Area Forecast Discussion
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000 FXUS61 KPBZ 302359 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 659 PM EST FRI JAN 30 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN THROUGH SATURDAY. LOW PRESSURE WILL BRING WINTRY WEATHER SUNDAY INTO MONDAY. && .NEAR TERM /THROUGH SATURDAY/... THE REGIONAL RADAR MOSAIC INDICATES SNOW SHOWER ACTIVITY...WHILE STILL FAIRLY PERVASIVE...IS DEFINITELY IN A DOWNWARD TREND ACROSS THE CWA THIS EVENING. MODEL SOUNDINGS FROM BOTH THE RAP AND HRRR SHOW A SCENARIO WHEREBY INVERSION HEIGHTS ARE FALLING SIMULTANEOUSLY WITH BOUNDARY LAYER MOISTURE DEPTH DECREASING AS WELL. LIKEWISE...UPSTREAM ACTIVITY OFF OF LAKE HURON IS QUICKLY FALLING APART...AND THE TREND TOWARD ANY ADDITIONAL INPUT FROM THE SLIVER OF LAKE ERIE THAT IS OPEN WILL NOT BE PARTICULARLY HELPFUL TO REGENERATION OF ANY OF THE BANDS. THAT SAID...ACTIVITY WILL LIKELY TAKE A FEW HOURS TO WANE WITH THE UPSLOPE AREAS TAKING THE LONGEST TO FULLY HALT THEIR SNOW SHOWER AND FLURRY ACTION. HOWEVER...GIVEN THE DOWNWARD TREND IN ACTIVITY AND MINIMAL ACCUMULATION EXPECTATIONS THE REST OF THE EVENING...WINTER WEATHER ADVISORIES FOR THE HIGHER TERRAIN HAVE BEEN ALLOWED TO EXPIRE AS SCHEDULED AT 7 PM. NORTHWESTERLY FLOW CONTINUES THROUGH MUCH OF THE EVENING HOURS BEFORE SLOWLY TURNING WEST OVERNIGHT AS A SURFACE HIGH BUILDS GENERALLY JUST TO THE SOUTH OF THE REGION. WITH AT THE VERY LEAST PARTIAL CLEARING...IF NOT FULL CLEARING AT TIMES...TEMPERATURES SHOULD DROP RAPIDLY WITH NEW SNOW COVER. THIS COMBINED WITH DECREASING YET STILL BRISK SURFACE FLOW WILL ALLOW FOR WIND CHILL ADVISORY CRITERIA WIND CHILL INDEX VALUES BY MORNING OVER THE HIGHER TERRAIN AND NORTHEASTERN CWA. THIS IS IN LINE WITH CURRENT HEADLINES...AND NO ADDITIONAL EXPANSION OF THESE HEADLINES ARE ANTICIPATED AT THIS TIME. HOWEVER...WITH RAPID CLEARING AND NEW SNOW ON THE GROUND...ALL AREA WILL LIKELY BE VERY COLD BY MORNING...WITH MANY PORTIONS OF THE CWA CHALLENGING ZERO BY THAT JUNCTURE. SOME WARMER AIR DOES START TO FLOW NORTHWARD ON SATURDAY AS THE SURFACE HIGH AXIS MOVES TO THE EAST OF THE AREA AND SOUTHWESTERLY FLOW PREVAILS FOR A TIME. EXPECTATIONS SHOULD BE MUTED...THOUGH...AS SUCH A COLD START AND WEAK VERTICAL MIXING WILL LIKELY KEEP MOST OF THE AREA IN THE 20S. FRIES && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... HIGH PRES SHOULD CONT DRY WEA INTO SAT EVE. A DIGGING UPR TROF IS PROGGED TO ADVN OUT OF THE PLAINS AND TRACK ACRS THE GT LKS AND OH VLY RGN SUN INTO MON. ASSOCIATED SFC LOW PRES IS PROGGED TO DEEPEN AS IT MOVES ACRS THE TN AND OH VLY RGNS ALSO. THIS WL SPREAD SNW INTO THE RGN LT SAT NGT THRU MON MRNG WITH DEEP AVAILABLE MSTR AND OMEGA. WITH A CLOSED 850MB LOW...A MORE PROLONGED PCPN EVENT IS EXPD AS OPPOSED TO THE OPEN SYSTEM EARLIER IN THE WK. WITH ENOUGH POTENTIAL FOR HEAVY SNW OR A SNW/ICE MIX...ISSUED A WINTER STORM WATCH FOR MUCH OF THE AREA. LEFT AREAS GENLY S OF I 70 OUT OF THE WATCH...EXCEPT FOR THE WV/MD RIDGES...AS ENOUGH WRM AIR IS EXPD TO WRAP IN AHD OF THE LOW TO ALLOW FOR A RAIN/SNW MIX OR EVEN A PD OF ALL RAIN. AREAS BETWEEN I 70- AND I 80 COULD SEE ENOUGH WRM AIR ALOFT FOR FRZG RAIN TO MIX IN AT TIMES AS WELL. GENLY FOLLOWED A SREF/GFS/ECMWF MDL BLEND TO WORK OUT THE DETAILS...AND USED CRITICAL THICKNESSES/MDL SOUNDING PROFILES FOR PCPN TYPE. BEST POTENTIAL FOR GREATER THAN 6 INCHES OF SNW EXISTS N OF PIT BASED ON LATEST MDL GUIDANCE...THOUGH THIS WL BE REFINED OVR THE NXT COUPLE OF DAYS. SNW SHOULD CONT MON UNTIL THE UPR TROF AXIS SHIFTS E IN THE AFTN. NUDGED TEMPS TO THE LATEST COLDER THAN SEASONAL AVG SREF GUIDANCE. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A COLD...WINTER PATTERN WILL CONTINUE FOR THE REST OF THE LONG TERM. THE NEXT BEST CHANCE FOR SNOW SHOWERS WILL ARRIVE LATE IN THE PERIOD. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... MVFR CIGS WITH IFR VSBY IN SNOW SHWRS WL CONT THIS AFTN. GENL IMPROVEMENT CAN BE ANTICIPATED THEREAFTER AS DRY ADVCTN AND SBSDNC INCRS. SFC WIND ARE EXPECTED TO CONTINUE TO GUST FROM THE W AND NW AT 15 TO 25 KNOTS THROUGH THE DAY. FURTHER IMPROVEMENTS CAN BE EXPECTED AS HIGH PRES BLDS THROUGH SATURDAY MRNG. .OUTLOOK.../SATURDAY NIGHT THROUGH WEDNESDAY/... WIDESPREAD RESTRICTIONS CAN BE EXPECTED WITH SUNDAY LOW PRES AND WITH A MONDAY CDFNT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH MONDAY MORNING FOR MDZ001. WIND CHILL ADVISORY UNTIL 10 AM EST SATURDAY FOR MDZ001. OH...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH MONDAY MORNING FOR OHZ039>041-048>050-057>059. PA...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH MONDAY MORNING FOR PAZ007>009-013>016-020>023-029-073>076. WIND CHILL ADVISORY UNTIL 10 AM EST SATURDAY FOR PAZ008-009- 015-016-023-074-076. WV...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH MONDAY MORNING FOR WVZ001>003-023-041. WIND CHILL ADVISORY UNTIL 10 AM EST SATURDAY FOR WVZ023-041. && $$

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