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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 231825
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
225 PM EDT THU MAY 23 2013

.SYNOPSIS...
SHOWER AND THUNDERSTORM CHANCES WILL CONTINUE UNTIL A FRONT CROSSES
THE REGION THIS EVENING. MUCH COOLER WEATHER CAN BE EXPECTED FOR
THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A WEAKENING SHEAR PROFILE IS EVIDENT OVER THE AREA THIS AFTERNOON
COMING DOWN FROM ROUGHLY 30 KTS OF UNIDIRECTIONAL SHEAR AND
UPWARD OF 1000 J/KG OF CAPE. DUE TO CONVECTIVE TEMPERATURES BEING
REACHED EARLY IN THE DAY...SHOWERS AND THUNDERSTORMS BLOSSOMED
BEFORE NOON...AND CONTINUE TO INCREASE IN COVERAGE WITH EACH
PASSING HOUR. THIS IS DUE TO RAPID COOLING IN THE MID-LEVELS
EVIDENT ON ALL MODEL SOLUTIONS THROUGH THE AFTERNOON WHILE
BOUNDARY LAYER TEMPERATURES CONTINUE TO INCREASE. STEEPENING LAPSE
RATES AS WELL AS YET ANOTHER INCOMING SHORTWAVE HAVE MANAGED TO
HARNESS THIS INSTABILITY INTO SHORT LINE SEGMENTS OF SHOWERS AND
EMBEDDED THUNDERSTORMS THAT HAVE PRODUCED GUSTY WINDS AND ISOLATED
SMALL HAIL. THIS WILL LIKELY CONTINUE INTO THE EVENING HOURS UNTIL
THE LOW LEVEL START TO STABILIZE.

A SECONDARY COLD FRONT STARTS TO TRACK INTO THE AREA FROM
NORTHWEST TO SOUTHEAST STARTING ROUGHLY 6-7 PM IN OHIO AND
REACHING PITTSBURGH 9-11 PM OR SO. WINDS WILL ABRUPTLY TURN
NORTHWEST AND GUST THROUGH THE NIGHT BEHIND THE FRONT. MUCH COLDER
AIR WILL FLOOD INTO THE REGION WITH SHOWER CHANCES RAPIDLY
DECREASING TONIGHT INTO FRIDAY MORNING. FRIES
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
-- Changed Discussion --
COLDER AND MUCH DRIER AIR WILL CONTINUE TO RAPIDLY INVADE THE AREA
ON FRIDAY WITH DEWPOINTS RAPIDLY DECREASING THROUGH THE 40S AND
INTO THE LOWER 30S AND UPPER 20S BY SATURDAY MORNING. AS WIND
BACKS OFF FRIDAY NIGHT AND THE BOUNDARY LAYER DECOUPLES...CLEAR
SKIES WILL RESULT IN SUPERIOR RADIATIONAL COOLING. AS
SUCH...WIDESPREAD FROST IS LIKELY AND LOCAL FREEZING CONDITIONS
ARE POSSIBLE IN THE COLDER SPOTS.

WITH LITTLE OVERALL PATTERN EVOLUTION FROM FRIDAY NIGHT INTO
SATURDAY NIGHT AND SIMILAR RH PROFILES AND WIND PROFILES...YET
ANOTHER FROSTY NIGHT IS POSSIBLE SATURDAY NIGHT. BY
SUNDAY...SLIGHTLY WARMER 850 MB TEMPERATURES AND A TINY BIT OF
MIXING MAY ALLOW HIGHS TO START TO STRUGGLE UP MORE INTO THE 60S
RATHER THAN STRADDLING 60F ITSELF. FRIES
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
DRY WEA IS EXPD THRU THE PERIOD WITH HIGH PRESSURE IN CONTROL. A
WARM FRONT WILL APPROACH THE DISTRICT FOR WEDNESDAY INTO THURSDAY
BRINGING AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS. TEMPS
WL START OUT BLO AVG OVR THE WEEKEND...THEN MODERATE TO SEASONAL
LVLS AS HIGH PRESSURE SHIFTS E OF THE AREA AND FLOW TURNS SRLY.
-- End Changed Discussion --

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
GENERAL VFR CONDITIONS CAN BE EXPECTED ACROSS THE PORTS THIS
EVENING WITH SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS.
MVFR RESTRICTIONS OR BRIEF IFR ARE POSSIBLE WITH THE HEAVIER
SHOWERS. AS A COLD FRONT APPROACHES THE AREA THIS EVENING...WIND
GUSTS ARE EXPECTED TO PICK UP AS WELL AS THE ARRIVAL OF MVFR CIGS.
WINDS WILL VEER TO THE NORTHWEST BEHIND THE FRONT...AND WIDESPREAD
IFR CONDITIONS ARE EXPECTED AFTER MIDNIGHT.

.OUTLOOK.../FRIDAY THROUGH TUESDAY/...
RESTRNS ARE LIKELY WITH REMAINING SHWRS INTO FRIDAY...BUT BLDG HIGH
PRES WL QUICKLY RTN VFR TO AREA PORTS BY FRIDAY AFTN. GENL VFR WL
THEN PERSIST INTO TUESDAY.
-- End Changed Discussion --


&&

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

&&

$$