Area Forecast Discussion
Issued by NWS

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000 FXUS61 KPBZ 031035 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 535 AM EST TUE MAR 3 2015 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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HIGH PRESSURE CENTERED OVER THE FORECAST AREA WILL TRANSITION EAST TODAY AS A DEVELOPING AREA OF LOW PRESSURE ACROSS THE CENTRAL PLAINS QUICKLY MOVES NORTHEAST...CENTERED OVER THE GREAT LAKES BY EARLY THIS EVENING. MOISTURE AND TEMPERATURES ALOFT WILL CONTINUE TO INCREASE SUBSTANTIALLY THROUGH THE MORNING AND AFTERNOON UNDER STRONG SOUTHWESTERLY FLOW...AND WITH TEMPERATURES STILL BELOW FREEZING ACROSS MUCH OF THE REGION...CONDITIONS CONTINUE TO LOOK IDEAL FOR A BRIEF PERIOD OF FREEZING RAIN LATE THIS MORNING AND THIS AFTERNOON AT MOST LOCATIONS BEFORE CHANGING OVER COMPLETELY TO RAIN. MAIN CHANGES TO THE ONGOING FORECAST IN THE NEAR TERM WERE TO PUSH BACK TIMING OF PRECIPITATION SLIGHTLY AS THERE IS A SUBSTANTIAL DRY LAYER IN THE LOWER LEVELS TO OVERCOME BEFORE PRECIPITATION BREAKS OUT...AND A SLIGHT INCREASE TO HOURLY TEMPERATURES BASED ON LATEST TRENDS...WHICH HAVE BEEN A FASTER TO WARM UP THAN PREVIOUSLY EXPECTED SO FAR THIS MORNING. IF THIS TREND CONTINUES....AREAS FURTHEST SOUTH AND UNDER CURRENT WINTER WEATHER ADVISORIES MAY SEE A VERY BRIEF PERIOD OF FREEZING RAIN OR POTENTIALLY NO FREEZING RAIN AT ALL...BUT IT IS TOO EARLY TO KNOW JUST YET. THEREFORE HAVE HELD OFF ADJUSTING THE CURRENT ADVISORY FOR NOW. AS MENTIONED PREVIOUSLY...THE NORTHEASTERN PORTIONS OF THE FORECAST AREA LOOK LIKELY TO SEE THE LONGEST PERIOD OF ICING TODAY...NOT CHANGING OVER TO RAIN UNTIL LATE AFTERNOON/EARLY EVENING.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
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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.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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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.
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&& .AVIATION /10Z TUESDAY THROUGH SATURDAY/...
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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.
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&& .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...
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MD...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 2 PM EST THIS AFTERNOON FOR MDZ001. FLOOD WATCH FROM THIS EVENING THROUGH WEDNESDAY EVENING FOR MDZ001. OH...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 2 PM EST THIS AFTERNOON FOR OHZ039>041-048>050-057>059-068. FLOOD WATCH FROM THIS EVENING THROUGH WEDNESDAY EVENING FOR OHZ049-050-057>059-068-069. PA...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 2 PM EST THIS AFTERNOON FOR PAZ029-075-076. FLOOD WATCH FROM THIS EVENING THROUGH WEDNESDAY EVENING FOR PAZ014-020>023-029-031-073>076. WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 PM EST THIS EVENING FOR PAZ007-013-014-020>023-073-074. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 9 PM EST THIS EVENING FOR PAZ008-009-015-016. WV...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 2 PM EST THIS AFTERNOON FOR WVZ001>003-023-041. FLOOD WATCH FROM THIS EVENING THROUGH WEDNESDAY EVENING FOR WVZ001>004-012-021>023-041.
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&& $$

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