-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 092334
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
634 PM EST MON DEC 9 2013

.SYNOPSIS...
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COLDER AIR WILL CONTINUE TO PUSH IN AHEAD OF A FAST MOVING
DISTURBANCE THAT WILL SPREAD SNOW ACROSS THE REGION EARLY TOMORROW
AFTERNOON THROUGH MID AFTERNOON. WELL BELOW NORMAL TEMPERATURES
ARE EXPECTED THIS WEEK...WITH TEMPERATURES 25 DEGREES BELOW
NORMAL BY THURSDAY.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TUESDAY/...
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NO UPDATE NEEDED EARLY THIS EVENING AS THE CURRENT FORECAST LOOKS
RIGHT ON TRACK BASED ON LATEST OBS AND GUIDANCE. PREVIOUS
DISCUSSION FOLLOWS..

COLD ADVECTION CONTINUES ACROSS THE REGION WITH TEMPERATURES
EXPECTED TO FALL INTO THE 20S TONIGHT.

AS UPPER TROUGH APPROACHES OVERNIGHT A SHORTWAVE WILL RACE
NORTHEAST ALONG A SECONDARY COLD FRONT LATE TONIGHT AND TUESDAY.
MODELS HAVE COME INTO GENERAL AGREEMENT ON A MORE AMPLIFIED
SOLUTION WITH OVERRUNNING SNOW NOW BEING SPREAD FARTHER NORTH AND
WEST. BUFKIT SOUNDINGS FROM 12Z RUNS ARE ACTUALLY FAIRLY CLOSE ON
SNOW AMOUNTS AND WITH A NON MIXED PRECIP SCENARIO SHOULD BE
HANDLING PRECIP AMOUNTS FAIRLY WELL.

ADVISORY ISSUED FOR SNOW ACROSS THE SOUTHERN TIER COUNTIES OF
SOUTHWEST PA INTO NORTHERN WEST VIRGINIA AND THE WESTMORELAND
RIDGES. TIMING OF BETTER SNOWFALL ALSO WAS CONSIDERED IN ADVISORY
AS BEST ACCUMULATIONS LOOK TO BE BEFORE DAYBREAK INTO MID MORNING
AND CAUSE THE MOST PROBLEMS FOR THE MORNING COMMUTE.

3-5 INCHES IN THE RIDGES AND 2-4 ELSEWHERE IN THE ADVISORY AREA.
IN A SWATH NORTHWEST OF THE ADVISORY FROM WHEELING TO PITTSBURGH
AND INDIANA 1-2 EXPECTED FOR THE MORNING RUSH AND THIS WAS
MENTIONED IN THE HWO. AN INCH OR LESS ELSEWHERE.

SNOW WILL QUICKLY DIMINISH BY AFTERNOON WITH DRIER AND COLDER AIR
WORKING ACROSS THE REGION.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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LAKE ENHANCED SNOW SHOWERS ACROSS THE I-80 CORRIDOR ARE THEN
EXPECTED TO DEVELOP TUESDAY NIGHT AS COLD ADVECTION INTENSIFIES
UNDER ENCROACHING UPPER TROUGH. A WEAK CLIPPER TYPE SYSTEM MAY
ENHANCE SNOW SHOWERS ACROSS THE NORTH WEDNESDAY. BEHIND THIS
SHORTWAVE FLOW MAY TURN NORTHWEST FOR A TIME WITH A WINDOW OF
OPPORTUNITY FOR LAKE BANDS TO DEVELOP BUT WILL NOT EMPHASIZE FOR
NOW AND LET LATER SHIFTS TAKE A LOOK. OTHERWISE DRY AND COLD
THROUGH THE PERIOD.
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&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
WHILE THE UPPER LEVEL PATTERN LEADING INTO THE WEEKEND IS
SIMILAR...WITH AN UPPER TROUGH PHASING WITH SOUTHERN STREAM
SHORTWAVE...THE STRENGTH AND EVOLUTION OF THE ASSOCIATED SURFACE LOW
REMAINS LESS CLEAR. OPTED TO BUMP POPS UP CLOSER TO THE MOST RECENT
MEX AND WPC GUIDANCE VALUES BUT STILL KEPT MOST OF THE REGION AT
CHANCE WITH VARYING LOW PRESSURE SPEEDS AND PLACEMENTS. TEMPERATURES
WERE BUMPED UP SLIGHTLY WITH THE WARMER MODEL GUIDANCE...ESPECIALLY
WITH THE SYSTEM SATURDAY...BUT STILL REMAIN 5 TO 10 DEGREES BELOW
SEASONAL NORMALS THROUGH THE MUCH OF THE PERIOD.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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MVFR CONDITIONS ARE CURRENTLY BEING OBSERVED ACROSS THE
REGION...AND SOME MODEL GUIDANCE EVEN SUGGESTS THAT CEILINGS COULD
RISE BRIEFLY TO VFR THIS EVENING. HAVE TAKEN A MORE CONSERVATIVE
APPROACH AND KEPT MVFR CIGS THROUGH MUCH OF THE NIGHT. A FAST
MOVING LOW PRESSURE SYSTEM BRINGS SNOW TO THE REGION TOWARDS
MORNING. A DETERIORATION TO IFR IS EXPECTED WITH THE MOST
PERSISTENT SNOW AROUND 12Z FOR MOST OF THE SITES SOUTH OF I-80.
FURTHER NORTH...MAINTAINED MVFR WITH THE PERIOD OF SNOW REMAINING
RELATIVELY BRIEF. CONFIDENCE IN IFR VISIBILITIES IS HIGHER FARTHER
TO THE SOUTH WHERE THE BULK OF THE PRECIPITATION WILL OCCUR.
CONDITIONS SHOULD GRADUALLY IMPROVE BY MIDDAY TUESDAY...WITH SOME
OF THE GUIDANCE TRENDING TOWARDS VFR BY THE AFTERNOON.

.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
A BRIEF RETURN TO VFR MAY BE POSSIBLE WEDNESDAY BEFORE A CLIPPER
SYSTEM BRINGS LIGHT SNOW AND OCCASIONAL RESTRICTIONS. CIG
RESTRICTIONS IN COLD NORTHWEST FLOW WILL LIKELY CONTINUE THROUGH
THE REMAINDER OF THE WEEK. A SYSTEM DEVELOPING TOWARDS THE GULF
COAST COULD BRING FURTHER RESTRICTIONS SATURDAY.
-- End Changed Discussion --

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY FROM 3 AM TO 5 PM EST TUESDAY FOR
     MDZ001.
OH...NONE.
PA...WINTER WEATHER ADVISORY FROM 1 AM TO 2 PM EST TUESDAY FOR
     PAZ031-075.
     WINTER WEATHER ADVISORY FROM 3 AM TO 5 PM EST TUESDAY FOR
     PAZ074-076.
WV...WINTER WEATHER ADVISORY FROM 1 AM TO 2 PM EST TUESDAY FOR
     WVZ012-021-022.
     WINTER WEATHER ADVISORY FROM 3 AM TO 5 PM EST TUESDAY FOR
     WVZ023-041.

&&

$$