Area Forecast Discussion
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000 FXUS61 KPBZ 110935 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 435 AM EST THU FEB 11 2016 .SYNOPSIS... SNOW SHOWERS WILL GRADUALLY DIMINISH THURSDAY. TEMPERATURES WILL CONTINUE TO FALL THROUGH THE WEEK WITH BITTER COLD TO START THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AN AXIS OF LOW LEVEL DEFORMATION CONTINUES TO SLOWLY EDGE SOUTHEASTWARD INTO THE NORTHERN REACHES OF THE AREA EARLY THIS MORNING. GIVEN THAT SURFACE TEMPERATURES ARE IN THE DENDRITIC GROWTH THERMAL LAYER AND SURFACE-BASED INSTABILITY IS PRESENT...THIS AXIS OF DEFORMATION IS SUMMARILY CO-LOCATED WITH A BAND OF SNOW SQUALLS THAT HAS PLAGUED THE AREA JUST SOUTH OF I-80 TOWARD THE TURNPIKE VIRTUALLY ALL NIGHT. AS THE MORNING ENSUES...LOW LEVEL CONVERGENCE IN THIS LAYER SHOULD START TO SUBSIDE...AS FLOW TURNS MORE UNI-DIRECTIONALLY FROM THE NORTHWEST...WHICH SHOULD ALLOW FOR FAR LESS DOMINANT BANDING ALONG THIS AXIS...THUS ALLOWING FOR THE SQUALLS TO DIMINISH. HOWEVER...IN THE INTERIM...A FEW MORE INCHES OF LOCAL ACCUMULATION WILL BE POSSIBLE...ESPECIALLY ALONG HIGHWAY 422. ELSEWHERE...UNSTABLE NORTHWESTERLY FLOW WILL BEGIN TO BE OVERCOME BY DRY CANADIAN AIR ADVECTING IN FROM THE NORTHWEST. THE ONLY PLACE WHERE THIS MAY NOT ENTIRELY BE THE CASE IS IN FOREST AND VENANGO COUNTIES. HIGH RESOLUTION GUIDANCE SUGGESTS BANDING FROM LAKE HURON WILL TREND SOUTHWARD LATE THIS MORNING. THIS WOULD ALLOW FOR A MULTI-LAKE FETCH TO BRING SNOW SHOWERS FROM LAKE HURON...ACROSS LAKE ERIE...AND INTO THE FAR NORTHEASTERN REACHES OF THE CWA. THUS POPS AND THE WINTER WEATHER ADVISORY WILL LIKELY BE MAINTAINED HERE TO ASCERTAIN WHETHER THIS DEVELOPMENT DOES OCCUR. IN THE RIDGES...VISIBILITIES HAVE CONTINUED TO GENERALLY BE BETWEEN 1 AND 2 MILES THROUGH THE NIGHT. A PERIOD OF A ENHANCED SNOW SHOWER ACTIVITY WILL BE LIKELY AS FLOW TURNS TO THE NORTHWEST...HOWEVER WEAKENING SATURATION WILL MEAN LESS EFFICIENT SNOW GENERATION BY AFTERNOON. THUS A FEW MORE INCHES WILL BE POSSIBLE IN THE RIDGES...HOWEVER TRENDS BY AFTERNOON SHOULD ALLOW FOR SNOW SHOWER ACTIVITY TO TAPER OFF. ELSEWHERE...SCATTERED SNOW SHOWERS WILL BE PRESENT...HOWEVER ACCUMULATIONS SHOULD BE LIGHT/LOCAL AS DRIER AIR MOVES INTO THE AREA. IN FACT...GOING INTO THE NIGHTTIME TONIGHT...LOW LEVEL FLOW STARTS TO WEAKEN CONSIDERABLY AND TURN A BIT TO THE SOUTHWEST. THIS WILL LIKELY ERADICATE BOUNDARY LAYER RH VALUES...AND ALLOW FOR DECENT TEMPERATURE FALLS. THEY WILL LIKELY BE TEMPERED BY MORNING AS MID AND HIGH CLOUDS INCREASE...HOWEVER SINGLE DIGITS WILL LIKELY STILL BE COMMON WITH WIND CHILLS INCREMENTALLY BELOW ZERO. FRIES && .SHORT TERM /FRIDAY THROUGH SUNDAY/...
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FRIDAY BEGINS DRY AND COLD AS HIGH PRESSURE TEMPORARILY CUTS OFF THE SNOW PRODUCTION. DEEP NORTHWESTERLY FLOW KEEPS THE DOOR TO COLDER AIR WIDE OPEN...SO HIGH TEMPERATURES WILL REMAIN WELL BELOW AVERAGE. MULTIPLE UPPER-LEVEL SHORTWAVES WILL SLIDE OUT OF THE NORTHERN PLAINS...PASSING THROUGH THE BASE OF THE PINWHEELING VORTEX IN CANADA. THE FIRST WEAKER WAVE WILL DIVE TO OUR SOUTH ON THE FRONT OF THE UPPER-LEVEL JET STREAK. THIS WILL BRING LITTLE MORE THAN INCREASED CLOUD COVER AND PERHAPS A FEW LIGHT SNOW SHOWERS THROUGH MIDDAY FRIDAY. A MORE POTENT WAVE WILL THEN DROP SOUTH THROUGH THE WESTERN GREAT LAKES...RE-INVIGORATING SNOW SHOWERS ALONG AND AHEAD OF THE COLD FRONT. MODERATE TO HEAVY SNOW SQUALLS AGAIN LOOK POSSIBLE AS THE FRONT PASSES FRIDAY NIGHT. LARGELY LEFT SNOW TOTALS INTACT FROM THE PREVIOUS FORECAST...WHICH LOOKS TO BE BELOW ADVISORY CRITERIA FOR A MAJORITY OF THE FORECAST AREA. ALONG WITH THE POTENTIAL FOR SCATTERED MODERATE SNOW BANDS...WINDS WILL BE INCREASING FRIDAY NIGHT AS THE PRESSURE GRADIENT TIGHTENS IN THE BASE OF THE LOW. SUSTAINED WINDS GREATER THAN 10KTS...AND TEMPERATURES DROPPING INTO THE SINGLE DIGITS BY SATURDAY MORNING WILL LIKELY NECESSITATE WIND CHILL ADVISORIES AT LEAST FOR THE RIDGES AND ALONG THE NORTH. SNOW SHOULD TAPER DOWN ACROSS THE WEST SATURDAY MORNING AS THE AXIS OF THE TROUGH SHIFTS TO OUR EAST. HOWEVER...WITH VERY COLD AIR PASSING OVER THE STILL UNFROZEN WATERS OF THE GREAT LAKES...ADDITIONAL LAKE-EFFECT SNOW SHOWERS ARE POSSIBLE. MODEL GUIDANCE SHOWING NORTH-NORTHWESTERLY FLOW SETTING UP AN AREA OF CONVERGENCE DOWN WIND OF LAKE ERIE. WITH A FAVORABLE HURON-TO- ERIE CONNECTION...LAKE-EFFECT SNOW SHOWERS SHOULD PERSIST ACROSS OUR NORTH THROUGH SATURDAY AFTERNOON. LEFT SNOW TOTALS ASSOCIATED WITH THIS ACTIVITY BROAD AND ON THE LIGHT SIDE...WITH HOPES FUTURE MODEL RUNS WILL BETTER RESOLVE THE SNOW BAND LOCATION. THE NORTH-NORTHWESTERLY FLOW WILL CONTINUE THE BARRAGE OF ARCTIC AIR INTO OUR REGION SATURDAY...WITH A LOW CELLING FOR HIGH TEMPS EXPECTED. MANY LOCATIONS MAY NOT GET OUT OF THE SINGLE DIGITS ALL DAY SATURDAY. WIND CHILL ADVISORIES WILL AGAIN BE LIKELY HEADING INTO SATURDAY NIGHT/SUNDAY MORNING...EVEN AS THE WINDS SLACKEN. TAX
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&& .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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SUNDAY WILL BEGIN DRY AS SURFACE HIGH PRESSURE WILL AGAIN MAKE A TEMPORARY VISIT TO THE REGION. MODELS STILL HAVING SOME DIFFICULTY WITH THE NEXT DISTURBANCE MOVING IN SUNDAY NIGHT. TIMING IS NOW FAIRLY CONSISTENT ACROSS THE GUIDANCE...BUT THE ECMWF QUICKLY WEAKENS THE WAVE UPON ARRIVAL. STILL...EXPECTING AT LEAST A CHANCE OF LIGHT SNOW MONDAY. MODELS NOW SHOW ANOTHER DEEPER WAVE IN THE WAKE OF THE MONDAY SYSTEM. THIS COULD POTENTIALLY BRING ACCUMULATING SNOW BACK INTO THE EASTERN FRINGE OF THE FORECAST AREA BY EARLY TUESDAY. WILL NEED SEVERAL MORE MODEL CYCLE TO SORT OUT THOSE DETAILS. TEMPERATURES WILL BEGIN TO MODERATE BY MIDDLE OF NEXT WEEK. TAX
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&& .AVIATION /09Z THURSDAY THROUGH MONDAY/... SNOW SQUALLS WILL LIKELY REMAIN BETWEEN KBVI AND KFKL THROUGH THE MORNING BEFORE DISSIPATING. LOCAL SNOW SHOWERS WILL BE POSSIBLE AT MOST SITES...HOWEVER NO HEAVIER SNOW SHOWERS SHOULD AFFECT ANY SITE. CIGS WILL SLOWLY IMPROVE THROUGH THE DAY...WITH VFR CONDITIONS LIKELY AT MOST SITES BY TONIGHT .OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... OCCASIONAL RESTRICTIONS ARE EXPECTED THROUGH THE PERIOD UNDER COLD UPPER-LEVEL TROUGHING. WHILE THURSDAY NIGHT AND SUNDAY SHOULD BE GENERALLY DRY...SCATTERED TO WIDESPREAD SNOW SHOWERS ARE EXPECTED FRIDAY...SATURDAY...AND MONDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MDZ001. OH...NONE. PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR PAZ013- 014-016-022-023. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ007>009-015-074-076. WV...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR WVZ510>514. && $$

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