Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221430 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 930 AM EST MON DEC 22 2014 .SYNOPSIS... A WEAK AREA OF LOW PRESSURE WILL TRACK UP THE MID-ATLANTIC COAST TODAY INTO TUESDAY. STRONGER LOW PRESSURE WILL PUSH NORTH ALONG THE APPALACHIANS ON WEDNESDAY...SENDING A COLD FRONT EASTWARD WEDNESDAY NIGHT. BREEZY CONDITIONS WILL FOLLOW THE FRONT ON THURSDAY...THEN HIGH PRESSURE WILL BUILD BACK INTO THE REGION TO CLOSE OUT THE WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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LOW PRESSURE WILL MOVE UP THE MID-ATLANTIC COAST TODAY AND TONIGHT WHILE A SURFACE RIDGE FROM HIGH PRESSURE OVER NEW ENGLAND REMAINS OVERHEAD. WARM AND MOIST AIR WILL OVERRUN THE SURFACE COLD AIR IN PLACE...CAUSING PLENTY OF CLOUDS ALONG WITH PRECIPITATION THAT WILL CONTINUE TO OVERSPREAD THE AREA FROM SOUTHWEST TO NORTHEAST. PRECIPITATION HAS ALREADY OVERSPREAD CENTRAL VIRGINIA AND IT IS MOVING INTO THE WASHINGTON METROPOLITAN AREA. TEMPERATURES REMAIN CLOSE TO FREEZING WITH DEWPOINTS IN THE 20S. THEREFORE...THE FREEZING RAIN ADVISORY HAS BEEN EXTENDED NORTHEAST TO INCLUDE THE WASHINGTON METROPOLITAN AREA. HOWEVER...ANY ICE NEAR INTERSTATE 95 WILL BE LIGHT AND CONFINED MAINLY TO ELEVATED SURFACES. TEMPERATURES ARE COLDER FARTHER NORTH AND WEST...BUT TIMING OF PRECIPITATION IS STILL UNCERTAIN WITH AREAS ACROSS THE POTOMAC HIGHLANDS LIKELY ENDING UP DRY FOR MOST OF TODAY. THIS ADDS TO THE UNCERTAINTY FOR FREEZING RAIN ACROSS THESE AREAS. WILL CONTINUE WITH A FREEZING RAIN ADVISORY ACROSS NORTHERN AND CENTRAL VIRGINIA WHERE CONFIDENCE IS HIGHEST FOR PRECIPITATION AND COLD AIR TO INTERSECT...CAUSING ICE ACCUMULATION FROM FREEZING RAIN. WEAK LOW PRESSURE CONTINUES MOVES UP THE MID-ATLANTIC COAST TONIGHT. HIGHEST POPS WILL BE CLOSEST TO THE BAY...LOWER IN THE MOUNTAINS. MUCH OF THE CWA LOOKS WARM ENOUGH FOR PRIMARILY RAIN TONIGHT BUT THERE STILL MAY BE POCKETS OF SUB-FREEZING AIR WEST OF THE BLUE RIDGE AND ANY RAIN OR DRIZZLE MAY FREEZE AND ADVISORY MAY NEED TO BE EXTENDED INTO TONIGHT FOR THOSE AREAS.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... IN THE WAKE OF THE LOW...MID-ATLANTIC REMAINS IN A WEDGE/LIGHT FLOW REGIME ON TUESDAY THEREFORE CLOUDY SKIES AND THE CHANCE FOR LIGHT RAIN OR DRIZZLE WILL CONTINUE. TEMPERATURES SHOULD BE WARM ENOUGH FOR JUST LIQUID PRECIPITATION. WHILE THERE IS GENERAL SYNOPTIC AGREEMENT IN THE COMPUTER MODELS THROUGH THE MIDDLE OF THE WEEK...THERE IS STILL QUITE A BIT OF SPREAD IN THE SMALLER SCALE FEATURES. AMPLIFIED UPPER LEVEL PATTERN THROUGH THE MIDDLE PORTION OF THE WEEK. TROUGH OVER THE CENTRAL CONUS WILL LIFT EAST...INDUCING CYCLOGENESIS OVER THE WESTERN GULF OF MEXICO TUESDAY NIGHT. THIS LOW WILL RIDE UP THE WESTERN SIDE OF THE APPALACHIANS...REACHING CENTRAL QUEBEC BY THURSDAY. A STRONG LOW LEVEL JET AHEAD OF THE DEEPENING LOW WILL TRANSPORT MOISTURE UP THE EASTERN SEABOARD TUESDAY NIGHT...BRINGING INCREASING CHANCES OF RAIN. TEMPERATURES DROP LITTLE FROM TUESDAYS HIGHS...SO NO FROZEN PRECIP CONCERNS. WHILE PROBABLY NOT CONTINUOUSLY RAINY THROUGH THE PERIOD...90-100 POPS ARE WARRANTED...WITH MODERATE RAIN POSSIBLE AT TIMES. THE NATURE MAY BECOME MORE SHOWERY ON WEDNESDAY...BUT NOT A COMPELLING REASON TO BREAK THAT OUT AT THIS TIME. 00Z NAM/MET GUIDANCE MUCH COOLER FOR HIGHS ON WEDNESDAY...LIKELY DUE TO A MUCH WEAKER SFC LOW THAN THE GLOBAL MODELS...WHICH ALLOWS THE COLD POOL TO LINGER EAST OF THE MOUNTAINS. HOWEVER...THE OTHER GUIDANCE OF 60S MAY BE A BIT OVERDONE...EXCEPT PERHAPS EAST OF I-95. IF THIS OCCURS...WILL ALSO HAVE TO MONITOR FOR THE POTENTIAL OF STRONG WIND GUSTS IF CONVECTIVE ELEMENTS DEVELOP. THE COLD FRONT TRAILING THE LOW WILL PUSH THROUGH THURSDAY NIGHT...BRINGING AN END TO THE PRECIP EXCEPT SOME POSSIBLE UPSLOPE. HOWEVER WITH THE WARM START...IT WILL TAKE UNTIL LATE IN THE NIGHT FOR THE TEMPERATURES TO DROP COLD ENOUGH TO SUPPORT ANY SNOW. ALL TOLD...IMPRESSIVE PWAT VALUES AND A DYNAMIC SYSTEM COULD LEAD TO STORM TOTAL RAINFALL IN EXCESS OF AN INCH...ESPECIALLY EAST OF THE MOUNTAINS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... THURSDAY WILL BE BREEZY BEHIND THE FRONT. ANY UPSLOPE SNOW SHOWERS SHOULD GRADUALLY COME TO AN END. THERE WILL ONLY BE A GLANCING BLOW OF CAA...AS HIGH PRESSURE WILL BE BUILDING IN FROM THE SOUTHWEST. THIS HIGH WILL REMAIN OVER THE SE STATES THROUGH SATURDAY AND TEMPERATURES ARE EXPECTED TO REMAIN ABOVE NORMAL. THE NEXT CHANCE OF PRECIP WILL ARRIVE AS THE NEXT TROUGH APPROACHES SATURDAY INTO SUNDAY. MODEL SOLUTIONS STILL DIFFER QUITE A BIT...SO POPS REMAIN LOW. THERE WILL BE POTENTIAL FOR TEMPERATURES TO COOL BACK DOWN BEHIND THIS SYSTEM FOR THE SECOND PART OF THE WEEKEND. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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PRECIP IS EXPECTED TO SPREAD NORTH THROUGH EARLY AFTERNOON. PERIOD OF LIGHT FREEZING RAIN/SLEET IS MOST LIKELY AT CHO/IAD AND POSSIBLY BWI. MAY BE TOO WARM AT DCA FOR FREEZING RAIN...BUT INITIAL PERIOD OF SLEET CAN/T BE RULED OUT BEFORE TURNING TO RAIN. EXPECT CONDITIONS TO DROP INTO MVFR THIS AFTERNOON...THEN LIKELY IFR OR LIFR TONIGHT AND CONTINUING INTO TUESDAY. BELOW-VFR CIGS WILL LINGER THROUGH WEDNESDAY NIGHT. VSBY COULD DROP BELOW VFR IN HEAVIER RAIN/SHOWERS AT TIMES FROM TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. WINDS WILL SHIFT FROM SOUTHERLY TO WESTERLY WEDNESDAY NIGHT AND COULD GUST ABOVE 25 KT ON THURSDAY. NO SIGNIFICANT WEATHER EXPECTED AFTER THURSDAY EVENING.
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&& .MARINE... WEAK LOW PRESSURE MOVES OFF THE MID-ATLANTIC COAST TONIGHT. MARGINAL SCA EXPECTED ON THE LOWER PORTIONS OF THE WATERS THIS AFTERNOON OTHERWISE WINDS BELOW SCA THROUGH TUESDAY. A STRONG LOW PRESSURE SYSTEM WILL MOVE THROUGH THE REGION BETWEEN TUESDAY AND WEDNESDAY NIGHT...BRING MODERATE RAIN AT TIMES OVER THE WATERS. A SCA IS LIKELY WEDNESDAY THROUGH THURSDAY...WITH THE STRONGEST GUSTS EXPECTED ON THURSDAY. WINDS WILL DIMINISH THURSDAY NIGHT AS HIGH PRESSURE BUILDS IN. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...FREEZING RAIN ADVISORY UNTIL 6 PM EST THIS EVENING FOR DCZ001. MD...FREEZING RAIN ADVISORY UNTIL 6 PM EST THIS EVENING FOR MDZ013- 014-503>506. VA...FREEZING RAIN ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ025>031-036>040-051>054-501>508. FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR VAZ050-055-056. WV...FREEZING RAIN ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ055- 505-506. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ534- 537-543.
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&& $$ SYNOPSIS...ADS NEAR TERM...BJL/BPP SHORT TERM...ADS LONG TERM...ADS AVIATION...BJL/ADS/BPP MARINE...BJL/ADS/BPP

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