Area Forecast Discussion
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226 FXUS61 KPBZ 081010 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 510 AM EST MON FEB 8 2016 .SYNOPSIS... LOW PRESSURE IS POISED TO SPREAD RAIN AND SNOW OVER THE REGION ON MONDAY...AND SNOW ON TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH TUESDAY/... CONDITIONS RELATIVELY QUIET THIS MORNING AS HIGH CLOUDS BEGIN TO STREAM IN FROM THE WEST. RADAR ECHOES HAVE BEGUN TO INCREASE TO OUR WEST...BUT DRY AIR SAMPLED BY THE 00Z SOUNDING WILL CONTINUE TO HOLD OFF THE BULK OF THE PRECIPITATION UNTIL NEAR DAYBREAK. FAIRLY SHARP ELONGATED FRONT SITS JUST TO OUR WEST...STRETCHING SOUTHWARD FROM AN APPROACHING LOW PRESSURE SYSTEM. STRONG MID-LEVEL FRONTOGENESIS WILL RESULT IN A BLOSSOMING OF PRECIPITATION ALONG THE FRONT THIS MORNING. BOUNDARY LAYER TEMPERATURES WILL INITIALLY FAVOR RAIN...BUT WITH THE CURRENTLY LARGE DEWPOINT SPREADS OBSERVED OVER EASTERN OHIO...TEMPERATURES MAY WET BULB DOWN TO BELOW FREEZING. HI-RES WRF AND NAM MODELS DEPICT A RAIN/SNOW MIX SWITCHING COMPLETELY OVER TO SNOW AT TIMES. BETWEEN THE AFOREMENTIONED WET BULBING AND SOME ADDED DYNAMIC COOLING...THINK SURFACE TEMPERATURES OVER EASTERN OHIO WILL STAGNATE THROUGH THE EARLY PART OF THE DAY...KEEPING A RAIN/SNOW MIX POSSIBLE THROUGH EARLY AFTERNOON. ELSEWHERE...TEMPERATURES WILL WARM INTO THE LOW 40S AS THE FRONTAL ZONE SLOWLY SWINGS THROUGH THIS AFTERNOON. RAIN IS EXPECTED FOR MUCH OF THE REST OF THE LOCAL FORECAST AREA THROUGH THE EARLY EVENING. TONIGHT THE FRONT DOOR TO THE COLD AIR SWINGS OPEN AS THE LOW DIVES INTO THE AREA AND THE UPPER-LEVEL LOW DEEPENS. MODELS HAVE BEEN TRENDING UPWARD IN THE INTENSIFICATION OF THE LOW...AND RESULTANT QPF OVERNIGHT. 00Z NAM OMEGA FIELDS APPEAR TO BE OVERDONE...WITH SEVERAL BULLSEYES OF QPF NEARING 1". STILL...THE BROADER OPERATIONAL MODELS OF THE GFS AND ECMWF SHOW AN UPTICK OF QPF WITH AN AREA OF MID-LEVEL DEFORMATION ALONG THE MASON DIXON LINE. THIS TREND HAS RESULTED IN THE RAISING OF SNOW AMOUNTS OVERNIGHT...AND THE NEED FOR AN EXPANSION BOTH IN TIME AND AREA OF THE WINTER WEATHER ADVISORY. WILL NEED TO MONITOR GUIDANCE CLOSELY TODAY FOR ANY POSSIBLE NORTHWARD EXPANSION...OR WARNING UPGRADES. TAX && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... TRICKY FORECAST CONTINUES INTO THE SHORT TERM PERIOD. SURFACE LOW CONTINUES TO CHURN TO OUR NORTH OVER THE EASTERN GREAT LAKES TUESDAY. MODELS GENERALLY AGREE ON PLACEMENT OF HIGHER SNOW TOTALS ACROSS THE SOUTHERN PORTION OF THE CWA. A WEAK TROWAL SETUP/FRONTOGENTIC FORCING ARE PRESENT WHICH WILL HELP TO ENHANCE SNOW TOTALS AS COMPARED TO AREAS TO THE NORTH. THERE IS SOME VERY MINOR DISAGREEMENT ON NORTHERN EXTENT OF THIS MORE FAVORABLE FORCING...BUT MODEL AGREEMENT IS RELATIVELY GOOD. CONTINUED SLOW COLD ADVECTION WILL ALLOW CLOUD MICROPHYSICAL CONDITIONS TO IMPROVE WITH TIME...ALONG WITH SNOW RATIOS. THIS COULD LEAD TO LOCALLY HIGHER TUESDAY SNOW TOTALS THAN CURRENTLY DEPICTED DEPENDING ON WHERE BEST DYNAMICS ULTIMATELY SET UP. BEST FORCING BEGINS TO WANE LATER ON TUESDAY AS THE COLDER AIRMASS STARTS TO SETTLE IN. CATEGORICAL POPS WERE PLACED FROM PIT ON SOUTH. TO THE NORTH...LIKELY POPS WERE MAINTAINED...BUT THE LACK OF SIGNIFICANT FORCING...ESPECIALLY AS COMPARED TO THE SOUTH...COULD LEAD TO A SHARPER CUTOFF IN SNOW COVERAGE THAN CURRENTLY DEPICTED. A MORE TYPICAL NW FLOW SNOW PATTERN BEGINS TO SET UP TUESDAY NIGHT INTO WEDNESDAY AS H500 CLOSED LOW IS ABSORBED INTO EASTERN CONUS TROUGH. RESULTING MIDLEVEL TROUGH AXIS ROTATES ACROSS THE CWA ON WEDNESDAY WHICH WILL HELP TO KEEP SHSN GOING. HIGH CHANCE TO LIKELY POPS WERE MAINTAINED FOR THE CWA THROUGH WEDNESDAY. AS TIME WEARS ON...CONTINUED COLD ADVECTION WEDNESDAY NIGHT WILL PUSH MUCH OF THE MOISTURE INTO COLDER THAN IDEAL DENDRITIC GROWTH CONDITIONS. THIS WILL ACT TO SLOW DOWN ADDITIONAL SNOW ACCUMULATION AS ICE CRYSTALS WILL NOT BE ABLE TO AGGREGATE EFFICIENTLY. THIS PROCESS CONTINUES INTO THURSDAY...WITH SHSN COVERAGE GREATLY DECREASING BY AFTERNOON. AS FAR AS SNOW TOTALS...CURRENTLY CONSTRUCTED GRIDS DO APPROACH BUT DO NOT MEET/EXCEED WARNING CRITERIA IN ANY GIVEN 12 OR 24 HOUR PERIOD IN THE RIDGES. THIS IS EVEN MORE THE CASE IN LOWER ELEVATION AREAS TO THE WEST. AFTER COLLABORATION WITH OTHER OFFICES...ELECTED TO GO WITH LONG-LASTING ADVISORIES FOR ROUGHLY THE SOUTHERN HALF OF THE CWA...WITH LONGER DURATION IN THE RIDGES. CANNOT RULE OUT THE NEED TO UPGRADE TO A WARNING IF BANDING STRUCTURES CAN FORM AND SIT OVER A PARTICULAR REGION...BUT CONFIDENCE IS TOO LOW TO PLACE SUCH A WARNING AT THIS TIME. && .LONG TERM /FRIDAY THROUGH SUNDAY/... THE NW FLOW SNOW SHOWER MACHINE SHOULD FINALLY WIND DOWN THURSDAY NIGHT AS TROUGHING PATTERN TEMPORARILY RELAXES. HOWEVER...AN ARCTIC COLD FRONT WILL DROP DOWN IN NW FLOW AND CROSS BY THE END OF THE WORK WEEK. ISOLATED TO SCATTERED SNOW SHOWERS WILL ACCOMPANY IT AND LINGER INTO SATURDAY...BUT THE HEADLINE MAY END UP BEING THE FRIGID AIRMASS. SATURDAY NIGHT LOOKS PARTICULARLY COLD...WITH SOME BELOW ZERO READINGS POSSIBLE. SUNDAY WILL BE DRY AND COLD. TROUGH RELAXES ONCE AGAIN MONDAY...ALLOWING FOR TEMPERATURE MODERATION...BUT ANOTHER SNOW CHANCE MAY ARRIVE AS WELL. THE SUPERBLEND GUIDANCE WAS USED HEAVILY FOR THIS PERIOD...WITH MODIFICATIONS. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... VFR CONDITIONS WILL CONTINUE INTO MIDDAY...UNTIL A COLD FRONT SWINGS THROUGH. PRECIPITATION CURRENTLY IN CENTRAL OHIO WILL APPROACH ZZV THIS MORNING WITH SEVERAL HOURS OF POSSIBLE RAIN/SNOW AND ASSOCIATED RESTRICTIONS. AS THE FRONT MOVES WEST TO EAST...RAIN WILL BRING BRIEF MVFR FURTHER DETERIORATING TO IFR AS IT SWITCHES OVER TO SNOW TONIGHT. EXPECTING IFR AND POSSIBLE LIFR IN SNOW TONIGHT AND TUESDAY MORNING...WITH SOUTHERN PORTS IMPACTED THE MOST. LIGHT SOUTHERLY FLOW WILL SWING AROUND TO THE WEST AS THE LOW MOVES OVERHEAD. .OUTLOOK.../TUESDAY THROUGH FRIDAY/... RESTRICTIONS IN SNOW SHOWERS WILL CONTINUE INTO THE MIDDLE PART OF THE WEEK WITH GRADUAL IMPROVEMENT EXPECTED. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 PM EST WEDNESDAY FOR MDZ001. OH...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST WEDNESDAY FOR OHZ049-050-057>059-068-069. PA...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST WEDNESDAY FOR PAZ021-029-031-073-075. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST WEDNESDAY FOR PAZ074-076. WV...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST WEDNESDAY FOR WVZ001>004-012-021-509. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST WEDNESDAY FOR WVZ510-511-513. WINTER WEATHER ADVISORY FROM NOON TODAY TO 7 PM EST WEDNESDAY FOR WVZ512-514. && $$

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