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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 220425
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1225 AM EDT WED MAY 22 2013

.SYNOPSIS...
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THUNDERSTORM CHANCES WILL INCREASE WEDNESDAY AND THURSDAY AS A
COLD FRONT APPROACHES AND MOVES ACROSS THE REGION.
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&&

.NEAR TERM /THROUGH WEDNESDAY/...

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MIDNGT UPDATE WAS ISSUED TO ADJUST HOURLY TRENDS OF POPS AND TEMPS
WHICH FEATURE A DIMINISHING AREA OF SHWRS AND TSTMS MOVG OUT OF WV
SPPRTD BY SHRTWV IN SW FLOW ALOFT.

EXPECT THIS AREA TO CONT FADING TO SCT/ISOLD SHWRS AS RMNG
INSTABILITY POCKETS FADE.

LOW PRES WHICH HAS PLAGUED THE PLAINS IS STILL FORECAST TO DVLP
NEWD AND PHASE WITH ERN CANADIAN TROF BY THURSDAY. TAIL OF
COUPLING JET ALOFT IS EXPECTED TO APPRCH THE UPR OHIO LATE TODAY
AND CROSS THE REGION TNGT. WITH RELATIVELY MOIST AIRMASS ALREADY
IN PLACE...POST DAYBREAK DESTABILIZATION WL SPPRT NMRS
THUNDERSTORM COVERAGE DURING THE AFTN AND INTO THE EVE...ALTHOUGH
DEGREE OF INSTABILITY IS STILL SOMEWHAT QNABLE GIVEN EXPECTED
CLOUD COVER.

HOWEVER...GIVEN THE STRENGTHENING WIND FIELD AS MENTIONED ABOVE...CONCUR
WITH THE STORM PREDICTION CENTER ASSESSMENT OF SEVERE POTENTIAL AS
EVENING APPRCHES. RISK WL RMN SLIGHT AS MID LVL JET STREAK IS
CURRENTLY TIMED TO CROSS AS DIURNAL HEATING FADES...BUT DAMAGING
WIND GUSTS AND HAIL WL CERTAINLY BE POSSIBLE.

NEAR TERM TEMPS WERE FORECAST USING LAMP GUIDANCE.
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&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...

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COLDER AIR IS PROJECTED TO ADVECT OVR THE REGION ON THURSDAY AS
SFC FRONT PROGRESSES EWD. HOWEVER... WITH THE MID-LEVELS COOLING
AS WELL...CONVECTIVE THRESHOLDS WL LOWER CONSIDERABLY WITH SHWRS
AND TSTMS AGAIN BCMG LIKELY AS THE DAY PROGRESSES.

A REINFORCING FRONT IS PROGGED FOR FRIDAY WITH RESIDUAL SHWR CHCS
FADING BY AFTN WITH PASSAGE OF THAT FEATURE. AS NW FLOW DVLPS WITH
PASSAGE OF THE AFOREMENTIONED PHASED TROF AXIS...COLD ADVCTN WL
LIMIT TEMP RECOVERY. EXPECT HIGHS ABOUT 10 DEGREES BELOW THE
SEASONAL AVERAGES UNDR THE RESULTING HIGH AMPLITUDE...ERN CONUS
TROF PTN.
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&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE MODELS ARE IN GOOD AGREEMENT ON THE OVERALL UPPER LEVEL PATTERN
THROUGH THE EXTENDED WITH AN UPPER LEVEL RIDGING OF THE CENTRAL
CONUS AND TROUGHING IN BOTH THE WEST AND EAST. WHILE THIS WOULD
GENERALLY LEAD TO A MUCH LESS THAN CONFIDENT FORECAST IN THE
SHORTWAVES WITHIN THE FLOW...THIS DOESN`T SEEM TO BE THE CASE AS
BOTH THE GFS AND ECMWF SUGGEST THAT MUCH OF THE PRECIPITATION WILL
BE SUPPRESSED SOUTH OF THE REGION THROUGH MUCH OF THE PERIOD.
THUS...OPTED TO TAKE A BLEND OF THE MODELS AND HPC
GUIDANCE. ALSO...HEDGED A BIT COOLER WITH TEMPERATURES WITH
NORTHWEST FLOW PRESENT ESPECIALLY FOR THE FIRST HALF OF THE
PERIOD. THIS KEPT TEMPERATURES BELOW SEASONAL AVERAGES SAT/SUN
BEFORE MODERATING CLOSER TO NORMAL FOR THE REST OF THE PERIOD.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
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GENL VFR EXPD OVRNGT...ALTHOUGH ISOLD SHWRS CAN BE EXPECTED AS
SHRTWV CROSSES IN SW FLOW ALOFT. A PD OF MVFR VIS IN BR EXPD TWD
SUNRISE THEN VFR RETURNS THRU ERLY AFTN. SCT TSTMS EXP LATER IN
THE AFTN AS A CDFNT BEGINS TO APRCH SO INCLUDED VCTS.

.OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
OCNL RESTRNS LIKELY WED EVE INTO THU NGT WITH SHWRS/TSTMS AS A
CDFNT APRCHS AND MOVES ACRS THE RGN. AN UPR LVL DISTURBANCE WL
BRING PSBL RESTRNS IN SHRA FRI BEFORE HIGH PRES AND VFR CONDS
RETURN FRI NGT THRU SUN.
-- End Changed Discussion --

&&

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

&&

$$

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