Area Forecast Discussion
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000 FXUS61 KPBZ 041052 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 552 AM EST WED MAR 4 2015 .SYNOPSIS... RAIN WILL TURN TO SNOW TONIGHT...WITH SEVERAL INCHES OF SNOW EXPECTED INTO NORTHERN WEST VIRGINIA. TEMPERATURES WILL BE UNSEASONABLY COLD INTO THE WEEKEND. && .NEAR TERM /UNTIL 4 PM THIS AFTERNOON/... QUICK UPDATE AT 545AM TO ACCOUNT FOR SNOW TURNING TO RAIN SLIGHTLY AHEAD OF SCHEDULE. STILL ANTICIPATE THAT PRECIPITATION SHIELD WILL TREND SOUTHWARD OVER THE NEXT FEW HOURS...BUT HAVE ADDED MINIMAL MENTION OF SNOW INTO THE MORNING PORTION OF THE FORECAST AS SOME OF THE SNOW IS ALREADY MANAGING TO STICK. PREVIOUS DISCUSSION FOLLOWS. RAIN CONTINUES ACROSS MUCH OF THE REGION OVERNIGHT WITH MUCH WARMER TEMPERATURES THAT HAVE RECENTLY BEEN EXPERIENCED. TEMPERATURES WILL SLOWLY FALL THROUGH THE DAY...ALLOWING FOR A SLOW TRANSITION IN PRECIPITATION TYPE FROM RAIN TO SNOW NOW THAT A COLD FRONT HAS MOVED THROUGH THE REGION. ANY SNOWFALL ACCUMULATIONS DURING THE DAY SHOULD BE MINIMAL DUE TO ABOVE FREEZING SURFACE TEMPERATURES. HOWEVER...PLENTY OF PRECIPITATION WILL REMAIN BEHIND THE FRONT...WITH ADDITIONAL RAINFALL RANGING FROM A TENTH OF AN INCH ALONG THE INTERSTATE 80 CORRIDOR TO THREE QUARTERS OF AN INCH TOWARDS MORGANTOWN. NO CHANGES WERE MADE TO THE FLOOD WATCH CURRENTLY IN EFFECT FOR MOST OF THE FORECAST AREA THROUGH MID AFTERNOON. RAINFALL WILL NOT BE THE ONLY CONTRIBUTING FACTOR TO FLOODING...AS MELTING SNOW FROM THE SNOWPACK AND ICE JAMS COULD ALSO PRODUCE LOCAL FLOODING. SEVERAL FLOOD ADVISORIES HAVE ALREADY BEEN ISSUED...GENERALLY TO THE SOUTH AND EAST OF PITTSBURGH. && .SHORT TERM /4 PM THIS AFTERNOON THROUGH FRIDAY/... THE MAIN CHANGEOVER FROM RAIN TO SNOW WILL HAPPEN DURING THE LATE AFTERNOON INTO EARLY EVENING. ALTHOUGH THE COLDER AIR WILL MOVE IN BEHIND THE COLD FRONT...THE FRONT ITSELF WILL TAKE ITS TIME MOVING OUT OF THE REGION...ALLOWING PRECIPITATION TO CONTINUE TONIGHT INTO THURSDAY. MOST DIFFICULT PART OF THE FORECAST WILL BE DETERMINING THE WESTERN EDGE OF THE HEAVIEST SNOWFALL...AS A TIGHT GRADIENT IS EXPECTED. ALL COUNTIES PREVIOUSLY UNDER THE WINTER STORM WATCH HAVE BEEN PUT INTO A WINTER WEATHER ADVISORY OR WINTER STORM WARNING...WITH A FEW ADDITIONAL COUNTIES ADDED INTO THE ADVISORY AS WELL. HAVE GONE SOMEWHAT CONSERVATIVE WITH THE AREA IN THE WARNING...AND AM CONCERNED THAT HIGHER SNOW TOTALS COULD EDGE A LITTLE BIT FARTHER NORTH AND WEST. AN ADDITIONAL CONCERN WAS MODEL SOUNDINGS SHOWING THAT A WARM LAYER ALOFT COULD REMAIN FOR A FEW HOURS ACROSS THE WV/MD RIDGES...WHICH COULD ALLOW FOR A BRIEF PERIOD OF FREEZING RAIN DURING THE EVENING HOURS. IF FREEZING RAIN DEVELOPS...IT WOULD CUT INTO OVERALL SNOWFALL TOTALS...BUT WOULD PRESENT ITS OWN SET OF PROBLEMS DUE TO ICE ACCUMULATION. 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 /FRIDAY 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 /12Z WEDNESDAY THROUGH SUNDAY/... IFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE MAJORITY OF THE DAY AS LOW PRESSURE CROSSES THE GREAT LAKES REGION. A GRADUAL CHANGEOVER TO SNOW IS EXPECTED FROM NORTH TO SOUTH THROUGH THE MORNING WITH KMGW THE LAST TO CHANGE OVER JUST BEFORE NOON. AN IMPROVEMENT TO LOW END MVFR WILL BE POSSIBLE FROM PIT NORTH BY AFTERNOON AS THE ASSOCIATED COLD FRONT PUSHES SOUTH. .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 WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR MDZ001. OH...FLOOD WATCH THROUGH THIS EVENING FOR OHZ049-050-057>059-068- 069. WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR OHZ049-050-057>059-068. WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR OHZ069. PA...FLOOD WATCH THROUGH THIS EVENING FOR PAZ014-020>023-029-031- 073>076. WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR PAZ021-023-029-031-073>075. WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR PAZ076. WV...FLOOD WATCH THROUGH THIS EVENING FOR WVZ001>004-012-021>023- 041. WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR WVZ001>004. WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM EST THURSDAY FOR WVZ012-021>023-041. && $$

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