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000
FXUS61 KCTP 231837
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
237 PM EDT THU MAY 23 2013

.SYNOPSIS...
A COLD FRONT WILL CROSS COMMONWEALTH TONIGHT AND EARLY FRIDAY.
AN UPPER LOW WILL TRAVERSE THE REGION ON FRIDAY...PROVIDING COOL
AND SHOWERY CONDITIONS. CANADIAN HIGH PRESSURE WILL BUILD OVER
PENNSYLVANIA FROM THE GREAT LAKES AND BRING IMPROVING AND DRIER
WEATHER THROUGH THE MEMORIAL DAY 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/...
SHALLOW CONVECTION IN PROGRESS ACROSS MUCH OF THE CWA AS SFC
HEATING HAS BEEN MEAGER THUS FAR. SFC TEMPS ~15F COOLER THAN 24
HOURS AGO AND SPEED SHEAR IS ALSO 15 KTS LESS OVERALL...
ACCOUNTING FOR LESSER ORGANIZATION AND UPDRAFT INTENSITY THUS FAR.
STILL...UPSTREAM CLEARING IS EVIDENT IN LATEST VIS IMAGERY OVER
THE LAUREL HIGHLANDS AND MAY AID IN DESTABLIZATION FOR THE SOUTH
CENTRAL MOUNTAINS AND LOWER SUSQ LATE AFTERNOON AND EVENING.
BUFKIT CROSS SECTIONS ONLY INDICATE TAPPING OF 15 TO 25 KTS AT
15-20K FEET.

ARE WILL CONTINUE TO BE MONITORED FOR CONVECTIVE DEVELOPMENT BUT
AT THIS TIME THINGS ARE LOOKING RATHER MARGINAL...WITH BRIEF HEAVY
RAIN AND PEA SIZED HAIL THE MAIN THREATS. SOME TRAINING OCCURRING
OVER THE LOWER SUSQ RIVER VALLEY IS PRODUCING A MINOR FLOOD THREAT
OVER LANCASTER COUNTY...AND MAY NEED TO BE VIGILANT FOR ADDITIONAL
DEVELOPMENTS IN THE SLIGHTLY HIGHER SHEAR ENVIRONMENT ACROSS MY
SOUTHEAST THIS AFTERNOON AND EVENING...AS A PLUME OF ABOVE NORMAL
PRECIPITABLE WATER ALONG WITH DECENT BLYR CONVERGENCE/UPPER LEVEL
DIVERGENCE ARE SUPPORTIVE OF LOCALIZED AMTS APPROACHING 2 INCHES.

COOLER...MORE STABLE AIR WILL BEGIN TO WORK INTO THE AREA LATER
TONIGHT IN THE WAKE OF THE COLD FRONT. DEFORMATION AXIS PIVOTS
ACRS CENTRAL AND NORTHERN PA EARLY FRIDAY MORNING...CONTINUING
UNSETTLED CONDITIONS. ONLY EXPECTING A FEW TENS OF AN INCH FROM
THIS ADDITIONAL RAINFALL.

&&

.SHORT TERM /FRIDAY/...
A GOOD CHC OF RAIN SHOWERS CONTINUES FRIDAY AS UPPER LOW CUTS OFF
AND PROPOGATES EASTWARD. COOL AIR BEHIND THE SFC COLD FRONT WILL
MAMKE FOR A VERY UNPLEASANT DAY. KEPT HIGHEST POPS ACROSS THE
NORTH CENTRAL MTNS IN 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 MAY SHUT OFF
ANY SHOWERS EARLY IN THE DAY ACROSS WARREN CO.

WELL CHANNELED NORTHWEST FLOW AND A TIGHTENING SFC PRESSURE
GRADIENT WILL RESULT IN A BLUSTERY DAY FOR LATE MAY. NORTHWEST
WINDS SHUD GUST BTWN 25-30KTS DURING THE 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.
BRRR...

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
MAIN CONCERN FRIDAY NIGHT WILL BE THE POTENTIAL OF FROST/FREEZE
HEADLINES ACROSS THE ALLEGHENY PLATEAU. 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.


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 /19Z THURSDAY THROUGH TUESDAY/...
NMRS SHOWERS AND TSTMS THIS AFTN AND EVE. 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...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...DEVOIR
LONG TERM...FITZGERALD
AVIATION...DEVOIR/STEINBUGL