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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 161942
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
342 PM EDT SUN JUN 16 2013

.SYNOPSIS...
-- Changed Discussion --
A FRONTAL BOUNDARY WILL SAG SOUTHEASTWARD INTO THE AREA
TONIGHT...BRINGING SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM
INTO MONDAY...WITH A LOW CHANCE OF SHOWERS THROUGH THIS PERIOD. THE
FRONT WILL PUSH SOUTHEAST OF THE AREA LATE ON TUESDAY AND HIGH
PRESSURE WILL THEN BUILD IN FROM THE NORTHWEST AND ALLOW FOR A DRY
MID-WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
THE LATEST RAP UPPER LEVEL ANALYSIS INDICATES THE UPPER OHIO
VALLEY IN A ZONAL FLOW WITH A 300MB 100KT JET AXIS CENTERED OVER
SOUTHERN ONTARIO. AT THE MID-LEVELS...A 500MB SHORT WAVE IS WEAKENING
AS IT SHIFTS INTO CENTRAL PA. AT THE SURFACE...A 1004MB SURFACE
LOW IS LOCATED NORTH OF LAKE SUPERIOR WITH A ILL- DEFINED FRONTAL
BOUNDARY EXTENDING SOUTH OF THIS FEATURE INTO NORTHERN OHIO.
SHOWERS INITIALLY ASSOCIATED WITH THE MID-LEVEL WAVE HAVE MOSTLY
DIMINISHED AND SHIFTED EAST OF THE AREA.

THIS EVENING...THE FRONTAL BOUNDARY WILL SAG SOUTHEASTWARD INTO
THE AREA. EXTENSIVE UPSTREAM CLOUD COVERAGE WILL CONTINUE TO
MOSTLY LIMIT CONVECTIVE TEMPS FROM BEING REACHED. THUS...HAVE GONE WITH
SCATTERED SHOWERS AND ISOLATED THUNDERSTORM WORDING TO NOT
COMPLETELY DISCOUNT THE HRRR/WRF-NMM SOLUTIONS WHICH INDICATE A
CLUSTER OF SHOWERS AND THUNDERSTORMS DEVELOPING. WITH ALL OF THIS IN
MIND...THE STORM PREDICTION CENTER STILL HAS THE AREA MENTIONED IN
ITS SEE TEXT. TEMPS HAVE BEEN LOWERED A FEW DEGREES CLOSER TO
LAMP GUIDANCE...WITH HIGHS RANGING FROM THE LOWER TO MID 70S
ACROSS THE AREA.

TONIGHT...THE FRONTAL BOUNDARY WILL CONTINUE TO EDGE SOUTHEASTWARD
ACROSS THE AREA...WITH ANY LINGERING COVERAGE OF SHOWERS MOSTLY
DIMINISHING BY 06Z. MOSTLY CLOUDY SKIES WILL BEGIN TO GIVE WAY TO
MORE BREAKS IN CLOUD COVERAGE WITH SHOWERS COMING TO AN END AS A
POCKET OF DRIER AIR ADVECTS IN FROM THE NORTHWEST. CLOUD COVERAGE
FOR MUCH OF THE NIGHT WILL SERVE TO MODERATE LOW TEMPS. FORECAST
IS CLOSEST TO THE WARMER MAV...WITH LOWS RANGING FROM THE LOWER TO
MID 60S ACROSS THE AREA.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
-- Changed Discussion --
GFS/ECMWF SOLUTIONS ARE IN AGREEMENT THAT THE UPPER OHIO VALLEY WILL
CONTINUE TO BE IN A ZONAL MID-LEVEL FLOW ON MONDAY WITH THE POORLY
DEFINED SURFACE FRONTAL BOUNDARY BECOMING NEARLY STATIONARY NEAR
THE MASON-DIXON LINE. WITH THE BOUNDARY SERVING AS A FOCAL POINT
FOR POSSIBLE AFTERNOON CONVECTION...HAVE LEFT THE SLIGHT CHANCE OF
THUNDERSTORMS IN THE FORECAST FOR MONDAY. HIGHS ON MONDAY ARE A
FEW DEGREES ABOVE GFS/NAM/ECMWF GUIDANCE...RANGING FROM THE UPPER
70S ACROSS THE ALLEGHENY FRONT TO THE MID 80S IN EASTERN OHIO.

ON MONDAY NIGHT...POP FORECAST INCREASES TO CHANCE AS THE ECMWF
INDICATES A WAVE MOVING IN FROM THE WEST. STILL QUITE A BIT OF
UNCERTAINTY IN THE TIMING OF SHOWERS IN A ZONAL FLOW. DESPITE THE
FRONTAL BOUNDARY MOVING SOUTHEASTWARD ON MONDAY NIGHT...WEAK
ISODROSOTHERMAL GRADIENT WILL ALLOW TDS TO REMAIN IN THE UPPER 50S
TO LOWER 60S AND THUS LOWS ARE A ECMWF/NAM BLEND IN THE LOWER 60S
ACROSS MUCH OF THE AREA.

WEAK SHORT WAVE VORT ENERGY WILL MOVE ACROSS THE AREA ON TUESDAY AS
THE AREA IS IN MORE OF A WEAK MID-LEVEL CYCLONIC FLOW ASSOCIATED
WITH A BROAD TROUGH IN SERN CANADA. THE GFS IS INDICATING WEAK
INSTABILITY  (SBCAPE <1000 J/KG) WITH MODERATE SHEAR (0-6KM BULK
SHEAR 30-35KTS) DURING THE PASSAGE OF THE WAVE. THE NAM TAKES A MUCH
MORE AGGRESSIVE APPROACH WITH THE CONVECTIVE ENVIRONMENT THAT IS CURRENTLY
BEING DISCOUNTED. THE FORECAST LEANS CLOSER TO THE GFS...WITH THE
CHC OF SHOWERS AND THUNDERSTORMS ACROSS THE AREA. AT THIS
TIME...AM NOT ANTICIPATING A SEVERE THREAT...BUT WILL CONTINUE
MONITOR THIS DUE TO THE FACT THAT IF THE NAM SOLUTION IS REALIZED
A FEW STRONG TO SEVERE STORMS WILL BE POSSIBLE. WITH THE LOSS OF
HEATING AND THE BOUNDARY SLIDING SOUTHEAST OF THE AREA...THE
FORECAST WILL BECOME DRY TUESDAY NIGHT.

HIGH PRESSURE ALONG WITH A DEEP LAYER OF DRY AIR WILL BUILD IN FROM
THE NORTHWEST ON WEDNESDAY AND ALLOW FOR A BREAK FROM SHOWERS AND
THUNDERSTORMS WITH MOSTLY SUNNY SKIES. DESPITE THE ABUNDANT SUNSHINE
ANTICIPATED...COOLER/DRIER AIR MASS WILL LIMIT HIGH TEMPS TO A FEW
DEGREES BELOW NORMAL.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
LATEST GFS AND ECMWF DETERMINISTIC SOLNS AGREED GENLY IN
DEPICTIONS OF THE PROGGED FLOW PTN OVR THE ERN CONUS FOR THE
LATTER HALF OF THE WEEK...WITH ECMWF AMPLIFYING THE PTN CLOSER TO
GFS WITH A RIDGE AXIS EXTENDING FM THE SRN PLNS ACRS THE GREAT
LAKES.

THE LONG TERM FORECAST THUS CONSERVATIVELY FEATURES TEMPS
GRADUALLY WARMING TO SLIGHTLY ABOVE THE SEASONAL AVERAGES BY THE
WEEKEND. PCPN CHCS WERE FORECAST AOB CLIMO NMBRS...BUT WERE GENLY
INCRSD USING A GFS/ECMWF BLEND FOR SHRTWV TIMING INTO THE WEEKEND.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
CURRENTLY GENERAL MVFR CONDITIONS AT MOST SITES WITH RAIN
SHOWERS. GRADUALLY IMPROVING CONDITIONS CAN BE EXPECTED AS A WEAK
COLD FRONT CONTINUES MOVING SOUTHEAST THROUGH REGION. CIGS SHOULD
GRADUALLY IMPROVE TO VFR EVERYWHERE THIS EVENING WITH PARTIAL
CLEARING TONIGHT. SLIGHTLY DRIER AIR GRADUALLY MOVING IN BUT WITH
WET CONDITIONS OVER THE AREA AND DEWPOINTS ONLY DROPPING SLIGHTLY WILL
LIKELY SEE SOME FG/BR TO DEAL WITH MONDAY MORNING AT SOME TAF SITES.

.OUTLOOK.../MONDAY THROUGH FRIDAY/...
PERIODIC RESTRICTIONS ARE ANTICIPATED THROUGH TUESDAY AS ANOTHER
LOW APPRCHS AND CROSSES THE REGION. BLDG HIGH PRES SHOULD RTN VFR
CONDITIONS FOR WEDNESDAY THROUGH FRIDAY.
-- End Changed Discussion --
&&

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

&&

$$

SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM
SHORT TERM...WOODRUM