000
FXUS61 KPBZ 220720
AFDPBZ

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

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

&&

.NEAR TERM /THROUGH TONIGHT/...
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...ALTHOUGH DEGREE OF INSTABILITY
IS STILL SOMEWHAT QNABLE GIVEN EXPECTED CLOUD COVER.

NEVERTHELESS...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 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.

&&

.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 /07Z WEDNESDAY THROUGH SUNDAY/...
GENL VFR EXPD THIS MRNG AS INCRSG PRES GRADIENT IS SPPRTG
SUFFICIENT SFC WIND TO PRECLUDE FOG DVLPMNT...WITH FURTHER
LIMITATION IMPOSED BY SCT TO BKN MID LVL CLDS. HOWEVER...SHWR AND
TSTM COVERAGE IS FORECAST TO INCRS AS THE DAY PROGRESSES. TAFS
THUS INCLUDE VCTS MENTION. THE BEST CHC FOR RESTRICTIONS AND WIND
ISSUES WL COME THIS EVE AS TSTM COVERAGE WIDENS IN A STRENGTHENING
WIND PROFILE.

.OUTLOOK.../TONIGHT THROUGH SUNDAY/...
OCNL RESTRNS 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.

&&

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

&&

$$

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