Area Forecast Discussion
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000
FXUS61 KPBZ 021842
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
242 PM EDT TUE SEP 2 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THIS EVENING...WITH SHOWERS AND
THUNDERSTORMS AHEAD OF IT. DRY AND LESS HUMID WEATHER RETURNS FOR
WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
FRONT MAKING EASTWARD PROGRESS AND APPROACHING THE WESTERN BORDER
OF THE CWA. IT WILL SWING THROUGH THIS AFTERNOON AND EXIT THE EAST
BY 00Z. SECONDARY DEWPOINT BOUNDARY BACK NEAR DTW AND FDY WILL
THEN MOVE THROUGH OVERNIGHT. STILL SOME FAIRLY THICK CLOUD COVER
IN SPOTS...ESPECIALLY ACROSS OUR NORTHERN COUNTIES...BUT MORE SUN
ACROSS THE SOUTH HAS LED TO BETTER DESTABILIZATION...WITH UP TO
2000 J/KG NOTED ON SPC MESOANALYSIS. STILL DO NOT SEE A WIDESPREAD
SEVERE THREAT...BUT AVAILABLE INSTABILITY PLUS MARGINAL 0-6KM
SHEAR OF 35-40 KNOTS MAY SUPPORT AT LEAST A COUPLE STORMS WITH
DAMAGING WIND GUSTS. CANNOT RULE OUT ISOLATED WATER PROBLEMS OVER
LOW FFG AREAS AS WELL GIVEN THE RIBBON OF UP TO 1.8 INCHES OF
PRECIPITABLE WATER ALONG THE FRONT...PLUS UNIDIRECTIONAL FLOW
SUPPORTING THE POSSIBILITY OF TRAINING CELLS. HAVE DECREASED POPS
A BIT FROM EARLIER BUT HAVE MAINTAINED LIKELY VALUES WITH FROPA.
KEPT CHANCE POPS BEHIND INITIAL FRONT AS ADDITIONAL SHRA/TSRA MAY
ACCOMPANY THE DEWPOINT BOUNDARY FURTHER WEST.

CLOUDS WILL CLEAR FROM WEST TO EAST OVERNIGHT. THINK LINGERING LOW
LEVEL MOISTURE WILL BE REALIZED MORE AS FOG THAN STRATUS
OVERNIGHT WITH GRADIENT SLACKENING...AND HAVE INSERTED VALLEY FOG
CWA-WIDE. WEDNESDAY WILL FEATURE PLENTY OF SUNSHINE UNDER HIGH
PRESSURE. EXPECTING AFTERNOON CU DEVELOPMENT...BUT SHRA POTENTIAL
SHOULD BE KEPT IN CHECK BY CAPPING ALOFT AND SUBSIDENCE.

TEMPERATURES WILL CONTINUE TO RUN ABOVE NORMAL EVEN BEHIND THE
FRONT...AS H500 HEIGHTS REMAIN A BIT HIGH FOR THIS TIME OF YEAR. CL

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
DRIER AND TEMPORARILY COOLER AIR INFILTRATES THE REGION WEDNESDAY
NIGHT INTO THURSDAY. WITH ABUNDANT RECENT RAINFALL AND STRONG
OVERNIGHT INVERSIONS WEDNESDAY NIGHT INTO THURSDAY MORNING...AT
LEAST SOME FOG FORMATION SEEMS POSSIBLE. OTHERWISE...LAYER RH
VALUES FALL OFF A CLIFF AND CLEARING SEEMS TO BE QUITE THE COMMON
THEME AMONGST THE MODEL SOLUTIONS FROM WEDNESDAY NIGHT INTO
THURSDAY NIGHT. THE MODEL CONSENSUS FAVORS THE NEXT SYSTEM
DROPPING TOWARD THE AREA ON FRIDAY. IN FACT...THE SPREAD AMONGST
THE OPERATIONAL GFS/EMCWF/CANADIAN IS SMALL ENOUGH TO BE
NEGLIGIBLE...SO TIMING FOR SHOWERS/THUNDERSTORMS WAS PINNED TO
INCREASE FRIDAY AFTERNOON AND EVENING...WITH LIKELY POPS FEATURED
MOST PLACES IN THE EVENING.

TEMPERATURES DO MANAGED TO INCREASED THURSDAY AND FRIDAY...WITH
850 MB CONSENSUS VALUES RUNNING UP TOWARD +18 TO +20C. GIVEN THE
LOWER SUN ANGLE...THESE VALUES WILL BE TOUGH TO MIX OUT TO THE
SURFACE WITHOUT A LOT OF MECHANICAL HELP BELOW THAT LEVEL. AS
SUCH...HIGHS SHOULD REMAIN LARGELY IN THE 80S THROUGH THE END OF
THE WEEK RATHER THAN MAKING ANY REALISTIC RUN UP TOWARD 90F. FRIES

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MUCH COOLER AND DRIER AIR FOR THE END OF THE LONG TERM WITH BROAD
SURFACE HIGH BUILDING IN FROM THE NORTHWEST.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
THE NEXT 4-6 HOURS WILL BE THE BUSIEST OF THE TAF PERIOD...WITH
FROPA DURING THAT TIME. EXPECTING SHRA/TSRA TO BECOME MORE
WIDESPREAD OVER THE NEXT COUPLE OF HOURS. SHOULD BE ENOUGH MVFR
RESTRICTIONS FOR TEMPO TSRA MENTION. BRIEF IFR ALSO POSSIBLE BUT
DID NOT WRITE UP AT THIS TIME. EXPECT CLEARING FROM WEST TO EAST
DURING THE 22Z-04Z PERIOD...WITH A FAIRLY MINOR WIND SHIFT TOWARDS
THE WSW. MVFR/IFR FOG LOOKS LIKE A GOOD BET OVERNIGHT GIVEN
RAIN...LINGERING LOW LEVEL MOISTURE AND SLACKENING GRADIENT. VFR
WILL RETURN WITH SCT CU ONCE FOG LIFTS BY 14Z. CL

OUTLOOK.../TONIGHT THROUGH SATURDAY/...
COLD FRONT MAY BRING RESTRICTIONS FRIDAY AND SATURDAY.

&&

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

&&

$$






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