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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 171522
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1122 AM EDT FRI MAY 17 2013

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

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
FOG AND STRATUS THAT IMPACTED MUCH OF THE REGION FROM I-76 SOUTHWARD
CONTINUES TO GRADUALLY LIFT/BURN OFF THIS MORNING AS BETTER MIXING
AND HEATING CONTINUES. MID 50/HIGH 60 DEWPOINTS LINE UP WELL WITH
THIS SAME INTERSTATE BOUNDARY AT THE MOMENT...INDICATING CURRENT
PLACEMENT OF STATIONARY BOUNDARY. THE HI RES MODELS SUGGEST THAT
THE BOUNDARY WILL SINK FURTHER SOUTH TODAY AS BUILDING HIGH
PRESSURE SUPPRESSES IT...WHICH IS ALREADY BEING INDICATED IN THE
SURFACE OBSERVATIONS. THIS SHOULD ALSO SUPPRESS MUCH OF THE
SHOWER/THUNDERSTORM ACTIVITY TO THE SOUTH WHERE THE RICHER
DEWPOINTS ARE LOCATED. WITH THE NEW NAM AND HI RES MODELS
SUGGESTING THIS WILL BE COMPLETELY SOUTH OF THE FORECAST
AREA...HAVE DECREASED POPS OVER MUCH OF THE REGION UNTIL LATER
TONIGHT.

DESPITE EARLY MORNING CLOUD COVER...TEMPERATURES SHOULD REBOUND
INTO THE UPPER 70`S TODAY.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
FOR TONIGHT INTO SUNDAY...GENERAL AGREEMENT THAT BOUNDARY WILL
PUSH NORTHWARD BUT AGAIN DISAGREE ON TIMING AND STRENGTH OF
POSSIBLE SHORTWAVES. CONTINUE THE PREVIOUS TRENDED TOWARD NAM
SOLUTION WITH HIGHEST SHOWER CHANCES ACROSS THE SOUTH AND RIDGES
THROUGH THE WEEKEND UNTIL SUNDAY.

TEMPERATURES A COMPROMISE BETWEEN 21Z SREF AND GFS MOS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MODEL AGREEMENT ON THE OVERALL UPPER LEVEL PATTERN IS BEGINNING TO
IMPROVE...AT LEAST THROUGH DAY 6 BEFORE THERE ARE GLARING
DIFFERENCES. IN GENERAL...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 SUNDAY THROUGH 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 ALSO KEPT
BELOW MOS GUIDANCE...ESPECIALLY ON TUESDAY AND WEDNESDAY AS AMPLE
MOISTURE AND CLOUD COVER WILL LIKELY KEEP TEMPERATURES FROM REACHING
THE MID 80`S SUGGESTED.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
A FAIRLY ABRUPT DEWPOINT DISCONTINUITY SNAKES THROUGH NORTHEASTERN
OHIO TO JUST SOUTH OF KBTP AND JUST NORTH OF KIDI. ALL OF THIS
SITES SOUTH OF THIS ARE LIKELY TO EXPERIENCE AT LEAST SOME FOG
THROUGH THE EARLY MORNING HOURS. IN PARTICULAR...LIFR CONDITIONS
IN FOG/STRATUS ARE LIKELY AT KZZV...KHLG...AND KMGW THROUGH
MORNING. BECAUSE SURFACE MOISTURE IS SLIGHTLY LOWER AROUND
KPIT...JUST MVFR VIS WAS CARRIED. BY ROUGHLY 13Z...DIURNAL MIXING
SHOULD INCREASE AND MIX OUT FOG EVERYWHERE...WITH VFR CONDITIONS
EXPECTED AT ALL TERMINALS AFTER THAT TIME. FRIES

.OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/...
GENERAL VFR SHOULD CONTINUE UNTIL SATURDAY AFTERNOON WHEN INCRSG
MSTR AND INSTABILITY SPPRT PCPN CHCS AND RESTRICTIONS...WHICH ARE
EXPECTED TO PERIODICALLY CONT THROUGH TUESDAY.

&&

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

&&

$$