Area Forecast Discussion
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000 FXUS61 KPBZ 040510 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1210 AM EST WED MAR 4 2015 .SYNOPSIS... LOW PRESSURE CROSSING THE GREAT LAKES WILL CONTINUE TO SPREAD RAIN OVER THE UPPER OHIO VALLEY REGION TONIGHT. RAIN WILL TURN TO SNOW WITH A WEDNESDAY COLD FRONT. && .NEAR TERM /THROUGH TODAY/... WITH MIDNIGHT UPDATE...MADE SOME MINOR CHANGES TO HOURLY TEMPERATURE AND PRECIPITATION TRENDS. SOME SLIGHT DOWNWARD ADJUSTMENTS WERE MADE ACROSS THE EXTREME NORTH WITH REGARDS TO CHANCES FOR PRECIPITATION AND QPF AS RAIN SHIELD HAS GENERALLY STAYED SOUTH OF MERCER AND VENANGO COUNTIES SO FAR. NO CHANGES WERE MADE FOR THE LATE EVE UPDATE...OTHER THAN TO TWEAK HOURLY TRENDS OF TEMPERATURE GIVEN THE WARMTH SURGING ACROSS THE REGION. AN UPDATED WINTER STORM WATCH WAS ISSUED TO UPDATE THE TIME STAMP...NO OTHER CHANGES AT MOMENT. OTHERWISE...THE FLOOD WATCH HAS BEEN MAINTAINED AS SNOW MELT WILL AGGRAVATE ANY ONGOING POOR DRAINAGE ISSUES RESULTING FROM A GENERAL 0.2 TO 0.4 INCHES OF RAIN EARLIER THIS EVENING. HOWEVER...AREAS ALONG AND SOUTH OF A LINE FROM ZANESVILLE TO LATROBE MAY WANT TO PAY SPECIAL ATTENTION THROUGH THE NIGHT AS A CROSSING JET STREAK IS MODEL PROGGED TO ENHANCE MID LEVEL FRONTOGENESIS FOR BETTER RAINFALL FOCUS. THINK AN ADDITIONAL 0.20 OVER NORTHERN AREAS TO ABOUT AN INCH OVER SOUTHERN COUNTIES IS A REASONABLE BASIN AVERAGE PROGNOSIS AT THIS TIME AND IS BASED ON MORE CONSERVATIVE ECMWF GUIDANCE. A TRANSITION TO SNOW WILL OCCUR WITH THE ENCROACHMENT OF THE COLD FRONT ON WEDNESDAY. ANY SNOW THAT FALLS THROUGH THE DAY SHOULD BE LIMITED BY INEFFICIENT SNOW RATIOS AND LITTLE ACCUMULATION IS EXPECTED INTO THE EVENING. && .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/... THE WINTER STORM WATCH FOR WEDNESDAY NIGHT AND THURSDAY HAS BEEN CONTINUED FOR AREAS ROUGHLY ALONG AND SOUTH OF A ZANESVILLE TO INDIANA LINE...BUT THE NORTHWARD EXTENT OF DEEPER MOISTURE AND ASCENT BEHIND THE WAVE SLOWED FRONTAL ZONE IS CERTAINLY QUESTIONABLE AND AN ADDITIONAL SET OF MODEL RUNS WILL BE NECESSARY FOR BETTER RESOLUTION. AT ANY RATE...SNOW SHOWERS WILL DIMINISH THROUGH THURSDAY AFTERNOON WITH ARCTIC HIGH PRESSURE CLEARING OUT SKIES. WITH LIGHT WINDS TEMPERATURES EXPECTED TO CRASH NEAR OR BELOW ZERO WITH FRESH SNOW COVER. SUNSHINE BUT CONTINUED COLD FRIDAY WITH TEMPERATURES 15 TO 20 DEGREES BELOW SEASONAL AVERAGES. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... THE LONG TERM PERIOD LOOKS RELATIVELY QUIET WITH A PROGRESSIVE PATTERN FEATURING PASSAGE OF A COUPLE OF SHORTWAVE TROUGHS. POPS WERE FORECAST GENERALLY BELOW CHANCE CLIMO NUMBERS USING GFS TIMING...BUT LONG TERM CONFIDENCE IS MINIMAL WITH DOUBTS ABOUT TIMING AND MOISTURE SUPPLY. SEASONALLY COOL TEMPERATURES WERE FORECAST VIA PERSISTENCE AND MOS. && .AVIATION /05Z WEDNESDAY THROUGH SUNDAY/... IFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MUCH OF WEDNESDAY AS LOW PRESSURE CROSSES THE GREAT LAKES REGION. A GRADUAL CHANGEOVER TO SNOW IS EXPECTED FROM NORTH TO SOUTH DURING THE DAY WEDNESDAY...WITH FKL/DUJ CHANGING LATE TONIGHT...PIT IN THE MORNING AND MGW TOWARD EVE. AN IMPROVEMENT TO LOW END MVFR IS EXPECTED FROM PIT NORTH BY AFTERNOON AS THE ASSOCIATED COLD FRONT PUSHES SOUTH. LOW LEVEL WIND SHEAR SHOULD PERSIST THIS EVENING BEFORE A LOW LEVEL JET EXITS. .OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... WIDESPREAD RESTRICTIONS ARE EXPECTED INTO THURSDAY AS A WAVE OF LOW PRESSURE MOVES ALONG A COLD FRONT...WITH SNOW MAINLY FROM PIT SOUTH. RESTRICTIONS ARE POSSIBLE WITH A SUNDAY COLD FRONT. && .HYDROLOGY... THE COMBINATION OF SNOW MELT AND DEVELOPING RAIN IS EXPECTED TO CAUSE SIGNIFICANT RISES ON THE CHEAT... MONONGAHELA AND YOUGHIOGHENY RIVER BASINS. THESE RISES WILL AID IN MOVING ICE INTO AREAS WHERE ICE JAMS ARE KNOWN TO DEVELOP. THE RISES WILL MOST LIKELY PERSIST THROUGH THURSDAY. CONFIDENCE IN RAIN AMOUNTS REMAINS LOW...BUT THE BETTER CHANCE FOR MORE SIGNIFICANT ACCUMULATION IS EXPECTED TO BE ALONG AND SOUTH OF A ZANESVILLE TO LATROBE LINE. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...FLOOD WATCH THROUGH THIS EVENING FOR MDZ001. WINTER STORM WATCH FROM THIS AFTERNOON THROUGH THURSDAY AFTERNOON FOR MDZ001. OH...FLOOD WATCH THROUGH THIS EVENING FOR OHZ049-050-057>059-068- 069. WINTER STORM WATCH FROM THIS AFTERNOON THROUGH THURSDAY AFTERNOON FOR OHZ057>059-068-069. PA...FLOOD WATCH THROUGH THIS EVENING FOR PAZ014-020>023-029-031- 073>076. WINTER STORM WATCH FROM THIS AFTERNOON THROUGH THURSDAY AFTERNOON FOR PAZ021-023-029-031-073>076. WV...FLOOD WATCH THROUGH THIS EVENING FOR WVZ001>004-012-021>023- 041. WINTER STORM WATCH FROM THIS AFTERNOON THROUGH THURSDAY AFTERNOON FOR WVZ002>004-012-021>023-041. && $$

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