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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 220342
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1142 PM EDT TUE MAY 21 2013

.SYNOPSIS...
A WARM AND HUMID SUMMERTIME AIR MASS WILL CONTINUE TO BRING WELL
ABOVE NORMAL TEMPERATURES TO CENTRAL PENNSYLVANIA THROUGH
WEDNESDAY. A COLD FRONT WILL CROSS THE REGION ON THURSDAY. A
SECOND FRONT WILL PUSH THROUGH ON FRIDAY AND USHER IN HIGH
PRESSURE FROM CENTRAL CANADA INTO THE NORTHEAST AND MID-ATLANTIC
STATES. THIS HIGH WILL BRING COOLER AND DRIER AIR TO THE AREA FOR
MEMORIAL DAY WEEKEND THAT COULD LAST RIGHT THROUGH MONDAY.

&&

.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
STORMS ONLY NOW TOUCHING NRN WARREN COUNTY AS BEST MOISTURE
CONVERGENCE STAYS ALONG THE NRN BORDER. TEMPS HAVE DROPPED OFF AT
THE SFC...BUT INSTABILITY STILL HIGH ALOFT. ISOLATED/SCT SHOWERS
AND STORMS MOVING THROUGH PIT AND CRW RIGHT NOW ARE ON TRACK TO
MOVE INTO THE SWRN COS BY MIDNIGHT AND COULD LAST INTO THE MIDDLE
OF THE NIGHT IF THEY HOLD TOGETHER. RUC HOLDS ONTO THE CELLS FOR
ANOTHER HOUR OR TWO...BUT THEN DISSIPATES THEM. THIS SEEMS
PLAUSIBLE SINCE THEY ARE NOT LOOKING VERY HEALTHY RIGHT NOW. THE
CLUSTER FROM WV SEEMS TO HAVE MORE ORGANIZATION AND WILL KEEP ON
WITH LOW CHC POPS FOR THE SW INTO THE WEE HOURS. THE RUC AND HRRR
ARE AT ODDS WITH EACH OTHER WRT THE CONVECTION ALONG THE NY
BORDER. RUC CONTINUES IT THROUGH MUCH OF THE NIGHT...BUT HRRR
BREAKS IT APART. WILL ALSO HOLD THE LINE WITH CHC POPS FOR THE NRN
TIER OF COUNTIES SEEING NO PREPONDERANCE OF GUIDANCE THAT IS
AGAINST SOME MEASURE OF ELEVATED INSTABILITY AND POTENTIAL FOR
CONVECTION THERE. WILL KEEP MENTIONS OF PATCHY FOG AS WELL..WITH
MAINLY CLEAR SKIES RIGHT NOW AND HIGH DEWPOINTS. CLOUDS FROM
UPSTREAM WILL PROBABLY LEVEL TEMPS OFF IN A FEW HOURS...BUT FOG
MAY YET CREEP INTO THE VALLEYS.

&&

.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
A S/W MOVG EWD ACRS THE UPPER MS VLY INVOF IA WILL PHASE WITH A
CANADIAN UPPER LOW/TROUGH DROPPING SWD ACRS HUDSON/JAMES BAY DURING
THE DAY WEDNESDAY...REACHING THE MIDWEST BY F48. AT THE SFC...A
COLD FRONT PUSHING EWD THRU THE OH VLY WILL BE THE MAIN FOCUS FOR
TSTM DEVELOPMENT/SVR POTENTIAL THIS PERIOD.

AM CLOUDS WITH SOME SPOTTY SHOWERS AND AREAS OF 1-2SM FIG WILL
COMBINE WITH WEAK RIDGING WITHIN THE PREDOMINANT SWRLY FLOW
ALOFT...TO LIMIT DIURNAL HEATING TO SOME EXTENT ACRS THE DAY 2 SPC
SLGT RISK AREA - WHICH COVERS NEARLY ALL OF THE CWA WITH THE
EXCEPTION OF THE FAR SERN ZONES. ALTHOUGH LOW TO MID LEVEL WINDS
WILL BE STRONGEST ACROSS THE NW HALF OF PENN...LATEST SREF AND SHORT
RANGE MODEL GUIDANCE PAINTS THE GREATEST PROBABILITY FOR CAPE
GREATER THAN 1200 J/KG ACROSS THE LOWER SUSQ VALLEY LATE WEDNESDAY
AFTERNOON.

DESPITE THE TEMPERED DESTABILIZATION...EXPECT AN AFTN INCREASE IN
TSTM COVERAGE /WITH LOWER CLOUD BASES COMPARED TO TUESDAY`S/ ALONG
WITH SOME PICK-UP IN INTENSITY AS BELT OF STRONGER FLOW ALOFT SHIFTS
EWD AHEAD OF THE MID-UPPER TROUGH. BANDS OF TSTMS CAPABLE OF
PRODUCING DMGG WNDS/MARGINAL HAIL WILL BE POSSIBLE AND THUS WILL
CONTINUE TO HIGHLIGHT AN ELEVATED SVR WX THREAT IN THE HWO FOR
WEDNESDAY. BETTER FORCING PORTENDS HIGHER POPS RANGING FROM THE
MED-HIGH CHC RANGE IN THE SE TO LOW LKLYS IN THE NW. SHOWERS/TSTMS
MAY PERSIST AFTER DARK INTO WED NGT.

MAX TEMPS WILL LIKELY BE 3-5F LOWER THAN TUESDAY...BUT STILL AROUND
12F ABOVE NORMAL.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE UPPER RIDGE WILL BREAK DOWN AS A TROUGH DEEPENS INTO THE GREAT
LAKES REGION BY THURSDAY AFTERNOON. THIS WILL CORRESPOND WITH A
FRONT MOVING THROUGH THE NORTHEAST THURSDAY. TIMING FOR THIS FRONT
IS STILL VARYING BUT CURRENT EC BRINGS THE FRONT THROUGH MIDDAY
THURSDAY. COUPLE THIS FRONT WITH DAYTIME HEATING AND STRONG
SOUTHWEST FLOW...THURSDAY COULD BE THE BEST DAY FOR DAYTIME
CONVECTION THIS WEEK. BOTH THE OPERATIONAL GFS AND THE ECMWF CONTINUE
TO OUTPUT THE POSSIBILITY OF A LOW LEVEL JET THURSDAY
AFTERNOON...WHICH WITH 35-40KTS OF DEEP-LAYER SHEAR WILL ONLY
INCREASE PROBABILITIES FOR PRECIPITATION THURSDAY AFTERNOON. THIS
EASTERN NORTH AMERICA TROUGH AXIS EXTENDING FROM JAMES BAY SWD
THRU THE GRT LKS/MID- SOUTH TO THE CENTRAL GULF COAST WILL PUSH
SLOWLY EWD AND SHOULD REACH THE EAST COAST BY 00Z SAT. THIS WILL
ALLOW FOR PERSISTENT INSTABILITY OVER THE AREA THROUGH THE END OF
THE WEEK...WITH COLD NORTHWESTERLY FLOW BEHIND THE FRONT. THE
GUIDANCE IS SHOWING SOME NOTABLE DIFFS WITH THE H5 SYSTEM. THE
NAM/GFS/GEFS ARE SLOWER AND SHARPER WITH TROUGH AS IT CROSSES THE
OH VLY INTO THE MID- ATLC. THE 00Z GFS EVEN CLOSES OFF THE H5 LOW
OVER NRN VA FRI EVE. THE LAST TWO RUNS OF THE CMC HAVE BEEN TRYING
TO GENERATE A TROPICAL CYCLONE- LIKE SYSTEM NEAR THE OUTER BANKS.
THE KNOWN SLOW/TROPICAL BIASES OF THE NAM/CMC AND STRONG/CLOSED
SOLN OF THE GFS LEADS TO A UKMET/ECMWF PREFERRED SOLN WHICH FAVORS
MORE EWD PROGRESSION WITH THE TROUGH AND ITS ASSOCD COLD FRONT.

BEHIND THE DEPARTING COLD FRONT...A STG AND LARGE ANTICYCLONE
SHOULD DOMINATE PATTERN IN THE FRI-MON TIMEFRAME...BUILDING SEWD
FROM NUNAVUT CANADA ACROSS THE GRT LKS INTO THE NORTHEAST. AN
UNSEASONABLY COLD/DRY AIRMASS WILL ACCOMPANY THE HIGH RESULTING IN
BELOW NORMAL TEMPS FOR MEMORIAL DAY WEEKEND. ECENS MOS DATA SHOWS
TEMPS ON FRI/SAT STRUGGLING TO CRACK THE 60F MARK LOCALLY...WITH
SEVERAL OPPORTUNITIES FOR A LATE-SEASON FROST OVER THE NRN MTNS
SAT/SUN/MON MORNINGS. HOWEVER CURRENT LOW TEMPS REMAIN ABOVE 40
FOR MOST OF THE REGION WITH THE EXCEPTION BEING ALONG THE NEW YORK
BORDER. WINDS SHOULD REMAIN GUSTY SATURDAY MORNING. THE BETTER
CHANCE FOR FROST WILL BE SUNDAY MORNING...TEMPERATURES WILL BE
SLIGHTLY WARMER BUT THE WINDS SHOULD BE LIGHT TO CALM. THERE
SHOULD BE A MODERATION INTO THE MIDDLE OF NEXT WEEK WITH TEMPS
GETTING BACK TO NEAR NORMAL AROUND 5/28.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
NOT A LOT OF CHANGE. STILL AN ISOLATED STORM POSSIBLE NEAR
THE NY BORDER OVERNIGHT. ALSO MAYBE A BRIEF SHOWER CLOSE
TO JST...LEFT OUT THE FCST FOR NOW.

EARLIER DISCUSSION BELOW.

MAIN FRONT AND ACTION ACROSS NY STATE...TOOK MENTION OF SHOWERS
AND STORMS OUT OF ALL SITES BUT BFD. LEFT VCSH IN BFD UNTIL 03Z.

SOME FOG LATER...BASED MAINLY ON WHAT WENT ON LAST NIGHT.

NOT SEEING MUCH DIFFERENCE FOR WED...VERY SIMILAR TO TODAY...
WILL BE IN THE WARM SECTOR...WITH NOT MUCH GOING ON.

MORE IN THE WAY OF WIDESPREAD SHOWERS AND STORMS LATER THU
INTO THU NIGHT. COULD BY BUSY ACROSS THE FAR SE THU NIGHT...
IF A WAVE FORMS ON THE FRONT.

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...LAMBERT/STEINBUGL
NEAR TERM...DANGELO
SHORT TERM...LAMBERT/STEINBUGL
LONG TERM...CERU/STEINBUGL
AVIATION...LAMBERT/MARTIN