Area Forecast Discussion
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000 FXUS61 KPBZ 010258 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 958 PM EST SAT FEB 28 2015 .SYNOPSIS... LOW PRESSURE WILL SPREAD SNOW AND RAIN OVER THE UPPER OHIO REGION ON SUNDAY. WARMER...MORE SEASONABLE...WEATHER CAN BE EXPECTED FOR THE COMING WEEK. && .NEAR TERM /THROUGH SUNDAY NIGHT/...
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ANOTHER LATE EVE UPDATE WAS ISSUED TO ACCOUNT FOR AN EARLIER SNOW START LATE TONIGHT...AS WELL AS AN EARLIER DIMINISHMENT ON SUNDAY EVE. SNOW TOTALS WERE TWEAKED DOWNWARD SLIGHTLY...BUT NO CHANGE WAS NEEDED FOR THE OVERALL SITUATION AND ADVISORY. PREVIOUS APPLIES... BROAD...PERSISTANT...WARM...MOIST ADVECTION WILL SPREAD SNOW...AND SOME RAIN OVER THE REGION ON THE EASTERN FLANK OF A SHORTWAVE TROUGH. PASSAGE OF THE SYSTEM WL DRAG A COLD FRONT ACROSS THE REGION IN THE PREDAWN OF MONDAY AND CHANGE REMAINING PRECIPITATION BACK TO SNOW BEFORE SUPPRESSING IT VIA STRENTHENING SUBSIDENCE. MODELS REMAIN IN GENERAL AGREEMENT WITH THE SCENARIO AND OVERALL SNOW AMOUNTS ARE EXPECTED TO BE LIMITED BY DIMINISHING EFFICIENCY WITH THE WARM ADVECTION...AS WELL AS A LACK OF STRONG DYNAMICS IN THE QUASI ZONAL MID LEVEL FLOW. THE WINTER WEATHER ADVISORY THUS REMAINS APPROPRIATE AND HAS BEEN MAINTAINED FOR PROLONGED SNOW ACCUMULATION...AND A TOUCH OF POSSIBLE ICE OVER SOUTHERN ZONES IN THE MORNING.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... SURFACE HIGH PRESSURE SNOW IS PROJECTED TO RAPIDLY BUILD AND SQUASH AND REMAINING SNOW SHOWERS ON MONDAY. HOWEVER...A SOUTH-SOUTHWESTERLY 850MB JET ON THE EASTERN FLANK OF MIDWESTERN LOW PRESSURE IS PROJECTED TO STRENGTHEN ON MONDAY NIGHT AND FUEL ANOTHER ROUND OF WARM...MOIST ADVECTION WITH LIGHT PRECIPITATION AGAIN DEVELOPING OVER THE REGION. THAT PRECIPITATION LIKELY WILL BEGIN AS LIGHT SNOW...BUT WITH RAPID WARMING ALOFT...A PERIOD OF FREEZING RAIN IS LIKELY IN THE ENTRENCHED SURFACE COLD. THAT PERIOD IS EXPECTED TO BE RELATIVELY BRIEF WITH THE SURFACE LOW PROJECTED TO PASS NORTHWEST OF THE FORECAST AREA...LEAVING THE OHIO VALLEY WELL WITHIN THE WARM...HENCE THE RAIN SECTOR UNTIL COLD FRONTAL PASSAGE ON WEDNESDAY. AS MODELS TEND TO OVERDO QPF IN WARM AIR ADVECTION PATTERNS...AND GIVEN THAT THIS PROJECTED SYSTEM IS AN OPEN WAVE...QPF ON TUESDAY WAS TONED DOWN SLIGHTLY FROM THE MORE ASSERTIVE GFS VALUES. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... COLD AIR ADVECTION IN THE WAKE OF THE TUESDAY NIGHT COLD FRONTAL PASSAGE WILL RETURN THE REGION TO NEAR- OR SUB-FREEZING TEMPERATURES FOR THE REMAINDER OF THE WEEK. UPSLOPE SNOW SHOWERS LIKELY WILL PERSIST THROUGH WEDNESDAY EVENING...BUT SHOULD SEE A MARKED DECREASE IN COVERAGE BY LATE WEDNESDAY NIGHT. A QUICK-MOVING SHORTWAVE TROUGH COULD AFFECT THE REGION LATE IN THE WEEK WITH LITTLE FANFARE ANTICIPATED. THE DRY AIRMASS AT THE SURFACE PRECLUDES SIGNIFICANT IMPACTS AT THE MOMENT SAVE MODEST LAKE-ENHANCED SNOW. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... SNOW IS EXPECTED TO DEVELOP LATE TONIGHT...AROUND 6Z NEAR ZZV TO AROUND 9Z NEAR LBE/DUJ. ONCE SNOW COMMENCES...CONDITIONS WILL DETERIORATE TO IFR BY MORNING. SNOW WILL MIX WITH AND CHANGE TO RAIN AT MOST TERMINALS /EXCEPT FKL AND DUJ/ MID-DAY...WITH MGW SEEING MOSTLY RAIN THRU THE DAY. A WIND SHIFT IS EXPECTED SUNDAY EVE ASSOCIATED WITH A COLD FRONTAL PASSAGE. PRECIPITATION WILL CHANGE BACK TO SNOW IN THE WAKE OF THE COLD FRONT. .OUTLOOK.../SUNDAY NIGHT THROUGH THURSDAY/... RESTRICTIONS LIKELY WILL PERSIST THROUGH MUCH OF MONDAY. LOW PRESSURE CROSSING THE GREAT LAKES IS LIKELY TO SPAWN WIDESPREAD RESTRICTIONS ONCE AGAIN BY LATE TUESDAY. && .HYDROLOGY... MANY OF THE AREA RIVERS AND STREAMS ARE ICE COVERED. AN INCREASE IN FLOW AND STAGE IS EXPECTED TO CAUSE ICE MOVEMENT STARTING TUESDAY...BEGINNING ON THE SOUTHERNMOST RIVER BASINS. THE CURRENT FORECAST CONTINUES TO HAVE A HIGH LEVEL OF UNCERTAINTY ABOUT PRECIPITATION PHASE AND AMOUNTS AS WELL AS THE DEGREE OF SNOW MELT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 7 AM EST MONDAY FOR MDZ001. OH...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 7 AM EST MONDAY FOR OHZ039>041-048>050-057>059. PA...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 7 AM EST MONDAY FOR PAZ007>009-013>016-020>023-029-073>076. WV...WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 7 AM EST MONDAY FOR WVZ001>003-023-041. && $$

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