-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 180328
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1128 PM EDT MON JUN 17 2013

.SYNOPSIS...
-- Changed Discussion --
AN UPPER LEVEL DISTURBANCE WILL CREATE PERIODIC SHOWERS AND
THUNDERSTORMS ALONG A STALLED FRONTAL BOUNDARY THROUGH TUESDAY
NIGHT. HIGH PRESSURE WILL KEEP CONDITIONS DRY FOR THE REST OF THE WEEK.
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&&

.NEAR TERM /THROUGH TUESDAY/...
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UPDATED POPS IN NORTHERN ZONES TO ADJUST FOR THUNDERSTORM ACTIVITY
MOVING ONSHORE FROM LAKE ERIE DUE TO WEAK UPPER LEVEL SHORTWAVE
ABOVE A SITUATED FRONT. AREA OF RAIN IS MOVING INTO A MORE STABLE ENVIRONMENT...HOWEVER...WIND
SHEAR OF 45KTS WILL LIKELY SUSTAIN THE ACTIVITY UNTIL THE
SHORTWAVE EXITS THE AREA.

AS A COLD FRONT SAGS SOUTHWARD WITH THE HELP OF A MORE BROAD UPPER
LEVEL SHORTWAVE...SHOWERS AND THUNDERSTORMS MAY ONCE AGAIN BE
REINVIGORATED SO CHANCE POPS WERE REINTRODUCED OVERNIGHT. WILL ALSO
CONTINUE TO MONITOR TRENDS IN CONVECTION MOVING NORTHWARD FROM A
DEVELOPING LOW THAT COULD MAKE IT INTO THE SOUTHERN HALF OF THE
FORECAST AREA...AS SUGGESTED BY THE DETERMINISTIC RUNS.

INCREASING CLOUD COVER SHOULD KEEP TEMPERATURES ELEVATED OVERNIGHT
SO MINS WERE KEPT SLIGHTLY WARMER THAN MET GUIDANCE.

THE COLD FRONT WILL CONTINUE A SOUTHWARD PROGRESSION
TUESDAY...OWING TO INCREASED SHOWER AND THUNDERSTORM COVERAGE
THROUGHOUT THE DAY. THE AMOUNT OF INSTABILITY CONTINUES TO REMAIN
IN QUESTION AS THE NAM SUGGESTS MUCH MORE INSTABILITY THAN THE
GFS. ULTIMATELY...THE AMOUNT OF CLOUD COVER WILL HAVE AN IMPACT.
OVERALL...EXPECTING SEVERE THREAT TO REMAIN LOW WITH SHEAR BEING THE
PRIMARY FACTOR IF STORMS REACH SEVERE LEVELS.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
CDFNT WILL CONT TO SAG SEWD TUE EVE AND WILL BE ACCOMPANIED BY
LINGERING SHWRS AND TSTMS. NAM IS MORE AMPLIFIED WITH ASSOCIATED
H5 SHRTWV TROF AND MAINTAINS PCPN THRU WED MRNG IN THE MTNS...BUT
GFS IS MORE PROGRESSIVE WITH THE SYSTEM...ENDING PCPN BY LATE TUE
NGT. LOW POPS WERE RETAINED THRU WED MRNG TO REFLECT THIS
UNCERTAINTY.

AMID BUILDING SFC HIPRES...POST-FRONTAL AMS WILL DRY SOMEWHAT. AS
A RESULT...INSTBY WILL BE LMTD TO HIGHER TERRAIN WED-THU. THUS...
POPS WERE INCLUDED ONLY IN ZONES WITH HIGHER TERRAIN. ANY CNVCTN
WILL BE DIURNALLY DRIVEN.

POST-FRONTAL MAXIMA WILL BE ON THE COOLER SIDE IN THE MID-UPR 70S.
MINIMA WILL BE DICTATED BY DEG OF DRYING OF LOW-LVL AMS...LKLY IN
THE 50S.   UPDATE...KRAMAR

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
MDLS CONT TO DEPICT DVLPMNT OF A BROAD SRN CONUS RIDGE FOR THE
LONG TERM PD WITH GENL RIDGE AXIS POSITIONING ACRS THE GREAT
LAKES. WARMER TEMPS ARE THUS IN STORE FOR THE UPR OH VALLEY REGION
WITH WEEKEND READINGS PROGGED WELL INTO THE 80S AS PER HIGHER MOS
GUIDANCE.

GRADUALLY INCRSG POPS...TO CHC NMBRS FOR THE WEEKEND...WERE ALSO
INCLUDED...BUT TIMING WL BE DEPENDENT ON SHRTWV PASSAGE ACRS THE
NRN PERIPHERY OF THE RIDGE...SO CONFIDENCE IN THAT PARAMETER IS
MINIMAL AT THIS JUNCTURE OF THE FORECAST PROCESS.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
ISOLD TSTMS WL CONT TO DSPT THIS EVE. TSTM COMPLEX OVR LK ERI HAS
BEEN WKNG PER RECENT VIL LOOPS AND WARMING CLOUD TOPS ON STLT...AND
EXP THIS TO DMNSH BEFORE IT REACHES OUR AREA. EXPTG MAINLY VFR CONDS
THRU MUCH OF TUE...WITH PTCHY MVFR VSBY IN BR ARND SUNRISE. A CDFNT
WL SLOWLY DROP SWD ACRS THE RGN TUE. LOW CONFIDENCE ON TIMING AND
COVG OF ANY TSTMS SO ONLY MENTIONED VCSH IN THE TAFS ATTM.

OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
RESTRNS ARE PSBL S OF PIT TUE NGT AS THE CDFNT EXITS...THEN HIGH
PRES IS EXPD TO BRING VFR CONDS INTO SAT.

&&

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

&&

$$