Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260859 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EST WED NOV 26 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL MOVE UP THE ATLANTIC COAST TODAY. 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 TONIGHT/... WINTER WEATHER EXPECTED FOR MOST OF THE MID-ATLANTIC TODAY... LOW PRESSURE WILL CONTINUE TO DEEPEN AS IT MOVES N-NE ALONG THE CAROLINA COASTLINE WHILE HIGH PRESSURE IS LOCATED ACROSS THE GREAT LAKES AND NEW ENGLAND THIS MORNING. NRLY WINDS FROM THE HIGH TO THE NORTH WILL ADVECT DRY AND COOLER AIR INTO THE REGION WHILE PRECIPITATION MOVES OVER THE MID ATLANTIC TODAY. LOW PRESSURE IS ON TRACK TO MOVE ALONG THE NC COAST AND EAST OF THE DELMARVA BY THIS AFTERNOON. THE SFC LOW IS SLIGHTLY DEEPER THAN GFS/ECMWF AND IS MOVING SLOWER THAN INTENDED. RAIN WILL CONTINUE TO SPREAD ACROSS THE REGION EARLY THIS MORNING AS MOISTURE PUMPS INTO THE AREA. TEMPS ARE CURRENTLY IN THE 40S TO NEAR 50 EAST OF THE BLUE RIDGE MTNS AND MOSTLY RAIN IS EXPECTED. RAIN SHOULD QUICKLY CHANGE TO SNOW ACROSS THE HIGHER ELEVATIONS THIS MORNING WHERE TEMPERATURES ARE IN THE LOW 30S. A SHARP DEWPT GRADIENT EXISTS ACROSS THE REGION AS NRLY WINDS PULL DOWN DRIER AIR. DEWPTS AROUND FREEZING OR BELOW ARE OBSERVED IN THE NRN HALF OF THE CWA WITH DEWPTS IN THE 40S TO THE SOUTH. THIS WILL ALLOW RAIN TO CHANGE OVER TO SN OR RASN FASTER WHEN PRECIPITATION GETS THERE. TEMPS WILL CONTINUE TO FALL THROUGH THE DAY TODAY WITH MAX TEMPERATURES REACHED THIS MORNING. TEMPS WILL CONTINUE TO FALL THROUGH THE DAY AND RAIN/SNOW SHOWERS WILL LIKELY TURN TO ALL SNOW WEST OF THE BLUE RIDGE AFTER DAWN. RAIN WILL CHANGE TO RAIN/SNOW JUST EAST OF THE BLUE RIDGE INTO MID MORNING. THICKNESSES ALOFT CONTINUE TO SHOW A TRANSITION ZONE NEAR INTERSTATE 95. LITTLE CHANGE TO THE SNOWFALL FORECAST WAS DONE OVERNIGHT DUE TO THE CONSISTENCY OF MODEL RUNS. MOST SNOWFALL ACCUMULATION WILL BE ACROSS HIGHER ELEVATIONS ALONG AND WEST OF THE BLUE RIDGE AND NEAR THE MASON DIXON LINE. AT THIS TIME...USING HI RES MODELS TO ANTICIPATE BOUNDARY LAYER CONDITIONS. ALTHOUGH THE SFC HIGH TO THE NORTH WILL BE SUPPLYING SOME COLD AND DRY AIR...AS THE LOW MOVES NORTHWARD THAT SUPPLY WILL DIMINISH AND DYNAMICAL COOLING WILL BE THE BEST CHANCE FOR SNOWFALL ACCUMULATION EAST OF THE BLUE RIDGE MTNS. THERE IS A BANDING POTENTIAL THAT IS SHOWN IN THE FN VECTORS IN THE NAM AND GFS FOR MIDDAY ACROSS I-95. IF THIS OCCURS...ALL SNOW WOULD BE ABLE TO PRODUCE ACCUMULATION. IT WILL BE LIKELY MELT ON PAVEMENT BUT ACCUMULATE ON GRASSY SURFACES. LOW PRESSURE WILL MOVE AWAY FROM THE MID-ATLANTIC LATE THIS AFTERNOON AND EVENING TAKING THE PRECIP SHIELD WITH IT. NRLY WINDS WILL BECOME NW AND DRY/COLD AIR WILL FILTER INTO THE REGION. ANY SHOWERS WILL LIKELY CHANGE TO ALL SNOW ACROSS THE ENTIRE REGION BY LATE AFTERNOON AND EARLY EVENING BEFORE TAPERING OFF. FCST MIN TEMPS WILL BE IN THE UPPER 20S TO LOW 30S TONIGHT. THIS WILL CAUSE WET SURFACES TO FREEZE. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... UPPER TROUGH WITH EMBEDDED SHORTWAVE IS PROGGED TO SWING ACROSS THE MID-ATLANTIC THANKSGIVING DAY. SHORTWAVE WILL PRODUCE PLENTY OF CLOUDS ALONG WITH SCATTERED PRECIPITATION. INITIAL P-TYPE LIKELY WOULD BE SNOW...BUT BY AFTERNOON THERMAL PROFILES BECOME MORE MARGINAL FURTHER EAST THROUGH THE CWA THEREFORE HAVE RW/SW AS P-TYPE EAST OF THE BLUE RIDGE. SHORTWAVE EXITS BY EARLY EVENING THURSDAY...BUT EXPECT SOME UPSLOPE SNOW SHOWERS WITH W/NW WIND BEHIND THE SHORTWAVE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... HIGH PRESSURE BUILDS IN FRIDAY NIGHT THEN PUSHES OFFSHORE SATURDAY. WARM FRONT LOOKS TO LIFT NORTH LATE SATURDAY INTO SATURDAY NIGHT. THIS SHOULD HELP TEMPERATURES WARM ABOVE NORMAL FOR SUNDAY. THIS LIKELY LASTS INTO MONDAY EVEN THOUGH A COLD FRONT MOVES THROUGH. COOLER AIR IS SLATED FOR TUESDAY. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... LOW PRESSURE WILL MOVE UP THE EAST COAST TODAY. RAIN AND SNOW IS EXPECTED. VFR CONDITIONS WILL BECOME IFR WITH LOW CIGS AND VSBYS BY AFTERNOON ACROSS THE TERMINALS. SN IS EXPECTED AT MRB FOR MOST OF THE EVENT TODAY WHEREAS WARMER TEMPS EASTWARD WILL LEAD TO RASN OR RA ELSEWHERE. NRLY WINDS ARE EXPECTED TODAY WITH GUSTS UP TO 18KTS AT IAD/DCA/BWI/MTN. SHOWERS WILL BECOME SN BY LATE AFTERNOON. LOW PRESSURE MOVES AWAY FROM THE COAST TONIGHT. CIGS AND VSBYS WILL IMPROVE TO VFR THIS EVENING. DISTURBANCE WILL BRING A CHANCE OF SW/RW THANKSGIVING DAY...THEN NO SIGNIFICANT WX EXPECTED FRIDAY INTO THE WEEKEND WITH HIGH PRESSURE GENERALLY IN CONTROL. && .MARINE... LOW PRESSURE WILL MOVE UP THE EAST COAST TODAY. NRLY WINDS ACROSS THE WATERS WILL INCREASE AND SCA CONDITIONS ARE EXPECTED TODAY. AS THE GRADIENT TIGHTENS AS THE LOW NEARS...GALE FORCE WINDS WILL BE POSSIBLE ACROSS THE LOWER TIDAL POTOMAC AND MIDDLE CHESAPEAKE BAY THROUGH THE AFTERNOON. LOW PRESSURE WILL MOVE AWAY FROM THE WATERS THIS AFTERNOON AND EVENING. NW WINDS WILL SUBSIDE TONIGHT AND INTO THURSDAY. TROUGH MOVES THROUGH THANKSGIVING DAY...WITH POTENTIAL SCA CONDITIONS BEHIND IT FOR THURSDAY NIGHT INTO FRIDAY. HIGH PRESSURE BUILDS IN THEREAFTER. && .CLIMATE... 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. DCA 2.2" (1898) BWI 4.5" (1898) IAD 1.1" (1978) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR MDZ003- 501-502. WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR MDZ004>006. WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST THIS EVENING FOR MDZ007-009>011. VA...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR VAZ025>031-036>040-503-504. WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR VAZ042- 501. WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST THIS EVENING FOR VAZ050>053-502. WV...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ532- 540-542. SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR ANZ533- 534-537-541-543. SMALL CRAFT ADVISORY FROM 6 PM TO 10 PM EST THIS EVENING FOR ANZ533-534-537-541-543. GALE WARNING FROM 11 AM THIS MORNING TO 6 PM EST THIS EVENING FOR ANZ533-534-537-541-543. SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530- 531-538-539. SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 6 PM EST THIS EVENING FOR ANZ535-536. && $$ SYNOPSIS...HAS/BPP NEAR TERM...HAS SHORT TERM...BPP LONG TERM...BPP AVIATION...HAS/BPP MARINE...HAS/BPP CLIMATE...DFH

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