Area Forecast Discussion
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000 FXUS61 KPBZ 290822 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 421 AM EDT WED OCT 29 2014 .SYNOPSIS...
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COOL HIGH PRESSURE IS EXPECTED FOR MID WEEK. A POTENT SYSTEM WILL BRING MUCH COLDER AIR...AND SOME SNOWFLAKES...BY THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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FRONT IS THROUGH A MAJORITY OF THE CWA AS TEMPS AND DEWPOINTS HAVE DROPPED OFF DRAMATICALLY OVER THE LAST FEW HOURS. DESPITE THE SFC FRONT BEING THROUGH...THE MID-LEVEL FRONT AND ASSOCIATED MOISTURE WILL TAKE SOME TIME TO FINALLY CLEAR THE SERN 1/3 OF THE FORECAST AREA. EXPECTING A FEW WEAK WAVES TO PASS SW TO NE ALONG THE MID-LEVEL BOUNDARY THROUGH MID-MORNING. DESPITE THE DRIER AIR NEAR THE SFC...CURRENTLY SOME ENHANCEMENT SHOWING UP ON MOSAIC RADAR IMAGERY SOUTH OF MORGANTOWN AND SE THROUGH TUCKER CO WV. WHILE MUCH OF THE ENHANCEMENT CAN BE ATTRIBUTED TO BRIGHT-BANDING NEAR THE MELTING LAYER...RAINFALL HAS BEEN REPORTED ACROSS A HANDFUL OF OBS IN THAT REGION. WILL CONTINUE TO CARRY POPS IN THE FORECAST IN THE HIGHER TERRAIN OF THE SE THROUGH MID-MORNING. MID- LEVEL TROF AXIS FINALLY PUSHES THE DEEPER MOISTURE EAST OF THE CWA BY MIDDAY. DRY SLOT DOES ENCOMPASS THE ENTIRETY OF THE AREA BY EARLY AFTERNOON. EXPECTING A FAIR AMOUNT OF CLEARING DURING THE DAY BEFORE LLVL LAPSE RATES STEEPEN GIVING RISE TO A CU FIELD IN COLD AIR ADVECTION. LLVL FLOW WILL REMAIN FROM THE SW THROUGH MUCH OF THE DAY...KEEPING ANY LAKE INDUCED SHOWER ACTIVITY AT BAY THROUGH EARLY EVENING. BY 00Z THURS...THE H7 TROF AXIS REACHES THE SERN WATERS OF LAKE ERIE...VEERING THE LLVL FLOW TO WNW. WITH THE UPPER LOW AND ATTENDANT COLD POOL DIRECTLY OVERHEAD...THE RELATIVELY WARM LAKE ERIE WATERS WILL ENHANCE RAIN SHOWERS PRIMARILY NORTH OF I-80 THROUGH EARLY THURS MORNING. TEMPS EARLY THURS WILL BE HELD SOMEWHAT IN CHECK DUE TO LINGERING CLOUD COVER BLANKETING THE AREA...LOWS SHOULD GENERALLY RANGE IN THE MID TO UPPER 30S...MUCH CLOSER TO OUR AVG. THAN THE LAST FEW NIGHTS. TAX
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY/...
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PERIOD STARTS WITH A WEAK SHORTWAVE ROTATING ACROSS AHEAD OF A FLAT RIDGE. DISTURBANCE IS MOISTURE-STARVED...BUT AREAS NORTH OF I-80 MAY HANG ON TO A FEW SHRA FOR A FEW HOURS PAST 12Z THU. CANNOT RULE OUT A FLAKE OR TWO MIXING IN...BUT THINK BOUNDARY LAYER STAYS WARM ENOUGH TO MELT MOST HYDROMETEORS. DRY WEATHER HOLDS ON THROUGH THURSDAY AFTERNOON AND EVENING AS THE H500 RIDGE AXIS MOVES THROUGH. TEMPERATURES WILL RUN A FEW DEGREES BELOW NORMAL. WHAT FOLLOWS WILL BRING THE FIRST REAL CHANCE THIS SEASON OF SEEING SNOWFLAKES FOR MANY IN THE CWA. A MUCH MORE POTENT SHORTWAVE WILL START TO DIG ACROSS THE THE GREAT LAKES THURSDAY NIGHT AND DIVE SOUTHWARD. IT WILL EVENTUALLY FORM A CLOSED UPPER LOW IN THE VICINITY OF THE SOUTHERN APPALACHIANS BY 12Z SATURDAY. NORMALIZED ANOMALIES FROM PREVIOUS 12Z ENSEMBLE RUNS FOR GEFS/NAEFS SHOW H500 HEIGHTS OF AROUND 3 STANDARD DEVIATIONS BELOW NORMAL ON SATURDAY. NOT SURPRISINGLY...GIVEN THIS ANOMALOUS PATTERN...THE MODELS ARE STRUGGLING TO SETTLE ON THE DETAILS. STILL...THERE IS REASONABLE CONFIDENCE IN MUCH BELOW TEMPERATURES COME SATURDAY...ALONG WITH AT LEAST SOME FROZEN PRECIPITATION. AHEAD OF THE DIGGING TROUGH...OUR FLOW TURNS SOUTHWEST LATER THURSDAY NIGHT AND ESPECIALLY FRIDAY...PUSHING BETTER MOISTURE BACK INTO THE AREA. MIDLEVEL RIPPLES IN THE BASE OF THE DEEPENING TROUGH...PLUS MODEST ISENTROPIC LIFT...JUSTIFY LIKELY POPS AREAWIDE ON FRIDAY. COLD FROPA WILL ALSO TAKE PLACE DURING THE DAY...WHICH WILL KNOCK TEMPERATURES FURTHER BELOW NORMAL FRIDAY NIGHT AND SATURDAY. EXPECTING A SLOW DECREASE IN COVERAGE BEHIND THE FRONT FRIDAY NIGHT AND INTO SATURDAY..WITH LIKELY POPS HANGING ALONG THE RIDGES THE LONGEST. CONCERNING SNOW...WHILE H850 TEMPS OF ZERO TO -2C WILL BE IN PLACE FRIDAY...THE STRENGTH OF THE SYSTEM WILL ACT TO TEMPER THE SNOW. MODELS SHOW WARM AIR WRAPPING COMPLETELY AROUND THE SYSTEM...WITH H850 TEMPS SLIGHTLY ABOVE ZERO CURLING BACK AROUND AND ENTERING THE CWA ON EAST AND NORTHEAST WINDS FRIDAY NIGHT. DOWNSLOPING MAY PLAY A ROLE AS WELL. THUS...CANNOT REMOVE RAIN ENTIRELY FROM PORTIONS OF THE SOUTHERN CWA AT THIS TIME. ANY SNOW ACCUMULATION FRIDAY NIGHT/SATURDAY WILL BE CONFINED MAINLY TO THE RIDGES AND AREAS NORTH OF I-80. LOW CONFIDENCE VALUES THROUGH 12Z SATURDAY ARE GENERALLY AROUND AN INCH OR LESS FOR NOW...BUT MORE COULD FOLLOW INTO SATURDAY IN THE EAST. PRECIPITATION SHOULD MOSTLY WRAP UP BY 00Z SUNDAY. CL
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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WPC SUGGESTS FOLLOWING ENSEMBLE MEANS IN THIS ANOMALOUS PATTERN AND SEE NO REASON TO DISAGREE. HIGH PRESSURE WILL BUILD IN BEHIND THE DEPARTING DEEP SYSTEM. WITH THE NORTHEAST TROUGH HANGING AROUND THROUGH THE WEEKEND...TEMPERATURES WILL CONTINUE TO RUN WELL BELOW NORMAL. SATURDAY NIGHT MAY BE THE COLDEST OF THE SEASON THUS FAR WITH WIDESPREAD READINGS IN THE 20S. MODERATION CAN BE EXPECTED FOR MONDAY AND TUESDAY AS RIDGING DEVELOPS ONCE AGAIN. THE NEXT FRONT MAY ARRIVE COME TUESDAY NIGHT OR WEDNESDAY WITH RAIN SHOWER CHANCES.
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&& .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... MID-LEVEL MOISTURE WILL LINGER ALONG THE BACK EDGE OF THE FRONT THIS MORNING...BRINGING OCCASIONAL MVFR SHRA INTO KMGW. WITH THE FRONT PUSHING EAST OF MOST PORTS...HIGH CLOUDS HAVE MOVED OVER A MAJORITY OF TERMINALS. COULD SEE SOME CLEARING...ESPECIALLY WRN TERMINALS LATER THIS MORNING BEFORE DIURNAL CUMULUS DEVELOPS NEAR MIDDAY. GUSTY WEST WINDS TODAY AROUND 15-20 KTS. OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... THE NXT WIDESPREAD RESTRICTION POTENTIAL IS EXPECTED WITH A FRIDAY CDFNT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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