Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260153 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 853 PM EST THU DEC 25 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD IN THROUGH FRIDAY...BEFORE MOVING OFFSHORE ON SATURDAY. A WEAK COLD FRONT WILL PUSH IN FROM THE NORTHWEST SUNDAY WITH LOW PRESSURE FROM THE DEEP SOUTH RIDING UP ALONG THAT FRONT AND PASSING JUST TO THE SOUTH MONDAY. COLDER HIGH PRESSURE WILL FOLLOW FOR MID WEEK.
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&& .NEAR TERM /THROUGH FRIDAY/...
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SFC HIGH PRESSURE BUILDING NORTH TONIGHT THROUGH FRIDAY AS RIDGING SETS UP ALOFT. MAINLY CLEAR SKIES ACROSS THE CWA WITH SUBSIDENCE AND A DRIER AIRMASS IN PLACE. ONLY AREA WITH CLOUD COVERAGE STILL WESTERN MD/ALLEGHENY FRONT REGION WHERE PASSING VORT MAX/WEAK TROUGH STILL PRODUCING BKN-OVC CLOUDS. HAD ANTICIPATED TEMPS TO DROP OFF QUICKER IN CLEAR AREAS WITH RADIATIONAL COOLING...BUT ENOUGH MIXING STILL ON GOING KEEPING WNW FLOW 7-8 KTS. HOWEVER...WINDS SHOULD DIMINISH ENOUGH BY 04Z WITH PRESSURE GRADIENT SLACKING AS HIGH NUDGES FURTHER NORTH...WITH TEMPS QUICKLY DROPPING OFF THEREAFTER. CLOUDS HANGING ON A BIT LONGER OVER THE NW EXTREME OF THE CWA WILL KEEP TEMPS DROPPING AT SLOWER RATE. OVERALL...LOW TEMPS ACROSS THE AREA SUB-FREEZING EXCEPT RIGHT ALONG THE WATERS HOLDING IN THE MID 30S. DRY WX FRIDAY WITH CENTER OF HIGH PASSING JUST TO THE SOUTH AS IT STARTS TO PUSH EAST. FEW HIGH LVL CLOUDS PSBL FROM SYSTEM OVER THE CENTRAL US. AFTER THE QUICK SHOT OF CAA...SURGE OF WAA WITH SOUTHERLY FLOW ON THE BACKSIDE OF THE HIGH UNDER PLENTY OF DAYTIME HEATING WITH MOSTLY SUNNY SKIES WILL PUSH HIGH TEMPS INTO THE 50S...ALMOST 10 DEGREES ABOVE NORMAL.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... TEMPS OVERNIGHT WILL ONLY TOUCH THE FREEZING MARK ACROSS THE SHELTERED VLYS/LOW LANDS OVER THE PIEDMONT/SHEN VLY. HIGHER TERRAIN WILL ACTUALLY HAVE THE WARMEST VALUES IN THE AREA W/ THE ELEVATED INVERSION. CLEAR/CALM CONDITIONS EVEN AS A WEAK UPPER TROUGH PASSES OVERHEAD AND WEAKENS AS IT APPROACHES THE COAST - A PRECURSOR THE NEXT UPPER WAVE. MUCH OF SATURDAY WILL REMAIN CLEAR AND QUIET...W/ ONLY A FEW PASSING CLOUDS AND RELATIVELY WARM CONDITIONS. THE CENTER OF THE HIGH WILL BE DRIFTING OFF THE CAROLINA COAST AND ALLOW FOR TEMPS TO REACH THE M-U50S ACROSS MUCH OF THE REGION. OUR BRIEF REPRIEVE FROM ACTIVE WX WILL BE INTERRUPTED BY LATE SAT NIGHT...AS THE BEGINNINGS OF THE NEXT WAVE OF LOW PRESSURE ARRIVE IN THE FORM OF DENSE MID-UPPER LEVEL CLOUDS. THE ONSLAUGHT OF DENSE CLOUD COVER WILL PREVENT TEMPS FROM DROPPING BACK TOWARD THE FREEZING MARK...UNLIKE THE PREVIOUS COUPLE OF NIGHTS. THIS WILL ALSO BE KEY IN MITIGATING THE POTENTIAL FOR FROZEN PRECIP OVER THE REGION DURING THE INITIAL STAGES OF THE INCOMING SYSTEM. && .LONG TERM /SUNDAY THROUGH THURSDAY/... A COLD FRONT WILL PUSH ACROSS THE REGION SUNDAY BEFORE SLIDING INTO THE CAROLINAS SUNDAY NIGHT. SOME STRATIFORM RAIN WILL ACCOMPANY THE FRONT SUNDAY THROUGH MONDAY. SOME LIGHT SNOW COULD MIX WITH A LITTLE RAIN IN THE POTOMAC HIGHLANDS AND ALONG PORTIONS OF THE MASON-DIXON LINE SUNDAY NIGHT AS COLDER AIR IS EXPECTED TO PUSH INTO THESE AREAS FIRST. WE`LL HANG ONTO A SLIGHT CHANCE OF SOME LIGHT RAIN OR SNOW MONDAY NIGHT...MAINLY ACROSS THE SOUTH...AS THERE IS STILL SOME DEGREE OF UNCERTAINTY OF A LOW DEVELOPING ALONG THE FRONT TO THE SOUTH. THE 00Z EURO TRIES TO FORM A LOW ALONG THE NORTH AND SOUTH CAROLINA BORDER. THE LATEST 12Z GFS WANTS TO FORM A LOW 12 HOURS EARLIER AND ALONG THE VIRGINIA AND NORTH CAROLINA BORDER BEFORE QUICKLY KICKING THE LOW OUT TO SEA. HIGH PRESSURE WILL BUILD INTO THE REGION MONDAY NIGHT AND TUESDAY...THUS PERSISTING WEDNESDAY AND THURSDAY. DRIER AND COOLER AIR WILL MOVE INTO THE REGION...ESCORTED BY THE HIGH. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/...
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VFR THRU TAF PERIOD. LIGHT WNW FLOW BCMG LIGHT/VRB OVERNIGHT. SLY FLOW FRI AFTN...5-7 KTS. VFR CONDITIONS WITH LIGHT SLY FLOW CONTINUE FRI NIGHT-SAT WITH HIGH PRESSURE IN PLACE. MVFR TO IFR CONDITIONS MAY OCCUR WITH LIGHT RAIN SUNDAY INTO SUNDAY NIGHT. WINDS SOUTHWEST SHIFTING NORTH 5 TO 10 KNOTS WITH FRONTAL PASSAGE. MVFR CONDITIONS POSSIBLE MONDAY WITH LINGERING LIGHT RAIN. WINDS NORTHEAST 5 TO 10 KNOTS.
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&& .MARINE...
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SUB-SCA CONDITIONS THROUGH FRIDAY AS HIGH PRESSURE BUILDS IN...WITH WEAK FLOW IN PLACE AT THE SFC AND ALOFT. LIGHT WINDS OVER THE WATERS TO END THE WEEK W/ ONLY SOME MINOR SLY CHANNELING SAT NIGHT AS A SFC HIGH MOVES OFF THE CAROLINA COAST.
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&& .EQUIPMENT...
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KLWX 88D WILL REMAIN OUT OF SERVICE UNTIL SATURDAY...WHEN THE PARTS TO REPAIR THE RADAR ARE EXPECTED TO ARRIVE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...HTS NEAR TERM...SEARS SHORT TERM...GMS LONG TERM...KLW AVIATION...SEARS/KLW MARINE...GMS/SEARS EQUIPMENT...HTS

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