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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 240957
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
557 AM EDT FRI MAY 24 2013

.SYNOPSIS...
A COLD FRONT EXTENDING FROM THE POCONOS TO THE LOWER SUSQUEHANNA
VALLEY EARLY TODAY WILL PUSH OFF THE MID ATLANTIC COAST THIS
AFTERNOON. AN UPPER LOW WILL TRAVERSE THE REGION DURING THE DAY
TODAY PROVIDING UNSEASONABLY COOL...SHOWERY...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 /THROUGH TONIGHT/...
STRONG...SFC COLD FRONT EXTENDED FROM KAVP...SW TO KSEG AND JUST
WEST OF KMDT AT 09Z. TEMPS WERE IN THE U50S TO L60S JUST AHEAD OF
THE FRONT...ACROSS THE LOWER SUSQ VALLEY...WHILE READINGS RANGED
THROUGH THE 40S ACROSS THE NRN AND WRN MTNS...AND AROUND 50F ACROSS
THE CENTRAL MTNS.

SCATTERED RAIN SHOWERS WILL BE DRIFTING EAST OR NORTHEAST ACROSS THE
ENTIRE CWA THROUGH THE MID MORNING HOURS AS THE CFRONT /AND STRONG
DIFF PVA IN ITS WAKE/ MOVES OVER THE REGION.

900-850MB WET BULB TEMPS WILL FALL TO -1 TO -2C ACROSS THE NRN AND
WRN MTNS OF PENN BEGINNING IN THE 09-12Z PERIOD...AND REMAIN THERE
THROUGH 16Z BEFORE MODERATING A TAD THIS AFTERNOON.

08Z GFS LAMP GUIDANCE AND 00Z NAM INDICATES THE POTENTIAL FOR SOME
FLEETING WET SNOW TO BE MIXED IN AT TIMES WITH THE SHOWERS ACROSS
MAINLY ELEVATION AOA 1800 FT MSL ACROSS THE LAURELS AND NW MTNS
DURING THE MID TO LATE MORNING HOURS.

ONLY EXPECTING A FEW HUNDREDTHS /TO PERHAPS ONE TENTH OF AN INCH OF
ADDITIONAL RAINFALL IN A FEW LOCATIONS/ THROUGH THE MID
MORNING...THEN MORE NUMEROUS AND BRIEFLY HEAVIER SHOWERS ARE LIKELY
DO DEVELOP IN THE COOL/UNSTABLE AIRMASS FOR THE AFTERNOON HOURS
BRINGING AN ADDITIONAL TENTH OF AND INCH OR SO TO SOME LOCATIONS.

TEMPS WILL DIP INTO THE MID AND UPPER 30S FOR SEVERAL HOURS DURING
THE LATE MORNING AND MIDDAY HOURS ACROSS THE NRN AND WRN MTNS BEFORE
REBOUNDING A BIT THIS AFTERNOON. THE MERCURY WILL SLOWLY FALL TO THE
UPPER 40S AND LOWER 50S ACROSS THE CENTRAL MTNS...AND RISE JUST A
FEW DEGREES THIS AFTERNOON. READINGS CURRENTLY IN THE LOWER 60S
ACROSS THE SUSQ VALLEY...WILL SLOWLY FALL INTO EARLY THIS
AFTERNOON...REACHING THE LOWER TO MID 50S...THEN STAY STEADY FOR THE
REST OF THE DAY.

WELL CHANNELED NORTHWEST FLOW AND A TIGHTENING SFC PRESSURE GRADIENT
WILL RESULT IN A BLUSTERY DAY FOR LATE MAY. NORTHWEST WINDS SHOULD
GUST BTWN 25-30KTS DURING THE AFTN. TEMPS IN THE 40S AND
50S...COMBINED WITH THESE GUSTY WINDS...WILL LIKELY RESULT IN
APPARENT TEMPS IN THE 30S DURING THE AFTN ACROSS THE
ALLEGHENIES...AND 40S ELSEWHERE.

THE SHOWERS WILL GRADUALLY DIMINISH LATE TODAY/EARLY THIS EVENING
ACROSS CENTRAL AND WESTERN SECTIONS OF THE CWA...WITH SOME ISOLATED
TO SCTD SHOWERS LIKELY LINGERING INTO EARLY SATURDAY ACROSS THE SUSQ
VALLEY AND POINTS EAST AS THE UPPER LOW CUTS OFF AND PROPAGATES ONLY
SLOWLY EASTWARD.

THE AIRMASS IS COLD ENOUGH EARLY SATURDAY TO SUPPORT MIN TEMPS
SETTLING AROUND...OR PERHAPS A FEW DEG F BELOW THE FREEZING MARK
ACROSS THE NW MTNS AND LAURELS. COORDINATED WITH SURROUNDING OFFICES
TO POST A FREEZE WARNING FOR THE 06-13Z PERIOD SATURDAY..

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
MORNING SUNSHINE SATURDAY WILL BECOME MIXED WITH FLAT TO MDT
AFTERNOON CU ACROSS MOST AREAS. ONE OR TWO POCKETS OF COLDER AIR
ALOFT AND STEEPER MID-LEVEL LAPSE RATES WILL BE SLIDING SE ACROSS
THE EASTERN HALF OF PENN DURING THE DAY. THIS EXPECTED BOOST OF
INSTABILITY ALOFT SHOULD BRING PERIODS OF AT LEAST BKN CLOUDS AND
ISOLATED SHOWERS TO AREAS NEAR AND TO THE EAST OF THE SUSQ MAINSTEM
AND NORTH BRANCH.

TEMPS FOR SATURDAY AFTERNOON SHOULD MODERATE BY SOME 8-12F COMPARED
TO FRIDAY/S HIGHS.

SIMILARLY COLD CONDITIONS /TO THOSE OF EARLY SATURDAY/ ARE VERY
POSSIBLE FOR EARLY SUNDAY MORNING...AND THE CHANCE FOR FROST WILL
ALSO BE GREATER ACROSS THE NORTHERN AND WESTERN MTNS GIVEN
DIMINISHING NW WINDS AND CLEAR TO PTLY CLOUD SKIES.

PATCHY FROST IS EXPECTED ACROSS THE CENTRAL RIDGE AND VALLEY REGION
WHERE MIN TEMPS IN THE MID AND UPPER 30S WILL BE COMMON. LOWS ACROSS
MUCH OF THE LOWER SUSQ VALLEY WILL BE WITHIN A DEG OR TWO OF 40F.

HEIGHTS GRADUALLY RISE SUNDAY AS THE DEEP UPPER LOW PULLS SLOWLY
AWAY ACROSS THE NEW ENGLAND STATES. HIGH PRESSURE CENTERED OVER THE
UPPER GLAKES WILL RIDGE SE ACROSS THE COMMONWEALTH BRINGING ABUNDANT
SUNSHINE AND A NORTHWEST BREEZE OF 7-12KTS DURING THE LATE MORNING
AND AFTERNOON.

HIGH PRESSURE WILL BE OVERHEAD SUNDAY NIGHT BRINGING CLEAR
SKIES...NEAR CALM AIR AND A THIRD...AND FINALLY NIGHT OF CHILLY /AND
POSSIBLE FROSTY/ CONDITIONS. MIN TEMPS EARLY MONDAY WILL VARY FROM
THE LOWER 30S ACROSS THE NW MTNS...TO THE LOWER AND MID 40S
THROUGHOUT THE MIDDLE AND LOWER SUSQ VALLEY.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
-- Changed Discussion --
THE 24/00Z GLOBAL GUIDANCE AGREES FAIRLY WELL THAT A STRENGTHENING
UPPER RIDGE WILL BUILD OVER THE ERN CONUS THROUGH THE MEDIUM RANGE
PERIOD...WHILE MEAN TROUGHING EVOLVES OVER THE WESTERN U.S.

THE MAIN MODEL DIFFS ARE WITH THE ORIENTATION OF THE NERN CONUS
FLOW. THE 00Z OPRN ECMWF BRINGS A SHORTWAVE TROUGH THROUGH SERN
CANADA AND ADJACENT NORTHEAST STATES MID-LATE NEXT WEEK IN
CONTRAST TO FLATTER FLOW IN ITS ENSEMBLE MEAN AND MORE PRONOUNCED
RIDGE IN THE CMC/GEFS/GFS. THIS WILL BE AN IMPORTANT DETAIL AS IT
WILL MODULATE THE ADVANCEMENT OF WARM FRONT LIFTING NEWD FROM THE
PLAINS THRU THE MS/OH/TN VLYS. THE OPRN ECMWF IS SLOWER WITH THE
NEWD MVMT COMPARED TO THE GFS...OWING TO A MORE SUPPRESSED 500-MB
HT FIELD ASSOCD WITH A STRONGER ERN CANADIAN SHORTWAVE. EXPECT
THIS RETREATING BOUNDARY TO BE A FOCUS FOR CONVECTION IN "RING OF
FIRE" TYPE PATTERN...WITH THE HIGHEST POPS CURRENTLY ON DAYS 5-6.

IN TERMS OF SENSIBLE WEATHER...THE PERIOD WILL START OFF DRY FOR
MEMORIAL DAY WITH THE BEST CHC FOR SHOWERS/TSTMS ON TUE-WED.
TEMPERATURES WILL START OFF A TAD ON THE COOL SIDE OF CLIMO
FOLLOWED BY A CONSIDERABLE WARMING TREND THROUGH LATE NEXT WEEK.
PROJECTED HIGHS SHOULD BE AT LEAST +5-10F ABOVE NORMAL BY THE
FINALS DAYS OF MAY 2013.
-- End Changed Discussion --

&&

.AVIATION /10Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
24/09Z UPDATE...CIG TRENDS HAVE GENERALLY PLAYED OUT AS EXPECTED
WITH IFR OVR THE MTN SITES...MVFR IN THE CNTRL RIDGE/VALLEY
TERMINALS AND VFR ACRS THE SERN AIRFIELDS. NNWLY WINDS ARE ON THE
UP-TICK...ALREADY GUSTING TO AROUND 30KTS AT JST.

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
CONTINUING THROUGH THE FIRST PART OF TODAY. 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. VFR/MVFR CIGS LATE
TODAY WILL EVENTUALLY GIVE WAY TO A PROLONGED PERIOD OF VFR FLYING
OVER 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...SCT PM TSTM IMPACTS POSSIBLE.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...STEINBUGL
AVIATION...STEINBUGL