-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 221043
AFDPBZ

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

.SYNOPSIS...
THUNDERSTORM CHANCES WILL INCREASE TODAY AS A COLD FRONT
APPROACHES THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
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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 THIS EVE AND
CROSS THE REGION TNGT WHILE SFC LOW IS PROJECTED TO MOVE RAPIDLY
NEWD ACRS LAKE ERIE.

WITH RELATIVELY MOIST AIRMASS ALREADY IN PLACE...POST DAYBREAK
DESTABILIZATION AND EWD SLIDING MID/UPR TROF WL LIKELY SPPRT TSTM
DVLPMNT BY AFTN AND INTO THE EVE.

GIVEN THE STRENGTHENING WIND FIELD AS MENTIONED ABOVE...CONCUR
WITH THE STORM PREDICTION CENTER ASSESSMENT OF SEVERE POTENTIAL AS
EVENING APPRCHES. RISK WL RMN IN THE SLIGHT CATEGORY...I.E. APPROX
30 PERCENT CHC OF THE PRIMARY THREAT...WHICH IS OF DAMAGING WIND
VIA SHORT BOWING SEGMENTS.

NR TERM POPS WERE STRUCTURED COLLABORATIVELY FOR THE MOST
PART...WITH CATEGORICAL NMBRS LTD TO OHIO AND PARTS OF NW PA
IMMEDIATELY ALNG THE OH BORDER. CURRENT THINKING IS THAT THESE
AREAS WL HAVE THE BETTER CHC OF WIDESPREAD THUNDERSTORM COVERAGE
AS POTENTIAL MCS PROGRESSES COINCIDENT WITH THE LLVL JET...BEFORE
SFC LOW LIFTS NEWD AND DIURNAL WARMTH/SFC BASED INSTABILITY BGN TO
DIMINISH AFTER NIGHTFALL.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
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.

&&

.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 /12Z WEDNESDAY THROUGH SUNDAY/...
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15-20 KT GUSTS CAN BE EXPECTED TO DEVELOP BY NOON AT MOST
TERMINALS ALONG WITH DIURNAL CUMULUS. SHOWERS AND THUNDERSTORMS
ARE EXPECTED TO DEVELOP BY MID AFTERNOON...AND HAVE CONTINUED VCTS
MENTION AT THIS TIME. IF ANYTHING...WIND GUSTS MAY BE
UNDERESTIMATED WITH POSSIBILITY FOR TSRA. THE BEST CHANCE FOR
RESTRICTIONS AND WIND ISSUES WILL COME THIS EVENING AS TSTM
COVERAGE WIDENS IN A STRENGTHENING WIND PROFILE.

.OUTLOOK.../THURSDAY THROUGH SUNDAY/...
OCNL RESTRNS ARE LIKELY INTO THU NGT WITH SHWRS/TSTMS AS A CDFNT
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.

&&

$$