Area Forecast Discussion
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000
FXUS61 KPBZ 232349
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
749 PM EDT TUE SEP 23 2014

.SYNOPSIS...
DRY WEATHER CAN BE EXPECTED FOR THE REMAINDER OF THE WEEK AND TEMPERATURES
WILL GRADUALLY WARM.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
ONLY CHANGES NEEDED FOR THE EARLY EVE UPDATE WERE SOME DOWNWARD TWEAKS
TO OVRNGT LOWS BASED ON THE LATEST DEWPOINT AND GUIDANCE TRENDS.

OTHERWISE...SFC HIPRES CNTRD IN ERN OH WILL DVLP NEWD AS AN UPR
TROF OVER THE COASTAL SERN CONUS CUTS OFF AND BUILDS NWD SLOWLY
THRU WED NGT. AT THE SAME TIME...UPR RDG OVER THE NRN PLNS WILL
AMPLIFY.

SERN CONUS TROF WILL MOVE NWD ALONG THE APLCNS ON WED AS ASSOCIATED
COASTAL LOPRES DVLPS TWD THE CHSPK BAY. CI ASSOCIATED WITH THIS
TROF WILL BGN TO SPREAD NWWD ACRS FCST AREA ON WED MRNG.

PCPN IS NOT XPCD TO REACH THE FCST AREA AS STRONG UPR RDG TO W
SHOULD BE SUFFICIENT TO PREVENT WWD MVMT OF UPR LOW.

RISING HTS/WARM ADVCNT WL SPPRT AN INCR IN TEMPS FOR WED TO SLGTLY
ABV CLIMO AMID DPR MIXING AND STRONG MRNG SUNSHINE.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
MODEL GUIDANCE IS SOMEWHAT SPLIT ON THE TRACK OF A MID-LEVEL LOW
UP THE EAST COAST GOING INTO THURSDAY. MOST DOMESTIC GUIDANCE
KEEPS THE MAJORITY OF THE HEIGHT FALLS AND MOISTURE TO OUR
EAST...WHILE THE ECMWF WRAPS ATLANTIC MOISTURE A TAD FARTHER
WEST...AND THE CANADIAN WRAPS IT ALL THE WAY BACK INTO OUR
FORECAST AREA. THIS IS A MANIFESTATION OF A WEAKENING OF THE MID-
LEVEL RIDGE OVER THE CENTRAL GREAT LAKES FROM WEDNESDAY AFTERNOON
INTO THURSDAY ON ALL THE MODELS...HOWEVER A TRACKING OF THE SYSTEM
UP THE COAST DIRECTLY INTO THIS WEAKENING RIDGING SEEMS A BIT FAR-
FETCHED. AS SUCH...THE DOMESTIC PREPONDERANCE OF GUIDANCE WAS
FOLLOWED MORE CLOSELY...WHICH MAINTAINS A DRY FORECAST THROUGH
THURSDAY WITH ONLY NOMINAL INCREASES IN SKY COVER ALONG THE
EASTERN PERIPHERY OF THE FORECAST AREA. IT WOULD SEEM LATER MODEL
CYCLES WILL BE LIKELY TO FOCUS IN ON A MORE WELL CLUSTERED
SOLUTION OVER THE NEXT FEW CYCLES...BUT FOR THE MOMENT...IT WOULD
SEEM THE MOST PRUDENT FORECAST IS CONTINUITY.

BY THURSDAY NIGHT AND FRIDAY...WHATEVER TRACK THAT MID-LEVEL
SYSTEM TAKES QUICKLY BECOMES IRRELEVANT AS THE PREPONDERANCE OF
GUIDANCE HAS WEAKENED IT AND ABSORBED IT INTO THE POLAR JET FLOW
WELL TO OUR NORTH. THIS ALLOWS FOR STRONG RIDGING TO OVER-ARCH A
WEAK MID-LEVEL LOW IN THE CENTRAL PLAINS...BRINGING A STRONG MID-
LEVEL RIDGE FROM THE FOUR CORNERS TO THE RED RIVER VALLEY OF
ND/MN...TOWARD LAKE ONTARIO. THIS MEANS ABUNDANT WARM AIR
ALOFT AND STRONG STABILIZATION. AS SUCH...THE CHANCE OF RAINFALL
LOOKS TO BE ESSENTIALLY ZERO...AND EVEN CLOUDS WILL BE DIFFICULT
TO MUSTER AS THE LAPSE RATES WILL BE SO UNFAVORABLE IN A VERY DRY
COLUMN. ADDITIONALLY...GIVEN THAT WE WILL BE ON THE DOWNSTREAM
SIDE OF THE RIDGE...DEWPOINTS SEEM UNLIKELY TO JUMP UP TOO QUICKLY
WITH VERY LIGHT EAST/NORTHEAST FLOW IN THE LOW LEVELS LIKELY TO
CONTINUE. THIS MEANS A GRADUAL WARM UP WITH LOW HUMIDITY SEEMS
LIKELY.

WHILE 500 MB HEIGHT VALUES WILL BE IMPRESSIVE...A LACK OF VERTICAL
MIXING AND STRONG STABILITY WILL KEEP 850 MB TEMPERATURE VALUES
FROM BEING REALIZED DRY ADIABATICALLY AT THE SURFACE...EVEN WITH
THE DRY COLUMN. AS SUCH...WHILE THE +13 TO +15C THAT CAN BE NOTED
ON MOST MODELS BY LATE IN THE WEEK IS IMPRESSIVE AT 850 MB FOR
SEPTEMBER...MID TO A FEW UPPER 70S SEEM MORE LIKELY THAN THE 80S
THAT WILL BE MORE LIKELY OVER THE UPPER MIDWEST ON THE UPSTREAM
SIDE OF THE SURFACE HIGH...WHERE MIXING WILL BE MUCH MORE
EFFICIENT.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
TEMPERATURES WILL HOVER BETWEEN 5 TO 10 DEGREES ABOVE NORMAL INTO
EARLY NEXT WEEK AS A LARGE RIDGE OF HIGH PRESSURE TRANSITIONS
ACROSS THE REGION.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
VF AND LGT SFC WIND CAN BE EXPECTED INTO THE PRE DAWN HRS...WHEN
IFR VSBY RESTRICTIONS BECOME POSSIBLE...MAINLY RIVER FOG AT THE
SAME LOCATIONS AS YESTERDAY MORNING. THE SHALLOW FOG WILL LIFT BY
13-14Z.

OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
HIGH PRES WL MAINTAIN GENL VFR THROUGH THE WEEKEND.

&&

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

&&

$$





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