Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250843 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 343 AM EST Sun Feb 25 2018 .SYNOPSIS... A stationary boundary draped across southern Virginia will lift northward today as a warm front. A cold front will approach from the west and cross the area by this evening. High pressure will then build in over the region, migrating off the Mid Atlantic coast by midweek. A broad area of low pressure will approach the Great Lakes region on Thursday, bringing unsettled weather to our region through weeks end. && .NEAR TERM /THROUGH TONIGHT/... The wave of moderate to heavy rain that traversed the area earlier this morning is clearing northeast MD, with additional light to moderate shower activity moving into western MD and the eastern WV Panhandle. High res model guidance brings this area of rain eastward through daybreak, nearing the metro areas, but keeping the bulk of rain along and north of the District. Visibilities have dropped this morning in the wake of the earlier rainfall, ranging 1 to 3 miles in the most restricted areas, but it`s not the widespread dense fog we experienced 18-24 hours ago. Temperatures are holding generally in the middle to upper 40s area wide, and they could fall a few more degrees before bottoming out for the night. A west to east oriented station boundary across southern Virginia this morning will lift northward as a warm front today, and how far northward it progresses will have implications on how warm temperatures reach across the area. Some model guidance wants to bring 70s as far north as D.C., but think that may be a bit over done. Do think the 70s are obtainable along the southern tier of our CWA where the warm front will be to the north, while the lower 60s are more likely across the northern tier, and middle to upper 60s in between. After somewhat of a lull in rain coverage early this morning, expect showers to fill in from mid morning onward as a cold front moves across our area. Not seeing a lot of QPF from model consensus, on average of a quarter to half inch possible through this afternoon, with highest amounts found over our northern and western zones. Have removed the chance of thunder from the forecast with temperatures and moisture are not as high as previously forecast, and a lack of strong forcing as the front crosses our area by this evening. Southerly winds will uptick ahead of the front later this morning, gusting upwards of 20-25 mph. The front will clear our area by early this evening, turning winds light out of the northwest as drier air moves in with high pressure building in from the west. Clouds will stick around tonight with shortwave energy and an upper level jet residing overhead. Meager cold air advection tonight in the wake of the front, with temperatures remaining mild for late February, settling in to the middle 40s surrounding the metro areas and southward, with upper 30s and lower 40s to the north and west. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... High pressure continues to move eastward over the Mid Atlantic on Monday, with a shortwave trough crossing overhead and pressing off to our east by Monday evening. This will help skies to finally start to clear by Monday afternoon, bringing a welcome return of some sunshine. Did keep slight chance POPs in the gridded forecast for the first half of Monday for our extreme southern zones as some guidance wants to keep the frontal boundary just close enough to have the possibility of light shower activity for these areas. Temperatures remain above normal on Monday, with highs in the middle to upper 50s. High pressure will settle overhead Monday night, coupled with light winds, this allow temperatures a good chance to radiate under mostly clear skies. Middle to upper 30s will be prevalent in the metro areas, with lows at or slightly below freezing along and west of the Blue Ridge. Clear and dry conditions continue Tuesday and Tuesday night as high pressure dominates the region, migrating off the Mid Atlantic coast by Tuesday night. Highs on Tuesday will be in the upper 50s to near 60 degrees, with lows Tuesday night in the upper 30s to near 40 degrees. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The extended portion of the forecast will start out with high pressure moving offshore. Warm advection in the return flow will provide enough lift for scattered showers to arrive during the day Wednesday. The warm front will approach the forecast area Wednesday night, and arrive on Thursday as mid level energy runs through rather fast flow. Therefore, PoPs will spread from central Virginia across the entire area by Thursday. Temperatures will be mild for the period. A deep cyclone will be developing in the Great Lakes/Midwest Thursday, which will be sending a moisture-rich cold front across the area Thursday night, with some precip likely lingering into Friday. Believe that rain will be the dominant type with this system; cold air will be rushing in Friday PM on gusty northwest winds after the precip departs. This could provide some upslope snow showers to the Appalachians Friday night. High pressure will be building across the area Saturday as the deepening cyclone continues northeast. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... IFR conditions have returned to the terminals early this morning, owing mostly to low CIGs. IFR VIS is also a possible occurrence this morning in the wake of earlier rainfall, and shower activity approaching from the west. A cold front will approach the terminals after 25/15z, moving east of the area by around 26/00z. As a result, winds will veer from the south this morning, to the west southwest this afternoon, and out of the northwest by this evening. Ahead and along of the front, winds will gust to around 20 knots during the day, along with MVFR/IFR conditions as -SHRA moves over the terminals. VFR conditions return in the wake of the front this evening, continuing through the first half of the work week as high pressure builds over the region, promoting light winds and only mid to high level clouds. Scattered showers will be near the terminals Wednesday, mainly to the west. While flight restrictions will be possible, confidence is low. The chances increase sharply Thursday as a warm front heads north toward the terminals. && .MARINE... Patchy dense fog is possible early this morning across portions of our waters, with SCA conditions expected today as a warm front lifts northward in to the area and a cold front approaches from the west. Have left the upper portion of the Bay out of the SCA at this time as not expecting the warm front to travel this far north, thus keeping wind gusts down in these areas. The cold front will sweep through the waters this afternoon, potentially accompanied by some gusty showers. High pressure builds over the waters through the first half of the work week, resulting in light winds over the waters with no headlines anticipated. Small Craft Advisories not anticipated Wed or Thu either, due mainly to poor mixing in vicinity of a warm front and complex storm system. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ532>534-536-537-540>543. && $$ SYNOPSIS...BKF NEAR TERM...BKF SHORT TERM...BKF LONG TERM...HTS AVIATION...BKF/HTS MARINE...BKF/HTS

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