Area Forecast Discussion
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000 FXUS61 KPBZ 271124 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 624 AM EST THU NOV 27 2014 .SYNOPSIS... ANOTHER SHOT OF COLD AIR WILL MOVE THROUGH LATER TODAY AND TONIGHT. THIS WILL PROVIDE THE RISK FOR SNOW SHOWERS. HIGH PRESSURE WILL IMPROVE CONDITIONS ON FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A WEAK SURFACE TROUGH IS CURRENTLY SHIFTING SOUTHEASTWARD OUT OF NORTHERN OHIO AND FAR NORTHWEST PENNSYLVANIA. A RATHER STAGNANT LOW LEVEL ENVIRONMENT PRECEDES THIS BOUNDARY WITH AMPLE LOW LEVEL MOISTURE AVAILABLE. RADAR SIGNATURES INDICATE WEAK ECHOES ARE STILL PRESENT IN THIS AREA...AND MODEL CROSS SECTIONS FAIL TO PORTRAY SUFFICIENT SATURATION DEPTH FOR EFFICIENT SNOW CRYSTAL GROWTH. WITH THAT SAID...A FEW OBS IN NORTHEASTERN OHIO HAVE OSCILLATED BACK AND FORTH FROM SNOW TO OTHER PRECIPITATION TYPES WITH TEMPERATURES BELOW FREEZING. WHILE IT IS MOST LIKELY THAT IN THE PRE-TROUGH ENVIRONMENT...THE MAJORITY OF THE WEAK ECHOES ARE LIKELY SNOW GRAINS...THERE REMAINS A POSSIBILITY THAT SOME FREEZING DRIZZLE MAY BE OCCURRING. THIS HAS BEEN ADDED TO FOR THE MORNING HOURS AHEAD OF THIS TROUGH AS IT MOVES SOUTHEASTWARD. IN ADDITION...WITH UPSLOPE COMMENCING BY LATE MORNING INTO THE RIDGES WITH DEEPER MOISTURE LAGGING SIGNIFICANTLY. IT WAS ADDED FOR UPSLOPE AREAS AS WELL. WITH SURFACE TEMPERATURES VERY NEAR FREEZING...IT SEEMS RATHER UNLIKELY THAT IT WOULD BE A TRANSPORTATION HAZARD...MORE OF ELEVATED SURFACE ISSUE THROUGH THE MORNING. FRIES DURING THE AFTERNOON...MIXING HEIGHTS WILL RISE AS LARGE SCALE ASCENSION INCREASES AHEAD OF A SHORTWAVE TROUGH. COLDER AIR AT 850 MB WILL MARCH EASTWARD AND THE FLOW ALOFT WILL INCREASE AND BECOME BETTER ORGANIZED. MIXING HEIGHTS WILL RISE ENOUGH TO REACH THE SNOW GROWTH ZONE. WILL SLOWLY INCREASE POPS THIS AFTERNOON...WITH THE HIGHEST NUMBERS ACROSS THE NORTH AND RIDGES. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... A SERIES OF WEAK UPPER LEVEL WAVES WILL CROSS THE AREA TONIGHT. THIS WILL DRIVE THE HEART OF THE COLD AIR SOUTHEASTWARD ACROSS THE REGION. FLOW WILL REMAIN GENERALLY OUT OF THE NORTHWEST TONIGHT...SO WILL EXPECT SNOW SHOWERS TO CONTINUE UNTIL THE SECOND WAVE EXITS AROUND DAWN FRIDAY. AGAIN...WILL FOCUS THE HIGHEST POPS ACROSS THE NORTH(LAKE INFLUENCE)...AND RIDGES(OROGRAPHIC EFFECT). SHORTWAVE WILL QUICKLY EXIT TO THE EAST FRIDAY MORNING... INVERSIONS WILL LOWER AND SUBSIDENCE WILL INCREASE AS BROAD HIGH PRESSURE MOVES EASTWARD ACROSS THE LOWER OHIO VALLEY. ANY LINGERING SNOW SHOWERS WILL QUICKLY END FRIDAY MORNING. THE COLD POOL ALOFT WILL SLOWLY EJECT TO THE NORTH WHICH WILL ALLOW FOR A DECREASE IN CLOUD COVER. WAA WILL CONTINUE SATURDAY NIGHT AS A WARM FRONT CROSSES THE AREA AND FLOW IN THE LOWER AND MID-LEVELS BECOMES SOUTH-SOUTHWESTERLY. MODELS ARE HINTING AT THE DEVELOPMENT OF ISOLATED SNOW SHOWERS DEVELOPING WITH THE PASSING FRONT. WILL INCLUDE SCHC POPS FRIDAY NIGHT. A WEAK DISTURBANCE WILL CROSS ON SATURDAY...WHICH WILL TEMPORARILY PUT THE BREAKS ON THE WAA. COULD SEE A PASSING SHOWER SATURDAY AFTERNOON...BUT DEEP MOISTURE IS LACKING AND THE WAVE IS UNIMPRESSIVE. FOR NOW WILL LEAVE SATURDAY DRY. TEMPERATURES WILL MODERATE ON SATURDAY. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... SHOWER CHANCES WILL INCREASE SUNDAY...AHEAD OF THE NEXT COLD FRONT. FRONT WILL CLEAR THE AREA EARLY MONDAY MORNING. SHOWERS WILL END BUT TEMPS WILL COOL DOWN ON MONDAY. HIGH PRESSURE WILL PROVIDE A DRY AND CHILLY TUESDAY...WITH TEMPS MODERATING ON WEDNESDAY. && .AVIATION /11Z THURSDAY THROUGH MONDAY/... WIDESPREAD MVFR CONDITIONS WILL CONTINUE TO BE THE CASE THROUGH THE DAY AS ABUNDANT LOW LEVEL MOISTURE GIVES WAY TO MORE NUMEROUS SNOW SHOWERS AS WNW FLOW AND COLD ADVECTION WORK TO SCOUR MOISTURE OUT OF THE LOWER ATMOSPHERE AND ENCOURAGE UPWARD MOTION. BOTH OF THESE TWO THINGS WILL ALLOW FOR SNOW SHOWER DEVELOPMENT...AND THOUGH COVERAGE WILL NOT BE PERVASIVE...PICKING START AND END TIMES FOR SNOW SHOWERS IS FAR TOO AMBITIOUS TO DO AT THIS POINT. FRIES OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... NON VFR DEVELOPING THURSDAY IN -SHSN...LINGERING ACROSS NW PA INTO FRIDAY. NON-VFR SUNDAY IN -SHRA WITH THE NEXT FRONT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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