-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 041514
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1014 AM EST WED DEC 4 2013

.SYNOPSIS...
RAIN WILL SPREAD OVER THE REGION ON THURSDAY AS A COLD FRONT
SLIDES TOWARD THE REGION. PASSAGE OF THAT FRONT WILL CHANGE THE
RAIN TO SNOW ON FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
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WITH 1015AM UPDATE...BIGGEST CHANGE WAS TO DELAY ARRIVAL OF
PRECIPITATION BY A COUPLE OF HOURS DURING THE AFTERNOON AND EARLY
EVENING WITH THE CLOSEST RADAR ECHOES ACROSS NORTHERN KENTUCKY.
PREVIOUS DISCUSSION FOLLOWS.

A MILD DAY CAN BE EXPECTED FOR THE UPR OH VALLEY REGION TODAY AS
WARM AIR FLOWS NWD ON THE ERN FLANK OF BROAD LOW PRES DVLPG TWD
THE UPR MS VALLEY. EXPECT HIGHS 10 TO 15 DEGREES ABOVE THE
AVGS...FORECAST OF WHICH WAS COMPLETED USING BIAS CORRECTED
MOSGUIDE AND SREF MEANS.

RAIN CHCS ARE ALSO FORECAST TO INCRS THROUGH TNGT AS THE ASSOCIATED
CDFNT IS MDL PROGGED TO PROGRESS STEADILY ACRS THE MIDWRN STATES.
CHC POPS HAVE THUS BEEN CONTD...WHILE STRENGTHENING WARM ADVCTN
ENSURES OVRNGT LOWS ABOUT 20 DEGREES ABOVE THE AVGS.
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&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
FORECAST OF POP ESCALATION TO LIKELY AND CATEGORICAL NMBRS IS ON
TRACK FOR THE THURSDAY AND FRIDAY PD AS MSTR DEEPENS IN STRONG
SWLY FLOW ALOFT. WARM ADVCTN AND JET DYNAMICS ARE EXPECTED TO
MAINTAIN SPPRT FOR A PROLONGED RAIN EVENT HIGHLIGHTED BY TWO
PRIMARY SHRTWV SURGES...WHICH MAY GENERATE AN INCH TO INCH AND A
HALF OF PCPN OVR THE TWO DAYS...WITH THE HIGHER NMBRS ANTICIPATED
OVR AREAS SOUTH OF PITTSBURGH. FOR NOW...HAVE COMPLETED QPF USING
SMOOTHED WPC GUIDANCE...WHICH WAS CONSTRUCTED CLOSER TO THE HIGHER
ECMWF OUTPUT.

IN ADDITION...EWD PROGRESS OF THE FRONT IS FORECAST TO GRADUALLY
CHANGE RAIN TO SNOW ON FRIDAY. LINGERING BNDRY LYR WARMTH IS
EXPECTED LIMIT ACCUMULATION POTENTIAL THROUGH THE DAY...WHILE MID
LVL DRY SLOT AND RAPIDLY DIMINISHING DYNAMICS SHOULD CAP POTENTIAL
AS NGT FALLS. NEVERTHELESS...HAVE CONSERVATIVELY FORECAST AN INCH
OR TWO OF SNOWFALL FOR MOST OF THE REGION DURING THIS INITIAL
COLD ADVCTN PD...WHICH IS CLOSER TO GFS PROJECTIONS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
MORE ACTIVE WEATHER IS EXPECTED EARLY NXT WEEK AS PTN OF CNTRL
CONUS TROFG AND WRN ATLANTIC RIDGING MAINTAINS OVRALL SWLY FLOW
OVR THE UPR OH REGION. ECMWF AND GFS INDICATE RAPID EMERGENCE OF
LOW PRES FM THE LWR MS VALLEY TO THE GREAT LAKES ON SUNDAY AND MONDAY.

AS THESE MDLS HAVE CONSISTENTLY SHOWN A TRACK WEST OF THE
IMMEDIATE AREA OVR THE LAST CPL OF DAYS...HAVE ACCEPTED A WARMER
WPC SOLN AS IS TYPICAL OF THAT WINTER PATH. UNFORTUNATELY...THE
WARM ADVCTN ON THE ERN FLANK OF THE LOW...COMBINED WITH COLD AIR
ENTRENCHMENT REINFORCED VIA NEW ENGLAND HIGH PRES...MAY SPPRT
PROLONGED FREEZING RAIN FOR PART OF THE AREA. FOR NOW...HAVE OPTED
FOR A MORE AGGRESSIVE PCPN PHASE CHANGE FM SNOW AND FREEZING RAIN
TO ALL RAIN AS SUNDAY NGT PROGRESSES. A HAZARDOUS WEATHER OUTLOOK
WILL ALSO BE INCLUDED AND MONITORING WILL CONTINUE.

OTHERWISE...COLDER AND DRIER AIR WL BE SHUNTED OVR THE UPR OHIO
REGION IN THE WAKE OF THAT SYSTEM...WITH TEMPS AND POPS FORECAST
USING A COMBO OF WPC AND MOS GUIDANCE.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
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GENLY VFR SC/AC IS EXPD THRU TNGT. A WK DISTURBANCE IS EXPD TO
CROSS THE AREA THIS AFTN BUT NO PCPN IS EXPD.

.OUTLOOK.../THURSDAY THROUGH SUNDAY/...
RSTRNS ARE PSBL TNGT THROUGH SAT MRNG AS SEVERAL DISTURBANCES
DVLP AND MOVE ALG A SLOW MOVG FRONTAL BOUNDARY CROSSING THE RGN.
VFR CONDS WILL RTN LATER SAT ONCE THE FNT PUSHES SOUTH. ANOTHER
CHANCE FOR RSTRNS WILL COME WITH YET ANOTHER SYSTEM SUN.
-- End Changed Discussion --

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$