Area Forecast Discussion
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000
FXUS61 KPBZ 291321
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
921 AM EDT FRI MAY 29 2015

.SYNOPSIS...
A WEAK DISTURBANCE THIS AFTERNOON WILL BE FOLLOWED BY A SLOW
MOVING COLD FRONT OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
A WEAK SHORTWAVE IN SOUTHWEST FLOW IS PROGGED TO CROSS THE REGION
THIS AFTERNOON. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO DEVELOP WITH THIS FEATURE...THOUGH PROGGED INSTABILITY IS
LIMITED WITH WARM AIR ALOFT. THIS ACTIVITY SHOULD DECREASE THIS
EVENING AS THE WAVE EXITS. MORNING SOUNDINGS SUPPORT HIGHS IN THE
LOW TO MID 80S...WITH LOWS TONIGHT REMAINING AROUND 10 DEGREES
ABOVE AVERAGE.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
WARM SOUTHERLY FLOW WILL CONTINUE INTO SATURDAY WITH THE COLD FRONT
STILL WELL TO OUR WEST AND A BROAD ATLANTIC HIGH TO THE EAST. STRONG
SURFACE HEATING WILL BOLSTER LOW-LEVEL LAPSE RATES...COMBINING WITH
THE MOIST AIRMASS WILL GENERATE PRE-FRONTAL SHOWERS AND
THUNDERSTORMS. STRONGER MID- AND UPPER-LEVEL FLOW REMAINS WELL TO
OUR NORTH...CLOSER TO THE DEEPER WAVE. STILL...ENOUGH INSTABILITY
AND SHEAR EXISTS FOR THUNDERSTORM DEVELOPMENT...ESPECIALLY IN THE
LATE EVENING HOURS AS THE BOUNDARY NEARS OUR NORTHWEST AND UPSTREAM
THUNDERSTORMS CAN PROGRESS EASTWARD.

DEEP UPPER-LOW ADVANCES TO NEAR JAMES BAY CANADA LATE SATURDAY WITH
AN ELONGATED DEEP MOISTURE FIELD EXTENDING FROM THE MISSISSIPPI
DELTA THROUGH EASTERN QUEBEC. BIGGEST QUESTION REMAINS HOW FAR EAST
THAT DEEP MOISTURE PROGRESSES SATURDAY NIGHT INTO SUNDAY. 00Z GFS IS
FAST AS IT HAS MODERATE PERPENDICULAR MID-LEVEL FLOW DRIVING THE
BOUNDARY AND ASSOCIATED MOISTURE THROUGH PGH BY MIDDAY SUNDAY. THE
00Z NAM AND ECMWF DAMPEN THE MID-LEVEL FLOW AND STALL THE BOUNDARY
OVERHEAD...KEEPING AMPLE MOISTURE IN THE AREA. THINKING THE LATTER
SOLUTION IS MORE PLAUSIBLE GIVEN THAT THE DRIVER TO THE FRONTS
EASTWARD PROGRESSION EXITS WELL TO OUR NORTH AND EAST. WITH THIS IN
MIND...WILL KEEP HIGH CHANCE AND LIKELY POPS IN THE FORECAST FOR
SUNDAY AFTERNOON AND AGAIN MONDAY AS ANOTHER UPPER-LEVEL WAVE
APPROACHES.

TEMPERATURES WILL BE WELL-ABOVE AVERAGE SATURDAY AND SATURDAY NIGHT
WITH THE WARM SOUTHERLY FLOW. SUNDAYS TEMPS WILL BE SOMEWHAT
DEPENDENT ON THE PLACEMENT OF THE FRONT...BUT WITH INCREASED CLOUD
COVER...SHOULD BE HELD IN CHECK AND CLOSER TO THE AVERAGE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
UPPER-LEVEL WAVE APPROACHING THE GREAT LAKES MONDAY NIGHT WILL
EFFECTIVELY SWEEP THE DEEPER MOISTURE OUT OF THE AREA. MODEL
GUIDANCE A LOT MORE OPTIMISTIC THAN 24HRS AGO WITH RE-BUILDING THE
SURFACE HIGH OVER PENNSYLVANIA MIDDLE OF NEXT WEEK. THIS LEADS TO A
DRYING TREND WITH DECREASED CLOUDINESS. THE NEAR AVERAGE
TEMPERATURES THAT START THE WEEK WILL INCREASE THROUGH THE LATTER
PART OF THE WEEK AS THE HIGH PRESSURE SHIFTS EAST AND SOUTHERLY FLOW
IS RE-ESTABLISHED.

&&

.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
STILL EXPECT THE BULK OF THE NEXT 24 HOURS TO FEATURE VFR
CONDITIONS. HOWEVER...WITH MOISTURE INCREASING FROM THE
SOUTH...CLOUDS WILL BE ON THE INCREASE THIS MORNING. SCT-BKN CU
DECK BELOW SOME HIGHER CLOUDS AT FIRST...THEN SCATTERED SHRA/TSRA
WILL DEVELOP BEGINNING AROUND MIDDAY AS A MIDLEVEL WAVE ARRIVES.
STILL HANDLING THIS WITH VCTS AS ANY RESTRICTIONS WILL BE BRIEF
AND HARD TO TIME. ACTIVITY WILL WANE AS DAYTIME HEATING IS LOST
THIS EVENING...AND EXPECT ANOTHER MOSTLY QUIET NIGHT WITH
LINGERING MID CLOUDS. SOME SHRA MAY SNEAK CLOSE TO ZZV JUST PRIOR
TO 12Z SATURDAY AS A FRONT TRIES TO PUSH CLOSER FROM THE
NORTHWEST.

.OUTLOOK.../SATURDAY THROUGH TUESDAY/...
RESTRICTIONS ARE LIKELY THROUGH THE WEEKEND WITH A SLOW MOVING
COLD FRONT...AND COULD CONTINUE ESPECIALLY S OF PIT INTO EARLY
NEXT WEEK AS THE FRONT STALLS.

&&

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

&&

$$


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