Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221353 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 953 AM EDT Thu Mar 22 2018 .SYNOPSIS... Low pressure will move into the Canadian Maritimes today. High pressure will build in from the west through Saturday. Low pressure will move from the mid-Mississippi Valley Saturday to the Carolinas Saturday night. High pressure will follow for the beginning of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The Nor`easter is located east of Long Island this morning and continues to move away to the northeast. While low level clouds have mostly eroded, there`s a veil of high-level clouds. Skies partly cloudy at best. A shortwave trough currently over the Ohio Valley will cross the area today, so anticipate diurnal cumulus too. A seasonably cold airmass will remain in place, and with northwest wind gusts to 25 mph or so. Shaded gust forecast down a pinch based on latest meso guidance; do not expect full mixing. High temperatures are only expected to be in the 40s, perhaps reaching 50 in central VA. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/... The axis of high pressure centered near Hudson Bay will remain west of the area tonight and Friday. Another vort max will be crossing the area Friday, which could increase cloud cover at times. The GFS is one of the "wetter" models, showing potential for some light upslope snow showers and perhaps a sprinkle or flurry east of the crest. Have kept the forecast dry for now given relatively shallow moisture. There will remain enough gradient for 20-30 mph gusts again on Friday as well. After morning lows in the 20s, daytime highs will range from the lower 40s to lower 50s. The surface ridge axis will reach the area Friday night, resulting in lighter winds. Lows in the mid 20s will be common outside of the cities, with some teens likely west of the Blue Ridge. Attention turns to the next storm system which will be approaching from the mid-Mississippi Valley, which will dive into the Carolinas by Saturday night. We will be on the cold side of this system, and if any appreciable precipitation falls, it would likely become snow. The northern gradient of the precipitation is in question as strong high pressure will be positioned to our north in Canada. It is becoming more likely that our far southern tier of counties at a minimum could see some snow. While accumulations would likely be highly elevation dependent, some accumulations could occur in the valleys as well if precipitation continues into the evening (which is quite possible). Winter headlines may eventually need to be considered when confidence becomes higher. Outside of precipitation, highs should reach the 40s, with lows Saturday night back below freezing. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The disturbance across our southern and southwestern zones will move away early Sunday. High pressure will gain control of the region midday Sunday through Tuesday. Skies will be mostly sunny each day and mainly clear each night. Temperatures will remain nearly 10 degrees below average with highs in the middle 40s and lows in the middle 20s. The high is expected to move to the East Coast later Tuesday into Tuesday night to allow for a slight southeasterly wind to develop and thus, increasing clouds in our western zones and in the Blue Ridge Mountains. We should remain dry through Tuesday, then introduce a better chance for a rain or snow shower Tuesday night with the upslope flow. The high moves to the East Coast Wednesday to allow for a storm system to move east across the Great Lakes region. An associated cold front will drag across the Ohio Valley and mid-Atlantic region Wednesday night then possibly stall across the mid-Atlantic region Thursday. There is a chance of some rain and snow showers in our CWA Wednesday night into Thursday along this front. Temperatures will not be as cool Wednesday through Thursday. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Ceilings have lifted as low pressure continues to pull away and the threat for linger flurries is over. VFR is then expected through Friday, though cigs in stratocumulus are possible at times. The main concern will be gusty northwest winds which could gust above 25 knots during the daytime each day. VFR conditions expected early Saturday, before another system may affect us with wintry weather late Saturday into Saturday night. Highest chance of sub-VFR is at CHO. MVFR conditions remain possible at CHO with any snow showers around early Sunday. Otherwise, VFR conditions at all terminals Sunday through Monday night. Winds northeast 5 to 10 knots Sunday through Monday, becoming southeast then shifting northwest 5 to 10 knots Monday night. && .MARINE... While there is currently some lull in the winds, SCA conditions will return quickly today. There will be some diminishing of the winds on the tidal Potomac tonight, but then SCA will return for all waters during the day on Friday. Winds should diminish Friday night into Saturday as high pressure builds across the area. Weak low pressure will pass by to the south Saturday night. No marine hazards expected Sunday through Monday night. Winds northeast around 10 knots Sunday through Monday, becoming southeast 10 knots then shifting northwest 10 knots Monday night. && .TIDES/COASTAL FLOODING... Current water levels returning closer to normal as north winds push water out of the estuary. Only positive departures remaining are on the mid Bay and lower tidal Potomac...and those are less than a foot. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ531>534-537- 539>543. Small Craft Advisory until midnight EDT tonight for ANZ530-535- 536-538. Small Craft Advisory from 9 AM to 6 PM EDT Friday for ANZ530- 535-536-538. && $$ SYNOPSIS...ADS NEAR TERM...ADS/HTS SHORT TERM...ADS LONG TERM...KLW AVIATION...ADS/KLW MARINE...ADS/KLW TIDES/COASTAL FLOODING...HTS is the U.S. government's official web portal to all federal, state and local government web resources and services.