Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 270235 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 935 PM EST WED NOV 26 2014 .SYNOPSIS... COASTAL LOW PRESSURE WILL MOVE AWAY FROM THE AREA TONIGHT. AN UPPER- LEVEL DISTURBANCE WILL PASS THROUGH THE AREA THURSDAY AND HIGH PRESSURE WILL BUILD OVERHEAD FRIDAY. THE HIGH WILL MOVE OFF THE COAST DURING THE WEEKEND. && .NEAR TERM /THROUGH THURSDAY/... COASTAL LOW PRESSURE WILL CONTINUE TO RACE NORTHEAST OFF THE SOUTHERN NEW ENGLAND COAST TONIGHT. SUBSIDENCE BEHIND THE DEPARTING LOW HAS LARGELY KICKED INTO PLACE ACROSS THE REGION EXCEPT FOR A FEW PASSING FLURRIES/SPRINKLES OVER EASTERN SECTIONS OF THE AREA. THE NEXT WEAK SHORTWAVE TROUGH WILL APPROACH FROM THE WEST TONIGHT. FORCING WILL BE WEAK WITH THIS SYSTEM BUT NONETHELESS...THERE WILL BE A CHANCE FOR LIGHT UPSLOPE SNOW SHOWERS OVER THE POTOMAC HIGHLANDS OVERNIGHT. DECENT SNOW PACK AND LOW LEVEL MOISTURE WILL LEAD TO FOG DEVELOPMENT OVERNIGHT...PRIMARILY WEST OF THE BLUE RIDGE MOUNTAINS. SOME OF THE FOG COULD BE LOCALLY DENSE. WILL CONTINUE MENTION IN THE HWO. TEMPERATURES WILL FALL BELOW FREEZING IN MOST PLACES EXCEPT THE METRO CENTERS. THIS WILL LEAD TO REFREEZING CONCERNS ON SECONDARY ROADWAYS OR UNTREATED SURFACES OVERNIGHT INTO EARLY THURSDAY. THE UPPER-LEVEL DISTURBANCE WILL MOVE AWAY FROM THE AREA THURSDAY AFTERNOON AND HIGH PRESSURE WILL BUILD TOWARD THE REGION FROM THE OHIO VALLEY. A STRAY RAIN OR SNOW SHOWER CANNOT BE RULED OUT WITH AN UPPER-LEVEL TROUGH OVERHEAD...BUT MOST AREAS WILL BE DRY AND CHILLY WITH SOME SUNSHINE. MAX TEMPS WILL RANGE FROM THE 20S AND LOWER 30S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 40S IN CENTRAL VIRGINIA. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... SFC HIGH PRES CONTINUES TO BUILD EAST OVER THE AREA THROUGH FRIDAY. NWLY FLOW WILL CONTINUE TO CAUSE UPSLOPE SNOW WEST OF THE ALLEGHENY FRONT INTO LATE THURSDAY NIGHT BEFORE TAPERING OFF AS THE SATURATED LAYER DECREASES. SHOULD JUST BE WAVE CLOUDS EAST OF THERE SINCE THE UPR TROUGH AXIS MOVES EAST OF THE AREA THURSDAY EVENING. NWLY FLOW GUSTS PERIODICALLY TO 20 TO 25 MPH THURSDAY NIGHT IN COLD AIR ADVECTION...THEN MIXES DOWN AGAIN ACROSS THE AREA FRIDAY. GRADIENT SLACKENS THROUGH FRIDAY AFTERNOON. FRIDAY NIGHT...SFC HIGH CENTER CROSSES THE AREA WITH CLEAR AND CALM AND MIN TEMPS BACK BELOW FREEZING. PLACES WITH A REMAINING SNOWPACK OF MORE THAN A FEW INCHES (HIGHER ELEVATIONS) WILL SEE A MARKED DROP IN TEMPERATURES...POSSIBLY INTO THE TEENS. LOW 30S ALONG THE SHORE LINE. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE WILL MOVE OFFSHORE THIS WEEKEND SETTING UP A SOUTHERLY RETURN FLOW. TEMPERATURES WILL RETURN TO NEAR NORMAL UNDER THIS REGIME. A FRONT WILL BUMP INTO THIS HIGH LATE IN THE WEEKEND THEN STALL NEAR THE AREA NEXT WEEK. IT LOOKS WARM ENOUGH FOR RAIN SHOWERS ALONG THIS FRONT MONDAY. HIGH PRESSURE WILL MOVE BY TO THE NORTH BEHIND THE FRONT...BUT DEPENDING ON HOW FAR SOUTH THE FRONT GETS IT MAY NOT GET MUCH COOLER. MODELS DISAGREE ON THIS PLACEMENT SO TEMPERATURE FORECAST IS UNCERTAIN DURING THE MIDDLE OF NEXT WEEK. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... MOSTLY VFR EXPECTED AT THE TERMINAL SITES OVERNIGHT. SOME PATCHY FOG COULD DEVELOP ESPECIALLY WHERE SNOW PACK EXISTS. SOME OF THE FOG COULD BE LOCALLY DENSE. AN UPPER-LEVEL DISTURBANCE MAY BRING A RAIN OR SNOW SHOWER LATE TONIGHT THROUGH THURSDAY...BUT MOST AREAS WILL BE DRY. VFR CONDITIONS WITH NORTHWEST WINDS ARE EXPECTED FOR MOST OF THURSDAY. NWLY FLOW GUSTS 20 TO 25 KT THURSDAY NIGHT AND FRIDAY AS HIGH PRES BUILDS (VFR CONDS). HIGH OVERHEAD FRIDAY NIGHT WITH CONTINUED VFR. MAINLY VFR THROUGH THE WEEKEND W/ WIND BECOMING S AROUND 10 KT. && .MARINE... SMALL CRAFT CONDITIONS WILL CONTINUE FOR A SHORT TIME BEFORE WINDS DIMINISH BEHIND THE DEPARTING COASTAL LOW PRESSURE SYSTEM. NORTHWEST WINDS ARE EXPECTED THURSDAY...BUT SPEEDS SHOULD REMAIN BELOW SCA CRITERIA. SURGE OF NWLY FLOW THURSDAY EVENING WITH 20 TO 25 KT GUSTS OVER MOST OF THE WATERS (SCA FOR ALL BUT UPPER TIDAL POTOMAC...PATAPSCO AND PATUXENT)...THEN ACROSS THE WATERS FRIDAY. WINDS WILL QUICKLY DIMINISH WITH SUNSET AS GRADIENT SLACKENS. HIGH PRESSURE OVERHEAD FRIDAY NIGHT WITH SLY FLOW BEGINNING SATURDAY MORNING. SOUTHERLY FLOW TO SMALL CRAFT ADVISORY LEVELS POSSIBLE AHEAD OF A FRONT OVER THE WEEKEND INTO EARLY NEXT WEEK. && .CLIMATE... RECORDS FOR EARLIEST MEASURABLE SNOW ALREADY PASSED A FEW WEEKS AGO...BUT BELOW IS A LIST OF DAILY MAXIMUM SNOWFALL RECORDS SPECIFIC TO THE DATE OF NOVEMBER 26TH. THE SNOWFALL REPORTED AT DULLES SO FAR TODAY HAS BEEN 1.6 INCHES /AS OF 3 PM/ AND THIS BREAKS THE OLD RECORD BELOW OF 1.1 INCHES SET IN 1978. DCA/BWI RECORDS ARE SAFE. DCA 2.2" (1898) BWI 4.5" (1898) IAD 1.1" (1978) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ530>534- 536>543. SMALL CRAFT ADVISORY FROM 7 PM THURSDAY TO 6 PM EST FRIDAY FOR ANZ530>534-536-537-539>541-543. SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EST FRIDAY FOR ANZ535- 538-542. && $$ SYNOPSIS...KRW NEAR TERM...KRW SHORT TERM...BAJ LONG TERM...DFH AVIATION...KRW/DFH MARINE...KRW/DFH CLIMATE...DFH/KRW

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