Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 211614
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1214 PM EDT SUN SEP 21 2014

.SYNOPSIS...
A COLD FRONT WILL PASS THROUGH LATER TODAY. A LARGE AREA OF HIGH
PRESSURE WILL BUILD OUT OF CENTRAL CANADA AND PROVIDE GENERALLY
FAIR AND COOL WEATHER FOR MOST IF NOT ALL OF THIS WEEK.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
LOW STRATUS HAS DISSIPATED ACROSS PRACTICALLY ALL OF OUR SE ZONES
EXCEPT FOR THE IMMEDIATE KMUI VCNTY. EXPECT A PLEASANTLY
WARM/MOSTLY SUNNY LATE SEPT AFTERNOON ACROSS MUCH OF THE MID AND
LOWER SUSQ VALLEY FOLLOWED BY INCREASING MID LEVEL CLOUDS
IN THE 19-21Z PERIOD.

WEAKENING AREA OF SHOWERS WITHIN AN EXTENSIVE SHIELD OF MID LEVEL
CLOUDS WILL DRIFT ACROSS THE CENTRAL RIDGE AND VALLEY REGION EARLY
THIS AFTERNOON...AND LIKELY FIZZLE OUT AS THEY APPROACH THE SUSQ
VALLEY...WHERE WARMER TEMPS ALOFT AND RIDGING AT THE SFC AND ALOFT
WAS PRESENT.

ACROSS THE WESTERN THIRD OF THE STATE...INCREASING UPPER
DIFFLUENCE AND POSITIVE LLVL THETA-E ADVECTION WILL LEAD TO ONE OR
TWO FAST-MOVING LINES OF SHOWERS DURING THE MID TO LATE AFTERNOON
HOURS.

AS THE AFOREMENTIONED.../FIRST/ AREA OF MID LEVEL CLOUDS AND
SHOWERS MOVES TO THE SUSQ VALLEY LATE THIS AFTERNOON. PERIODS OF
SUNSHINE AND HIGHER PWAT AIR OF 1 TO 1.5 INCHES IN THE WAKE OF
THIS CLOUD AREA WILL BOOST SFC-BASED CAPES TO 1000-1500 J/KG
ACROSS THE CENTRAL AND WRN PARTS OF THE CWA...HELPING TO
STRENGTHEN A SECOND LINE OF CONVECTION INTO SOME LOCALLY
GUSTY...LOW-TOPPED TSRA.

THE LATEST...14Z HRRR FOCUSES THE BULK OF THE CONVECTION /AND
ASSOCIATED HIGHER QPF AMOUNTS/ ACROSS THE CENTRAL AND NRN MTNS OF
PENN THROUGH 00Z MONDAY. SHOWERS AND PERHAPS A FEW TSRA ENTER THE
MID/LOWER SUSQ VALLEY 22-23Z AND CONTINUE INTO EARLY THIS EVENING.

THE REAL COLD FRONT/DRY AIR SEEMS LIKE IT WILL BE PASSING THROUGH
IN THE AFTN WEST...LATE AFTN CENTRAL AND AROUND SUNSET OR JUST
AFTER IN THE EAST. THE BEST LIFT WILL BE ALONG THE FRONT - SO WILL
ALSO HOLD THE MENTION OF THUNDER INTO THE EVENING IN THE EAST.
TEMPS HAVE A CHANCE TO GET ABOVE 80F AGAIN IN THE SE - BUT EARLY
LOW CLOUDS AND SOME FOG COULD BUST THAT FORECAST. THE CLOUDS ARE
SHALLOW THOUGH...AND WINDS WILL BE INCREASING FROM THE SSW...WHICH
IS A NORMALLY-DRYING INFLUENCE - ESP IN THE EASTERN CWA. SPC STILL
MENTIONS THE REGION IN SEE TEXT FOR DAY 1 OUTLOOK OF SEVERE WX.
PLUSES FOR ISOLD SVR GUSTS ARE THE WELL-ALIGNED WINDS AND GENERAL
INCREASE IN SPEED SHEAR THROUGH THE LOWEST 20KFT. KNOCKS AGAINST
SVR WILL BE THE OVERALL LACK OF MOISTURE AND INSTABILITY AND THE
LACK OF 50KT WINDS BELOW 15KFT. WILL STILL MENTION THE POSS OF
ISOLD SVR GUSTS IN THE HWO...BUT CONFIDENCE CONTINUES TO BE
MODERATE TO HIGH FOR A MINIMAL OR EVEN NIL SVR THREAT TODAY.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM MONDAY/...
AFTER THE FRONT PUSHES THROUGH...THE WINDS OUT OF THE WNW WILL
LEAD TO A TYPICAL POST-FRONTAL SET-UP...AND THE RESIDUAL AND LAKE
MOISTURE ASCENDING THE MTNS AND COLD AIR MOVING IN ALOFT WILL
GENERATE INSTABILITY AND SCT SHRA FOR THE NWRN THIRD OF THE AREA
TONIGHT AND PERHAPS THROUGH MID MORNING ON MONDAY. 8H TEMPS DO DIP
INTO THE LOWER SINGLE DIGITS MONDAY AND MAXES MAY BE LIMITED TO
THE M50S IN THE MTNS BUT STILL GET CLOSE TO 70F IN THE DOWNSLOPE-
WARMED SOUTHEASTERN PIEDMONT.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
HIGH PRESSURE BUILDS IN AS THE LONG TERM IS BEGINNING AND IT SORT
OF PARKS ITSELF OVER NEW YORK AND NEW ENGLAND WITH +2 TO +3 SIGMA
ABOVE NORMAL MSLP ANOMALIES BY WEDNESDAY-THURSDAY. THE MODELS SEEM
TO BE IN FAIR AGREEMENT SHOWING A BLOCKING 500 HPA ANTICYCLONE TO
THE NORTHWEST AS A MASSIVE 500 HPA POSITIVE HEIGHT ANOMALY OF +2
TO +3 SIGMA DEVELOPS OVER CENTRAL CANADA BY THURSDAY AND INTO
FRIDAY.

THE MODELS AND EFS DO WELL FORECASTING ANTICYCLONES SO THERE SEEMS
TO BE MORE OF A CONSENSUS. ON THE FAIR WEATHER FORECAST NEXT
WEEK. EXPECT DIURNAL VALLEY FOG AND LOW CLOUDS LIKELY TO AFFECT
THE REGION EACH MORNING ONCE THE BIG HIGH TAKES HOLD....AND
CONTINUING DAILY INTO NEXT WEEKEND. THAT MASSIVE HIGH SHOULD
CONTINUE THE DRY FAIR WEATHER THROUGH NEXT WEEKEND. TEMPERATURES
ON MONDAY AND MONDAY EVENING WILL BE BELOW NORMAL...HOWEVER
OUTSIDE OF MONDAY...TEMPERATURES THERE WILL BE A PERIOD OF NEAR
NORMAL TEMPERATURES.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
LOW CLOUDS AND FOG THAT RESULTED IN IFR/LIFR ACROSS THE EASTERN
AIRFIELDS EARLIER THIS MORNING...WILL GRADUALLY MIX OUT AND DISSOLVE
THROUGH 16Z.

CLOUDS DECK ASSOCIATED WITH FIRST LINE OR TWO OF SHOWERS WERE
MAINLY IN THE MVFR CATEGORY...BUT CAUSING SOME BRIEF IFR
CIGS/VSBYS IN THE NORTHWEST. THESE TRANSIENT... BUT ADVERSE
CONDITIONS WILL SPREAD ACROSS THE ALLEGHENY FRONT AROUND
16Z...BEFORE REACHING THE SUSQ VALLEY IN A LIKELY WEAKENED STATE.
A SECOND AND PROBABLY STRONGER LINE OF SHOWERS AND TSRA ALONG THE
TRUE COLD FRONT WILL WILL MOVE ACROSS THE WESTERN MTNS THROUGH 20Z
BEFORE REGION THE CENTRAL ZONES AFTER 21Z.

ELSEWHERE...MAINLY VFR WILL DEVELOP/PERSIST THROUGH THE EARLY
AFTERNOON...AND STAY INTACT ACROSS THE LOWER SUSQ VALLEY PERHAPS
UNTIL DUSK.

THE COLD FRONT WILL ENCROACH ON THE REGION TODAY...LIKELY
REACHING KBFD AROUND 18Z...KUNV AROUND 21Z...AND THE SOUTHEAST
AIRFIELDS AROUND 00Z. PRIOR TO THE ACTUAL FRONT...A FEW PRE-
FRONTAL BAND/S/ OF SHOWERS AND EMBEDDED TSRA EXPECTED.

EXPECTING SOME POST FRONTAL SHOWERS TO POTENTIALLY LINGER IN THE
NORTHWEST SUNDAY. HOWEVER...IN GENERAL...AFTER FRONTAL
PASSAGE...VFR CONDITIONS SHOULD PREVAIL INTO MID/LATE WEEK WITH
THE EXCEPTION OF SOME PATCHY MORNING FOG.

OUTLOOK...
MON...AM LOW CIGS POSS W MTNS.
TUE...AM FOG POSS W MTNS.
WED...AM FOG POSS...MAINLY NORTHERN PA.
THU...PATCHY AM FOG POSSIBLE.

&&

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

&&

$$
SYNOPSIS...DANGELO/LAMBERT
NEAR TERM...DANGELO/LAMBERT
SHORT TERM...DANGELO
LONG TERM...GRUMM/CERU
AVIATION...JUNG


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