Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 090645
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
145 AM EST TUE FEB 9 2016

.SYNOPSIS...
A LONG-DURATION PERIOD OF SNOW WILL LIKELY RESULT IN A WIDESPREAD
LIGHT TO MODERATE ACCUMULATION FOR MUCH OF CENTRAL PA TONIGHT INTO
EARLY WEDNESDAY. LAKE EFFECT AND UPSLOPE SNOW SHOWERS WILL FOLLOW
FROM MID WEEK INTO THE FIRST PART OF THE WEEKEND...WITH ADDITIONAL
ACCUMULATION LIKELY IN THE FAVORED NORTHWEST SNOWBELT AND HIGHER
TERRAIN ALONG THE ALLEGHENIES AND LAURELS. THE COLDEST AIRMASS OF
THE WINTER IS POISED TO BRING FRIGID TEMPERATURES AND DANGEROUS
WIND CHILLS FOR VALENTINES WEEKEND.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
1230 AM UPDATE...
JUST A COATING SO FAR...BUT IT IS JUST THE BEGINNING. BOTH MDT
AND IPT CAME IN WITH 0.2IN OF SF AT MIDNIGHT. WEBCAMS PLAY UP A
BIT MORE SNOW OVER THE LAURELS...BUT MOST PLACES DRY OR JUST WET
ROADS AT THIS POINT. IT JUST SKIPPED RIGHT OVER HAPPY VALLEY. HRRR
AND RUC INDICATE THAT A WEAK TROUGH FORMS TO THE E OF UNV AND AOO
AND FOCUS THE LIGHT SNOW ALONG THE MID-LOWER SUSQ THROUGH THE REST
OF THE NIGHT. SLUG OF PRECIP MOVING UP FROM CENTRAL MD...SHOULD
RISE INTO THE SRN TIER/FAR LOWER SUSQ IN THE NEXT COUPLE OF HRS.
STILL...SF RATES WILL LIKELY NOT GET TO INCH/HR RATES OVERNIGHT.

PREV...
03Z RADAR LOOP SHOWS SPOTTY LIGHT SNOW HAS OVERSPREAD NEARLY ALL
OF CENTRAL PA AHEAD OF SHORTWAVE LIFTING NE FROM THE OHIO VALLEY.
LACK OF SIG MOISTURE OVER THE REGION /SATL DERIVED PWATS ONLY NR
SEASONAL AVG/ AND EXPECTATION THAT WEAKENING SHORTWAVE WILL PASS
NE OF THE AREA AFTER 06Z...BOTH POINT TOWARD ONLY LIGHT PRECIP
OVERNIGHT. IN ADDITION...MARGINAL BLYR TEMPS MAY RESULT IN AN
INITIAL PERIOD OF LGT RAIN OVR THE LOWER ELEVS OF SOUTHERN PA AND
COULD LIMIT SNOW ACCUMS THEREAFTER. WEB CAMS ACROSS THE SUSQ
VALLEY INDICATING ONLY WET ROADS AT 03Z.

FOR NOW WILL MAINTAIN THE IDEA OF AN INCH OR SO OF SNOW ACCUM
ACROSS MUCH OF CENTRAL PA BY DAWN. HOWEVER...GIVEN LIGHT SNOW
RATES AND TEMPS AOA FREEZING...DON/T ANTICIPATE BIG TRAVEL
PROBLEMS FOR THE AM COMMUTE. BLEND OF LATEST GUIDANCE POINTS
TOWARD OVERNIGHT MIN TEMPS IN THE U20S- L30S.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
AFTER DISCUSSION WITH PHI AND LWX...ALONG WITH NEW WPC
GRAPHICS...HAVE ISSUED WINTER WX ADVISORY FOR MUCH OF SOUTHERN PA
AND A WARNING FOR THE ADAMS/YORK/LANCASTER...WHERE WPC GUIDANCE
SUPPORTS TOTALS TO ARND 6 INCHES BY TUES NIGHT.

AFTER A LULL IN THE LGT SNOW EARLY TUE AM...SECOND SHORTWAVE
ROUNDING THE BASE OF UPPER LOW OVR THE GRT LKS WILL APPROACH BY
MIDDAY TUESDAY...PRODUCING A STEADIER LIGHT SNOW ALONG NEG TILTED
INVERTED SFC TROUGH AXIS AND ASSOC PLUME OF HIGHER PWATS OVR
CENTRAL PA. BEST LG SCALE FORCING...AS INFERRED BY MDL 500-300MB
QVEC CONV FIELDS...WILL BE FOCUSED ACROSS SOUTHERN PA...WHERE MDL
BLENDED QPF SUPPORTS SEVERAL INCHES OF ADDITIONAL ACCUM BTWN
MIDDAY TUES AND LATE TUES EVENING. MARGINAL BLYR TEMPS MAY
CONTINUE TO HINDER SNOW ACCUMS IN THE VALLEYS...AS NCAR MESO
ENSEMBLE AND SPC SSEO BOTH SUGGEST. SO...CONFIDENCE IN WARNING
TYPE SNOW IN THE POPULATION CENTERS OF SE PA IS NOT NEARLY AS HIGH
AS FOR THE RIDGETOP LOCATIONS. OTHER FACTOR TO CONSIDER IS THAT
LIGHT SNOW FALLING WITH SFC TEMPS AOA FREEZING DURING THE DAYLIGHT
HRS WILL LIKELY RESULT IN A GOOD DEAL OF MELTING ON ROAD SURFACES
AND COULD POTENTIALLY MAKE THIS A RELATIVELY LOW IMPACT
ADVISORY/WARNING.

EXPECT A TRANSITION TOWARD A LAKE EFFECT/UPSLOPE SNOW PATTERN
LATE TUES NIGHT INTO WEDNESDAY NIGHT...AS INVERTED SFC TROUGH
LIFTS NE AND BLYR FLOW TURNS TO THE WEST.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
*IMPACT WEATHER HIGHLIGHTS INCLUDE ADDITIONAL LAKE EFFECT AND
 UPSLOPE SNOW ACCUMULATIONS THURSDAY-SATURDAY...FOLLOWED BY FRIGID
 TEMPERATURES AND DANGEROUSLY COLD WIND CHILLS FOR VALENTINES
 WEEKEND.

ANOMALOUS WESTERN RIDGE/EASTERN TROUGH PATTERN WILL REMAIN IN
PLACE THROUGH THE WEEKEND. THE GLOBAL ENSEMBLE MEANS GENERALLY
KEEP THIS PATTERN CONFIGURATION INTACT INTO NEXT WEEK BUT AT A
DECREASING AMPLITUDE.

AS THE BROAD UPPER LEVEL CIRCULATION DEPARTS OVER THE NORTHEAST
TOWARD THE END OF THE WEEK...IT WILL BE REPLACED BY A POLAR
VORTEX DROPPING SOUTH ACROSS HUDSON BAY INTO SE CANADA. COLD AIR
WILL BEGIN SPILLING SOUTHWARD LATER IN THE WEEK...REINFORCED
INITIALLY BY A SECONDARY FRONT ON THURSDAY. CONFIDENCE CONTINUES
TO INCREASE IN A SIGNIFICANT ARCTIC AIR INTRUSION/COLD OUTBREAK
FOR VALENTINE`S WEEKEND.

LAKE EFFECT/UPSLOPE SNOWS FOR SEVERAL DAYS THU-SAT WILL BRING
ADDITIONAL LGT-MDT ACCUMULATION OVER THE FAVORED NORTHWEST
SNOWBELT DOWNWIND OF LAKE ERIE AND IN THE HIGHER TERRAIN OF THE
ALLEGHENIES/LAURELS. A NEW ELEMENT IN THE FCST IS DEVELOPING LOW
PRESSURE OFF THE MID-ATLANTIC/NORTHEAST COAST BY EARLY SATURDAY.
AT THIS TIME THE 08/00Z ECMWF LIES ON THE WESTERN EDGE OF THE
GUIDANCE ENVELOPE.

CONFIDENCE IS HIGH IN THE FCST COLD PATTERN/WELL-BELOW NORMAL
TEMPERATURES THROUGH THE PERIOD. THE COLDEST AIRMASS OF THE
WINTER APPEARS POISED TO ARRIVE THIS WEEKEND WITH GFS/EC BOTH
BRINGING -30C AIR AT 850MB INTO PA.

MAX/MIN TEMPERATURE DEPARTURES OF -20 TO -25 DEGREES BELOW CLIMO
ARE PROBABLE SATURDAY AND SUNDAY. WIDESPREAD SINGLE DIGIT
TEMPERATURES +/- ZERO ARE FCST SATURDAY NIGHT INTO EARLY SUNDAY.
A STRONG GRADIENT BETWEEN LOW PRESSURE OFF THE NEW ENGLAND COAST
AND 1040+MB ARCTIC HIGH DROPPING INTO THE UPPER MS VALLEY WILL
PRODUCE GUSTY WINDS AND DANGEROUSLY COLD WIND CHILLS -10F TO -25F
DEGREES BELOW ZERO.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
SNOW STILL REAL PATCHY.

06Z TAFS SENT.

WILL ADJUST AS NEEDED.

EARLIER DISCUSSION BELOW.

FIRST OF THE SNOW SHOWERS NOW WORKING INTO THE WESTERN MOUNTAINS.
WHILE OVERALL FORECAST CALLS FOR DETERIORATING CONDITIONS THIS
EVENING FROM WEST TO EAST...THE TIMING OF THE ONSET OF THE STEADY
SNOW IS THE CHALLENGING ASPECT OF THIS FORECAST. EXPECT
CONDITIONS TO VARY FOR SEVERAL HOURS AT THE ONSET OF THE
PRECIPITATION...LIKELY SWITCHING FROM VFR TO MVFR AND THEN BACK
AGAIN TO IFR. THIS THINKING IS DIFFICULT TO TRANSLATE INTO THE
TAFS. HAVE DECIDED TO GO WITH PREVAILING AREAS OF STEADY
SNOW...WITH LOWERING CONDITIONS...BUT REALIZING THE POTENTIAL FOR
HIGH VARIABILITY FOR A GOOD PORTION OF THE EVENING.

IFR CONDITIONS SHOULD DEVELOP OVERNIGHT...AND LAST THROUGH MUCH OF
THE TAF PERIOD IN WIDESPREAD SNOW. SOME AREAS OF LIFR MAY DEVELOP
IN BANDING OF HEAVIER SNOW...BUT DIFFICULT TO PUT IN AN EXACT
LOCATION AT THIS TIME.

THE COMPLEX WEATHER PATTERN WILL RESULT IN WIDESPREAD... BUT
MAINLY LIGHT TO OCCASIONALLY MODERATE SNOW OVERNIGHT TONIGHT INTO
TUESDAY NIGHT. WHILE THERE MAY BE BREAKS FROM TIME TO
TIME...EXPECT FAIRLY WIDESPREAD SNOW/SNOW SHOWERS AND ASSOCIATED
RESTRICTIONS OVER MUCH OF THE REGION THROUGH THAT PERIOD.

LOOKING AHEAD...SNOW SHOWERS BECOME MORE CONFINED TO WESTERN
HIGHER TERRAIN MID/LATE WEEK AS SHOT OF QUITE COLD AIR ARRIVES ON
NW FLOW.

OUTLOOK...

TONIGHT INTO TUE NIGHT...PERIODS OF LIGHT SNOW. IFR CONDITIONS
DEVELOPING. LOCALIZED LIFR POSSIBLE.
WED...MAINLY IFR IN SNOW WRN AIRSPACE. MVFR-VFR CIGS
CENTRAL/EAST.
THU-SAT...MVFR IN -SHSN W MTNS. VFR ELSEWHERE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR PAZ024-
033.
WINTER WEATHER ADVISORY UNTIL 5 AM EST WEDNESDAY FOR
PAZ025>028-034>036-056-057-059-063.
WINTER STORM WARNING UNTIL 5 AM EST WEDNESDAY FOR PAZ064>066.

&&

$$
SYNOPSIS...STEINBUGL
NEAR TERM...DANGELO/FITZGERALD
SHORT TERM...FITZGERALD/GARTNER
LONG TERM...STEINBUGL
AVIATION...JUNG/GARTNER/MARTIN


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