-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 161142
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
742 AM EDT THU MAY 16 2013

.SYNOPSIS...
AN WEST-EAST FRONTAL BOUNDARY ALONG THE MASON DIXON LINE EARLY
THIS MORNING WILL SINK SOUTHWARD INTO THE CENTRAL APPALACHIANS AND
BECOME QUASI-STATIONARY...PIVOTING TO A NW-SE ORIENTATION.
MEANWHILE...HIGH PRESSURE WILL MIGRATE EASTWARD ACROSS
SOUTHEASTERN CANADA WITH ONSHORE FLOW DEVELOPING ACROSS THE MID-
ATLANTIC REGION. THE FRONTAL BOUNDARY WILL SLOWLY PUSH BACK TO THE
NORTH AS A WARM FRONT OVER THE WEEKEND...AND LIFT NORTH OF THE
AREA BY EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
08Z SFC ANALYSIS PLACES QUASI-STATIONARY FRONT FROM SOUTHERN PA
WESTWARD TO SE IOWA. MOST CONVECTIVELY ACTIVE PORTION OF THIS FRONT
IS OVR SE OHIO/SW PA AT 08Z...THE RESULT OF LG SCALE FORCING AHEAD
OF SHORTWAVE MOVING OVR THE E GRT LKS. AS THIS FEATURE TRACKS
EAST...EXPECT THE BEST CHC OF SHRA AND A FEW TSRA TO SHIFT FROM THE
LAUREL HIGHLANDS TO THE LOWER SUSQ VALLEY BY 12Z. LATEST RAP AND
NAMPARA SIMULATED RADAR DATA BOTH INDICATE A SIMILAR SCENARIO
PLAYING OUT EARLY THIS AM.

SHORTWAVE WILL PASS EAST OF THE AREA BY LATE AM...WITH ENOUGH OF A
NWRLY FLOW BEHIND IT TO PUSH THE SFC FRONT JUST SOUTH OF THE MASON
DIXON LINE BY THIS AFTN. DIURNAL HEATING/DESTABILIZATION...COMBINED
WITH APPROACH OF NEXT SHORTWAVE OVR THE GRT LKS...SHOULD CAUSE A NEW
ROUND OF CONVECTION TO FIRE ALONG FRONT JUST SOUTH OF PA THIS AFTN.
WILL MAINTAIN ONLY A SLIGHT CHC ALONG OUR S TIER COUNTIES.

ALTHOUGH TODAY WILL DAWN MCLDY ACROSS SOUTHERN PA...A GOOD DEAL OF
SUNSHINE APPEARS LIKELY EVERYWHERE BY AFTN...AS WNW FLOW DRAWS DRIER
AIR INTO THE STATE. ENS MEAN 8H TEMPS OF ARND 13C SHOULD SUPPORT
HIGH TEMPS FROM THE M70S OVR THE ALLEGHENY PLATEAU...TO THE L80S IN
THE SUSQ VALLEY.

ALL MDL DATA INDICATING HIGH PRES RIDGE AND ASSOC DRY AIR MASS NOSES
SEWRD INTO PA TONIGHT...BRINGING MCLEAR SKIES AND LIGHT WINDS TO ALL
OF CENTRAL PA. THE DRIEST AIR...AS DEPICTED BY GEFS NEGATIVE PWAT
ANOMALIES...REMAIN ACROSS THE NORTHERN HALF OF THE STATE...WHERE
READINGS ARE LIKELY TO DIP INTO THE M/U30S. CAN/T RULE OUT SOME
PATCHY FROST UP THERE...BUT GROWING SEASON HAS NOT OFFICIALLY BEGUN
UP THERE...SO NO ADVISORY NEEDED.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
SFC HIGH PRES WILL SLIDE EWD FROM ONTARIO TO THE MARITIMES BY 12Z
SUNDAY...WITH ONSHORE FLOW DEVELOPING ACRS THE MID-ATLC STATES.
EXPECT SFC RIDGING AND LACK OF ANY SIGNIFICANT MID-UPPER LEVEL
FORCING TO LIMIT PCPN THROUGH MOST OF THE PERIOD. THE HIGHEST POPS
ARE OVER THE SERN ZONES SAT NGT AS AN UPPER LEVEL WAVE DRIFTS EWD
ACRS KY/TN INTO THE CNTRL APPLCHNS AND INTERACTS WITH ONSHORE MSTR
FEED INTERSECTING RETREATING Q-STNRY/WARM FRONT LIFTING NWD OVER
THE MID-ATLC. EXPECT LOW CLOUDS TO DEVELOP FROM SOUTH TO NORTH ON
SAT NGT IN SELY FLOW REGIME. TEMPS WILL BE WARMER ON FRIDAY WITH
MORE SUN.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
GUIDANCE CONTINUES TO TREND COOLER FOR SUNDAY WITH HIGHS IN THE
MID-UPPER 60S...AS MOIST ONSHORE FLOW STRENGTHENS /-2SD 850MB U
WIND ANOMALY IN GEFS/ AND BRINGS EXTENSIVE CLOUD COVER TO THE
REGION. MDL LI PROGS SHOW A CAD PATTERN IN THE LOW-LEVELS AS THE
WARM FRONT PIVOTS AND STALLS ALONG THE ALLEGHENY FRONT. WITH
STABLE CONDITIONS EXPECTED...CHANGED WX TYPE TO LGT RAIN AS
INSTABILITY SHOULD BE LOCATED WEST OF THE MTNS. FOCUS FOR PCPN
INTO MONDAY SHOULD REMAIN SOUTH OF PA OVER THE VA/NC IN CONJCT
WITH UPPER LEVEL WAVE AND MAX PWAT ANOM NR +2SD. HIGHEST POPS ARE
AGAIN OVER THE ERN 1/2 OF THE CWA AS SELY FLOW CONTS TO IMPINGE ON
SLOWLY RETREATING/DIFFUSE N-S WARM FRONT.

THE LG SCALE PATTERN IS FCST TO TURN DECIDEDLY MORE AMPLIFIED NEXT
WEEK...WITH THE MAIN SYNOPTIC FEATURE OF INTEREST BEING AN UPPER
LOW OVER THE NRN PLAINS/UPR MS VLY. H5 HGTS SHOULD RISE DOWNSTREAM
OF THIS SYSTEM...WITH CENTRAL PA LKLY BREAKING INTO THE WARM
SECTOR BY NEXT TUES AS THE PESKY WARM FRONT LIFTS NORTH INTO NEW
ENGLAND. THIS SHOULD AFFORD ONE OR TWO VERY WARM LATE SPRING DAYS
WITH HIGHS 75-80F. THERE IS A HIGH SPREAD BETWEEN THE GFS/ECMWF
CONCERNING THE POTENTIAL UPPER MIDWEST CUT-OFF. THEREFORE UTILIZED
A 50/50 BLEND OF THEIR RESPECTIVE MOS PRODUCTS FOR THE DAY 5-7
FCST.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
A SLOW-MOVING COLD FRONT WILL BE ACCOMPANIED BY A ROUND OF SHRA
AND PERHAPS EVEN AN ISOLATED TSRA EARLY THIS MORNING ACROSS THE
SOUTHERN PA AIRFIELDS. 11Z RADAR LOOP SUGGESTS AOO/JST/MDT WILL
LIKELY IMPROVE TO VFR BTWN 12Z-13Z....WHILE SHRA/REDUCED VSBYS
MAY LINGER AT LNS UNTIL 13Z-14Z.

BY LATE MORNING...THE FRONTAL BOUNDARY SHOULD SHIFT SOUTH OF
PA...RESULTING IN A HIGH DEGREE OF CONFIDENCE IN VFR CONDS ACROSS
THE ENTIRE STATE.

.OUTLOOK...

FRI-SUN...NO SIG WX EXPECTED.
MON...AM LOW CIGS POSSIBLE.
-- End Changed Discussion --

&&

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

&&

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