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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 171939
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
339 PM EDT FRI MAY 17 2013

.SYNOPSIS...
STALLED FRONT WILL FLUCTUATE LITTLE TODAY THROUGH MOST OF SATURDAY
KEEPING MOST OF THE SHOWERS AND THUNDERSTORMS SOUTH. FRONT WILL
SHIFT NORTHWARD SUNDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
FRONTAL BOUNDARY THAT WAS MUCH MORE APPARENT THIS MORNING HAS
BECOME A BIT MORE WASHED OUT THIS AFTERNOON. HOWEVER...LOOKING AT
THE MESOANALYSIS...SOME INSTABILITY...WEAK SHEAR...AND HIGHER
DEWPOINTS STILL REMAIN OVER PORTIONS OVER THE REGION. THIS IS
PUSHING A BIT FURTHER SOUTH BUT A FEW SHOWERS AND THUNDERSTORMS
COULD DEVELOP IN THIS MORE SUPPORTIVE AREA WITH HELP FROM
DIVERGENCE FROM A DEPARTING UPPER LEVEL JET. FOR NOW...GENERALLY
KEPT POPS TIED TO THE RIDGES WHERE A FEW CELLS HAVE ALREADY
DEVELOPED BUT LOW END CHANCE MAY NEED TO BE INTRODUCED ELSEWHERE.

THE MODELS CONTINUE TO SUGGEST...WITH SOME TIMING DIFFERENCES...THAT
THE BOUNDARY WILL ONCE AGAIN FLUCTUATE ACROSS THE REGION SATURDAY.
THE BIGGEST QUESTION WILL BE THE NORTHERN EXTENT OF LIFT FROM AN
APPROACHING SHORTWAVE THAT IS PROGGED TO REACH THE REGION IN THE
AFTERNOON. EACH OF THE DETERMINISTIC MODELS HANDLES THIS
DIFFERENTLY...THUS NOTHING MORE THAN CHANCE POPS WERE ADDED
SATURDAY AFTERNOON. WITH MORE CLOUD COVER EXPECTED
SATURDAY...TEMPERATURES WERE KEPT A FEW DEGREES COOLER THAN TODAY.
-- End Changed Discussion --


&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
THE BOUNDARY SHOULD MAKE IT`S FINAL PUSH NORTHWARD BY SATURDAY
NIGHT/SUNDAY LEADING TO BETTER MOISTURE AND INSTABILITY THROUGH
THE REMAINDER OF THE SHORT TERM. HOWEVER SHORTWAVE TIMING AND
PLACEMENT CONTINUES TO DIFFER OWING TO LOWER CONFIDENCE IN THUNDERSTORM
COVERAGE. SO CHANCE POPS WERE CONTINUED...MAINLY IN THE AFTERNOONS
BOTH SUNDAY AND MONDAY.

STRENGTHENING SOUTHERLY FLOW SHOULD ALLOW TEMPERATURES TO WARM
EACH DAY...EVEN IF THERE IS CLOUD COVER SO HIGHS IN THE LOWER 80`S
WERE INTRODUCED BY MONDAY AFTERNOON.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
-- Changed Discussion --
UPPER LEVEL RIDGING WILL CONTINUE TO AMPLIFY OVER THE EASTERN
HALF OF THE CONUS AS A CUTOFF LOW DEVELOPS OVER THE NORTHERN
PLAINS. THIS LOW WILL SLOWLY MAKE IT`S APPROACH THROUGH THE
PERIOD...HELPING TO SWING AN ASSOCIATED FRONT ACROSS THE REGION BY
LATE WEDNESDAY/EARLY THURSDAY. HOWEVER...DIFFERENCES STILL REMAIN
IN THE AMOUNT OF CONVECTIVE ACTIVITY THERE WILL BE IN THE WARM
SECTOR TUESDAY AND WEDNESDAY AS DIFFERENT SHORTWAVES MOVING
THROUGH THE UPPER LEVEL FLOW ARE TIMED DIFFERENTLY FROM RUN TO
RUN. TO TAKE INTO ACCOUNT THESE DIFFERENCES...OPTED TO REMAIN
CONSERVATIVE WITH POPS UNTIL LATE TUESDAY BEFORE INCREASING
CHANCES IMMEDIATELY AHEAD OF THE COLD FRONT. TEMPERATURES WERE KEPT
NEAR MOS/HPC GUIDANCE BUT AMPLE MOISTURE AND CLOUD COVER COULD KEEP
TEMPERATURES FROM REACHING THE MID 80`S SUGGESTED.
-- End Changed Discussion --

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
WEAK SOUTHEAST FLOW WILL BRING INCREASING LOW LEVEL MOISTURE
OVERNIGHT. SCATTERED CUMULUS THIS AFTERNOON WILL CLEAR AFTER
SUNSET. THE GOOD RADIATIONAL COOLING OVERNIGHT WILL BRING SOME
PATCHY FOG FOR THE EARLY MORNING HOURS. SOME SCATTERED TO BROKEN
CU WILL FORM AGAIN ON SATURDAY WITH THE HEATING OF THE DAY WITH JUST
A CHANCE OF SHOWERS...MAINLY AT THE SOUTHERN PORTS. SOME BRIEF
RESTRICTIONS ARE POSSIBLE IN THE SHOWERS OR ISOLATED THUNDERSTORMS.

.OUTLOOK.../SATURDAY NIGHT THROUGH WEDNESDAY/...
GENERAL VFR WILL CONTINUE THROUGH THE FORECAST PERIOD. THERE WILL BE
AN INCREASING RISK OF SHOWERS AND SCATTERED THUNDERSTORMS DURING THE
LATE AFTERNOON AND EVENING HOURS. SOME RESTRICTIONS ARE POSSIBLE IN
THE HEAVIER SHOWERS.

&&

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

&&

$$