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Area Forecast Discussion
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000
FXUS61 KPBZ 031438
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
938 AM EST TUE MAR 3 2015

.SYNOPSIS...
LOW PRESSURE CROSSING THE GREAT LAKES WILL SPREAD RAIN OVER THE
UPPER OHIO VALLEY REGION TODAY. PRECIPITATION MAY BEGIN AS
FREEZING RAIN OR A WINTRY MIX...AND WILL END BY TURNING BACK TO
SNOW ON WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LATEST RADAR IMAGERY SHOWING WEAK ECHOES ENCAPSULATING THE
AREA...BUT COPIOUS DRY AIR IN PLACE IS KEEPING MOST PRECIPITATION
AT BAY. 12Z SOUNDING SHOWING NEARLY A 50C DEWPOINT SPREAD AT
850MB. UNTIL WE ERODE THIS COMPLETELY...VIRGA WILL BE PRESENT. THE
DRY AIR LOOKS TO HOLD INTO THE SOUTHEAST RIDGES THE LONGEST AS
925MB FLOW REMAINS FROM THE SOUTHEAST. THIS WILL KEEP MOST AREAS
SOUTH AND EAST OF PITTSBURGH DRY IN DOWNSLOPING FLOW UNTIL THE
AFTERNOON WHEN THE FLOW VEERS TO THE SOUTH.

HAVE RE-CONFIGURED THE WINTER WEATHER ADVISORIES WITH THE LARGEST
CHANGES INCLUDING CANCELLING THE ADVISORY IN THE RIDGES AND
SPEEDING UP THE START TIME EVERYWHERE ELSE. STILL...WITH ALL THE
DRY AIR IN PLACE AND THE LACK OF UPSTREAM RADAR ACTIVITY...THE
PROBABILITY OF A WIDESPREAD ICING EVENT HAS DROPPED. 

ONCE THE LOW-LEVEL FLOW VEERS TO THE SOUTH MUCH WARMER AIR SHOULD
STREAM IN AND ALLOW ANY REMAINING ICING THREAT TO END. THIS WILL
HAPPEN SOUTH TO NORTH THROUGH THE AFTERNOON/EVENING. HAVE TAILORED
THE ADVISORIES TO FOLLOW THIS TRANSITION. 
TAX

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
WITH ONGOING WARM AIR AND MOISTURE ADVECTION INTO THE
EVENING...RAIN WILL CONTINUE FALL AREA WIDE AND TEMPERATURES WILL
CONTINUE TO INCREASE UNTIL THE ASSOCIATED COLD FRONT SWEEPS
ACROSS THE REGION STARTING SHORTLY AFTER MIDNIGHT. RAIN WILL
REMAIN FAIRLY STEADY WITH THE GREATEST AMOUNTS FOCUSED WHERE MID-
LEVEL CONVERGENCE IS GREATEST...ALONG THE I80 CORRIDOR EARLY IN
THE EVENING AND SHIFTING SOUTH OF THE PA/WV BORDER BY WEDNESDAY
MORNING.
WITH STRONG MID-LEVEL MOISTURE TRANSPORT INTO THE AREA AND UPPER
LEVEL DIVERGENCE ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF A
+170KT JET...PORTIONS OF OUR FORECAST AREA COULD RECEIVE 1-1.5" OF
LIQUID THROUGH LATE WEDNESDAY. THIS...COMBINED WITH THE POTENTIAL
FOR SNOW MELT AND ICE ON LOCAL CREEKS AND STREAMS...COULD CAUSE
HIGH WATER ISSUES FOR AREAS MAINLY SOUTH OF PITTSBURGH. AN AREAL
FLOOD WATCH HAS BEEN ISSUED.

COLDER AIR WILL BEGIN TO FILTER IN WEDS AS THE UPPER TROF APPROACHES 
FROM THE WEST. EXPECTING TEMPERATURES TO HOLD PRETTY STEADY THROUGH 
THE DAY...WHICH KEEPS THE RAIN/SNOW LINE NEAR PITTSBURGH THROUGH THE 
AFTERNOON. BY LATE EVENING TEMPERATURES WILL HAVE FALLEN ENOUGH TO 
TRANSITION RAIN TO SNOW FOR ALL LOCATIONS. AGAIN THERE ARE QUESTIONS 
SURROUNDING HOW MUCH MOISTURE STAYS IN OUR FORECAST AREA THROUGH 
THURS MORNING AS THE GULF OF MEXICO MOISTURE FEED KICKS IN AND THE 
UPPER LEVEL TROF BEGINS TO KICK THE BOUNDARY OFF TO OUR EAST. 
POTENTIAL FOR ACCUMULATING SNOW EXISTS...MAINLY SOUTH AND EAST OF 
PITTSBURGH WHERE THE DEEPEST MOISTURE HOLDS. CONFIDENCE IN SNOW 
TOTALS AT THIS POINT IS FAIRLY LOW...AND WILL LIKELY CHANGE AS WE 
MOVE CLOSER TO MID-WEEK.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
OVERALL...THE LONG TERM PERIOD LOOKS QUIET WITH THE PASSAGE OF A
COUPLE OF WEAK FRONTS SATURDAY NIGHT AND THEN AGAIN LATE MONDAY.
AT THIS TIME...MODELS ARE SHOWING LITTLE MOISTURE ACCOMPANYING
EITHER OF THESE SYSTEMS. A SLOW MODERATION IN TEMPS IS EXPECTED
THROUGH THE ENTIRE PERIOD.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE MORNING UNDER
HIGH PRESSURE. AN ADVANCING WARM FRONT SHOULD BRING A MIX OF
SNOW...FREEZING RAIN AND RAIN AT THE ONSET...LATE MORNING INTO
THE AFTERNOON...WITH AN EVENTUAL CHANGEOVER TO RAIN AT ALL SITES
BY LATE IN THE DAY. CONDITIONS SHOULD DETERIORATE TO MVFR WHEN
PRECIP BEGINS...AND EVENTUALLY LOWER TO IFR BY THE LATTER PART OF
THE FORECAST PERIOD.

.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/... 
WIDESPREAD RESTRICTIONS ARE EXPECTED THROUGH WEDNESDAY NIGHT AS A
COLD FRONT SLOWLY CROSSES THE REGION. A PERIOD OF LOW LEVEL WIND
SHEAR IS POSSIBLE TUESDAY EVENING.

&&

.HYDROLOGY...
AN INCREASE IN FLOW AND STAGE IS EXPECTED TO CAUSE ICE MOVEMENT
STARTING TUESDAY...BEGINNING ON THE SOUTHERNMOST RIVER BASINS. THE
COMBINATION OF SNOW MELT AND DEVELOPING RAIN IS EXPECTED TO MOST
AFFECT THE MONONGAHELA AND YOUGHIOGHENY BASINS.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FLOOD WATCH FROM 7 PM EST THIS EVENING THROUGH WEDNESDAY 
     EVENING FOR MDZ001.
OH...WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR 
     OHZ039>041-048>050-057>059-068.
     FLOOD WATCH FROM 7 PM EST THIS EVENING THROUGH WEDNESDAY 
     EVENING FOR OHZ049-050-057>059-068-069.
PA...WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR 
     PAZ020-029.
     FLOOD WATCH FROM 7 PM EST THIS EVENING THROUGH WEDNESDAY 
     EVENING FOR PAZ014-020>023-029-031-073>076.
     WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR 
     PAZ007>009-013>016-022-023.
     WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR 
     PAZ021-073-074.
WV...WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR 
     WVZ001>003.
     FLOOD WATCH FROM 7 PM EST THIS EVENING THROUGH WEDNESDAY 
     EVENING FOR WVZ001>004-012-021>023-041.

&&

$$






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