Area Forecast Discussion
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000 FXUS61 KPBZ 260617 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 117 AM EST WED NOV 26 2014 .SYNOPSIS... LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP AND RIDE NORTHWARD ALONG THE COAST ON WEDNESDAY...BRINGING ACCUMULATING SNOW TO AREAS SOUTH AND EAST OF PITTSBURGH. A SECOND WEAKER SYSTEM WILL USHER IN COLDER TEMPERATURES AND LINGERING SNOW SHOWER CHANCES THROUGH THE END OF THE WEEK. && .NEAR TERM /THROUGH TODAY/...
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THE 00Z KPBZ RAOB INDICATED A VAST DEPTH WITH DEWPOINT DEPRESSIONS THAT REVEALED A VERITABLE CHASM BETWEEN THE TEMPERATURE AND DEWPOINT CURVE IN THE VERTICAL. AS SUCH...A DEEP LAYER OF DRY AIR HAS MADE RESIDENCE OVER THE AREA...WHICH SHOULD ALLOW FOR THE VAST MAJORITY OF THE CWA TO REMAIN DRY THROUGH THE NIGHTTIME HOURS IN ADVANCE OF THE SYSTEM ADVANCING NORTHEASTWARD UP THE EASTERN SEABOARD. WHILE NO CHANGES WERE MADE TO THE FORECAST FOR TOMORROW AT THE MOMENT...AN EARLY LOOK AT 00Z CANADIAN/GFS/NAM AND 04Z HRRR RUNS DOES STILL REVEAL SOME RATHER CONCERNING CHARACTERISTICS WITH REGARD TO THE EVOLUTION OF THE OVERALL PATTERN...PRODUCTION OF PRECIPITATION FROM THE MODELS THEMSELVES...VAST DISCREPANCIES WITH WARM ADVECTION...TROUBLE WITH WET BULB PROCESSES...NOT TO MENTION THE MORE EVERYDAY ISSUES WITH THE TRACK OF THE LOW LEVEL CENTER OF THE SYSTEM...LOW LEVEL THERMAL FIELDS...AND QPF PLACEMENT. ALL OF THESE ISSUES WILL HAVE TO BE ADEQUATELY CHEWED THROUGH DURING THE REMAINDER OF THIS SHIFT...HOWEVER LATER START TIMES DO LOOK BETTER AT THE MOMENT. AND IT SEEMS FAIRLY CLEAR THAT THE BEST WINDOW FOR ACCUMULATING SNOW WILL BE RATHER SHORT...AS IN REALLY NOT MUCH LONGER THAN 6 HOURS ANYWHERE...AND LIKELY ONLY MAYBE 2-3 HOURS IN PITTSBURGH ITSELF. COMBINING THAT WITH THE SYSTEM MOVING THROUGH DURING THE DAYTIME WITH WARM GROUND TEMPERATURES AND MARGINAL BOUNDARY LAYER TEMPERATURES...AND IT SEEMS CLEAR THAT WITHOUT INTENSE SNOW RATES...ACCUMULATIONS OUTSIDE THE RIDGES MAY BE TOUGH. THAT SAID...TEMPERATURES BASED UPON CURRENT TRENDS AND WET BULB PROFILES MAY WELL START OUT THE DAY TOMORROW A BIT LOWER THAN PREVIOUSLY FORECAST. ALL OF THIS WILL NEED TO BE MULLED INTO THE FULL UPDATE OF THE FORECAST FOR TODAY A BIT LATER THIS MORNING. FRIES
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&& .SHORT TERM /TONIGHT THROUGH FRIDAY/...
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ANY LINGERING SNOW IN THE FAR EAST THIS EVENING WILL END QUICKLY AS THE LIFT AND MOISTURE HEAD TOWARD THE COAST WITH THE EXITING LOW. HUGE DRY SLOT WILL OVERTAKE THE ENTIRE AREA THIS EVENING AND MIXING HEIGHTS WILL BE WELL BELOW THE DENDRITIC GROWTH ZONE... ENDING THE ATMOSPHERES ABILITY TO CREATE SNOW. CAA WILL BE GOING ALL NIGHT...BUT WITH THE LACK OF DEEP MOISTURE AND A RATHER WEAK AND UNORGANIZED FLOW ALOFT...DO NOT EXPECT ANY SNOW SHOWERS TO REDEVELOP. FOR THE MOST PART...THURSDAY MORNING LOOKS DRY AS THE FLOW ALOFT REMAINS UNORGANIZED AND MIXING HEIGHTS ARE JUST TOO LOW TO REACH INTO THE SNOW GROWTH ZONE. SHORTWAVE TROUGH WILL SWING THROUGH LATE THURSDAY...INCREASING LARGE SCALE ASCENSION AND BRINGING ANOTHER SHOT OF COLDER AIR THURSDAY NIGHT. WINDS ALOFT WILL INCREASE IN SPEED AND BECOME WEST-NORTHWESTERLY. THE SNOW GROWTH ZONE BEGINS TO LOWER AND LAKE ERIE WILL COME INTO PLAY. WILL BRING POPS BACK IN ACROSS THE NORTH AND RIDGES THURSDAY AFTERNOON. CAA CONTINUES THURSDAY NIGHT BEHIND EXITING SHORTWAVE TROUGH. FOR A TIME...WINDS ALOFT LOOK GOOD FOR LAKE INFLUENCES AND THE SNOW GROWTH ZONE WILL DROP INTO AN AREA OF HIGHER SATURATION. EXPECT AN INCREASE IN SNOW SHOWER COVERAGE THURSDAY NIGHT...WITH THE NORTH AND RIDGES THE MOST LIKELY LOCATIONS FOR ACCUMULATING SNOW. SURFACE HIGH WILL BUILD IN ON FRIDAY AND THE ENTIRE ATMOSPHERE WILL DRY OUT DURING THE MORNING HOURS. COULD SEE SOME LINGERING FLURRIES ACROSS THE NORTH AND RIDGES FRIDAY MORNING...BUT THESE TOO WILL END AS SUBSIDENCE AND THE DRIER AIR TAKES OVER. A COLD DAY FRIDAY WITH TEMPS WELL BELOW SEASONABLE LEVELS.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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MODELS COMING INTO GOOD AGREEMENT WITH ANOTHER WARM UP FOR THE WEEKEND. MODELS ARE STILL TRYING TO FIGURE OUT HOW MUCH PRECIP WILL DEVELOP SATURDAY NIGHT AND SUNDAY WITH PASSING WAVES IN THE ZONAL FLOW ALOFT. EXPECT MOST OF SATURDAY NIGHT TO BE DRY WITH A SHOWER POSSIBLE BY SUNDAY MORNING. LOOKING LIKE A BETTER CHANCE FOR SHOWERS SUNDAY...PARTICULARLY IN THE AFTERNOON...AHEAD OF AN APPROACHING COLD FRONT. AREA WILL DRY OUT MONDAY WITH ANOTHER COOL DOWN ON TUESDAY.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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VFR CONDITIONS SHOULD CONTINUE UNTIL DAWN AT MOST SITES. SNOW WILL ADVANCE NORTH-NORTHWESTWARD THROUGH THE MORNING HOURS AND AFFECT MOST SITES OTHER THAN KZZV IN THE EARLY AFTERNOON. SOME DETERIORATION TO IFR IS LIKELY GENERALLY EAST OF KPIT DURING THE HEAVIEST WINDOW OF SNOW...HOWEVER THE WINDOW FOR ACCUMULATION AT ALL SITES OTHER THAN KMGW SHOULD BE FAIRLY BRIEF. AS SNOW SHUTS OFF BY EVENING...ABUNDANT LOW LEVEL MOISTURE SHOULD ALLOW FOR STRATUS TO REMAIN A FIXTURE AT MOST SITES. FRIES OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... PERIODIC RSTRNS ARE PSBL THRU THE WKEND WITH SVRL FAST MOVG DISTURBANCES.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR MDZ001. OH...NONE. PA...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR PAZ074- 076. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR PAZ023- 073-075. WV...WINTER STORM WARNING UNTIL 6 PM EST THIS EVENING FOR WVZ023- 041. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ021- 022.
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&& $$

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