-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 221833
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
233 PM EDT WED MAY 22 2013

.SYNOPSIS...
-- Changed Discussion --
SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS WILL PRODUCE
LOCALLY STRONG WIND GUSTS OVER PORTIONS OF CENTRAL AND WESTERN PA
THROUGH EARLY TONIGHT. A COLD FRONT TRAILING THE LOW WILL CROSS
THE REGION ON THURSDAY...FOLLOWED BY A SECONDARY COLD FRONT ON
FRIDAY. A CANADIAN HIGH PRESSURE SYSTEM WILL USHER IN COOLER AND
DRIER AIR THAT WILL KEEP TEMPERATURES BELOW NORMAL FOR MEMORIAL
DAY WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
...UPDATED...
SVR WATCH #211 IN EFFECT UNTIL 1000 PM EDT FOR FAR WESTERN AND
NORTHERN COUNTIES...

EARLY AFTERNOON VISIBLE LOOP SHOWS STRATIFIED CU ACROSS
THE ALLEGHENY HIGHLANDS. LAPS SOUNDINGS STARTING TO DESTABLIZE
WITH SFC TEMPS APPROACHING CONVECTIVE TEMPS...AND UP TO 1400 J/KG
ABOVE THE LFC. UPSTREAM ACTIVITY OVER WV HAS CONTINUED TO BUT THIS
AREA HAS OVERALL BEEN WEAKENING AND SLIGHTLY SHRINKING IN COVERAGE
OVER THE PAST 2 HOURS.

MAIN FORECAST CONCERN IN THE NEAR TERM IS CONVECTIVE INITIATION
AND EVENTUAL INTENSITY THIS AFTERNOON AND TONIGHT. WITH THE AREA
IS ON THE WESTERN PERIPHERY OF AMPLIFIED UPPER RIDGE...AND
ADDITIONAL SHORTWAVES LIFTING THROUGH THE OHIO VALLEY... WESTERN
PA WILL BE IN AN INCREASINGLY CONVERGENT BOUNDARY LAYER FLOW AS
30-40 KT 850 MB JET NOSES INTO EASTERN OHIO. WITH CIN APPEARING TO
DISSIPATE ON SCHEDULE EXPECT TO SEE SCATTERED THUNDERSTORMS
DEVELOP AFTER 18Z OVER THE HIGHER TERRAIN AND WEST. WITH SPEED
SHEAR OF 25 TO 40 KTS AND MODERATE CAPE...SOME OF STORMS MAY BE
CAPABLE OF DAMAGING WIND GUSTS FROM BOWING LINE SEGMENTS AND
CLUSTERS INTO THIS EVENING. PEAK INTENSITY LKLY BTWN APPROX
21-03Z.

ANOTHER VERY WARM AND MUGGY AFTERNOON IS IN STORE WITH MAXES
REACHING WELL INTO THE 80S...~10F ABOVE NORMAL FOR THIS TIME OF
YEAR.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
-- Changed Discussion --
AREA REMAINS IN SPC SEE TEXT OUTLOOK THURSDAY. GENERALLY WEAK INSTABILITY
IS PROGGED IN THE PRE-FRONTAL WARM SECTOR...AND WILL BE DEPENDENT ON
THE EXTENT OF ANY PREFRONTAL WARMING/PARTIAL CLEARING. MODERATE
SHEAR PRESENT WHICH COULD PROMOTE A FEW STRONGER STORMS AHEAD OF
THE FRONT THU AFTERNOON...ESPECIALLY EAST.

CONTINUED EWD PROGRESSION OF THE EXPANSIVE ERN CONUS TROUGH IS
EXPECTED THIS PERIOD...HOWEVER IT MAY BE AT SLOWER PACE AS SOME
MODEL DATA IS TRENDING SLOWER/SHARPER BY THE END OF THE PERIOD.
THE ATTENDANT COLD FRONT WILL TRAVERSE THE AREA DURING THE AFTN
AND EVENING BEFORE EXITING THE ERN PART OF THE CWA AROUND
MIDNIGHT.

A LIGHTER...DEFORMATION PCPN AXIS IS PROGGED TO SET UP OVER THE
AREA THURS NIGHT INTO FRI AS A SHORTWAVE EMBEDDED IN THE LARGER-
SCALE TROUGH DIGS FROM THE GRT LKS TWD WV. THERE ARE SOME NOTABLE
MODEL DIFFS HEADING INTO DAY 3 SURROUNDING THE DEPTH AND SPEED OF
THE H5 TROUGH CROSSING THE MID-ATLC REGION. MORE ON THIS IN THE
LONG TERM SECTION.
-- End Changed Discussion --

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
THE 22/00Z NAM/GFS AND NOW ECWMF ARE SLOW AND SHARP WITH THE BASE
OF THE H5 TROUGH CROSSING THE MID-ATLC/NORTHEAST STATES FRI-SUN.
THESE DATA ALSO SHOW A CLOSED MID-LEVEL LOW ROTATING WITHIN THE
LARGER-SCALE TROUGH ACRS NRN VA FRI BEFORE PIVOTING NWD INTO NEW
ENGLAND THIS WEEKEND. WPC IS STILL LEANING AWAY FROM THE CLOSED
SOLUTION HOWEVER THEY HAVE GIVEN A LITTLE MORE WEIGHT TO THE OPRN
GFS/ECMWF TRENDS. THE IMPLICATIONS ARE IMPORTANT ESPECIALLY IN THE
DAY 4 PERIOD WHERE THE GUIDANCE SPREAD IS THE GREATEST/MOST
NOTICEABLE. TO COMBAT THIS...USED A INTERMEDIATE APPROACH TAKING A
BLEND OF THE 00Z ECMWF AND GFS...WITH SLIGHTLY MORE WEIGHTING
TOWARD THE GFS GIVEN WPC PREFERENCE TOWARD THE GEFS MEAN AND AN
OVERALL BETTER FIT TO THE OPRN/ENSEMBLE CONSENSUS.

EXPECT PLENTY OF CLOUDS AND LGT RAIN IN THE DEFORMATION ZONE ON
FRIDAY...WITH TEMPS FALLING BACK TO 55-65F. THE ECMWF SOLN WOULD
LINGER LIGHT RAIN OVER THE AREA /ESP IN THE EAST/ ON
SATURDAY...BUT DID NOT FULLY BUY-INTO THIS GIVEN HOW STRONG IT WAS
WITH THE CLOSED H5 LOW COMPARED TO THE OTHER GLOBAL GUIDANCE.
CANADIAN HIGH PRES EXTENDING SWD FROM NUNAVUT INTO THE UPPER
MIDWEST WILL SHIFT EWD ACRS THE GREAT LAKES AND EVENTUALLY TAKE UP
RESIDENCE OVER THE NORTHEAST BY MEMORIAL DAY. ENS DATA CONTINUES
TO SHOW NEGATIVE THERMAL/MOISTURE ANOMS SUPPORTING AN UNSEASONABLY
COOL AND DRY WEEKEND WITH THE POTENTIAL FOR FROST IN THE NRN AND
WRN MTNS SAT/SUN AM. THE GROWING SEASON IS UNDERWAY IN THIS AREA
/AS OF MAY 20TH/ AND THEREFORE WILL CONTINUE TO MENTION FROST IN
HWO. ELSEWHERE LOW TEMPS WILL BE CHILLY BY LATE-MAY STANDARDS...BUT
NOT QUITE COLD ENOUGH FOR FROST.

Q-STNRY/WARM FRONTAL ZONE INITIALLY CENTERED FROM IA-WV SHOULD
SLOWLY RETURN NWD THROUGH THE OH VLY EARLY NEXT WEEK. GFS/EC DIFFS
IN THE PATTERN EVOLUTION CONTINUE INTO THE END OF THE MEDIUM RANGE
PARTICULARLY UPSTREAM. IN GENERAL...THERE SHOULD BE A GRADUAL
EARLY-MID WEEK WARMING TREND WITH HTS RISING AS THE UPPER TROUGH
CONTINUES TO MOVE AWAY FROM THE NORTHEAST.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
SCT SHRA/TSRA AND MVFR CIGS THIS AFTERNOON AND EVENING FROM WEST TO
EAST. ISOLD IFR CIGS/VSBY AND STRONG WIND GUSTS TO 40 KTS MAY BE
POSSIBLE NEAR ANY THUNDERSTORMS INTO THIS EVENING. MVFR CIGS
SHOULD PREVAIL FOR A GOOD PART OF THE OVERNIGHT AND SOME FOG
IS POSSIBLE BETWEEN 10Z AND 13Z LOWER SUSQ.

COOLER AND BREEZY FOR FRIDAY INTO SUNDAY...AS A STRONG COLD
FRONT DROPS SE OF PA.

HO
.OUTLOOK...
THU...SCT THUNDERSTORM IMPACTS POSSIBLE...MAINLY IN THE PM.
FRI-MON...NO SIG WX EXPECTED.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...DEVOIR/STEINBUGL
LONG TERM...STEINBUGL
AVIATION...DEVOIR