-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 242133
AFDCTP

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

.SYNOPSIS...
COLD AIR ALOFT ASSOCIATED WITH A DEEP UPPER LOW WILL TRAVERSE THE
REGION THROUGH TONIGHT BRINGING UNSEASONABLY COOL AND QUITE BREEZY
CONDITIONS. CANADIAN HIGH PRESSURE WILL BUILD OVER PENNSYLVANIA
AND BRING DRIER WEATHER ON SATURDAY WHICH SHOULD LAST THROUGH REST
OF THE MEMORIAL DAY WEEKEND. TEMPERATURES WILL TREND COLDER OVER
THE NEXT FEW DAYS...BEFORE MODERATING THROUGH THE EARLY TO MIDDLE
PART OF NEXT WEEK. EARLY MORNING LOWS BOTH SATURDAY AND SUNDAY
WILL DIP NEAR...OR SLIGHTLY BELOW FREEZING OVER THE NORTHERN AND
WESTERN MOUNTAINS OF THE STATE.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
LATE AFTN WATER VAPOR LOOP SHOWING UPPER TROF AXIS OVR CENTRAL PA.
MOST OF THE SHOWERS HAVE HAVE PUSHED EAST OF THE STATE. HOWEVER...LG
SCALE FORCING AHEAD OF TROF SHOULD BE ENOUGH TO SUPPORT A FEW
LINGERING -SHRA/SPRINKLES ACROSS THE EASTERN HALF OF THE STATE
THIS EVENING...MAINLY OVR THE HIGHER TERRAIN OF THE POCONOS AND N
OF I-80.

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 NR 40F OVR THE W MTNS AT 21Z...SO NOT MUCH
COOLING NEEDED FOR A FREEZE. LATE AFTN VIS IMAGERY SHOWING
CLEARING SKIES DEVELOPING ACROSS THE 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 AFTER SUNSET ACROSS WESTERN PA...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.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
COLDEST AIR ALOFT SHIFTS EAST OF THE COMMONWEALTH SATURDAY. STILL
LAPSE RATES WILL BE STEEP ENOUGH FOR MORNING SUNSHINE TO LEAD TO
FLAT TO MDT AFTERNOON CUMULUS ACROSS MOST AREAS. BKN CLOUDS AND AN
OUTSIDE CHC OF A SHOWER WILL BE MOST LIKELY OVER FAR EASTERN
SECTION. LATEST GUIDANCE SUGGESTS THESE WILL BE MAINLY LIMITED TO
THE POCONO PLATEAU.

HIGHS SATURDAY AFTERNOON WILL MODERATE SOME 8-12F COMPARED TO
FRIDAY/S HIGHS...WITH MOST AREAS RANGING FROM 55F NORTH TO 65F SOUTH.

&&

.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 /21Z FRIDAY THROUGH WEDNESDAY/...
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 AND IFR CONDS
EXITING EASTERN SECTIONS EARLY THIS AFTERNOON.

PEAK WIND GUSTS THIS AFTN WILL TOP- OUT IN THE 25-35KT
RANGE...WITH THE HIGHEST GUSTS FCST AT MDT/LNS. GIVEN THE
ANOMALOUS PATTERN...GUIDANCE MAY BE TOO QUICK WITH IMPROVING CIGS
ALTHOUGH SHALLOW MIXING AND DRY AIR ADVECTION SHOULD LIFT BASES
OUT OF IFR RANGE IN THE MTNS BY AFTN. VFR/MVFR CIGS LATE TODAY
WILL EVENTUALLY GIVE WAY TO CLEARING /FROM WEST TO EAST/ AND A
PROLONGED PERIOD OF VFR FLYING THRU THE HOLIDAY WEEKEND...AS
CANADIAN HIGH PRESSURE DRIFTS SEWD FROM THE GREAT LAKES.

.OUTLOOK...
SAT-SUN...VFR. GUSTY NW WINDS.
MON...VFR. NO SIG WX EXPECTED.
TUE-WED...SCT PM TSTM IMPACTS POSSIBLE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING FROM 2 AM TO 9 AM EDT SATURDAY FOR PAZ004>006-
010-011-017-024-033.

&&

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