Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 131548 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1048 AM EST SAT DEC 13 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH MONDAY. A COLD
FRONT WILL PASS THROUGH THE AREA TUESDAY AND HIGH PRESSURE WILL
RETURN FOR THE MIDDLE AND LATTER PORTION OF NEXT WEEK.

&&

.UPDATE...
ISSUED NEW AFD TO REMOVE FREEZING RAIN ADVISORY FROM
WATCHES/WARNINGS/ADVISORIES SECTION BELOW.


.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE TO THE WEST WILL CONTINUE TO PROVIDE NORTHWEST FLOW
ACROSS THE MIDDLE ATLANTIC REGION TODAY. MOST AREAS OF THE CWFA
WILL EXPERIENCE DOWNSLOPING CONDITIONS WITH SOME HIGH LEVEL CLOUDS
AND NEAR SEASONABLE HIGH TEMPERATURES. DECENT MIXING WILL ALLOW
FOR BREEZY NW WINDS WITH GUSTS OF 15-25 MPH EXPECTED THROUGH LATE
AFTERNOON.

NW UPSLOPE FLOW WILL PERSIST OVER THE POTOMAC HIGHLANDS WITH SOME
LOW LEVEL MOISTURE AND ADDED CLOUD COVER EXPECTED. BAYARD OBSERVER
REPORTED MOSTLY CLOUDY WITH A FEW PEAKS OF SUNSHINE. CONDITIONS
ARE TRENDING AWAY FROM FREEZING DRIZZLE/FOG THREAT OVER THE
WESTERN FIVE. WILL GO AHEAD AND LET THE FREEZING RAIN ADVISORY
EXPIRE.

SEASONABLY CHILLY CONDITIONS ARE EXPECTED ACROSS THE REGION TONIGHT
AND IT WILL TURN OUT DRY FOR MOST AREAS. HOWEVER...MOISTURE IS
EXPECTED TO RIDE OVER THE MOUNTAINS AND WILL BE DEEPER THAN THIS
MORNING. THEREFORE...CONFIDENCE IS HIGHER IN MORE FREEZING DRIZZLE
AND PERHAPS EVEN LIGHT FREEZING RAIN ALONG AND WEST OF THE
ALLEGHENY FRONT. A FREEZING RAIN ADVISORY MAY BE NEEDED FOR THESE
AREAS.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
HIGH PRESSURE WILL REMAIN JUST TO OUR WEST THROUGH SUNDAY BEFORE
BUILDING OVERHEAD SUNDAY NIGHT INTO MONDAY. MOST AREAS WILL TURN
OUT DRY AND TEMPS WILL ACTUALLY BE A BIT ABOVE NORMAL DUE TO AN
UPPER-LEVEL RIDGE BUILDING OVERHEAD.

HOWEVER...MORE CLOUDS ALONG WITH FREEZING DRIZZLE/LIGHT FREEZING
RAIN IS EXPECTED ALONG AND WEST OF THE ALLEGHENY FRONT SUNDAY
MORNING. HOWEVER...TEMPS SHOULD RISE ABOVE FREEZING ACROSS THESE
AREAS SUNDAY AFTERNOON CAUSING PRECIP TO CHANGE TO JUST PLAIN
DRIZZLE/LIGHT RAIN. THE DRIZZLE WILL CONTINUE ALONG AND WEST OF
THE ALLEGHENY FRONT SUNDAY NIGHT...BUT OTHER LOCATIONS WILL BE
DRY.

DRY CONDITIONS AND SUNSHINE IS EXPECTED ACROSS MOST AREAS MONDAY
AS HIGH PRESSURE ROTATES THROUGH. IT WILL TURN OUT TO BE A MILD
AFTERNOON WITH HIGHS NEAR 50 FOR WASHINGTON AND BALTIMORE.
HOWEVER...LOW CLOUDS MAY HANG AROUND FOR LOCATIONS NEAR THE
ALLEGHENY FRONT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ELONGATED AREA OF HIGH PRESSURE COVERS THE EAST COAST BY MONDAY
NIGHT AS THE SFC HIGH BUILDS EAST. ALOFT...RIDGE AXIS PUSHES THROUGH
LATE IN THE DAY MONDAY...WITH MID LVL TROUGH SWINGING THROUGH THE
MID WEST. BACK TO THE SFC...LOW PRESSURE LIFTS NORTH INTO THE
MIDWEST MONDAY NIGHT. AS THE HIGH NUDGES EAST...RETURN FLOW WILL
START TO MOISTEN THE LOWER LVLS. HOWEVER...GENERAL CONSENSUS AMONGST
THE 00Z MODEL SUITE SUGGESTS ANY PCPN FORMATION HOLDS OFF TILL AFTR
06Z TUES WITH BUFKIT SOUNDINGS INDICATING THE VERTICAL COLUMN NOT
BECOMING SATURATED ENOUGH TILL CLOSER TO 12Z FOR FAR WESTERN REACHES
OF THE CWA...AND EVEN LATER FOR THE EASTERN AREAS. AS SUCH...HAVE
DRY FORECAST FOR THE FIRST HALF OF MONDAY NIGHT...WITH CHC POPS THEN
BLUE RIDGE AND WEST SECOND HALF OF THE NIGHT. FOR PCPN TYPE...GOOD
WAA WITH THE SOUTHERLY FLOW MONDAY SHOULD KEEP TEMPS WARM ENOUGH
EVERYWHERE EXCEPT ALLEGHENY FRONT FOR RAIN SHOWERS. NO SNOW ACCUM IS
EXPECTED OVERNIGHT.

FOR TUESDAY...SFC LOW CONTINUES TO LIFT NORTH INTO SOUTHEASTERN
CANADA...DRAGGING ITS ASSOCIATED COLD FRONT THROUGH THE REGION
SOMETIME LATE TUESDAY AFTN-EVENING. BROAD UPPER LVL TROUGH PIVOTS
OVER THE MIDWEST...SENDING MULTIPLE SHORTWAVES/ASSOCIATED VORT MAXES
THROUGH. COMBINATION OF LIFT AT THE SFC WITH THE FRONT AND FORCING
ALOFT WITH THE WAVES SHOULD RESULT IN AT LEAST SCT SHOWERS WITH THE
BEST CHC OF ANY PCPN OCCURRING RIGHT ALONG THE FRONT LATE TUES. TEMPS
IN THE 40S/50S WILL KEEP RAIN SHOWERS DURING THE DAY. THE PCPN
TAPERS OFF QUICKLY OVER EASTERN AREAS AS THE TROUGH ALOFT WEAKENS
AND BECOMES ALMOST ZONAL FLOW...THUS LOSING THE MOMENTUM WITH THE
FRONT. HOWEVER...HIGH PRESSURE BUILDING IN THE WAKE OF THE FRONT AT
THE SFC BRINGS WINDS TO A W-NW FLOW SO MAINTAINING POPS TO ACCOUNT
FOR UPSLOPE SNOW SHOWERS WEST OF THE ALLEGHENY FRONT.

SOME DISCREPANCIES IN THE MODEL SOLUTIONS FOR THE LATTER HALF OF THE
WEEK. AGREEMENT BETWEEN THE GLOBAL MODELS IN HIGH PRESSURE BUILDING
IN. THE GFS HOWEVER IS QUICKER TO WEAKER AND RETREAT THE HIGH AS
DEVELOPING LOW PRESSURE IN THE SOUTH CENTRAL US TAKES MORE OF AN
INSIDE RUNNER PATH...WHILE THE ECMWF IS SLIGHTLY SLOWER AND TRACKS
THE LOW MORE AS A COASTAL LOW PATH. AS SUCH...WITH LOW CONFIDENCE OF
HOW THIS LOW WILL EVOLVE...SIDED WITH A DRY FORECAST FRIDAY AND
SLIGHT CHC POPS FRIDAY NIGHT.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
A NORTHWEST FLOW WILL CONTINUE FOR TODAY WITH GUSTS AROUND 15 TO
20 KNOTS THROUGH THIS AFTERNOON. VFR CONDITIONS ARE EXPECTED
ACROSS MOST OF THE TERMINALS. HOWEVER...THERE WILL BE SOME
MOISTURE MOVING IN FROM THE NORTHWEST AND THIS MAY CAUSE A
STRATOCU DECK NEAR OR JUST BELOW 3KFT...ESPECIALLY ACROSS KBWI AND
KMTN.

A STRATOCU DECK MAY AFFECT THE TERMINALS TONIGHT WITH MVFR
CONDITIONS...BUT CONFIDENCE IS LOW AT THIS TIME. THE NORTHWEST
FLOW WILL CONTINUE THROUGH SUNDAY WITH GUSTS AROUND 15 TO 20 KNOTS
EXPECTED LATER SUNDAY MORNING AND AFTERNOON. HIGH PRESSURE WILL
BUILD OVERHEAD MONDAY. WINDS WILL BE LIGHTER AND VFR CONDITIONS ARE
EXPECTED.

GENERALLY VFR CONDITIONS MONDAY NIGHT...WITH DIMINISHING CONDITIONS
AS PCPN MOVES IN. SUB-VFR CONDITIONS LIKELY WITH ANY PCPN TUES.

VFR WED WITH WNW WINDS GUSTING 20-25 KTS. VFR CONDITIONS LAST
THROUGH THE END OF THE WEEK WITH DIMINISHING WINDS AS HIGH PRESSURE
BUILDS IN.

&&

.MARINE...
HIGH PRESSURE WILL BUILD TOWARD THE WATERS THROUGH THE WEEKEND. A
SMALL CRAFT ADVISORY IS IN EFFECT FOR PORTIONS OF THE WATERS
DURING THIS TIME. WINDS WILL DIMINISH SUNDAY NIGHT AND MONDAY AS
HIGH PRESSURE BUILDS OVERHEAD.

SUB-SCA CONDITIONS INITIALLY MONDAY NIGHT...THOUGH GUSTS INCREASING
BY TUESDAY MORNING AHEAD OF AN APPROACHING COLD FRONT. GUSTS TO 18
KTS PSBL DURING THE DAY TUES...WITH HIGHER CONFIDENCE OF OCCURRING
TUES EVENING. A BRIEF LULL TUES WITH THE PASSAGE OF THE FRONT...THEN
GUSTS INCREASE AGAIN INTO THE 20S AS WINDS SHIFT TO THE WEST BEHIND
THE FRONT. SCA CONDITIONS THEN EXPECTED THROUGH WED AND POSSIBLY
THROUGH WED NIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST SUNDAY FOR ANZ531>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR ANZ530-
     535-536-538-542.
     SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EST SUNDAY FOR ANZ530-
     535-536-538-542.

&&

$$
SYNOPSIS...BJL
UPDATE...KRW
NEAR TERM...KRW
SHORT TERM...BJL
LONG TERM...SEARS
AVIATION...SEARS/KRW
MARINE...SEARS/KRW







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