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Area Forecast Discussion
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000
FXUS61 KCTP 011308
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
808 AM EST SUN MAR 1 2015

.SYNOPSIS...
WEAK LOW PRESSURE AND A DISTURBANCE AT UPPER LEVELS OF THE
ATMOSPHERE WILL TRACK NORTHEAST UP THE OHIO VALLEY AND CROSS
PENNSYLVANIA TODAY. THIS PAIR OF WEATHER FEATURES WILL BRING PERIODS
OF LIGHT TO BRIEFLY MODERATE SNOW...THEN SOME MIXED PRECIPITATION
TO SOUTH-CENTRAL PA AND THE LOWER SUSQ VALLEY LATE TODAY AND
TONIGHT. HIGH PRESSURE WILL BRING FAIR AND COLD CONDITIONS TO
REGION MONDAY AND MONDAY NIGHT. A STRONGER AREA OF LOW PRESSURE
WILL LIKELY TRACK WEST OF PENNSYLVANIA LATE TUESDAY AND EARLY
WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE LEADING EDGE OF THE LARGE SHIELD OF LIGHT SNOW HAS SPREAD EAST
TO THE SUSQUEHANNA VALLEY AS OF 10Z. 

LATEST 00Z/06Z OPER MODELS AND 03Z SREF ARE QUITE CONSISTENT WITH
A GENERAL LIGHT TO MODERATE SNOWFALL ACROSS THE REGION TODAY INTO
EARLY TONIGHT FROM APPROX 2-4 TENTHS OF LIQ EQUIV QPF. 

MULTI MODEL BLEND ALSO CONTINUES TO DISPLAY THE THREAT FOR UP TO
AROUND 0.25 INCH OF ICE FROM FREEZING RAIN LATER THIS AFTERNOON
INTO THIS EVENING ACROSS THE LOWER SUSQ VALLEY...MAINLY TO THE
SOUTHEAST OF THE I-81 CORRIDOR...WITH THE BEST CHC BEING CLOSE TO
THE PA/MD BORDER. SINCE THE EVENT WILL START AS SEVERAL HOURS OF
SNOW THEN MIX WITH/CHANGE TO SLEET AND FZRA WITH ICE AMOUNTS STILL
UNCERTAIN AND BORDERLINE FOR A WARNING...WE WILL CONTINUE TO HOLD
OFF ON ANY UPGRADES TO WINTER STORM/ICE STORM WARNINGS AT THIS
TIME. ADDITIONAL HIGH RES MODELS THIS MORNING WILL LIKELY PROVIDE
BETTER DETAIL TO MAKE THE DECISION REGARDING POTENTIAL ICE AMOUNTS
AND LOCATIONS.

CONSISTENCY OF THE PAST SEVERAL MODEL RUNS AND ENSEMBLES WITH
RESPECT TO PTYPE INDICATES THAT THE BULK OF THIS WINTRY EVENT
WILL FALL AS SNOW TO THE NORTH OF THE RT22/322 CORRIDOR IN CENTRAL
PENN. TEMPS WILL BE NEARLY STEADY IN THE TEENS TO AROUND 20F
THROUGH 13Z...THEN SLOWLY RISE TO A LATE DAY HIGH IN THE UPPER 20S
ACROSS THE CENTRAL AND NORTHERN MTNS...AND LOWER TO MID 30S ACROSS
THE LOWER SUSQ VALLEY AND LAUREL HIGHLANDS RESPECTIVELY.

WINDS WILL SOUTHEAST TO SOUTH AT 5-8 KTS IN MOST PLACES THROUGH
TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
THE VERY WEAK LOW DEVELOPING ON THE DELMARVA AND RUSHING OFF
SHORE LATE TODAY INTO TONIGHT WILL ENHANCE THE MIXED PRECIP OR
FREEZING RAIN RATES OVER THE SERN COS FOR UP TO SEVERAL HOURS
/BETWEEN 19Z-00Z/.

VERY INTERESTING PART OF THE FORECAST WILL BE THE SNOW TYPE. THERE
IS A REALLY GOOD SIGNAL IN THE UPPER PART OF THE CLOUDS IN THE
MIDDLE OF THE DAY WHERE THE BEST VERTICAL MOTION IS SQUARELY IN
THE PREFERRED DENDRITIC GROWTH ZONE AROUND -15C. THEN...IT FALLS
THROUGH A HIGHLY MOIST/SATURATED COLUMN AND GETS ONLY CLOSE TO
MELTING INMOST PLACE. THIS COULD MAKE SOME GIANT BUT WET FLAKES.
THUS...A HIGH WATER CONTENT AND HEAVIER SNOW. THE SNOW PHYSICS...THE
WINDS ALOFT AND SFC TEMPS ALL WILL PULL THE SNOW ACCUMS ONE WAY
AND ANOTHER. HOWEVER...TEMP PROFILES LOOK PRETTY SIMILAR TO PAST
WEEKENDS VERY SIMILAR STORM. MANY SIMILARITIES EXIST WITH THAT
PREV STORM...BUT THE TEMPS APPEAR JUST SLIGHTLY COLDER. THINKING
THAT WE WILL GET BIGGER FLAKES BUT END UP WITH THE SAME WATER
CONTENT AND SLIGHTLY HIGHER SNOW ACCUMS OVER MOST OF THE AREA.

GREATEST FCST BUST POTENTIAL APPEARS TO EXIST IN THE SE...WHERE
IF THERE ENDS UP BEING NO TURNOVER TO MIXED PRECIP/ZR...IT WILL
MEAN THAT THE 0.6 INCHES OF WATER PROGGED THERE MAY NUDGE THEM
NEAR WARNING AMOUNTS. EVEN THIS SEEMS VERY SIMILAR TO THE FEB
21ST.

PRECIP LOOKS TO TAPER OFF IN ALL AREAS DURING THE LATE EVENING
THROUGH VERY EARLY MORNING HOURS OF MONDAY.

LOW TEMPS TONIGHT /UNDER PLENTY OF LINGERING AND MORE
SHALLOW...WARMER LOWER CLOUDS/ WILL RANGE FROM NEAR 20 DEG IN THE
NORTH TO 30F IN ACROSS THE SOUTH.

BLUSTERY AND COLDER CONDITIONS WILL MAKE A RETURN ON MONDAY AS
SYSTEM NUMBER ONE SLIDES OFF TO OUR EAST. OTHER THAN THE USUAL
POST FRONTAL SNOWS SHOWERS...FAVORING WESTERN HIGHER
ELEVATIONS...CONDITIONS WILL BE GRADUALLY IMPROVING OVERALL
THROUGHOUT THE DAY.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
HIGH PRESSURE AND ITS FAIR WEATHER AND LIGHT WIND WILL BE SHORT
LIVED MONDAY NIGHT INTO TUESDAY WHEN THE NEXT IN THE SERIES OF
STORM SYSTEMS IS SLATED TO ENTER THE LOCAL WEATHER SCENE. THIS ONE
PROMISES MORE OF A MESSY OUTCOME AS IT SHOULD TRACK WELL TO OUR
NW...MEANING WARM AIR EVENTUALLY INVADING THE REGION...WITH A SNOW
TO SLEET/FREEZING RAIN AND EVEN RAIN SCENARIO.

SNOW AMOUNTS DO NOT LOOK TO BE THE BIGGEST PART OF THE MIDWEEK
STORM AS WE ARE PROGGED TO WARM ALOFT RATHER QUICKLY. WITH A DEEP
SNOW PACK AND A LOT OF COLD AIR TO DISPLACE...WE WILL LIKELY SEE
A PERIOD OF ICING BEFORE WARM AIR EVENTUALLY CHANGES EVERYTHING TO
RAIN TUESDAY NIGHT INTO WEDNESDAY.

RAIN SHOULD TAPER OFF TO SCATTERED SHOWERS WITH THE PASSAGE OF
THE TRAILING COLD FRONT EARLY WEDNESDAY.

EARLIER MODEL RUNS SUGGESTED LATER WEDNESDAY INTO THURSDAY THERE
COULD BE A RETURN OF SNOW TO SRN PA ASSOCIATED WITH A FLAT SRN
STREAM WAVE...BUT LATEST OPERATIONAL ECMWF/GFS NOW KEEP THE
SURFACE WAVE SUPPRESSED MAINLY SOUTH OF THE REGION..HINTING THAT
ONLY FAR SERN AREAS WILL BE AT RISK FOR A PERIOD OF OVER RUNNING
SNOW. THE 06Z GEFS IS A LITTLE MORE GENEROUS WITH THE POPS SO IT'S
NOT OUT OF THE QUESTION THAT SOMETHING WILL YET HAPPEN AS MODELS
TRY AND RESOLVE SMALL SCALE FEATURES DROPPING OUT OF CENTRAL
CANADA INTO THE EASTERN US LONG WAVE. TOO FAR OFF TO LEAN ONE WAY
OR ANOTHER FOR A SOLUTION.

BEHIND THE MID WEEK SYSTEM...ANOTHER PUSH OF ARCTIC AIR WILL
BRING TEMPS AND POPS BACK WELL BELOW NORMAL FOR LATE THURSDAY INTO
FRIDAY. THE ONLY GOOD THING SEEMS TO BE EACH ARCTIC SHOT IS A
LITTLE LESS POTENT THAN THE LAST AS WE LEAVE THE RECORD COLD OF
FEBRUARY BEHIND.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
THIS MID MORNING..THE LEADING EDGE OF THE LARGE SHIELD OF LIGHT
SNOW HAS OVERSPREAD CENTRAL PA...REDUCING VSBYS TO 2 MILES OR LESS
/IFR CONDITIONS/ ACROSS A WIDESPREAD AREA.  

GENERALLY IFR TO LIFR CONDITIONS IN SNOW EXPECTED ALL DAY AND INTO
THIS EVENING. CIGS REMAIN ABOVE 1500FT AT 13Z...BUT WILL ALSO
DROP AS DAY WEARS ON. STILL THE THREAT OF SOME FZRA MIXING IN FOR
THE SOUTHERN TIER COUNTIES LATER THIS AFT AND THIS EVENING. 

VSBYS WILL IMPROVE OVERNIGHT AS SNOW COMES TO AN END...BUT CIGS
WILL REMAIN LOW KEEPING MAINLY IFR CONDITIONS GOING BEFORE LIFTING
TO MVFR IN THE CENTRAL AND EAST LATE.

CONDITIONS SHOULD CONTINUE TO SLOWLY IMPROVE ON MONDAY...BUT
EXPECT RESTRICTIONS TO LINGER IN THE WESTERN AND NORTHERN HIGHER
TERRAIN ON COLD NORTHWEST WINDS AND TYPICAL OROGRAPHIC SNOW
SHOWERS.

BRIEF RESPITE LATER MONDAY INTO EARLY TUESDAY...BEFORE THE NEXT
SYSTEM PUSHES ANOTHER ROUND OF PRECIPITATION AND REDUCED FLYING
CONDITIONS INTO THE AREA LATER TUESDAY AND WEDNESDAY.

OUTLOOK...

MON...CIG/VIS REDUCTIONS MAINLY AM...THEN IMPROVING CONDITIONS.
TUE...VFR AM. MIXED PRECIP WITH CIG/VIS REDUCTIONS POSSIBLE LATE.
WED...CIG/VIS REDUCTIONS CONTINUE IN WINTRY MIX/RAIN.
THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE.

&&

.CLIMATE...
THE BOOKS HAVE CLOSED AND WE NOW HAVE /AND MADE IT THROUGH/ THE
COLDEST FEBRUARY ON RECORD.

MONTHLY MEAN TEMPERATURES WERE...IPT 18.1...MDT 20.9.

THE PREVIOUS RECORDS FOR THE COLDEST FEBRUARY...IPT 19.3...MDT
21.4 BOTH SET IN 1934.

THIS FEBRUARY RANKED AS THE THIRD COLDEST CALENDAR MONTH EVER AT
IPT...AND FOURTH COLDEST EVER AT MDT.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 2 AM EST MONDAY FOR PAZ019-027-
028-037-041-042-045-046-049>053-056>059-063>066.
WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR PAZ004>006-
010>012-017-018-024-033.
WINTER WEATHER ADVISORY UNTIL 11 PM EST THIS EVENING FOR 
PAZ025-026-034>036.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LA CORTE/LAMBERT
AVIATION...RXR
CLIMATE...



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