Area Forecast Discussion
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858
FXUS61 KPBZ 091309
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
809 AM EST TUE FEB 9 2016

.SYNOPSIS...
COLDER WITH SNOW SHOWERS THROUGH WEDNESDAY AS A COLD FRONT PASSES
TONIGHT FOLLOWED BY SLOW MOVING LOW PRESSURE.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATEST RADAR IMAGERY SHOWS AREAL COVERAGE OF LIGHT SNOW EXPANDING. AXIS
OF THE UPPER-LEVEL LOW IS DIGGING IN ACROSS WESTERN
OHIO...DEEPENING A SECONDARY MID-LEVEL CIRCULATION NEAR THE OHIO
RIVER. THE RESULTANT DEFORMATION ZONE GAVE RISE TO A MODERATE
SNOW BAND THAT STRETCHED WEST TO EAST FROM WILMINGTON OH TO NEAR
CLARKSBURG WV. THIS FORCING IS EXPECTED TO GRADUALLY PIVOT AROUND
THE MID-LEVEL LOW...SPREADING LIGHT TO MODERATE SNOW ACROSS OUR
SOUTHERN ZONES. THIS SHOULD IMPACT THE REMAINING COMMUTE FOR THE
SOUTHERN PORTION OF THE ADVISED AREAS...WITH LESS OF AN IMPACT
NEAR THE PITTSBURGH METRO.

HI-RES MODELS CONTINUE TO INDICATE A FAIRLY SHARP GRADIENT ALONG
THE NORTHERN EDGE OF THE SNOW TODAY. LATEST HRRR RUN HAS COME MORE
IN LINE WITH THE WRF ARW/NMM...KEEPING THE HEAVIEST SNOW JUST
SOUTH OF PITTSBURGH BUT STILL IMPACTING SOUTHERN ALLEGHENY COUNTY.
HAVE ADJUSTED SNOW AMOUNTS ACCORDINGLY BY TIGHTENING THE GRADIENT
FROM NEAR PITTSBURGH TO NEAR ZANESVILLE. WHILE THIS MEANS A
FURTHER REDUCTION IN THE FORECAST SNOW AMOUNTS ALONG THE NORTHERN
EDGE OF THE ADVISORY COUNTIES...OPTED TO STAND PAT WITH THE
CURRENT HEADLINES.

LOCATIONS SOUTH OF PITTSBURGH AND INTO THE RIDGES SHOULD SEE
SEVERAL HOURS OF LIGHT TO MODERATE SNOW THROUGH THE
AFTERNOON/EARLY EVENING AS THE LIFT WEAKENS AND DEPARTS. STILL
EXPECTING 4 TO 6 INCHES OF ACCUMULATION FROM NEAR THE MASON-DIXON
LINE AND SOUTH. SNOW SHOWER COVERAGE SHOULD DIMINISH ACROSS THE
LOWLANDS TONIGHT...BUT WILL CONTINUE FOR THE RIDGE COUNTIES AS
THE FLOW TURNS TO THE NORTHWEST AND THE DENDRITIC GROWTH ZONE
DESCENDS UNDER COLD AIR ADVECTION. TEMPERATURES WILL CONTINUE
THEIR DOWNWARD TREND AS HIGHS WILL REMAIN NEAR OR BELOW FREEZING
TODAY...AND LOWS WILL DROP TO NEAR NORMAL TONIGHT.
TAX

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
H500 TROUGH AXIS SHIFTS EAST EARLY ON WEDNESDAY AS CLOSED LOW OPENS
UP.  NEXT SHORTWAVE WILL ARRIVE DURING THE DAY WITH AN INCREASE IN
COLD ADVECTION.  INVERSION HEIGHTS DROP A BIT AS COMPARED TO TODAY
AND OVERALL MOISTURE LEVEL IS LOWER...BUT ENOUGH MOISTURE IS
PRESENT IN DENDRITIC GROWTH ZONE TO PROMOTE ADDITIONAL SNOW
ACCUMULATION OF AN INCH OR TWO...ESPECIALLY IN THE RIDGES.

COLD ADVECTION SLOWS WEDNESDAY NIGHT AND MOISTURE BECOMES MORE
SHALLOW WITH TIME...WHICH WILL SLOW ACCUMULATION A BIT. ANOTHER
INCH OR SO IS POSSIBLE IN THE HIGHER ELEVATIONS...LESS TO THE
WEST. H850 THERMAL TROUGH ARRIVES AND CROSSES ON THURSDAY...WHICH
WILL HELP TO DIMINISH COVERAGE THROUGH THE DAY. ONLY A FEW SHSN
ARE EXPECTED TO LINGER ALONG THE RIDGES AND NORTH OF I-80 BY
EVENING...WITH A DRY WINDOW EXPECTED AREAWIDE OVERNIGHT.

TEMPERATURES WILL CONTINUE TO DROP FURTHER BELOW NORMAL THROUGH
THIS PERIOD.  ONLY MINOR CHANGES WERE MADE HERE.
CL

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
ANOTHER SHORTWAVE IS EXPECTED ARRIVE ON FRIDAY WITH SCATTERED SNOW
SHOWERS...LASTING INTO SATURDAY.  KEPT POPS IN THE CHANCE RANGE FOR
NOW. THE MAIN STORY HERE WILL BE THE POSSIBLE ARRIVAL OF THE COLDEST
AIR OF THE SEASON THUS FAR. H850 TEMPS ARE PROGGED TO FALL TO -25C
OR EVEN A BIT COLDER BY 00Z SUNDAY.  BELOW ZERO MIN TEMPS ARE A GOOD
POSSIBILITY SATURDAY NIGHT...PARTICULARLY IF SKIES CLEAR AND WINDS
DECOUPLE.

A DRY AND COLD SUNDAY IS EXPECTED AS THE ARCTIC HIGH PRESSURE
CROSSES. THIS WILL BE FOLLOWED BY MODERATING TEMPERATURES ON
MONDAY AS THE EASTERN U.S. TROUGH LOOSENS ITS GRIP...BUT
PRECIPITATION CHANCES WILL RETURN AS WELL WITH THE NEXT SHORTWAVE
TROUGH. THE SUPERBLEND GUIDANCE WAS USED AS A BASIS FOR MUCH OF
THE LONG TERM FORECAST.
CL

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
CONDITIONS CONTINUE TO DETERIORATE THIS MORNING AS SPATIAL
COVERAGE OF LIGHT TO MODERATE SNOW EXPANDS. SO FAR THIS MORNING IT
APPEARS THAT VISIBILITIES LESS THAN A MILE ARE MORE A RESULT OF
FOG THAN A RESULT OF HEAVIER SNOW SHOWERS. EXPECTING AT LEAST
MVFR/IFR RESTRICTIONS THROUGH THE DAY AS SNOW LIFTS NORTHWARD
UNDER THE UPPER-LEVEL LOW PRESSURE CENTER. GREATEST IMPACTS SHOULD
BE TO THE SOUTHERN TERMINALS OF LBE/MGW/AGC WITH SNOW LASTING INTO
THE EVENING. GUIDANCE HINTING AT GRADUAL IMPROVEMENT LATE TONIGHT
INTO EARLY WEDNESDAY AS THE AXIS OF THE LOW BEGINS TO SHIFT EAST.
STILL...LIGHT SNOW SHOWERS WILL CONTINUE THROUGH WEDNESDAY...SO
RESTRICTIONS ARE STILL TO BE EXPECTED. LIGHT SURFACE FLOW WILL
GRADUALLY SHIFT TO THE WEST AND INCREASE THROUGH TONIGHT. TAX

.OUTLOOK.../WEDNESDAY THROUGH SATURDAY/...
RESTRICTIONS ARE EXPECTED THROUGH SATURDAY UNDER COLD UPPER-
LEVEL TROUGHING.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR MDZ001.
OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR OHZ049-
     050-057>059-068-069.
PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR PAZ021-
     029-031-073-075.
     WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR PAZ074-
     076.
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR
     WVZ001>004-012-021-509.
     WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR
     WVZ510>514.

&&

$$



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