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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 111616
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1116 AM EST WED DEC 11 2013

.SYNOPSIS...
-- Changed Discussion --
A COLD CYCLONIC FLOW OVER THE GREAT LAKES WILL MAINTAIN BELOW
NORMAL TEMPERATURES THROUGH THE END OF THE WEEK...WITH LAKE
EFFECT SNOWS FOCUSED OVER FAR NORTHWEST PENNSYLVANIA IN THE
PERENNIAL SNOWBELT REGION. A PAIR OF WEAK CLIPPER SYSTEMS PASSING
TO THE NORTH WILL REINFORCE THE COLD AIR. FOR MOST OF THE AREA...THE
NEXT FEW DAYS WILL BE COLD AND DRY. THE ACTIVE EARLY SEASON WINTER
PATTERN LOOKS TO RESUME WITH ANOTHER STORM SYSTEM LIKELY IMPACTING
THE AREA SATURDAY INTO SATURDAY NIGHT...FOLLOWED BY MORE COLD AND
BRISK CONDITIONS INTO EARLY NEXT WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
SFC OBS/SAT IMAGERY SHOWS MOSTLY SUNNY SKIES ACROSS CENTRAL
PA. EVEN WITH INCREASING SWRLY SFC WINDS AFTERNOON TEMPS TODAY
WILL WIND UP BEING A COUPLE DEGREES COLDER THAN YESTERDAY AFTER
MINS BOTTOMED OUT THIS MORNING IN THE TEENS AND SINGLE DIGITS.

ONLY PCPN AT THIS POINT IS INTERMITTENTLY SNOW SHOWERS ACROSS THE
FAR NW...BFD. WATER VAPOR SAT IMAGERY SHOWS WEAK SHORTWAVE
CROSSING THE GREAT LAKES AND INTO OHIO VALLEY. THIS WILL HELP
REDIRECT LOW LEVEL FLOW INTO SOMEWHAT MORE FAVORABLE FLOW FOR LE
SNOW INTO NW PA...AT LEAST EXPANDING COVERAGE OF LIGHT SNOW
SHOWERS INTO THE AFTERNOON HOURS. LES ADVISORY REMAINS IN EFFECT
FOR WARREN CO...WITH THE BULK OF ACCUMS EXPECTED BTWN 18-06Z BASED
ON THE LATEST RUN OF THE MEAN HIRES CONSENSUS SHORT-RANGE MODEL.

FOR MOST AREAS...IT WILL JUST BE BRISK AND COLD WITH DAYTIME MAX
TEMP DEPARTURES AVERAGING 15 DEGREES BELOW EARLY DECEMBER CLIMO.
WILL CONTINUE TO HIGHLIGHT NEAR TO BELOW ZERO WIND CHILLS IN THE
HWO FOR THE EARLY MORNING AND NIGHTTIME HOURS.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A SERIES OF NRN STREAM IMPULSES ARE FCST TO RACE EWD ACRS THE GRT
LKS AROUND THE BASE OF LARGE POLAR VORTEX OVER HUDSON BAY. THE
VORTEX SHOULD GRADUALLY SHIFT TO THE NORTH AND EAST BY THE END OF
THE PERIOD AND ALLOW FOR AT LEAST MODEST 500MB HGT RISES AND
SLIGHTLY MODERATING TEMPS AS THE 1000-500DM THICKNESSES GRADUALLY
INCREASE. THERE IS SOME UNCERTAINTY FOCUSED ON THE UPSTREAM SIDE
OF THE TROUGH WITH PLACEMENT DIFFS OVER ONTARIO...WHICH APPEARS TO
IMPACT THE LOW-LEVEL TEMP GRADIENT AND MAGNITUDE OF HIGH PRES CELL
MOVING OVER MONTREAL CANADA BY 12Z SAT. THIS FEATURE LOOKS TO PLAY
A ROLE IN ANOTHER WINTER MIXED PCPN EVENT INTO THE WEEKEND.

IN GENERAL...EXPECT THE LAKE EFFECT SNOW MECHANISM TO FADE INTO
DAY 3 WITH THE FOCUS SHIFTING TO DEVELOPING LOW PRES/INVERTED
TROUGH OVER THE TN VLY AND ASSOCD WAA/OVERRUNNING PCPN POSSIBLY
REACHING THE AREA BY EARLY SATURDAY MORNING. DAY 2/THU LOOKS LIKE
THE COLDEST DAY BASED ON CONSENSUS GUIDANCE WITH HIGHS 20 DEGREES
BELOW NORMAL. WIND CHILLS WILL REMAIN A CONCERN AND WILL CONTINUE
TO HIGHLIGHT IN THE HWO. SUB-ZERO APPARENT TEMPS SEEM LKLY DURING
THE NIGHTTIME AND EARLY MORNING HOURS ACRS THE W-CNTRL MTNS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
THE ACTIVE EARLY/COLD-SEASON PATTERN ACRS THE ERN CONUS WILL
RESUME THIS WEEKEND...LIKELY BRING MORE WINTER WEATHER TO THE AREA
FROM SATURDAY INTO EARLY SUNDAY. A CONSENSUS OF THE 11/00Z
GFS/CMC/ECMWF DETERMINISTIC MODEL DATA AND THEIR RESPECTIVE
ENSEMBLE MEANS /INCLUDING THE NAEFS/ SHOW THE MOST LIKELY OUTCOME
BEING A TRANSFER OF SFC LOW PRESSURE FROM THE OHIO VALLEY TO THE
MID ATLANTIC COAST BY SATURDAY NIGHT...WITH SUBSEQUENT DEEPENING
OF THE COASTAL LOW AS AN ARCTIC VORTEX PLUNGES INTO THE GREAT
LAKES ON SUNDAY.

THE MOST CRITICAL REGION IN TERMS OF MODEL SPREAD INITIALLY LIES
UPSTREAM OVER THE MIDWEST WHERE SEVERAL SHORTWAVES ARE EXPECTED TO
CONVERGE...AND THEN TRANSLATES EWD TO THE COAST AS THE MILLER-B
CYCLOGENESIS PROCESS RUNS ITS COURSE. THE DISJOINTED/COMPLEX
NATURE OF THE SPLIT FLOW PATTERN EXPECTED TO EVOLVE AND MERGE/PHASE
OVER THE EASTERN STATES MAKES FORECASTING SPECIFIC HAZARDS SOMEWHAT
OF A LOW CONFIDENCE VENTURE. THE INTEGRITY OF THE RETREATING? COLD
AIR BANKED ALONG/E OF THE APPALACHIANS WILL UNDOUBTEDLY BE CRUCIAL
FOR P-TYPES. THE TRANSFER OF ENERGY TO THE COAST/DUMBELLING OF
MID-LVL SHORTWAVES WILL ULTIMATELY DICTATE WHERE MOISTURE WILL
CONVERGE AND WHERE DRY SLOTS WILL BE FORCED. LOTS OF VARIABLES TO
CONSIDER.

WHILE THERE REMAINS BETTER THAN AVERAGE CONVERGENCE OF SOLUTIONS
ON A STORM SYSTEM WHICH SUPPORTS GOING AOA MEDIUM RANGE CONSENSUS
MOS POPS...AS USUAL WITH SYSTEMS SEVERAL DAYS OUT...THE DETAILS
WILL NEED SORTING-OUT AT SHORTER RANGES TO DETERMINE SENSIBLE WX
IMPACTS. AT THIS POINT...MODEL THERMAL PROFILES INDICATE THAT
PRECIPITATION ARRIVING EARLY SATURDAY SHOULD START AS SNOW.
HOWEVER FROM THIS POINT ON PTYPES BECOME INCREASINGLY PROBLEMATIC
WITH THE OPRN ECMWF TRENDING SLOWER VS. THE OTHER GLOBAL GUIDANCE
WITH ITS SFC LOW TRACK...AND VERY AGGRESSIVE IN LOCKING IN VERY
COLD AIR ESPECIALLY NEAR THE SFC. MEANWHILE THE 00/06Z GFS AND 00Z
GEFS MEAN ARE MORE BULLISH ON ALLOWING WARMER AIR TO REACH AT
LEAST THE SRN HALF OF THE CWA SAT NGT...PERHAPS SUGGESTING PTYPE
TRANSITION TO PL/FZRA. FOR NOW WILL CONTINUE TO BROADBRUSH
MULTIPLE PTYPES IN AN ATTEMPT TO INDICATE A WINTRY MIX...HOWEVER
IF THIS CYCLES ECMWF VERIFIES IT WOULD BE AN ALL SNOW EVENT. TO
ADD A FINAL LAYER OF UNCERTAINTY TO THE FCST...EXPERIENCE AND
LOCAL RESEARCH SUGGESTS WIDE RANGE OF OUTCOMES IS POSSIBLE IN
MILLER-B SITUATIONS. I PERSONALLY CAN RECALL A LARGE VARIATION
FROM ONE SYSTEM TO THE NEXT. THE BOTTOM LINE IS THAT THIS SYSTEM
WILL HAVE THE POTENTIAL TO BRING WINTER WX IMPACTS TO THE AREA
THIS WEEKEND...AND ANYONE WITH TRAVEL PLANS SHOULD STAY TUNED TO
THE LATEST FORECASTS.

A COLD AND BLUSTERY WNW FLOW SHOULD FOLLOW BEHIND THE DEPARTING
COASTAL LOW WITH LAKE EFFECT/UPSLOPE SNOWS OVER THE NW MTNS AND
WRN HIGH TERRAIN LATER SUNDAY AND POSSIBLY INTO SUNDAY NIGHT.
HIGH PRES SHOULD ARRIVE BY EARLY NEXT WEEK. TEMPS SHOULD MODERATE
INTO TUE/WED AS FLOW VEERS TO THE W/SW AHEAD OF A CLIPPER WAVE
DROPPING ACROSS THE NRN GREAT LAKES. LARGE SCALE HGT FALLS ASSOCD
WITH ANOTHER POLAR SHORTWAVE SPREADING ACRS THE GRT LKS/MID-ATLC
MAY SPIN-UP ANOTHER LOW OFF THE COAST...BUT AT THIS POINT ITS
LATITUDE WOULD BE TOO FAR NORTH TO IMPACT THE LOCAL AREA.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
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VFR WILL DOMINATE MOST OF THE REGION TODAY. BFD WILL SEE REDUCED
CONDITIONS CONTINUE IN LAKE EFFECT CLOUDS AND SNOW SHOWERS. JST
COULD ALSO SEE BRIEF REDUCTIONS AS UPSLOPE FLOW BRINGS CLOUDS AND
SOME SNOW SHOWERS...MAINLY AFTER 00Z/12.

A WEAK COLD FRONT WILL MOVE ACROSS THE REGION THIS AFTERNOON BRINGING
THICKENING CLOUDS FROM WEST TO EAST AND SCATTERED SNOW
SHOWERS...MAINLY IN THE MTNS. DUE TO STRONG WINDS ALOFT COMBINED
WITH INSTABILITY FROM THE FRONT...WINDS ALOFT SHOULD MIX
DOWN...BRINGING GUSTY WEST WINDS AS HIGH AS 25MPH THIS AFTERNOON
AND EVENING.

ON THURSDAY...HIGH PRESSURE WILL BUILD OVER THE TN VALLEY AND SRN
APPALACHIANS BRINGING WIDESPREAD VFR CONDITIONS TO THE REGION ONCE
AGAIN. THOUGH BFD COULD LINGER IN THE MVFR DUE TO LAKE ENHANCED
CLOUDS/SNOW SHOWER INTO THURSDAY AFTERNOON.

OUTLOOK...

THU-FRI...NO WIDESPREAD SIG WX.

SAT-SUN...SNOW OR MIXED PRECIP WITH LOW CIGS/VSBYS POSSIBLE.
-- End Changed Discussion --

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST THURSDAY FOR PAZ004.

&&

$$
SYNOPSIS...STEINBUGL
NEAR TERM...GARTNER/STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...STEINBUGL
AVIATION...CERU/GARTNER