-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 221413
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1013 AM EDT WED MAY 22 2013

.SYNOPSIS...
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UPPER LEVEL IMPULSES BRINGS AN INCREASE IN SHOWERS AND
THUNDERSTORMS THROUGH THURSDAY NIGHT...UNTIL A COLD FRONT CROSSES. MUCH
COOLER WEATHER IS FORECAST THIS HOLIDAY WEEKEND UNDER HIGH
PRESSURE.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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AREA IS UNDER GOING STRONG HEATING WHICH IS EATING AWAY AT CAP
NEAR THE SURFACE. MODIFIED SOUNDINGS USING PROJECTED MAXT AND TD
SHOW 1.5 KJKG-1 OF SBCAPE AND NO CINH. THIS IS ABOUT HALF OF THE
ENERGY THAT WAS PRESENT YDY...BUT THE DIFFERENCE THIS AFTN IS INC
IN WIND SHEAR AND TRIGGERS. A WEAK IMPULSE WILL CROSS LATER TDY
AND GIVEN NO CAP WILL GENERATE RW/TRW. MAIN THREAT CONTINUES TO BE
DAMAGING WINDS...HOWEVER HAIL CAN NOT BE RULED OUT DESPITE FZL
LVL ARND 12KFT. TWEAKED POP GRIDS TO REFLECT DRY CONDITIONS THIS
MRNG AND FOCUS HIGHER NUMBERS DURING THE LATE AFTERNOON / EVENING
TIME FRAME.

ACTIVITY WILL WANE BY MIDNIGHT...BUT WITH POCKETS OF ENERGY
ASSOCIATED WITH MID LVL HEIGHT FALLS FROM APPROACHING
TROUGH...CONTINUED PCPN MENTION THROUGH THE NIGHT.

DUE TO PROGRESSIVE NATURE OF STORMS...DO NOT FORESEE A FLOOD
THREAT. THE ONLY SCENARIO WHICH MAY LEAD TO FLOODING WOULD BE IF A
LOCATION RECEIVES REPEATED ROUNDS OF RAIN. THE PROBABILITY IN THAT
IS LOW AT THIS TIME.
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&&

.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 /14Z 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/...
BRIEF IFR RESTRICTIONS ARE POSSIBLE THUR IN SHOWERS AND
THUNDERSTORMS...MAINLY VIS. OTHERWISE...PROBABILITY OF WIDESPREAD
IFR WEATHER IS LOW.
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&&

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

&&

$$

SYNOPSIS...98
NEAR TERM...98
SHORT TERM...15
AVIATION...33/98