Area Forecast Discussion
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000
FXUS61 KPBZ 271124
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
624 AM EST THU NOV 27 2014

.SYNOPSIS...
ANOTHER SHOT OF COLD AIR WILL MOVE THROUGH LATER TODAY AND
TONIGHT. THIS WILL PROVIDE THE RISK FOR SNOW SHOWERS. HIGH
PRESSURE WILL IMPROVE CONDITIONS ON FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A WEAK SURFACE TROUGH IS CURRENTLY SHIFTING SOUTHEASTWARD OUT OF
NORTHERN OHIO AND FAR NORTHWEST PENNSYLVANIA. A RATHER STAGNANT
LOW LEVEL ENVIRONMENT PRECEDES THIS BOUNDARY WITH AMPLE LOW LEVEL
MOISTURE AVAILABLE. RADAR SIGNATURES INDICATE WEAK ECHOES ARE
STILL PRESENT IN THIS AREA...AND MODEL CROSS SECTIONS FAIL TO
PORTRAY SUFFICIENT SATURATION DEPTH FOR EFFICIENT SNOW CRYSTAL
GROWTH. WITH THAT SAID...A FEW OBS IN NORTHEASTERN OHIO HAVE
OSCILLATED BACK AND FORTH FROM SNOW TO OTHER PRECIPITATION TYPES
WITH TEMPERATURES BELOW FREEZING. WHILE IT IS MOST LIKELY THAT IN
THE PRE-TROUGH ENVIRONMENT...THE MAJORITY OF THE WEAK ECHOES ARE
LIKELY SNOW GRAINS...THERE REMAINS A POSSIBILITY THAT SOME
FREEZING DRIZZLE MAY BE OCCURRING. THIS HAS BEEN ADDED TO FOR THE
MORNING HOURS AHEAD OF THIS TROUGH AS IT MOVES SOUTHEASTWARD. IN
ADDITION...WITH UPSLOPE COMMENCING BY LATE MORNING INTO THE RIDGES
WITH DEEPER MOISTURE LAGGING SIGNIFICANTLY. IT WAS ADDED FOR
UPSLOPE AREAS AS WELL. WITH SURFACE TEMPERATURES VERY NEAR
FREEZING...IT SEEMS RATHER UNLIKELY THAT IT WOULD BE A
TRANSPORTATION HAZARD...MORE OF ELEVATED SURFACE ISSUE THROUGH THE
MORNING. FRIES

DURING THE AFTERNOON...MIXING HEIGHTS WILL RISE AS LARGE SCALE
ASCENSION INCREASES AHEAD OF A SHORTWAVE TROUGH. COLDER AIR AT 850
MB WILL MARCH EASTWARD AND THE FLOW ALOFT WILL INCREASE AND BECOME
BETTER ORGANIZED. MIXING HEIGHTS WILL RISE ENOUGH TO REACH THE
SNOW GROWTH ZONE. WILL SLOWLY INCREASE POPS THIS AFTERNOON...WITH
THE HIGHEST NUMBERS ACROSS THE NORTH AND RIDGES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
A SERIES OF WEAK UPPER LEVEL WAVES WILL CROSS THE AREA TONIGHT.
THIS WILL DRIVE THE HEART OF THE COLD AIR SOUTHEASTWARD ACROSS THE
REGION. FLOW WILL REMAIN GENERALLY OUT OF THE NORTHWEST TONIGHT...SO
WILL EXPECT SNOW SHOWERS TO CONTINUE UNTIL THE SECOND WAVE EXITS
AROUND DAWN FRIDAY. AGAIN...WILL FOCUS THE HIGHEST POPS ACROSS THE
NORTH(LAKE INFLUENCE)...AND RIDGES(OROGRAPHIC EFFECT).

SHORTWAVE WILL QUICKLY EXIT TO THE EAST FRIDAY MORNING...
INVERSIONS WILL LOWER AND SUBSIDENCE WILL INCREASE AS BROAD HIGH
PRESSURE MOVES EASTWARD ACROSS THE LOWER OHIO VALLEY. ANY
LINGERING SNOW SHOWERS WILL QUICKLY END FRIDAY MORNING. THE COLD
POOL ALOFT WILL SLOWLY EJECT TO THE NORTH WHICH WILL ALLOW FOR A
DECREASE IN CLOUD COVER.

WAA WILL CONTINUE SATURDAY NIGHT AS A WARM FRONT CROSSES THE AREA
AND FLOW IN THE LOWER AND MID-LEVELS BECOMES SOUTH-SOUTHWESTERLY.
MODELS ARE HINTING AT THE DEVELOPMENT OF ISOLATED SNOW SHOWERS
DEVELOPING WITH THE PASSING FRONT. WILL INCLUDE SCHC POPS FRIDAY
NIGHT.

A WEAK DISTURBANCE WILL CROSS ON SATURDAY...WHICH WILL TEMPORARILY
PUT THE BREAKS ON THE WAA. COULD SEE A PASSING SHOWER SATURDAY
AFTERNOON...BUT DEEP MOISTURE IS LACKING AND THE WAVE IS
UNIMPRESSIVE. FOR NOW WILL LEAVE SATURDAY DRY.

TEMPERATURES WILL MODERATE ON SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
SHOWER CHANCES WILL INCREASE SUNDAY...AHEAD OF THE NEXT COLD
FRONT. FRONT WILL CLEAR THE AREA EARLY MONDAY MORNING. SHOWERS
WILL END BUT TEMPS WILL COOL DOWN ON MONDAY. HIGH PRESSURE WILL
PROVIDE A DRY AND CHILLY TUESDAY...WITH TEMPS MODERATING ON
WEDNESDAY.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
WIDESPREAD MVFR CONDITIONS WILL CONTINUE TO BE THE CASE THROUGH
THE DAY AS ABUNDANT LOW LEVEL MOISTURE GIVES WAY TO MORE NUMEROUS
SNOW SHOWERS AS WNW FLOW AND COLD ADVECTION WORK TO SCOUR MOISTURE
OUT OF THE LOWER ATMOSPHERE AND ENCOURAGE UPWARD MOTION. BOTH OF
THESE TWO THINGS WILL ALLOW FOR SNOW SHOWER DEVELOPMENT...AND
THOUGH COVERAGE WILL NOT BE PERVASIVE...PICKING START AND END
TIMES FOR SNOW SHOWERS IS FAR TOO AMBITIOUS TO DO AT THIS POINT.
FRIES

OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/...
NON VFR DEVELOPING THURSDAY IN -SHSN...LINGERING ACROSS NW PA INTO
FRIDAY. NON-VFR SUNDAY IN -SHRA WITH THE NEXT FRONT.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$






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