-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 240006
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
806 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 /UNTIL 6 AM FRIDAY MORNING/...
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 DESTABILIZATION 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 /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
A GOOD CHC OF RAIN SHOWERS CONTINUES FRIDAY AS UPPER LOW CUTS OFF
AND PROPAGATES EASTWARD. COOL AIR BEHIND THE SFC COLD FRONT WILL
MAKE 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/...
-- Changed Discussion --
MAIN CONCERN FRIDAY NIGHT WILL BE THE POTENTIAL OF FROST/FREEZE
HEADLINES ACROSS THE ALLEGHENY PLATEAU. AFOREMENTIONED PRESSURE
GRADIENT APPEARS LIKELY TO KEEP THE WINDS UP FRIDAY 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 CONTINUES 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. THE MODELS HAVE SLOWED THE PROGRESSION OF THE
EXITING LOW...SO WITH NW FLOW AND COLDER AIR OVER THE REGION WITH
LIGHT WINDS...THERE REMAINS A CHANCE FOR FROST OVER THE NW MTNS
SUNDAY NIGHT/MONDAY MORNING. THE REST OF THE REGIONS WILL BE IN
THE LOW 40S.

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.
-- End Changed Discussion --

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
ADJUSTED TAFS FOR BANDS OF SHOWERS AND ISOLATED STORMS.
MUCH OF THE AREA JUST HAS MID LVL CLDS AND DECENT VISIBILITY
AT THE CURRENT TIME.

EXPECT CONDITIONS TO GO DOWN HILL LATER TONIGHT...AS THE UPPER
LEVEL SYSTEM DIGS SE AND STARTS TO CLOSE OFF.

FRIDAY WILL BE A WINDY AND COLD DAY...WITH MVFR AND IFR
CONDITIONS IN MANY SPOTS. FOR NOW...DID BRING CONDITIONS
BACK TO VFR LATER IN THE AFT...GIVEN STRONG SUN ANGLE.

WEEKEND LOOKS OK...BUT BREEZY.

MONDAY SHOULD BE DECENT...AS HIGH BUILDS OVER THE AREA.

COULD BE A FEW SHOWERS AND THUNDERSTORMS LATE TUE...AS
STRONG WARM FRONT MOVES ACROSS THE REGION. STRONG STORMS
COULD FORM...GIVEN VERY STRONG WARM ADVECTION AND DIRECTIONAL
WIND SHEAR. BACK TO SUMMER FOR A FEW DAYS.

HAVE A GOOD HOLIDAY WEEKEND.


.OUTLOOK...
SAT-MON...VFR. NO SIG WX EXPECTED.
TUE...CHC OF SHOWERS AND STORMS LATE.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...DEVOIR
LONG TERM...FITZGERALD/CERU
AVIATION...MARTIN