FXUS61 KLWX 160149
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
849 PM EST TUE DEC 15 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH WEDNESDAY BRINGING
DRY AND COLDER CONDITIONS. HIGH PRESSURE PERSISTS OVER THE MID
ATLANTIC REGION THROUGH THE END OF THE WEEK AND INTO THE WEEKEND. A
STORM SYSTEM MAY IMPACT THE AREA LATE IN THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A COLD FRONT WILL CONTINUE TO MOVE OFF THE MID-ATLANTIC COAST WHILE
HIGH PRESSURE SLOWLY BUILDS TOWARD THE REGION FROM THE MIDWEST. A
NORTHWEST FLOW BEHIND THE COLD FRONT AND AHEAD OF THE APPROACHING
HIGH WILL BRING COLDER CONDITIONS OVERNIGHT. MIN TEMPS WILL RANGE
FROM THE TEENS IN THE POTOMAC HIGHLANDS TO THE UPPER 20S/LOWER 30S
NEAR THE CITIES OF WASHINGTON AND BALTIMORE.
HIGH/MID CLOUDS CONTINUE TO AFFECT THE REGION DUE TO A SOUTHWEST
FLOW ALOFT AHEAD OF AN UPPER-LEVEL DISTURBANCE. THIS DISTURBANCE
WILL MOVE THROUGH LATE THIS EVENING AND CLEARING IS EXPECTED BEHIND
THIS SYSTEM OVERNIGHT. HOWEVER...LOW CLOUDS ALONG WITH UPSLOPE SNOW
SHOWERS WILL HANG AROUND ACROSS THE POTOMAC HIGHLANDS INTO THE
OVERNIGHT HOURS BEFORE DRIER AIR WORKS ITS WAY IN TOWARD MORNING.
SNOWFALL ACCUMULATIONS AROUND AN INCH OR LESS ARE EXPECTED ALONG THE
WESTERN FACING SLOPES.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
DEEP WNWLY FLOW AND COLD ADVCTN CONT THRU WED. H9 TEMPS OF -4 TO
-7 DEG C SUGGEST MAXIMA IN LWR 30S F TMW...WHICH WOULD BE SVRL DEG
F BLW GUIDANCE. WILL FCST MAXIMA 2-4 DEG F BLW GUIDANCE...NOT
QUITE AS AGGRESSIVE AS MODEL OUTPUT SUGGESTS BUT IN THE SAME
DIRECTION. DRY FCST AS SUBSIDENCE DOMINATES IN WAKE OF UPR WAVE
PASSAGE.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
LOPRES STALLING NEAR SERN CANADA WILL PUT THE REGION INTO A CAA/NW
FLOW REGIME WITH HIPRES BUILDING OVER THE AREA. THIS WX PATTERN WILL
RESULT IN DRY AND SEASONABLY COOL TEMPS THRU THE END OF THE WEEK.
NEXT WAVE OF LOPRES FORMS OVER THE GULF OF MEXICO LATE THIS WEEK AND
TRACKS OFF THE SE COAST BY SAT. THIS FAR OUT...PLENTY OF UNCERTAINTY
WITH THE EVOLUTION/TRACK OF THIS SYSTEM AFTER IT MOVES OFF THE SE
COAST AS EVIDENT IN THE LARGE MODEL SPREAD AMONG BOTH OPERATIONAL
MEDIUM RANGE MODELS AND GEFS ENSEMBLES. ECMWF PROG SYSTEM TO PHASE
WITH AMPLIFYING NRN STREAM UPPER TROUGH OVER CNTRL CONUS...RESULTING
IN A DEEPENING NOREASTER THAT TRACKS UP THE ERN SEABOARD SAT AND
SUN WHILE THE MORE PROGRESSIVE SOLUTIONS FROM THE GFS/GEM PROVIDES
NO SUCH PHASING.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS EXPECTED THROUGH WEDNESDAY. WEST-NORTHWEST WIND GUSTS
AROUND 20 KNOTS ARE EXPECTED...ESPECIALLY LATE THIS EVENING AND
AGAIN WEDNESDAY.
VFR CONDITIONS EXPECTED THRU THE END OF THE WEEK. BREEZY NW WINDS
WED NGT AND THU WILL RELAX AS HIPRES SETTLES OVER THE REGION. A STORM
SYSTEM MIGHT AFFECT THE AREA THIS WEEKEND.
&&
.MARINE...
THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE MIDWEST AND A
COLD FRONT MOVING OFF THE MID-ATLANTIC COAST WILL BRING SCA WIND
GUSTS OVERNIGHT ACROSS THE WATERS. THE STRONGEST WINDS WILL BE
ACROSS THE MIDDLE PORTION OF THE BAY WHERE GUSTS AROUND 30 KNOTS ARE
EXPECTED. MORE SCA WINDS ARE EXPECTED WEDNESDAY.
SCA HAS BEEN EXTENDED INTO WED NGT. SCA CONDITIONS MAY CONT INTO THU
BEFORE THE FLOW WEAKENS AS HIPRES BUILDS OVRHD.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ530>534-
537>543.
SMALL CRAFT ADVISORY UNTIL 1 PM EST WEDNESDAY FOR ANZ535-536.
&&
$$
LASORSA/KRAMAR/KLEIN
