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...
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.

&&

.NEAR TERM /THROUGH FRIDAY/...
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.

&&

.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/...
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.

&&

.MARINE...
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.

&&

.EQUIPMENT...
KLWX 88D WILL REMAIN OUT OF SERVICE UNTIL SATURDAY...WHEN THE PARTS
TO REPAIR THE RADAR ARE EXPECTED TO ARRIVE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...HTS
NEAR TERM...SEARS
SHORT TERM...GMS
LONG TERM...KLW
AVIATION...SEARS/KLW
MARINE...GMS/SEARS
EQUIPMENT...HTS






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