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000
FXUS61 KCTP 241507
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1107 AM EDT FRI MAY 24 2013

.SYNOPSIS...
COLD AIR ALOFT ASSOCIATED WITH A DEEP 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/...
SHOWERS ACCOMPANYING UPPER FRONT PASSAGE OVER EASTERN PORTIONS OF
MY CWA THIS MORNING. MUCH DRIER DEEP LAYER ARRIVING ACROSS CENTRAL
AND WESTERN SECTIONS WITH WELL CHANNELED NORTHWEST FLOW
DELIVERING BRISK NORTHWEST WINDS MORE REMINISCENT OF MARCH THAN
LATE MAY.

TEMPS WILL ONLY RECOVER BY A FEW DEGREES FROM CURRENT READINGS
ACROSS THE NORTH...WITH HIGHS EXPECTED IN THE LOWER TO MIDDLE 40S.
FARTHER SOUTH...MOST AREAS WILL ONLY SEE 50S FOR HIGHS...WHICH IS
10 TO 15 DEGREES BELOW NORMAL.

NORTHWEST WINDS SHOULD GUST BETWEEN 25-30KTS THIS AFTERNOON. 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.

WELL CHANNELED NORTHWEST FLOW AND A TIGHTENING SFC PRESSURE GRADIENT
WILL RESULT IN A BLUSTERY DAY FOR LATE MAY.

ISOLATED SHOWERS MAY LINGER 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. FREEZE WARNING IN EFFECT FOR THE
06-13Z TIMEFRAME 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/...
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.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
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...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/LAMBERT
NEAR TERM...DEVOIR/LAMBERT
SHORT TERM...LAMBERT
LONG TERM...STEINBUGL
AVIATION...DEVOIR/STEINBUGL