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000
FXUS61 KCTP 231128
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
728 AM EDT THU MAY 23 2013

.SYNOPSIS...
AN AMPLIFYING UPPER-LEVEL TROUGH AND ITS ASSOCIATED COLD FRONTS
WILL CROSS THE NORTHERN MID-ATLANTIC STATES OVER THE NEXT 48
HOURS. CANADIAN HIGH PRESSURE WILL BUILD SOUTHEAST FROM THE GREAT
LAKES THROUGH THE MEMORIAL DAY WEEKEND. THE OVERALL PATTERN WILL
BE UNSETTLED THROUGH FRIDAY WITH IMPROVING CONDITIONS EXPECTED
DURING THE WEEKEND. TEMPERATURES WILL TREND COLDER OVER THE NEXT
FEW DAYS...BEFORE LIKELY MODERATING THROUGH THE EARLY TO MIDDLE
PART OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
WV SATL IMAGERY SHOWS TWO SHORTWAVE TROUGHS ROTATING OVER
HUDSON/JAMES BAY AND WI/MI EARLY THIS MORNING. THIS ENERGY WILL
PHASE AND DIG INTO THE WRN APPALACHIANS BY THE END OF THE PERIOD. THE
00Z GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE DETAILS OF THE
HT FALL EVOLUTION AND ARE WELL CLUSTERED THRU F36. AT THE SFC...A
COLD FRONT DRAPED ACRS SRN ONTARIO/LK HURON INTO CNTRL LWR MI WILL
PUSH SEWD ACRS THE LWR LKS THIS AFTN BEFORE CROSSING THRU THE REGION
LATE TNT. A PRE-FRONTAL TROUGH WILL SHIFT EWD ACRS CNTRL AND ERN
PORTIONS OF THE CWA THIS AFTN.

MESO MDLS SHOW A GRADUAL INCREASE IN SHOWER ACTIVITY THRU THE
MORNING HOURS...COINCIDING WITH APPROACH OF LARGE SCALE FORCING/HT
FALLS. THE MAIN CONCERN IN THE NEAR TERM IS AGAIN POTENTIAL FOR
SEVERE CONVECTION WITH THE FOCUS SHIFTING FROM W-CNTRL TO E-CNTRL
PA. SPC HAS UPGRADED THE ERN 1/3 OF THE CWA TO SLGT RISK. WHILE
INSTABILITY/DESTABILIZATION POTENTIAL MAY BE SOMEWHAT LIMITED BY
PERSISTENT BAND OF MULTI-LAYERED CLOUDS STREAMING NWD WITHIN MOIST
SSWLY FLOW ALOFT...BREAKS WILL LKLY OCCUR AND RESULT IN MODEST ML
CAPE VALUES. THIS SHOULD BE SUFFICIENT FOR STORM INITIATION IN THE
WARM SECTOR /PERHAPS AS EARLY AS 16Z WITH PEAK INTENSITY REACHED
"EARLY" IN THE 17-21Z TIMEFRAME PER HRRR/ WITH THE MAIN TSTM
DEVELOPMENT ALONG PRE-FRONTAL TROUGH LOCATED INVOF THE SUSQ VLY.
BELT OF STRONGER MID-UPPER LEVEL FLOW/30-40KTS OF EFFECTIVE SHEAR
ALONG THE ERN PERIPHERY OF THE APPROACHING UPPER TROUGH WILL BE
AVAILABLE FOR GRADUAL STORM INTENSIFICATION/ORGANIZATION OF
MULTICELLS CAPABLE OF PRODUCING DMGG WINDS. ANY SEVERE THREAT SHOULD
DIMINISH BY THE EARLY EVENING.

A POTENTIAL SECONDARY HAZARD MAY BE LOCALLY HEAVY RAINFALL. A
RESERVOIR OF ABOVE NORMAL PRECIPITABLE WATER FEEDING NWD FROM THE
WRN ATLC ALONG WITH DECENT BLYR CONVERGENCE/UPPER LEVEL DIVERGENCE
COUPLET SHOULD SUPPORT MOD RAINS OVER THE ERN HALF OF THE CWA WITH
AMTS BTWN 0.50-1.00 INCH. LOCALIZED AMTS APPROACHING 2 INCHES ARE
NOT OUT OF THE QUESTION WITH THE GREATEST RISK ALONG AND EAST OF
THE SUSQ RIVER.

COOLER...MORE STABLE AIR WILL BEGIN TO WORK INTO THE AREA TONIGHT IN
THE WAKE OF THE COLD FRONT. THE PCPN PROCESS BECOMES MORE
FRONTOGENETICALLY DRIVEN AS MDLS DEPICT A DEFORMATION AXIS PIVOTING
ACRS N-CNTRL PA LATE TNT INTO EARLY FRIDAY. QPF AMTS WILL BE ON THE
LGT SIDE /0.10-0.25 INCH/ IN THE 00-12Z PERIOD. THE SENSIBLE WX
PATTERN WILL TRANSITION FROM RECENT SUMMER-LIKE HEAT TO COOL/DAMP
AND CLOUDY CONDS WITH AN INCREASING N/NW WIND.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
MDL DATA ALL INDICATING DIGGING TROF WILL CUT OFF OVR WESTERN PA
ON FRIDAY. STRONG LG SCALE FORCING AHEAD OF THIS FEATURE...AS DEPICTED
BY MDL 500-300MB Q-VECTOR DIVERGENCE...SHOULD SUPPORT A GOOD CHC
OF RAIN SHOWERS IN THE COOL AIR BEHIND THE SFC COLD FRONT.
HAVE PLACED THE HIGHEST POPS /NR 80 PCT/ ACROSS THE NORTH CENTRAL
MTNS BASED ON LATEST GEFS OUTPUT AND ANTICIPATION OF OROGRAPHIC
ENHANCEMENT ALONG THE SPINE OF THE APPALACHIANS. THE ARRIVAL OF
MUCH DRIER AIR WRAPPING INTO THE WEST SIDE OF DEVELOPING CUT OFF
WILL LIKELY SHUT OFF ANY SHOWERS EARLY IN THE DAY ACROSS WARREN
CO.

A TIGHTENING PRES GRADIENT BTWN SFC HIGH OVR THE LAKES AND
DEVELOPING COASTAL WAVE WILL RESULT IN A BLUSTERY DAY FOR LATE
MAY. BUFKIT SOUNDINGS INDICATE NW WINDS WILL BE GUSTING BTWN
25-30KTS DURING FRI AFTN. TEMPS IN THE 50S...COMBINED WITH THESE
GUSTY WINDS...WILL LIKELY RESULT IN APPARENT TEMPS IN THE 40S
DURING THE AFTN ACROSS THE ALLEGHENIES.

MAIN CONCERN FRIDAY NIGHT WILL BE THE POTENTIAL OF A FREEZE ACROSS
THE ALLEGHENY PLATEAU. ATTM...AFOREMENTIONED PRES GRADIENT APPEARS
LIKELY TO KEEP THE WINDS UP FRI NIGHT...SO WIDESPREAD FROST SEEMS
UNLIKELY. HARD TO BELIEVE THERE WILL BE A WIDESPREAD FREEZE THIS
LATE IN THE SEASON WITHOUT A CALM WIND...SO HAVE LEANED ON THE
WARM SIDE OF MOS /CLOSER TO EC MOS/ AND KEPT TEMPS JUST ABV FREEZING
FOR MOST OF THE W MTNS FRI NIGHT.

MDL TREND HAS BEEN TO SLOW EASTWARD PROGRESSION OF UPPER LOW...SO
HAVE KEPT MENTION OF SHRA IN THE FCST THRU FRI NIGHT ACROSS THE
EASTERN ZONES...AND TAPERED THEM OFF LATER ACROSS THE CENTRAL
COUNTIES.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
EASTERN PA WILL REMAIN ON WESTERN PERIPHERY OF UPPER LOW SAT/SAT
NIGHT. SO...HAVE INCREASED THE CLOUD FCST A BIT OVR THE EASTERN
COUNTIES AND CAN/T COMPLETELY RULE OUT A STRAY SHRA OVR SULLIVAN
OR SCHUYLKILL CO. ELSEWHERE...CONFIDENCE IN A MSUNNY SATURDAY IS
FAIRLY HIGH...AS ALL MDL DATA PULLS LOW PWAT AIR SOUTHWARD ACROSS
CENTRAL/WESTERN PA ON SAT. HOWEVER...DESPITE STRONG MAY
SUNSHINE...MDL 8H TEMPS WELL BLW NORMAL SHOULD CAP READINGS IN THE
L/M 60S ACROSS MUCH OF THE AREA...WITH HIGHS IN THE U50S LIKELY
ACROSS THE HIGH TERRAIN. DEEP MIXING SHOULD DRAW SOME GUSTY WINDS
TO THE SFC AGAIN ON SATURDAY. 800MB WIND FIELDS SUGGEST MUCH OF
THE AREA WILL SEE GUSTS BTWN 25-30KTS BY AFTN.

BULK OF MED RANGE GUIDANCE CONTINUES TO INDICATE A HIGH DEGREE OF
CONFIDENCE IN DRY WX HOLDING THRU MEMORIAL DAY...ALONG WITH A
GRADUAL WARMING TREND...AS UPPER LOW OVR NEW ENG SLOWLY LIFTS AWAY
FROM THE AREA.

BY THE MIDDLE OF NEXT WEEK...A BUILDING UPPER LVL RIDGE IS
ADVERTISED BY THE MED RANGE GUIDANCE OVR THE MISS VALLEY. ACROSS THE
EAST...SFC HIGH WILL PASS OFF THE COAST...RESULTING IN A WARMER SW
FLOW. SOME MDL DIFFS WITH RESPECT TO HOW FAST THE LOW LVL MOISTURE
RETURNS. HOWEVER...HAVE GRADUALLY INTRODUCED A CHC OF DIURNAL
CONVECTION IN THE TUE/WED TIME FRAME.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
5/23/12Z...SOME RESTRICTIONS NOW BEING OBSERVED ACRS THE AIRSPACE
MAINLY DUE TO LOW CIGS. HOWEVER EXPECT VFR TO RESUME WITHIN A FEW
HOURS. TSTM IMPACTS WILL BE THE MAIN FOCUS FROM LATE MORNING INTO
THE AFTN.

LG SCALE FORCING ASSOCD WITH APPROACHING UPPER-LEVEL TROUGH AND
SFC COLD FRONT...IMPINGING ON RESERVOIR OF ABOVE NORMAL MOISTURE
STREAMING NWD INTO THE REGION...WILL RESULT IN NMRS SHOWERS AND
TSTMS FROM LATE MORNING THRU THE AFTN. SOME STRONG TO LCLY SVR
TSTMS ARE POSSIBLE ACRS THE ERN 1/3 OF THE AIRSPACE...MAINLY IN
ZNY SECTOR. EXPECT MAINLY VFR CONDS WITH OCNL MVFR RESTRICTIONS.

THE UPPER TROUGH WILL AMPLIFY AS S/W DIGS ACRS VA ON FRIDAY AND
MAY EVEN FORM A CUT-OFF/CLOSED LOW. THIS WILL RESULT IN A LOW
CIGS AND -RA WITH A BREEZY NNW WIND. THERE IS SOME UNCERTAINTY
WITH HOW FAST THIS SYSTEM WILL EXIT THE AREA HEADING INTO THE
WEEKEND. HOWEVER THE WORST FLYING CONDS SHOULD BE ON FRIDAY WITH
GRADUAL IMPROVEMENT AS CANADIAN HIGH PRES BUILDS SEWD FROM THE
GRT LKS.

.OUTLOOK...
FRI...LOW CIGS WITH AREA OF LIGHT RAIN. GUSTY NNW WINDS.
SAT-MON...VFR. NO SIG WX EXPECTED.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

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