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000
FXUS61 KCTP 310619
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
119 AM EST SAT JAN 31 2015

.SYNOPSIS...
ARCTIC AIR WILL BRING BITTER COLD TEMPERATURES AND SUBZERO WIND
CHILLS TO MUCH OF CENTRAL PENNSYLVANIA TONIGHT INTO EARLY SATURDAY.
CONFIDENCE IS INCREASING FOR A WIDESPREAD...HIGH IMPACT WINTER
WEATHER EVENT SUNDAY INTO MONDAY...WITH THE POTENTIAL FOR
SIGNIFICANT SNOW ACCUMULATION...ALONG WITH SOME MIXED WINTRY
PRECIPITATION ACROSS SOUTHERN PENNSYLVANIA. ANOTHER SHOT OF ARCTIC
AIR WILL FOLLOW FOR MONDAY AFTERNOON INTO TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
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INVERSION HEIGHTS FALLING RAPIDLY NEXT FEW HOURS AS HIGH PRESSURE
NEAR COLUMBUS OHIO BUILDS EAST AND THE MEAN...850-700MB THERMAL
TROUGH DRIFTS TWD THE NEW JERSEY COAST. REGIONAL RADAR MOSAIC
STILL DETECTING NARROW BANDS OF SNOW SHOWERS FEEDING INTO THE
LAUREL HIGHLANDS. BLOWING SNOW IS LIKELY MORE RESPONSIBLE FOR VSBY
REDUCTIONS THAN THAN THE SNOWFALL ITSELF. WESTERN UPSLOPE AREAS
AND OUR FAR NORTHEASTERN ZONES WILL HANG ONTO THE CLOUDS AND
LINGERING FLURRIES THE LONGEST.

SKIES WILL SLOWLY CLEAR ACROSS MOST OF THE REGION IN THE PRE DAWN
HOURS AS THE MEAN LLVL WIND BACKS TO THE WEST.

WINDS REMAINING IN THE 10-15 MPH RANGE LATE TONIGHT...WITH HIGHER
GUSTS WILL KEEP WIND CHILLS IN THE 10-20 BELOW ZERO RANGE OVER THE WESTERN
HIGHER TERRAIN,..AND FROM ZERO TO 10 BELOW THROUGHOUT THE CENTRAL
RIDGE AND VALLEY REGION.

ACTUAL LOWS AROUND SUNRISE SATURDAY WILL VARY FROM ZERO TO 5
BELOW ACROSS THE NORTHWEST MOUNTAINS...TO AROUND 10 ABOVE IN THE
SOUTHEAST.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
SATURDAY WILL START BRIGHT IN MOST AREAS AS THE HIGH CRESTS JUST
TO OUR SOUTH. HIGH CLOUDS MAY BEGIN TO INVADE FOR THE LAST HALF OF
THE AFTERNOON...BUT THEY SHOULD DO LITTLE TO MAR AN OTHERWISE FAIR
ALBEIT COLD MID WINTER`S DAY.

HIGHS FROM THE MID TEENS TO MID 20S NORTH TO SOUTH WILL BE ABOUT
15 DEG BELOW NORMAL ON AVERAGE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
*SIGNIFICANT WINTER WEATHER/SNOW EVENT POSSIBLE SUNDAY-MONDAY
*BITTER COLD TEMPERATURES AND DANGEROUS WIND CHILLS POSSIBLE
 MONDAY NIGHT INTO TUESDAY

MINOR CHANGES SEEN IN 18Z/21Z OPER AND ENS MODEL GUIDANCE
W/RESPECT TO SFC LOW TRACK AND ANTICIPATED SNOW AMOUNTS SUNDAY
INTO EARLY MONDAY /ALONG WITH THE APPROX AREA ACROSS SOUTHERN
PENN WHERE SNOW SHOULD AT LEAST MIX WITH SLEET AND FZRA SUNDAY
NIGHT/.

PREVIOUS LATE AFTERNOON DISCUSSION FOLLOWS BELOW...

A POTENTIALLY WIDESPREAD HIGH IMPACT WINTER WX EVENT APPEARS TO
BE SHAPING UP ACROSS CENTRAL PENNSYLVANIA FOR SUNDAY INTO MONDAY.
A WINTER STORM WATCH CONTINUES IN EFFECT FOR ALL CENTRAL PA
COUNTIES AND IS VALID FROM NOON EST SUNDAY THROUGH NOON EST MONDAY.
CONFIDENCE IN THE EVENT OCCURRING IS AVERAGE WITH SLIGHTLY LOWER
CONFIDENCE IN THE DETAILS SUCH AS LOCATION AND SNOW ACCUM NUMBERS
GIVEN THE UNCERTAINTY IN THE TRACK OF THE SYSTEM...AND POTENTIAL
FOR MIXED PCPN/WARMER TEMPS IN THE SRN 1/3 OF THE AREA.

A SHORTWAVE NOW ENTERING CENTRAL BRITISH COLUMBIA WILL BE DIGGING
SOUTHEAST DOWN INTO THE NORTHERN/CENTRAL PLAINS LATER SAT AND INTO
SUN. THIS ENERGY COUPLED WITH A MORE SUBTLE SHORTWAVE ON ITS HEELS
DROPPING DOWN FROM THE NORTHWEST TERRITORIES WILL PLAY A KEY ROLE
IN THE EVOLUTION OF SURFACE LOW PRESSURE THAT IS CURRENTLY
FORECAST TO DEVELOP OVER THE LOWER MO AND MID MS VALLEY REGION BY
EARLY SUN BEFORE THEN AIMING EAST TOWARD THE OH VALLEY AND MID-
ATLANTIC STATES SUN NIGHT AND MON. AS THIS STORM DEVELOPS...MUCH
COLDER AIR WILL BUILD NOT ONLY BEHIND THE SYSTEM AS A LARGE ARCTIC
ANTICYCLONE HEADS SOUTHWARD INTO THE NORTHERN PLAINS...BUT COLDER
AIR WILL ALSO BLEED EASTWARD AS PRESSURES RISE OVER SOUTHEASTERN
CANADA AND NORTHERN NEW ENGLAND IN ASSOCIATION WITH A PRONOUNCED
UPPER CONFLUENCE ZONE. THE COMBINATION OF THESE TWO SYSTEMS WILL
HELP GENERATE A INCREASINGLY TIGHT BAROCLINIC ZONE UPON WHICH THE
DEVELOPING SURFACE LOW WILL MOVE ALONG.

THE PREVAILING SHIFT IN THE 12Z MODELS WAS TO CONTINUE A MORE
NORTHERLY TRACK WITH THIS SYSTEM...WHICH IS REFLECTED IN THE WPC
FORECAST WHICH WAS WEIGHTED HEAVILY IN THE FINAL GRIDDED SNOW/ICE
ACCUMULATIONS. HOWEVER FORECAST CONFIDENCE IS TEMPERED BY THE RUN-
TO- RUN INCONSISTENCIES THE MODELS HAVE SHOWN ALONG THE WITH
DISTINCT POSSIBILITY THAT THE MODELS MAY REVERSE TRENDS IN
SUBSEQUENT RUNS. WITH SEVERAL FORECAST CYCLES COMING UP ANTICIPATE
SOME CHANGES REGARDING NUMBERS AND LOCATIONS OF SNOWFALL TOTALS.

A SHOT OF ARCTIC AIR IS FORECAST TO SURGE INTO THE AREA BEHIND THE
EARLY WEEK STORM WITH POTENTIAL FOR DANGEROUS WIND CHILLS MONDAY
NIGHT INTO TUESDAY. THIS COULD ADD TO STORM-RELATED IMPACTS. HIGH
PRESSURE SHOULD BRING COLD BUT QUIET WEATHER INTO MIDWEEK. MODELS
AND ENSEMBLES SHOW A COASTAL TYPE SYSTEM SOMETIME NEXT WED-FRI BUT
IT IS WAY TOO EARLY TO SPECULATE ON THIS SYSTEM.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
IFR AT KJST WILL CONTINUE INTO THE EARLY MORNING HOURS AS SNOW
SHOWERS AND LOW CIGS PERSIST IN THE NWRLY UPSLOPE FLOW. UPSLOPE
WINDS ALSO CONTINUE TO SUPPORT MVFR CIGS AT KBFD AND KAOO. VFR
HAS RETURNED ELSEWHERE AND SHOULD PREVAIL INTO TOMORROW...THOUGH A
STRAY REMAINING SNOW SHOWER COULD BRING SOME TEMP REDUCTIONS
OVERNIGHT.

GUSTY WINDS WILL CONTINUE INTO THE OVERNIGHT BUT DIMINISHING
SOMEWHAT TO BETWEEN 15-20KT.

OUTLOOK...

SAT...VFR.

SUN...WIDESPREAD IFR/MVFR DEVELOPING ASSOCIATED WITH A STORM
MOVING TOWARD THE REGION.

MON...REDUCED CONDS EARLY...IMPROVING AS THE STORM MOVES AWAY FROM
THE AREA.

TUE-WED...NO SIG WX.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
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WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY
MORNING FOR PAZ004>006-010>012-017>019-024>028-033>037-041-042-
045-046-049>053-056>059-063>066.
WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR
PAZ004>006-010>012-017>019-024-033-037-041-042-045-046-049-
051>053-058.
-- End Changed Discussion --

&&

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