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000
FXUS61 KCTP 250337
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1137 PM EDT FRI MAY 24 2013

.SYNOPSIS...
COLD AIR ALOFT ASSOCIATED WITH A DEEP UPPER LOW WILL TRAVERSE THE
REGION TONIGHT...BRINGING UNSEASONABLY COOL AND QUITE BREEZY
CONDITIONS. CANADIAN HIGH PRESSURE WILL BUILD OVER PENNSYLVANIA
DURING THE HOLIDAY WEEKEND ENSURING FAIR WEATHER. TEMPERATURES
WILL BEGIN THE WEEKEND WELL BELOW NORMAL BUT MODERATE BY MEMORIAL
DAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
LATE EVENING WATER VAPOR LOOP SHOWING UPPER TROF AXIS LIFTING
INTO EASTERN PA. LG SCALE FORCING AHEAD OF TROF SHOULD SUPPORT A
FEW LINGERING -SHRA/SPRINKLES ACROSS OUR EASTERN COUNTIES THROUGH
ARND 06Z.

CROSS POLAR FLOW DRIVING AN UNSEASONABLY CHILLY AIR MASS
SOUTHWARD INTO PA SHOULD SET THE STAGE FOR A LATE SEASON FREEZE
OVR PORTIONS OF THE ALLEGHENY PLATEAU TONIGHT. ALTHOUGH NOT MUCH
RADIATIONAL COOLING IS EXPECTED TONIGHT DUE TO A PERSISTENT NW
WIND...READINGS ALREADY IN THE U30S OVR THE W MTNS AT 02Z...SO
NOT MUCH COOLING NEEDED FOR A FREEZE. EVENING IR SATL IMAGERY
SHOWING CLEARING SKIES DOWNWIND OF LAKE ERIE...AS VERY DRY AIR
WORKS SOUTH INTO THE REGION. THIS IS DESPITE 8H TEMPS COLD ENOUGH
TO SUPPORT LAKE EFFECT. SO...BELIEVE SKIES WILL CLEAR FAIRLY
QUICKLY BTWN 03Z-06Z ACROSS THE WESTERN HALF OF THE STATE...WHILE
CLOUDS ASSOC WITH UPPER TROF LINGER OVR THE EASTERN COUNTIES.

WILL MAINTAIN FREEZE WARNINGS AS IS FOR TONIGHT. HIGHEST
PROBABILITY OF A FREEZE APPEARS TO BE OVR THE LAUREL HIGHLANDS
BASED ON LATEST GEFS/SREF AND HIGH RES NAM DATA. ALTHOUGH GUSTY
WINDS WILL DIMINISH SOMEWHAT OVERNIGHT...A TIGHT PRES GRADIENT
SHOULD KEEP AN ACTIVE NW BREEZE GOING THRU THE NIGHT AND PRECLUDE
FROST FORMATION. THEREFORE ONLY THE FREEZE HEADLINES ARE HOISTED
FOR TONIGHT.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
LG SCALE SUBSIDENCE AND ANOMALOUSLY DRY AIR WORKS OVR CENTRAL PA
ON SATURDAY IN WAKE OF DEPARTING UPPER LOW...BRINGING MSUNNY SKIES
TO MUCH OF THE REGION. TEMPS MAY STILL BE COLD ENOUGH ALOFT TO
SUPPORT A MORE EVEN MIX OF SUN AND CUMULUS ACROSS ACROSS THE
EASTERN COUNTIES...ESP SULLIVAN. HOWEVER...WILL KEEP MENTION OF
SHRA OUT OF THE FCST BASED ON AFOREMENTIONED LOW PWATS AND LACK OF
FORCING.

MDL SOUNDINGS SHOW MIXING TO 8H...WHICH SHOULD TRANSLATE TO HIGHS
FROM THE M50S HIGH TERRAIN...TO M60S SUSQ VALLEY...SOME 10-15F
WARMER THAN TODAY. AS BLYR DEPTH INCREASES...EXPECT NW WINDS TO
BECOME GUSTY AGAIN ON SATURDAY. BUFKIT SOUNDINGS SUPPORT GUSTS IN
THE 25-30KT RANGE BY AFTN.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
WE START THE EXTENDED OFF DEALING WITH THE ANOMALOUSY DEEP UPPER
LOW THAT WILL BE MOVING SLOWLY THROUGH NEW ENGLAND AND THE
COASTAL WATERS.

SUNDAY WILL BE FAIR AND DRY...ALBEIT ON THE CHILLY SIDE. THE DRY
WEATHER WILL CONTINUE THROUGH MONDAY AS WE BENEFIT FROM THE UPPER
RIDGE BUILDING IN FROM THE WEST. THOSE TWO DAYS WILL START THE
EXTENDED OFF IN A RATHER UNEVENTFUL FASHION.

FROM TUESDAY THROUGH AT LEAST MIDWEEK THE FORECAST GETS MURKY AS
THE BUILDING SUB TROPICAL RIDGE OVER THE SOUTHERN STATES SHOVES
THE WESTERLIES NORTHWARD. WITH US BEING ON THE SOUTHERN EDGE OF
THESE WESTERLIES/NORTHERN EDGE OF THE SUBTROPICAL RIDGE...WE WILL
BECOME VULNERABLE TO UPSTREAM MCS DEVELOPMENT AS THE HEAT AND
HUMIDITY BEGINS TO MAKE INROADS TO THE REGION ONCE AGAIN.

DIFFERENCES IN THE MODEL TIMING OF THESE CONVECTIVE COMPLEXES IS
BIG WITH THE OPERATIONAL GFS SHOWING A WET DAY TUESDAY...AND THE
ECMWF SUGGESTING THE CONVECTION STAYS MAINLY SOUTH OF HERE AT THAT
TIME. GEFS SPLASHES A FAIR AMOUNT OF DIURNALLY FAVORED PRECIP
AROUND JUST ABOUT EVERY DAY STARTING TUESDAY. THE MEAN UPPER FLOW
AND ACCOMPANYING SURFACE PATTERN SUGGEST WHATEVER SEMBLANCE OF A
WARM FRONT THERE IS PASSES THROUGH ON WEDNESDAY...WITH THE
REMAINDER OF THE WEEK FIRMLY UNDER THE INFLUENCE OF THE BERMUDA
HIGH AND WARM MUGGY SOUTHWEST FLOW. WITH THE OPERATIONAL
GFS/ECMWF BOTH PREDICTING A SURGE IN MID LEVEL TEMPS BY LATER WED
INTO THURSDAY...I AM THINKING WE WILL SPEND MUCH OF THE TIME AFTER
MID WEEK PRETTY CAPPED LEADING TO HAZY HOT AND HUMID CONDITIONS
WITH FAIRLY SMALL CHANCES FOR SHOWERS AND THUNDERSTORMS. I LIKE
OUR CURRENT FORECAST WHICH DOWNPLAYS THE CHANCES FOR RAIN AFTER
WEDNESDAY...AND WILL CONTINUE ALONG THOSE LINES THROUGH FRIDAY.

&&

.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
UPPER LVL TROUGH HAS CLOSED OFF AND GONE NEGATIVE TILT...
WHICH HAS PULLED SOME SHOWERS BACK TO THE WEST.

MINOR ADJUSTMENTS MADE TO 03Z TAFS.

EARLIER DISCUSSION BELOW.

AN UNSEASONABLY STRONG/DEEP UPPER-LEVEL TROUGH WILL ROTATE EWD
FROM THE LWR GRT LKS/OH VLY THROUGH THE MID-ATLC AND NORTHEAST
STATES OVER THE NEXT 48-72 HOURS. A COLD AND BLUSTERY NNW FLOW
WILL ACCOMPANY WIDESPREAD STRATUS/STRATOCU WITH MVFR ACROSS
THE WEST THIS EVENING.

PARTIAL CLEARING OVERNIGHT...BUT IT WILL REMAIN WINDY.

EXPECT SCT CU ON SAT...GIVEN COLD AIR ALOFT. IPT WILL LIKELY
GO BACK TO BKN SKIES...BUT VFR...GIVEN HOW DRY THE AIR WILL
BE.

WINDS WILL WEAKEN BY SUNDAY...WITH MONDAY BEING THE BEST
DAY.

WARM ADVECTION ON TUE COULD SET OFF A FEW SHOWERS OR STORMS...
MAINLY LATE. WARMER WED...BUT STILL A CHC OF A SHOWER OR STORM.

HAVE A GOOD HOLIDAY WEEKEND.

.OUTLOOK...
SUN-MON...VFR. NO SIG WX EXPECTED.
TUE-WED...SCT TSTM IMPACTS POSSIBLE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING UNTIL 9 AM EDT SATURDAY FOR PAZ004>006-010-011-
017-024-033.

&&

$$
SYNOPSIS...DEVOIR/FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...DEVOIR/FITZGERALD
LONG TERM...LA CORTE
AVIATION...MARTIN