Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 231810 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 210 PM EDT Fri Mar 23 2018 .SYNOPSIS... High pressure will build in from the west through Saturday. Low pressure will move from the mid-Mississippi valley Saturday to the southern Mid-Atlantic Saturday night. High pressure will follow for Sunday through Tuesday. A cold front will approach the area during the middle portion of next week. && .NEAR TERM /THROUGH TONIGHT/... Low pressure will continue to move north and east of the Canadian Maritimes while high pressure builds over the Great Lakes through late this afternoon. A blustery northwest flow will continue to usher in chilly conditions for this time of year. An upper-level disturbance will pass through the area late this afternoon and colder air aloft will allow for limited instability underneath the subsidence inversion. However, the airmass is very dry. Did allow for an isolated sprinkle or flurry across northern Maryland into the Shenandoah Valley of Virginia, eastern West Virginia and central Virginia...but most of the time will turn out dry with just a sct/bkn stratocu deck. The upper-level disturbance will move offshore tonight and high pressure will continue to build overhead from the Great Lakes. Dry and cold conditions are expected for this time of year. Min temps will range from the upper teens in the colder valleys of the Potomac Highlands and Shenandoah Valley to around 30 in the cities of Washington and Baltimore. Visible satellite shows snowpack over far northern and western suburbs of Washington and Baltimore and for locations near and west of the Blue Ridge and Catoctin Mountains. Any wet surfaces from melting snow will quickly freeze if untreated after sunset. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Low pressure will track through the Tennessee Valley Saturday and it will pass by to the south Saturday night. However...a strong confluent zone between upper-level low pressure over New England and upper-level ridging over the Great Lakes should suppress the low and keep its track farther south. Therefore...latest expectation is that much of the area will remain dry and the latest forecast indicates that with pops trimmed back to the south and west. However...for our extreme southwestern areas a period of accumulating snow cannot be ruled out. Confidence is lower as the latest guidance has shifted a bit farther south but it is still possible considering that a tight gradient between accumulating snow vs. no snow will be nearby. Areas that have the best chance for picking up a period of snow are across the ridge tops of Highland and Augusta counties as well as the central Virginia Blue Ridge Mountains. Will continue to mention in the HWO for now, but confidence is too low for any headlines. More chilly conditions are expected for this time of year Saturday and Saturday night. High pressure will build in from the north Saturday night and Sunday. A north to northeast flow will bring dry but more cold conditions for this time of year. && .LONG TERM /MONDAY THROUGH FRIDAY/... A strong upper level ridge will settle over the eastern U.S by Monday. Meanwhile a strong upper level low will be positioned over the western Atlantic. The high amplitude height pattern will lead to the slow progression of synoptic features for the upcoming week. The ridge axis will move eastward midway through next week as a front approaches from the west. Temperatures will be trending upwards through the period. A cold front will approach the region toward the the second half of the week bringing a chance of precipitation to the area. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... High pressure will build over the terminals through tonight. VFR conditions are expected during this time and wind gusts will diminish around sunset. Low pressure will pass through the Tennessee Valley Saturday and well to our south Saturday night. A period of snow may approach KCHO but latest thinking is that the better chance for snow will be to the south and west. High pressure will return for Sunday through Sunday night with more VFR conditions. No flight restriction expected Monday or Tuesday. && .MARINE... High pressure will continue to build over the waters through tonight. A Small Craft Advisory remains in effect for the waters through this evening and for the middle portion of the Bay and lower Tidal Potomac River late tonight into Saturday morning. Low pressure will pass by to the south Saturday night and a pressure surge ahead of building high pressure will cause wind gusts around SCA criteria late Saturday night through Sunday night. High pressure moves over the waters. No marine hazards are expected. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 11 AM EDT Saturday for ANZ531>534- 537-539>541-543. Small Craft Advisory until midnight EDT tonight for ANZ530-535- 536-538-542. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...HTS AVIATION...BJL/HTS MARINE...BJL/HTS is the U.S. government's official web portal to all federal, state and local government web resources and services.