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Area Forecast Discussion
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000
FXUS61 KPBZ 191050
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
550 AM EST FRI DEC 19 2014

.SYNOPSIS...
BUILDING HIGH PRESSURE IS EXPECTED THROUGH THE WEEKEND...THOUGH
CLOUDS WILL REMAIN.

&&

.NEAR TERM /THROUGH TONIGHT/...
MOISTURE TRAPPED UNDER THE INVERSION NEAR H85 CONTINUES TO FALL OUT 
AS FREEZING DRIZZLE MIXING AT TIMES WITH LIGHT SNOW. BEGINNING TO 
SEE SOME REPORTS IN THE PITTSBURGH METRO AREA...AND FURTHER SOUTH 
AND WEST INTO ERN OHIO. HAVE EXPANDED THE WINTER WEATHER ADVISORY TO 
INCLUDE THIS AREA. THE BULK OF THIS ACTIVITY REMAINS JUST WEST OF 
THE CWA BOUNDARY WHERE MOISTURE AVAILABILITY IS A LITTLE BETTER DUE 
TO THE PROXIMITY TO LAKE ERIE. 

RECENT RADAR TRENDS SHOW A LAKE-ENHANCED BAND NEAR CLE DISLODGE ITSELF 
FROM THE SRN SHORELINE OF LAKE ERIE. THIS IS IN RESPONSE TO THE 
WINDS VEERING TO NEARLY NORTHERLY AS THE LLVL SW TROF AXIS SWINGS 
SOUTHWARD. WHILE THE INDIVIDUAL BAND IS NOT EXPECTED TO IMPACT OUR 
AREA DIRECTLY...IT CAN BE USED AS A GOOD PROXY FOR WHERE THE 
DOWNSTREAM MOISTURE IS ENTERING OUR FORECAST AREA. AS THIS BAND 
CONTINUES TO PIVOT SOUTHWARD...EXPECT TO SEE LIGHT SNOW AND FREEZING 
DRIZZLE REPORTS IN OUR AREA TO FOLLOW SUIT.

THE HI-RES MODELS DID A GREAT JOB HANDLING THE LLVL MOISTURE AND 
PROGRESSION OF THE TROF...KEYING IN ON THE ATTENDANT MID-LEVEL 
DEFORMATION ZONE TO GENERATE SHOWER ACTIVITY. AS IT CONTINUES IT 
TREK SOUTH OF LAKE ERIE...THE MOISTURE BEGINS TO ERODE ALONG WITH 
THE DEFORMATION ZONE GETTING WASHED OUT. WITH STILL ABUNDANT LLVL 
MOISTURE AVAILABLE...WOULD EXPECT REPORTS OF DZ TO CONTINUE THROUGH 
SUNRISE...BUT NOT MUCH BEYOND THAT. HAVE EXTENDED THE ADVISORY 
THROUGH 9AM. 

CLOUDS WILL CONTINUE TO PLAGUE THE CWA FOR YET ANOTHER DAY KEEPING 
DAYTIME HIGHS IN CHECK. INCREASING SUBSIDENCE UNDER HIGH PRESSURE 
WILL GRADUALLY LOWER INVERSION HEIGHTS THROUGH THE DAY FRIDAY 
SQUASHING REMAINING PRECIPITATION CHANCES.
TAX

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
HIGH PRESSURE WILL REIGN OVER THE FORECAST AREA THROUGH THE
WEEKEND. A WEAK OPEN WAVE TRIES TO SKIRT THE SRN EXTENT OF THE SFC
HIGH SAT AFTERNOON...BUT MODELS CONTINUE TO TREND IT FURTHER SOUTH
WELL OUT OF OUR REGION. AFTER LARGELY ZONAL FLOW ALOFT THROUGH
SUNDAY THE UPPER LEVEL PATTERN FAVORS SWRLY FLOW ON THE BACKSIDE
OF THE SFC HIGH. THIS WILL WORK TO DRIVE WARMER TEMPS INTO THE
FORECAST AREA WITH HIGHS DRIVING ABOVE AVERAGE HEADING INTO EARLY
NEXT WEEK.
TAX

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
WHILE THE MODELS AGREE ON A DEEPENING UPPER LEVEL TROUGH TO CLOSE
OFF OVER THE GREAT LAKES THROUGH THE PERIOD THE DETAILS OF HOW
THIS EXACTLY UNFOLDS WILL BE CRITICAL. BY MONDAY SOUTHERN STREAM
SHORTWAVE AHEAD OF MAIN NORTHERN STREAM UPPER TROUGH DIGGING INTO 
THE NORTHERN PLAINS WILL PRODUCE LOW PRESSURE ACROSS THE CAROLINAS
MOVING OFF SHORE OF THE EAST COAST. THE SOUTHEAST RIDGES MAY BE
BRUSHED BY LIGHT RAIN FROM THIS SYSTEM. NEXT UP IS DEEPENING LOW
PRESSURE OVER THE OHIO VALLEY AHEAD OF SHARPLY DIGGING UPPER
TROUGH AND CLOSED LOW MOVING INTO THE WESTERN GREAT LAKES. UPPER
OHIO VALLEY LOOKS TO BE ON THE WARM SIDE OF THE SYSTEM TUESDAY
INTO WEDNESDAY WITH RAIN...FOLLOWED BY STRONG COLD FRONT AND COLD
ADVECTION LATER WEDNESDAY NIGHT AND THURSDAY WITH SNOW SHOWERS.
WITH SUCH A STRONG SYSTEM ALOFT AND FAST DEEPENING LOW PRESSURE AT
THE SURFACE TIMING OF COLD AIR AND EXACT TRACK WILL LIKELY CHANGE
AS WE GET CLOSER TO CHRISTMAS. ALL IN ALL PREVIOUS FORECAST IS
LITTLE CHANGED WITH ONLY MINOR ADJUSTMENTS BASED ON NEWEST WPC
EXTENDED PROGS.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
UPDATED TAFS TO INCLUDE MENTION OF FREEZING DRIZZLE FOR SITES
NORTH OF INTERSTATE 70 THROUGH EARLY THIS MORNING BASED ON LATEST
OBS AND LATEST HI RES AND RAPID REFRESH GUIDANCE SHOWING
INDICATING MOISTURE IN THE COLUMN LIMITED TO LOWER LEVELS NOT COLD
ENOUGH FOR ICE CRYSTAL FORMATION...THUS...FINE MIST AND LIGHT
DRIZZLE EXPECTED THROUGH 9AM WILL REMAIN LIQUID AND FREEZE ON
CONTACT. DO NOT EXPECT ANY PERIODS OF RAPID ICE DEVELOPMENT BUT
WILL LIKELY FOR A LIGHT GLAZE OVER THE NEXT SEVERAL HOURS.
ICE POTENTIAL WILL LIKELY BE OVER BY MID MORNING AS MOISTURE POOL
BECOMES TOO SHALLOW...WITH CIG RESTRICTIONS LARGELY MVFR THROUGH
MUCH OF THE DAY...IMPROVING TO VFR STARTING LATE THIS AFTERNOON.


OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/...
STRATUS AND RESTRICTIONS MAY PERSIST INTO THE WEEKEND. NEXT STORM
SYSTEM WILL BRING RESTRICTIONS TUESDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR 
     OHZ039>041-048>050.
PA...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR 
     PAZ007>009-013>016-020>022.
WV...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR WVZ001.

&&

$$






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