Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220008 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 708 PM EST WED JAN 21 2015 .SYNOPSIS... LOW PRESSURE WILL MOVE EAST FROM THE MID-ATLANTIC COAST THIS EVENING...WITH A SECONDARY LOW MOVING EAST ACROSS PENNSYLVANIA TONIGHT INTO THURSDAY MORNING. HIGH PRESSURE THEN BUILDS THROUGH THURSDAY NIGHT. A LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THE CAROLINA COAST FRIDAY NIGHT AND MOVE NORTHEAST ALONG THE MID- ATLANTIC SATURDAY. A SECONDARY LOW IS THEN EXPECTED TO CROSS THE AREA SUNDAY NIGHT INTO MONDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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NEW WINTER WEATHER ADVISORY UNTIL MIDNIGHT FOR FREEZING DRIZZLE POTENTIAL OVER THE GREATER BALTIMORE- WASHINGTON METRO AREA...AREAS EAST OF THE BLUE RIDGE AND NORTH FROM FAUQUIER/STAFFORD ALONG WITH SRN MD. HEADLINE IS UNTIL MIDNIGHT FOR NOW AND MAY NEED TO BE EXTENDED SHOULD CONDITIONS MERIT. AS OF 00Z...LOW LEVEL CLOUDS REMAIN TRAPPED OVER THE GREATER BALTIMORE-WASHINGTON METRO. MOISTURE IS QUITE SHALLOW...SO ICE CRYSTAL FORMATION IS NOT EXPECTED. THEREFORE FREEZING DRIZZLE OR FOG IS LIKELY. TEMPERATURES ARE BELOW FREEZING FOR MOST OF THE ADVISORY AREA. TRANQUIL CONDITIONS OVER SWRN ZONES INCLUDING KCHO WHERE SKIES BROKE THIS AFTERNOON. FREEZE UP ON MOIST ROADWAYS EXPECTED TONIGHT WHICH IS COVERED BY A SPECIAL WEATHER STATEMENT. FOG STILL MAY BECOME DENSE IN PLACES TONIGHT...AND WARRANT A DENSE FOG ADVISORY. FOR AFTER MIDNIGHT...LIGHT SNOW AND RAIN CONTINUES TO MOVE EAST FROM OHIO ALONG A WEAK SHORTWAVE TROUGH THAT WILL CROSS PA TONIGHT. UPSLOPE SNOW OF AROUND 2 INCHES EXPECTED...HIGHER AMOUNT WOULD WARRANT A WINTER WEATHER ADVISORY OUT THERE. UP TO AN INCH EAST FROM CUMBERLAND AS ENOUGH LIFT OVERCOMES DOWNSLOPING LOW LEVEL FLOW.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... DEEPENING LOW TRACKING WELL OFFSHORE DURING THE DAY THURSDAY WHILE SFC HIGH PRESSURE BUILDS IN FROM THE CENTRAL PLAINS. REGION REMAINS AT THE BASE OF AN UPPER LVL TROUGH...WITH MULTIPLE SHORTWAVES SWINGING THROUGH THE REGION AS THEY ROUND THE BASE. WESTERLY FLOW WILL KEEP DRIER AIR IN PLACE TO MAINTAIN A DRY YET CLOUDY FORECAST FOR MOST OF THE AREA. WILL CONTINUE TO MENTION UPSLOPE SNOW SHOWERS OVER THE ALLEGHENY FRONT THROUGH THURSDAY...THOUGH VERY WELL COULD BE HOLDING ONTO THE PCPN TOO LONG...POSSIBLY TAPERING OFF PRIOR TO SUNDOWN THURSDAY. SNOW TOTALS ARE THE LIGHTER SIDE...A COUPLE HUNDREDTHS OF AN INCH. TEMPS NEAR NORMAL FOR BOTH HIGHS THURSDAY/LOWS THURS NIGHT. INCREASING LIKELIHOOD OF PCPN LATE FRI HEADING INTO THE WEEKEND AS THE 12Z MODEL SOLUTIONS ARE COMING INTO A BETTER HANDLE ON A DEVELOPING COASTAL LOW. WHILE THE CONFIDENCE IS INCREASING WITH PCPN OCCURRING...THERE IS STILL LOW CONFIDENCE AS TO THE TYPE OF PCPN...WITH A MIX OF FREEZING RAIN...SNOW...SLEET AND RAIN ALL PSBL SOLUTIONS ACROSS THE CWA. ATTENTION WILL BE ON SHORTWAVE ENERGY CURRENTLY OVER THE MOUNTAIN WEST AS IT DIGS INTO THE SOUTHERN US THURS-FRI. GENERAL CONSENSUS BRINGS THE TROUGH UP OVER THE EASTERN PORTIONS OF THE AREA HEADING INTO THE WEEKEND. THE ASSOCIATED SFC LOW CURRENTLY IS PROJECTED TO TRACK JUST OFF THE COAST DURING THIS TIME...HOWEVER WITH UNCERTAINTY OF THE TIMING/TRACK...IT IS HARD TO PIN DOWN THE PCPN TYPE WITH THE CURRENT FORECAST. GENERALLY BACKING FLOW ON FRIDAY SHOULD PUSH TEMPS WARM ENOUGH DURING THE DAY TO BRING IN INITIALLY RAIN WITH PSBL SLEET MIXING IN SOUTH OF I-66 WHILE NORTH...IF THE PCPN MAKES IT FRIDAY EVENING...SHOULD BE COLD ENOUGH FOR SNOW INITIALLY. INCREASED POPS OVERNIGHT FRI TO LIKELY AS THE LLJ STRENGTHENS OVER THE EASTERN AREAS AND THE SFC LOW NEARS. SECOND HALF OF THE NIGHT VERY TRICKY IN TERMS OF PCPN TYPE...NORTHERLY FLOW NOT IMPRESSIVE BUT MIGHT BE JUST ENOUGH TO FUNNEL THE COLDER AIR DOWN ALONG THE MASON-DIXON LINE AND THROUGH NORTH-CENTRAL VA. AS SUCH...HAVE INCLUDED SLIGHT CHC WORDING OF FZRA FOR THIS AREA...IN COLLABORATION WITH WPC FOR PSBL ICE. TO THE NORTH AND WEST EXPECTING PRIMARILY SNOW...TO THE SOUTH AND EAST RAIN/SNOW MIX. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... SHORTWAVE AND SURFACE LOW CENTER ON THE SOUTHEASTERN COAST SATURDAY MORNING WILL MOVE UP TO THE CANADIAN MARITIMES BY SUNDAY MORNING. SERIES OF SHORTWAVES ON NORTHERN TRACK WILL PUSH SOUTHEASTWARD TAKING NEXT WEATHER PRODUCER ACROSS SOUTH-CENTRAL VIRGINIA KEEPING CWA ON THE COLD SIDE OF THE SYSTEM. THERMAL PROFILE IS SOMEWHAT UNCERTAIN...AND CONTINUE WITH CHANCE OF SNOW OR RAIN SATURDAY. ANY OTHER PRECIPITATION DURING THE PERIOD EXPECTED TO BE IN THE FORM OF SNOW. ONE SUCH SYSTEM COULD BRING SNOW ON MONDAY. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... IFR CIGS/VSBYS LINGER THROUGH TONIGHT INTO THURSDAY AS WEAK ONSHORE FLOW CONTINUES AS WEAK LOW CROSSES PA TONIGHT. LIGHT SNOW ALSO ALONG THE MASON-DIXON LINE...COULD GRAZE MRB AND BWI/MTN. PATCHY DRIZZLE/FREEZING DRIZZLE DEVELOPING LATER THIS EVENING AS WELL...ALTHOUGH CONFIDENCE IS LOW ATTM. HIGH PRESSURE BUILDS IN THURSDAY FOR RETURN TO VFR CONDITIONS. VFR CONDITIONS THURSDAY-FRIDAY. SUB-VFR CONDITIONS...WITH INCREASING CHC OF IFR OR LOWER FRIDAY NIGHT WITH PCPN. WINTRY MIX PSBL AT TAF SITES WEST OF I-95 LATE FRI NIGHT AND SAT...THOUGH LOW CONFIDENCE OF PCPN TYPE AT THIS TIME. && .MARINE... LOW PRESSURE PULLS AWAY FROM THE COAST TONIGHT WITH SECONDARY LOW CROSSING PA. LIGHT SOUTH FLOW TONIGHT...THEN SHIFT TO THE NORTHWEST THURSDAY AND INCREASE TO 15 KT BY THE AFTERNOON ACROSS THE WATERS. SUB-SCA CONDITIONS THURSDAY NIGHT-FRIDAY...WITH THE NEXT CHC FOR GUSTS TO 20 KT SAT MORNING WITH THE PASSING COASTAL LOW. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR DCZ001. MD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ004>006-011-013-014-016>018-503>508. VA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ052>055-057-501-502-505-506. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...BAJ NEAR TERM...BAJ SHORT TERM...SEARS LONG TERM...CEM AVIATION...BAJ/SEARS/BPP MARINE...BAJ/SEARS/BPP

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