FXUS61 KPBZ 221950
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
250 PM EST TUE DEC 22 2009
.SYNOPSIS...
HIGH PRESSURE BUILDING INTO THE DISTRICT THIS AFTERNOON WILL BRING
COLD AND DRY CONDITIONS FOR TONIGHT INTO THURSDAY. A LOW PRESSURE
SYSTEM IS THEN EXPECTED TO BRING MIXED PRECIPITATION FOR THURSDAY
NIGHT AND FRIDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
WITH UPPER LEVEL LOW CURRENTLY OVER LAKE ONTARIO EXPECTED TO MOVE
ACROSS NEW ENGLAND...EXPECT SNOW SHOWERS TO DIMINISH THIS EVENING.
AS A HIGH PRESSURE RIDGE BUILDS IN FROM THE NORTH TONIGHT INTO
WEDNESDAY...CONDITIONS ARE EXPECTED TO SLOWLY CLEAR OUT.
TEMPERATURES WILL BE ABOUT 5 DEGREES BELOW NORMAL.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
HIGH PRESSURE IS EXPECTED TO REMAIN IN CONTROL OF THE WEATHER FOR
THE DISTRICT WEDNESDAY NIGHT AND THURSDAY BEFORE A POTENT SURFACE
LOW DEVELOPS IN THE PLAINS. MODELS HAVE BEEN TRENDING SOMEWHAT
SLOWER AND COLDER WITH THIS SYSTEM. IT NOW APPEARS THAT
PRECIPITATION SHOULD NOT ARRIVE UNTIL LATE THURSDAY NIGHT IN THE
WESTERN FORECAST AREA...AND AROUND DAYBREAK CHRISTMAS IN THE EAST.
SURFACE TEMPERATURES WILL BE SLOW TO WARM...AND WARM ADVECTION
AROUND 850 MB IS EXPECTED BEFORE TEMPERATURES WARM AT THE SURFACE.
EXCEPT FOR THE SOUTHERNMOST COUNTIES IN THE FORECAST AREA...MOST
LOCATIONS COULD START WITH A MIX OF RAIN AND FREEZING RAIN BEFORE
CHANGING OVER TO ALL RAIN BY FRIDAY AFTERNOON. AREAS NORTH AND EAST
OF PITTSBURGH WOULD HAVE THE GREATEST THREAT OF RECEIVING
ACCUMULATING FREEZING RAIN. HAVE ALSO INCREASED POPS TO CATEGORICAL.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
ON CHRISTMAS NIGHT STRONG CLOSED LOW OVER WESTERN LAKES WILL ALLOW
A SECONDARY LOW CENTER TO DEVELOP INLAND OF THE DELMARVA PENINSULA
WITH MOISTURE LOOKING TO BE THROWN BACK ACROSS EASTERN 2/3RD OF THE
CWA FRIDAY NIGHT INTO EARLY SATURDAY. HPC PROGS NOT TOO FAR OFF
00Z ECMWF AND 12Z GFS WITH THIS DEVELOPMENT. LOOKS TO BE A VERY
COMPLICATED SCENARIO SO FOR NOW BUMPED UP POPS TO LIKELY WITH A
MIX OF PRECIPITATION FRIDAY NIGHT TRANSITIONING TO ALL SNOW
EARLY SATURDAY MORNING... WITH SNOW DIMINISHING IN THE AFTERNOON
AS SURFACE LOW HEADS TO NEW ENGLAND. SUNDAY AND MONDAY CLOSED LOW
SLOWLY SLIDES EAST ACROSS UPPER OHIO VALLEY WITH BELOW NORMAL
TEMPERATURES AND SNOW SHOWERS. COLD SURFACE HIGH SHOULD ALLOW A
DRY DAY TUESDAY.
&&
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
MVFR AND SPOTTY IFR WILL CONTINUE INTO THE EVENING AS NORTHWEST
FLOW BRING CLOUDS AND SNOW SHOWERS TO THE NORTH AND FAST MOVING
SHORTWAVE SLIDES BY SOUTHERN TERMINALS WITH CLOUDS AND SCATTERED
LIGHT SNOW. SURFACE RIDGE WILL NOSE INTO REGION FROM NORTHERN
GREAT LAKES LATER TONIGHT FOR GENERAL VFR WHICH WILL CONTINUE INTO
WEDNESDAY AND THURSDAY. LATER THURSDAY NIGHT AND FRIDAY STRONG
STORM SYSTEM IN THE CENTRAL STATES WILL PUSH MOISTURE AND MIXED
PRECIPITATION TOWARD REGION WITH RESTRICTIONS LIKELY. FRIDAY NIGHT
AND SATURDAY A DEVELOPING SURFACE LOW INLAND OF THE MID ATLANTIC
COAST WILL BRING MIXED PRECIPITATION FRIDAY NIGHT CHANGING TO
SNOW BY DAYBREAK SATURDAY WITH MORE RESTRICTIONS EXPECTED.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
