Area Forecast Discussion
Issued by NWS State College, PA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KCTP 071440
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1040 AM EDT TUE JUL 7 2015

.SYNOPSIS...
A WEAKENING UPPER LOW WILL TRACK EAST OF THE REGION
THIS MORNING. A WEAK RIDGE WILL BRING VERY WARM AND HUMID CONDITIONS
TO THE REGION TODAY. A COLD FRONT WILL APPROACH TONIGHT...THEN STALL
OUT ALONG...OR JUST SOUTH OF THE MASON DIXON LINE FOR THE MID TO
LATE WEEK PERIOD. A FEW WAVES OF LOW PRESSURE WILL RIPPLE EAST ALONG
THIS BOUNDARY BRINGING THE LIKELIHOOD FOR SHOWERS AND THUNDERSTORMS
WEDNESDAY AFTERNOON AND EVENING...AND AGAIN ON THURSDAY. HIGH
PRESSURE WILL BUILD IN FOR FRIDAY AND BRING SLIGHTLY COOLER AND
NOTABLY LESS HUMID WEATHER WITH LITTLE CHANCE FOR RAIN.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS AN UPPER LEVEL TROUGH EXITS THE REGION EARLY THIS AFTERNOON
EXPECT SOME CLEARING FROM WEST TO EAST AND A MIX OF CLOUDS AND
SUN FOR THE REST OF THE DAY. HIGH TEMPERATURES TODAY WILL TOP OUT
A FEW DEGREES ABOVE NORMAL THANKS TO DEEP WEST /SOUTHWEST FLOW AND
INCREASING SUNSHINE.

MOST OF THE AREA WILL REMAIN DRY THROUGH THE EVENING AS WE
EXPERIENCE A PERIOD OF WIDESPREAD SUBSIDENCE. THIS PERIOD IS
SHORTLIVED AS A COLD FRONT APPROACHES NORTHWEST PENNSYLVANIA THIS
EVENING. SOME STRONG MULTICELL THUNDERSTORM CLUSTER ARE LIKELY TO
FORM AS THE FRONT CROSSES INTO THE NORTHWEST ZONES THIS EVENING.

**SOME CONCERN THAT A WEAK LEE TROUGH OVER...AND TO THE EAST OF
 THE SUSQ VALLEY WITH A SLIGHT WEAKNESS IN THE MID LEVEL CAP
 /NOTED BY A RIBBON OF 700 MB TEMPS OF AROUND 6C/ COUPLED WITH THE
 CLOSE PROXIMITY OF THE EXIT REGION OF AN UPPER LEVEL JETLET COULD
 SPARK ISOLATED-SCT COVERAGE OF PULSE SHRA/TSRA FOR A FEW HOURS
 DURING THE MID TO LATE AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
SFC COLD FRONT SLIDES SLOWLY TO THE SOUTHEAST ACROSS THE
COMMONWEALTH TONIGHT THROUGH WED MORNING...BEFORE STALLING OUT
NEAR...OR JUST TO THE SOUTH OF THE MASON-DIXON LINE.

MAIN FCST PROBLEM/CHALLENGE FOR THE UPCOMING SHIFTS WILL BE TO
TRY TO PIN DOWN /VIA SOME SEMBLANCE OF MODEL CONSENSUS/ THE
LOCATION AND TIMING OF CONVECTIVE FEATURES/AREAS OF LOW PRESSURE
THAT WILL FORM AND RIDE EAST ALONG THIS BOUNDARY WEDNESDAY INTO
THURSDAY.

CURRENTLY...A GEFS/NAM/SREF BLEND POINT TWD THE BEST CHC FOR RAIN
WITH EMBEDDED TSRA FOCUSED ACROSS THE SOUTHERN THIRD TO HALF OF
PENN WEDNESDAY...WHERE PWAT WILL STAY AOA 2.0 INCHES. THE SHARP
GRADIENT TO MUCH LOWER PWAT /AOB 0.75 OF AN INCH/ WILL STAY NEAR
OR JUST TO THE NORTH OF THE PENN/NEW YORK BORDER WHERE CHCS FOR
RAIN WILL BE QUITE LOW WEDNESDAY AND MOST OF WED NIGHT.

MAX TEMPS WEDNESDAY COULD EASILY TURN OUT TO BE SEVERAL DEG F OR
MORE BELOW CURRENT FCST VALUES DEPENDING ON THE TIMING AND EXTENT
OF CONVECTION ACROSS THE CENTRAL AND SOUTH. CURRENT TEMP FCST
BUSTING ON THE LOW SIDE FOR WEDNESDAY`S HIGH IS A VERY LOW
PROBABILITY. WILL BE ADJUSTING THESE TEMPS WITH 03Z SREF AND 06Z
OP GUIDANCE WHERE NEEDED.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE LINGERING QUASI-STATIONARY FRONTAL ZONE EXTENDING FROM THE
MID ATLANTIC COAST WWD INTO THE OHIO VALLEY IS EXPECTED TO REMAIN
A FOCUS FOR PCPN ON DAY 3/THURS. THERE IS REASONABLY GOOD MODEL
AGREEMENT IN A CONVECTIVELY ENHANCED PERTURBATION/SFC WAVE
EMERGING FROM THE SRN PLAINS AND PROGRESSING EWD AROUND THE
PERIPHERY OF A SUBTROPICAL RIDGE OVER THE SOUTHEAST STATES. THE
GLOBAL MODELS TEND TO HAVE A NORTHERN BIAS WITH QPF AXES ASSOCD
WITH THESE MESO FEATURES...AND THEREFORE FOLLOWED WPC LEAD WITH
CLUE FROM THE HI-RES MODELS IN SHIFTING MAX POPS SWD OF CONSENSUS.
THERE IS THE POTENTIAL FOR THIS FEATURE TO MAINTAIN INTENSITY OR
RE-INTENSIFY AS IT REACHES CENTRAL PA THURSDAY AFTERNOON..IN WHICH
CASE IT WOULD BE ACCOMPANIED BY SEVERE WX AND HEAVY RAINFALL
RISK. LATER FORECASTS SHOULD BE ABLE TO PROVIDE GREATER VISIBILITY
AND INCREASED CONFIDENCE IN THE EVOLUTION AND POTENTIAL IMPACTS
ASSOCD WITH THIS SYSTEM.

THE MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE REMAINS CONSISTENT
IN ITS PROJECTION THAT THE FLOW ALOFT WILL STEADILY EVOLVE TOWARD
AN AMPLIFIED TROUGH/RIDGE/TROUGH PATTERN FROM WEST TO EAST ACROSS
THE LOWER 48. THIS SHOULD OCCUR BY WAY OF NRN PAC ENERGY FEEDING
INTO A TROUGH ALONG THE WEST COAST...A STRENGTHENING UPPER RIDGE
THAT RETROGRADES WWD FROM THE SOUTHEAST INTO THE PLAINS EVENTUALLY
EXPANDING NWD OVER THE ROCKIES INTO WRN CANADA...AND DOWNSTREAM
TROUGHING FROM THE BUILDING RIDGE OVER THE EAST EXTENDING SWD FROM
HUDSON BY VORTEX.

A 24-48HR PERIOD OF DRY WEATHER...WHICH HAS BEEN QUITE ELUSIVE AS
OF LATE...COULD BE IN STORE FOR THE AREA BY THE END OF THE WEEK
AS WEAK RIDGING FOLLOWS IN THE WAKE OF THE D3 CONVECTIVE LOW. THE
PLACEMENT OF PIVOTING FRONTAL BOUNDARY AND ASSOCIATED MSTR/PW AXIS
WILL BE CRUCIAL FOR DETERMINING PCPN RISK INTO THE WEEKEND...WITH
THE LATEST MODEL CONSENSUS KEEPING MOST OF THE ACTIVITY TO THE NW
OR SW OF CENTRAL PA. THE OTHER FACTOR WILL BE WHAT HAPPENS TO
ENERGY EJECTING FROM UPPER LOW MOVING ONSHORE CA IN THE SHORT
RANGE. THERE IS REASONABLE AGREEMENT IN PRINCIPLE THAT THIS
ENERGY SHOULD ROUND THE BUILDING ROCKIES/HIGH PLAINS RIDGE AND
THEN HELP TO CARVE OUT THE DEVELOPING ERN TROUGH DOWNSTREAM.
HOWEVER SOLUTIONS HAVE NOT LOCKED ONTO HOW SHEARED THE ENERGY WILL
BECOME...WHICH ALONG WITH A FEW ADDITIONAL FACTORS LEADS TO
DIFFERENCES IN THE DEPTH OF THE TROUGH AND TIMING OF NEXT PCPN
OPPORTUNITY.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...

CURRENT MVFR CONDITIONS ARE EXPECTED TO IMPROVE THIS AFTERNOON AS
THE LOW CLOUDS BURN OFF. AS A COLD FRONT APPROACHES THIS EVENING
THUNDERSTORMS ARE LIKELY TO FORM AND IMPACT BFD TONIGHT WITH MVFR
CONDITIONS.

THE COLD FRONT WILL PUSH SLOWLY SEWD ACROSS THE AIRSPACE
OVERNIGHT INTO WEDNESDAY BEFORE STALLING OUT WEST-TO-EAST ALONG
THE OH RIVER AND MASON DIXON LINE. WAVES OF LOW PRESSURE WILL MOVE
ALONG THE FRONT AND BRING PERIODS OF SHOWERS/TSTMS AND REDUCED
CONDITIONS LATER WEDNESDAY INTO THURSDAY.

OUTLOOK...

FRI-SAT...MAINLY VFR. CHC OF SHOWERS/TSTMS SW 1/3 OF AIRSPACE.

&&

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

&&

$$
SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...LA CORTE/LAMBERT/KEARNS
SHORT TERM...LAMBERT
LONG TERM...STEINBUGL
AVIATION...LA CORTE/STEINBUGL



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.