Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 271545 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1045 AM EST SAT DEC 27 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE MID-ATLANTIC TODAY...BEFORE
MOVING EAST OF CAPE HATTERAS TONIGHT. A COLD FRONT WILL STALL
ACROSS THE REGION EARLY SUNDAY...THEN LOW PRESSURE WILL MOVE ALONG
THE STALLED FRONT SUNDAY AFTERNOON AND EVENING. ANOTHER LOW
PRESSURE SYSTEM WILL MOVE ACROSS THE CAROLINAS MONDAY AND MONDAY
NIGHT...FOLLOWED BY HIGH PRESSURE BUILDING INTO THE REGION ON
TUESDAY...AND REMAINING THROUGH THE REMAINDER OF THE WORK WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SKIES CLEARING OUT AGAIN BEHIND THE WEAK UPPER SHORTWAVE PASSAGE.
THIS FEATURE BROUGHT SOME MID CLOUD DECKS EARLIER THIS MORNING
THAT ARE NOW DISSIPATING OVER SRN MD/VA PIEDMONT. A FEW MORE HRS
OF SUN INTO THE AFTN...THEN THE BEGINNINGS OF YET ANOTHER MULTI-
DAY RAIN EVENT FOR THE MID-ATLC. CIRRUS AND MID CLOUD DEBRIS FROM
THE INCOMING LOW PRESSURE SYSTEM WON`T ARRIVE UNTIL LATER THIS
AFTN/EVE. TEMPS ATTM STILL FAIRLY MODERATED BUT EXPECTING HIGHS
TODAY TO STILL APPROACH 60F IN THE LOWER SHEN VLY/NRN VA PIEDMONT
W/ M-U50S ELSEWHERE BUT STILL A FEW DEG BELOW GUIDANCE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
AN AREA OF LOW PRESSURE WILL BE TRACKING FROM THE GREAT LAKES INTO
QUEBEC TONIGHT. THE TRAILING COLD FRONT WILL BE APPROACHING THE
APPALACHIANS BUT BEGIN TO LOSE STEAM AS IT RUNS INTO THE UPPER
LEVEL RIDGE AND BECOMES PARALLEL TO THE UPPER FLOW. FORCING AND
MOISTURE WILL BE LIMITED...WITH A CHANCE OF SHOWERS REACHING THE
WRN RIDGES AFTER MIDNIGHT. WITH CLOUD COVER...WAA AND INCREASING
LOW LEVEL MOISTURE...TEMPERATURES SHOULD HOLD ABOVE FREEZING AND
THUS ELIMINATE ANY PTYPE ISSUES.

A WAVE OF LOW PRESSURE ORIGINATING FROM THE GULF COAST WILL TRACK
ALONG THE FRONT AND BRING THE HIGHEST PROBABILITY OF RAIN TO THE
ENTIRE AREA ON SUNDAY. TIMING MAY BE A HAIR QUICKER THAN THE
PREVIOUS FORECAST...BUT THE HIGHEST POPS STILL RESIDE IN THE
AFTERNOON. DESPITE PWATS INCREASING TO AROUND AN INCH...FORCING IS
RATHER SCANT...AND IT APPEARS MOST AREAS WILL RECEIVE LESS THAN A
QUARTER INCH OF RAINFALL. TEMPERATURES DURING THIS STAGE OF THE
FRONT WILL UNDERGO MORE INFLUENCE ALOFT THAN AT THE SFC...WITH
HIGHS SUNDAY EXPECTED IN THE UPPER 40S TO LOWER 50S...POSSIBLY A
LITTLE COOLER IN THE NW DEPENDING ON TIMING OF FROPA.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
MODELS LOOK VERY COINCIDENT ON SUNDAY NIGHT HAVING HIGH
POPS...HOWEVER THE GFS HAS SUBSTANTIALLY MORE QPF. BOTH MODELS
DROP THE QPF SOUTH THROUGH THE CWA ON MONDAY...WITH DECREASING
POPS DURING THE DAYLIGHT HOURS MONDAY.

HOWEVER...MONDAY NIGHT THE 00Z ECMWF AND THE 00Z GFS DIVERGE ON
THEIR QPF...WITH THE GFS HAVING MORE QPF. BOTH MODELS HAVE LOW
PRESSURE MOVING FROM THE SE U.S ACROSS THE CAROLINAS...BUT THE GFS
THROWS THE PCPN SHIELD ALL THE WAY BACK WEST OF THE BLUE RIDGE
INTO THE COLD AIR. I AM DISCOUNTING THIS SOLN AND WILL GO WITH
THE ECMWF QPF WHICH PAINTS THE HEAVIEST QPF ACROSS SOUTHERN
VIRGINIA.

POPS BELOW CLIMO WILL COMMENCE TUE NIGHT AND CONTINUE THROUGH THE
END OF THE WORK WEEK...WITH THE PERIOD TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT BEING BELOW CLIMO FOR MIN TEMPS AND MAX TEMPS ON
WED. OTHERWISE LOOKS LIKE A FAIRLY SEASONABLE LATE DECEMBER WEEK
FOR BOTH TEMPS AND PCPN...WITH NEW YEARS EVE A FEW DEGREES COLDER
THAN NORMAL BUT DRY...AND NEW YEARS DAY REMAINING DRY WITH NEAR
NORMAL DAYTIME MAX TEMPS.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE WILL SLIDE OFFSHORE TODAY. VFR EXPECTED THROUGH
TONIGHT...WITH MID/HIGH LEVEL CIGS LOWERING LATE TONIGHT. WINDS
LIGHT/VRB...BECOMING MORE PRONOUNCED OUT OF THE SOUTH BY THIS
AFTERNOON/EVENING BUT REMAINING LESS THAN 10 KT.

SUNDAY...MVFR/IFR AT TIMES WITH LOW CLOUDS AND RAIN. COLD FRONT
PASSES...VEERING WINDS TO THE NORTH.

SUNDAY NIGHT AND MONDAY THE TERMINALS WILL SEE CONTINUED MVFR
CONDITIONS DUE TO LOW CIGS AND VSBYS...IMPROVING ON TUE.

&&

.MARINE...
HIGH PRESSURE WILL BRING CONTINUED LIGHT WINDS ACROSS THE WATERS
TODAY. AS THE HIGH MOVES OFFSHORE TONIGHT...WINDS WILL BECOME
SOUTHERLY BUT SHOULD REMAIN LESS THAN SCA LEVELS. LOW PRESSURE AND
A COLD FRONT WILL BRING RAIN ON SUNDAY...BUT STABLE CONDITIONS
WILL KEEP WINDS LIGHT.

WINDS MAY APPROACH SCA CONDITIONS DURING DAYLIGHT HOURS WED AND
THU.

&&

.EQUIPMENT...
KLWX WSR-88D WILL REMAIN OUT OF SERVICE UNTIL AT LEAST LATER TODAY AS
REPAIR PARTS AND TECHNICIANS ARE EXPECTED TO ARRIVE LATER THIS
MORNING.

&&

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

&&

$$
UPDATE...GMS
PREV DISCUSSION...ADS/LEE





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