cross the region Friday. Low pressure may affect the area Sunday. && .NEAR TERM /THROUGH TONIGHT/... Overcast stratus deck from earlier today has scattered out this afternoon for most areas, leading to a mix of filtered sunshine and clouds. Temperatures have responded nicely, and highs will peak late this afternoon around 60F for most locations, except mid to upper 60s across portions of central Virginia where sun broke out a bit earlier. A strong cold front moving through the midwest this afternoon will push rapidly southeastward towards the region tonight. Will see mid level clouds increase again tonight, and there may be enough moisture to touch off some light rain showers out ahead of the front. Will keep precipitation chances in the slight to low chance range. Following frontal passage late tonight and into the early morning hours of Wednesday, will see a marked increase in northwesterly winds with gusts by morning nearing 30 mph. Temperatures also fall behind the front into the 30s by morning. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Winter-like conditions return once more for Wednesday and Thursday with well below normal temperatures and gusty winds. Despite near full sunshine Wednesday, 850 mb temperatures dropping to near -10C will keep highs in the low to mid 40s for most. Exception will be central Virginia where some locations will near 50F due to later cold frontal passage and slightly modified air. These are about 10-15 degrees below the climatological normals. Gusty northwest winds expected as well with gusts peaking 30-35 mph during the first half of the day. Strong Canadian surface high pressure will then build in Wednesday night and crest directly overhead Thursday morning. This will lead to near ideal radiational cooling conditions with clear skies and slackening winds. Thus quite a cold night expected with lows in the teens and 20s. High pressure will remain in control on Thursday with sunny skies and light winds. Temperatures will remain below normal however, with highs in the 40s for most. The high will then slide offshore Thursday night with southerly return flow developing. A warm front will also approach the region from the west, and some light precip is possible after midnight/towards morning, especially north/west. With cold surface temperatures and overrunning warmer air, some light mixed precipitation is possible north/west. && .LONG TERM /FRIDAY THROUGH TUESDAY/... High pressure will continue shifting offshore Friday and Friday night, allowing for a return flow and milder air to develop for the mid- Atlantic. Some light precipitation is possible Friday morning with initial surge of warm/moist air aloft. A cold front will sag across the Eastern Great Lakes Saturday before stalling across our region Saturday night. A chance for rain showers will develop during this period. A storm system will develop along the west end of this stalled front on Sunday, keeping the chance for rain showers in the region. The storm system will move east along the front toward the East Coast. The chance for rain showers linger throughout Sunday night. More rain showers could develop along an associated cold front that should also stall across our region on Monday. Temperatures will be more seasonable. A stalled front will push northward as a warm front Tuesday, allowing for rain chances to linger into Tuesday night. Temperatures will become milder. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR and relatively light winds expected through the first half of tonight with a mix of lingering scattered-broken cumulus and increasing mid/high clouds. A strong cold front will then cross late tonight and early Wednesday morning. An isolated rain shower is possible ahead of the front. Winds become gusty out of the northwest behind the front with gusts up to 30 knots developing Wednesday morning. VFR conditions continue Wednesday through Thursday with high pressure moving overhead. Gusty winds diminish Wednesday night. Some light precipitation is possible late Thursday night as a warm front moves towards the region, but significant reductions are not likely. VFR conditions Friday and Friday night. MVFR to IFR conditions with rain showers are possible Saturday into Sunday. Winds becoming south 5 knots Friday. Winds southwest 5 to 10 knots Friday night and Saturday. Winds southwest 10 to 15 knots Saturday night. && .MARINE... Relatively light winds will continue into tonight. A strong cold front will cross the waters later tonight and early Wednesday morning. This will bring gusty north to northwest winds, with gusts up to around 30 knots expected. Thus a SCA is in effect for all waters beginning at midnight tonight. It is possible that gale conditions are briefly observed Wednesday morning. Gusty winds continue into Wednesday night, but a slackening trend is expected. SCA ends for some locations at 8 PM Wednesday, but continues for the lower tidal Potomac and the central Chesapeake until 4 AM Thursday. Relatively light winds expected Thursday into Thursday night as high pressure builds across the area. Wind direction will become southerly by Thursday night. Small craft advisory conditions possible Friday with increasing southerly winds. Winds mainly sub-SCA Saturday and Sunday. && .FIRE WEATHER... Dry conditions and gusty winds expected Wednesday following strong cold frontal passage. Relative humidities will drop into the 20 to 30 percent range with sustained north to northwest winds from 15 to 20 mph, gusting 30 to 35 mph. However following recent rain and snow, fuel moistures are currently between 9 and 15 percent. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT Wednesday for ANZ530-531-535-536-538>540. Small Craft Advisory from midnight tonight to 4 AM EDT Thursday for ANZ532>534-537-541>543. && $$ SYNOPSIS...MM NEAR TERM...MM SHORT TERM...MM LONG TERM...KLW AVIATION...MM/KLW MARINE...MM/KLW FIRE WEATHER...MM

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