-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 131141
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
741 AM EDT THU JUN 13 2013

.SYNOPSIS...
LOW PRESSURE WILL MOVE ACROSS THE GREAT LAKES AND OHIO VALLEY
REGION THROUGH THE DAY...FOLLOWED BY BUILDING HIGH PRESSURE LATE
FRIDAY AND SATURDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE SEVERE THUNDERSTORM WATCH HAS NOW BEEN CANCELLED OR EXPIRED
FOR THE ENTIRE FORECAST AREA. THE SQUALL LINE HAS PUSHED EAST AND
SOUTHEAST OF THE AREA...WITH ALL THREAT FROM HIGH WINDS AND HAIL
HAVING ENDED FOR AT LEAST THE MORNING HOURS. DRIER AIR IS
PUNCHING IN BEHIND THE SQUALL LINE...ACTUALLY ALLOWING FOR A FEW
SUN BREAKS AS FAR SOUTHEAST AS PITTSBURGH AS OF 7 AM. THE POPS
HAVE BEEN SAWED BACK OVER MUCH OF THE NORTHERN HALF OF THE AREA TO
COMPENSATE FOR THE EVOLUTION OF DEEPER DRY AIR INTO THE AREA.

WHILE THINGS DO LOOK NOMINALLY BETTER...UPSTREAM ADDITIONAL
CONVECTION IS DEVELOPING THIS MORNING. SHOWERS AND THUNDERSTORMS
ARE DEVELOPING JUST AHEAD OF THE MAIN MID-LEVEL WAVE IN INDIANA.
AS LATE MORNING AND EARLY AFTERNOON ENSUES...THIS MAIN MID-LEVEL
TROUGH PASSES THROUGH THE SOUTHERN AND SOUTHEASTERN PORTIONS OF
THE AREA BY ROUGHLY 18Z. RIGHT ALONG THE MID-LEVEL TROUGH AXIS THE
INCREASINGLY CURVED UPPER JET RIGHT ENTRANCE REGION LOOKS TO FOCUS
THE BEST UPPER DIVERGENCE AS WELL AS DIFFERENTIAL PVA SOUTH AND
EAST OF PITTSBURGH BY EARLY AFTERNOON. IN ADDITION...0-6 KM BULK
SHEAR VALUES CONTINUE TO BE ROUGHLY 45 KTS AHEAD OF THE MAIN SHORT
WAVE AND BY EARLY AFTERNOON...CAPE VALUES AGAIN LOOK TO RUN UP
TOWARD 2000 J/KG OVER THE SOUTHEASTERN PORTIONS OF THE AREA FROM
ROUGHLY 15-18Z TODAY. WITH THE ASSISTANCE OF STRONG SYNOPTIC
ASCENT AS WELL AS INCREASED DIURNAL INSTABILITY BY THAT
JUNCTURE...ISOLATED SEVERE THUNDERSTORMS MAY WELL AGAIN BE
POSSIBLE. DAMAGING WINDS WILL BE THE MAJOR THREAT ALONG WITH
ADDITIONAL HEAVY RAINFALL. SPC HAS PLACED THIS PORTION OF THE AREA
IN YET ANOTHER SLIGHT RISK...WHICH MODEL AND SATELLITE ANALYSIS
DOES SEEM TO SUPPORT. AS SUCH...WEATHER GRIDS WERE MODIFIED TO ADD
YET ANOTHER SEVERE THREAT LATE THIS MORNING AND EARLY AFTERNOON
SOUTHEAST OF PITTSBURGH.

BY LATE AFTERNOON...THE MID-LEVEL WAVE PUSHES EAST OF THE
AREA...WITH LOW LEVEL COLD ADVECTION REALLY KICKING IN. CAPE
VALUES FALL OFF A CLIFF...WHILE MID-LEVEL COOLING TAKES QUITE A
BIT TO KICK IN. AS SUCH...THUNDER CHANCES FALL OFF ENOUGH TO NO
LONGER MENTION...AND DRIER LAYER RH VALUES ACTUALLY SHOULD START A
DRYING TREND FROM SOUTHWEST TO NORTHEAST ACROSS THE AREA. FRIES

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
WHILE THE COLD FRONT IS PROGGED TO BE EAST OF THE RIDGES
TONIGHT...MODELS ALL AGREE THAT A WEAK SHORTWAVE DIVING DOWN THE
BACK EDGE OF THE TROUGH IN THE NORTHWEST FLOW COULD SPAWN ADDITIONAL
SHOWERS AND MAYBE A THUNDERSTORM FRIDAY AFTERNOON. BUFKIT SOUNDINGS
SUGGEST VERY MINIMAL INSTABILITY SO ADDED A SLIGHT CHANCE THUNDER
MENTION INTO THE FORECAST. SUBSIDENCE SHOULD QUICKLY END PRECIP
FRIDAY NIGHT WITH SATURDAY LOOKING TO BE A PLEASANT DAY AS HIGH
PRESSURE BRIEFLY BUILDS OVERHEAD. TO VARYING DEGREES...ALL OF THE
MODELS THEN SUGGEST A WEAK SHORTWAVE WILL APPROACH LATE
SATURDAY/SUNDAY ALONG WITH A RETURN TO SOUTHERLY FLOW. SINCE TIMING
REMAINS IN QUESTION...OPTED TO KEEP PRECIP PROBABILITIES AT CHANCE.

TEMPERATURES WERE KEPT AT A BLEND OF GUIDANCE VALUES...WHICH WAS
BELOW SEASONAL AVERAGES FRI MODERATING TO NEAR NORMAL SAT AND SUN

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
THE LONG WAVE PATTERN LOOKS TO FAVOR TROUGHING OVER THE GREAT LAKES
AND NORTHEASTERN REGION OF THE COUNTRY THROUGH THE PERIOD WITH
SEVERAL ILL-TIMED SHORT WAVE SYSTEMS LIKELY TO EVOLVE IN THE
NORTHWESTERLY FLOW ALOFT. THIS WILL BRING CHANCES OF SHOWERS AND
THUNDERSTORMS THROUGH MOST OF THE EXTENDED FORECAST. THIS SHOULD
KEEP TEMPERATURES FROM REALLY GETTING TOO WARM DURING ANY PARTICULAR
PERIOD OF THE LONG TERM AT LEAST UNTIL MID-WEEK NEXT WEEK. BY THAT
TIME...LONG WAVE RIDGING SHOULD START TO EDGE FROM THE PLAINS TOWARD
THE WESTERN GREAT LAKES...BRINGING A GRADUAL END TO UNSETTLED
CONDITIONS OVER OUR REGION.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
MCS HAS MOVED SE OF THE AREA...ALTHOUGH SFC CDFNT REMAINS BACK
ACRS NW PA INTO OH. THIS SHOULD CROSS THE AREA THRU THIS AFTN.
GENL VFR CONDS EXP UNTIL MVFR DVLPS WITH FROPA. KEPT TSTMS OUT OF
TAFS BUT WL MONITOR MGW TO SEE IF CNVCTN FIRES W. EXP GUSTY WRLY
WNDS IMMEDIATELY AFT FROPA...WITH A GRDL TURN TO THE NW LTR IN THE
DAY. GENL VFR CONDS EXP TNGT WITH DMNSHG WNDS.

.OUTLOOK.../FRIDAY THROUGH MONDAY/...
VFR EXP FRI AND SAT...WITH PSBL RESTRNS SUN AND MON AS LOW PRES
CROSSES THE RGN.
-- End Changed Discussion --

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FLASH FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR MDZ001.
OH...FLASH FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR OHZ039-
     048>050-057>059-068-069.
PA...FLASH FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR PAZ021-023-
     029-031-073>076.
WV...FLASH FLOOD WATCH UNTIL 6 PM EDT THIS EVENING FOR WVZ001>004-
     012-021>023-041.

&&

$$