Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200850 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 350 AM EST Wed Feb 20 2019 .SYNOPSIS...Low pressure will track from the Mississippi valley into the Great Lakes today through tonight. Coastal low pressure will develop along the Mid-Atlantic Coast tonight before moving off to our northeast Thursday. High pressure will return Thursday night and Friday before another low pressure impacts the area early next week. && .NEAR TERM /THROUGH TONIGHT/... WAA overrunning snow has begun across our southwest with snow now being reported as far north as Opal VA and Petersburg WV. Upstream reports across west central VA (Roanoke area) indicate a 4-hr period of heavy snow with an inch per hour snowfall rates with snow having transitioned to sleet and freezing drizzle in that area. Expect snow to continue to develop northeast later this morning with snow transitioning to fzra/pl after 12Z in the Charlottesville area and across northern VA and DC around midday and the rest of the CWA by 21Z as warm nose lifts northward. Then, freezing rain/rain in the late afternoon and early evening becoming all rain everywhere by midnight tonight. Expect generally 3-6 inches of snow in the warning area with higher snow totals of 6-8 across northern and western MD and significant icing across northwestern VA, eastern WV, and western MD roughly west of Rt 15 and north of Rt 33 in Harrisonburg. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Cdfnt clears the area early on Thu with rain ending by 09Z if not sooner. High pressure then builds over the area Thu night with next round of overrunning precip associated with developing southern Plains cyclone beginning late Fri night. Given milder period ahead and high pressure at a more eastward position, this appears to be a mostly rain event except possibly in far NW Maryland where some freezing rain is possible. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Warm front will be crossing the area Saturday, with more than enough isentropic lift to induce a swath of precipitation. Thermal profiles will be sufficiently warm for this to be all rain. With a trajectory off of the Gulf of Mexico, anticipate that moisture won`t be a hinderance. Model guidance suggesting precipitable water will be exceeding an inch...and approaching an impressive (for February) 1.5 inches by Saturday night. Any remaining snow should be melted away, as temperatures drop little Saturday night in continued warm advection. But, the rainfall and snowmelt could lead to flooding concerns, as suggested by the NAEFS MMERF. Temperatures will continue to rise well into the 60s on Sunday ahead of a cold front, which may lead to additional showers. A tight thermal gradient should lead to strong cold advection, and thus windy conditions. High pressure will build across the northeast Monday-Tuesday. Since broad ridging remains 850-500 mb, temperatures don`t drop considerably...and will remains at or above climo normals Monday, receding to near normal by Tuesday. (Cold advection/breezy conditions will continue into Monday.) With a jetmax along the central Atlantic coast, systems will be progressive. Chance PoPs will return by the end of the day Tuesday. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... Developing LIFR/IFR conditions this morning as snow develops. A 4-hr period of heavy snow is expected with intense snowfall rates of 1+ inch per hour is likely mainly in the 11Z-17Z time frame. Then, snow changing to sleet and freezing rain in the afternoon and eventually to rain late today or early this evening. KMRB will be the last to change to rain not likely until 03Z tonight. Rain ends late tonight around 09Z with cigs and vsbys improving. Flight restrictions (MVFR to IFR) likely this weekend in rain. Conditions may lift slightly Saturday night between warm and cold frontal passages. && .MARINE... Marginal SCA conditions possible this afternoon and evening, but confidence too low to issue an SCA. Otherwise, light winds 10 kt or less through Fri night. Light (at or below 10 kt) south winds Saturday as a warm front passes north of the waters. Mixing improves considerably Sunday behind a cold front. Small Craft Advisory conditions likely on Sunday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Winter Storm Warning until 7 PM EST this evening for DCZ001. MD...Winter Storm Warning until 7 PM EST this evening for MDZ013- 503>506. Winter Storm Warning until 1 AM EST Thursday for MDZ003-004- 501-502. Winter Storm Warning until 7 PM EST this evening for MDZ005- 006-011-014-507-508. Winter Weather Advisory until 4 PM EST this afternoon for MDZ016>018. VA...Winter Storm Warning until 10 PM EST this evening for VAZ025- 026-036>038-503-504-507-508. Winter Storm Warning until 7 PM EST this evening for VAZ039- 050>054-502-506. Winter Storm Warning until 1 AM EST Thursday for VAZ027>031- 040-501-505. Winter Weather Advisory until 4 PM EST this afternoon for VAZ055>057. WV...Winter Storm Warning until 10 PM EST this evening for WVZ505- 506. Winter Storm Warning until 1 AM EST Thursday for WVZ050>053- 055-501>504. MARINE...Small Craft Advisory from noon today to 6 PM EST this evening for ANZ531>533-539>542. Small Craft Advisory from 10 AM this morning to 10 PM EST this evening for ANZ534-537-543. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...HTS AVIATION...LFR/HTS MARINE...LFR/HTS

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