654
FXUS61 KCTP 190534
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1234 AM EST SUN JAN 19 2025
SYNOPSIS
*QUICK-HITTING, PLOWABLE TO LOCALLY HEAVY SNOWFALL ON SUNDAY
WITH HIGHEST ACCUMULATIONS ACROSS THE SOUTHEAST.
*ARCTIC BLAST AND DANGEROUSLY COLD WIND CHILLS MONDAY-WEDNESDAY
*DRY CONDITIONS LATER THIS WEEK WITH SCATTERED SNOW SHOWERS.
NEAR TERM /UNTIL 7 AM THIS MORNING/
BREAKS STILL VISIBLE HERE AND THERE TO THE EAST OF UNV, BUT,
GENERALLY 100PCT SKY COVER ACROSS THE CWA. DRY AIR IS MOVING
DOWN ACROSS WRN PA, BUT LAGGING A BIT OVER CENTRAL PA. BFD JUST
LET GO OF THE FLURRIES THEY'VE HAD ALL EVENING. JST AND SOMERSET
MAY NOT STOP FLURRYING ALL NIGHT BEFORE THE BROADER AREA OF SNOW
ARRIVES IN THE MORNING. ONSET TIMING SEEMS JUST AN HR OR SO
LATER VS MDL RUNS 12-24HRS AGO, BUT NOT A SIGNIFICANT ENOUGH
CHANGE TO NOT MENTION A LOW CHC OF A DUSTING ACROSS THE SWRN
COUNTIES BEFORE SUNRISE. TEMPS SHOULD GET DOWN INTO THE MID
TEENS IN THE NW AS THE AIR DRIES OUT, DESPITE NOT LOSING ALL
THEIR SKY COVER.
SHORT TERM /7 AM THIS MORNING THROUGH 6 PM MONDAY/
STILL HOLDING THE LINE ON ALL THE WWA PRODUCTS. NEW 00Z HREF
24HR PMM SNOWFALL LOOKS ALMOST EXACTLY LIKE OUR CURRENT OFFICIAL
STORM TOTAL MAP. THE HREF ALSO HAS A LIKELIHOOD (60-80PCT) OF
1"/HR RATES OCCURRING IN THE WARNING AREA DURING THE 20-23Z
TIME PERIOD. THAT SHOULD HELP US GET TO 5+" THERE. SOME CHC
(20-50PCT) OF THOSE HIGH RATES ALSO OCCURRING IN THE CURRENT
ADVY AREA. AGAIN, ALL GOOD NEWS FOR THE GOING FORECAST,
INCREASING THE CONFIDENCE.
PREV...
OTHER THAN A MINOR TWEAK TO THE TIMING FOR THE EASTERN COUNTIES
(AN HOUR OR TWO LATER), WE'VE TRIED TO HOLD THE SF FORECAST AS
MUCH AS POSSIBLE. BUT, IT LOOKS LIKE IT'LL ONLY SNOW FOR 5-7HRS
IN THE SE. THAT'S INCH/HR RATES FOR MOST OF THAT TIME TO GET TO
5+" FOR THE STORM. IT IS POSSIBLE, AS THE HREF PROB >1"/HR RATES
ARE HIGHEST DURING THE AFTN. BUT, THE HIGHEST PROBS ARE A LITTLE
FARTHER NORTH THAN WHERE THE CURRENT FORECAST MAX-AXIS LIES.
OVERALL, SEE NOT ENOUGH REASON TO CHANGE THE WWA MAP AT ALL.
WE HAVE STARTED TO THINK ABOUT HOISTING THE COLD WARNINGS/ADVYS.
BUT, ONLY IN PASSING, AS THE SNOW NUMBERS HAVE TAKEN SUCH A HIGH
PRIORITY AND COME FIRST IN TIME, TOO.
PREV...
THE BEGINNING STAGES OF THE SHORT-TERM WILL BE HONED IN ON THE
NEXT SYSTEM, IN THE FORM OF A FORMING COASTAL LOW ALONG THE
MID-ATLANTIC COAST THAT IS EXPECTED TO BRING PLOWABLE SNOWFALL
TO EASTERN PENNSYLVANIA. FIRSTLY, ONSET OF PRECIPITATION HAS
TRENDED SLIGHTLY LATER WITH A LESS PROGRESSIVE UPPER-LEVEL JET,
THUS HAVE TRENDED BACK ONSET OF SNOWFALL CLOSER TO SUNRISE WITH
COOLING TEMPERATURES DURING THE OVERNIGHT PERIOD CONTINUING TO
OUTLINE AN "ALL-SNOW" EVENT FOR THE REGION.
FRONTOGENESIS IN THE 850-700MB LAYER HAS CONTINUED TO HIGHLIGHT
AN INCREASING POTENTIAL FOR A HEAVIER SNOWBAND, WITH SNOWFALL
RATES APPROACHING (AND POTENTIALLY EXCEEDING) ONE INCH AN HOUR
RATES ACROSS PORTIONS OF THE LOWER SUSQUEHANNA VALLEY. OF NOTE,
RECENT HREF GUIDANCE ALSO DOES OUTLINE SOME BANDING POTENTIAL
FURTHER NORTH, WITH A SECONDARY AREA OF CONCERN ACROSS
SCHUYLKILL/COLUMBIA COUNTY THAT HAS LED TO AN INCREASE IN
SNOWFALL TOTALS FOR THESE ZONES, PUSHING THEM ABOVE WARNING
CRITERIA FOR THE EVENT. WHILE SOME MODEL DISCREPANCIES WITH
RESPECT TO TIMING DO STILL EXIST (WITH CURRENT FORECAST
OUTLINING LATE MORNING TO EARLY AFTERNOON AS THE BEST TIMING FOR
SNOW BANDING), FRONTOGENETIC FORCING REMAINS CONSTANT IN
BETWEEN MODEL CYCLES, INCREASING CONFIDENCE THAT THERE WILL BE A
HEAVIER SNOWBAND WITH SOME UNCERTAINTY WITH WHERE THE BAND WILL
SET UP. A FURTHER NORTH SOLUTION WOULD PROMOTE SOME EXPANSION
OF ADVISORIES FURTHER NORTH; HOWEVER, THIS SEEMS TO BE A LOWER
CONFIDENCE SOLUTION AT THIS TIME.
AS MENTIONED, HEAVIER SNOWFALL ACROSS THE LOWER SUSQUEHANNA
VALLEY IS EXPECTED TO LEAD TO LOCALLY HIGHER ACCUMULATIONS FOR
THIS COASTAL LOW EVENT, WITH THE BEST SIGNAL FOR SNOWFALL TOTALS
EXCEEDING 5" ACROSS THE LSV AND SLIGHTLY NORTH INTO SCHUYLKILL
COUNTY (WHERE WARNING CRITERIA IS 6"). HAVE COLLABORATED WITH
WFO PHI/BGM/PBZ/LWX, AND GIVEN THESE SIGNALS, WE HAVE UPGRADED
TO A WARNING FOR THE LOWER SUSQUEHANNA VALLEY, ALONG WITH
COLUMBIA/SCHUYLKILL WHERE 6" IS INCREASINGLY LIKELY GIVEN RECENT
MODEL GUIDANCE WITH A TIER OF ADVISORIES ON THE NORTH-END AND
INTO THE LAUREL HIGHLANDS WHERE LINGERING UPSLOPE ACCUMULATIONS
COULD PUSH ACCUMULATIONS CLOSER TO THE 3-4" RANGE.
COLD, DRY AIR ENTERS BEHIND THE SYSTEM SUNDAY NIGHT, ALLOWING
FOR A QUICK DRYING TREND IN PRECIPITATION WITH COLDER
TEMPERATURES BEGINNING TO TAKE HOLD OVER THE REGION, WITH MINTS
INTO MONDAY MORNING RANGING FROM THE SINGLE DIGITS ACROSS THE
LAURELS TO NEAR 15 DEGREES ACROSS THE LOWER SUSQUEHANNA VALLEY.
WINDS WILL BEGIN TO BECOME BREEZY TO GUSTY LATE SUNDAY EVENING
INTO MONDAY MORNING, WHICH COUPLED WITH THE AFOREMENTIONED COLD
TEMPERATURES ALLOWING FOR WIND CHILLS TO RANGE FROM THE -10/-15F
RANGE TO THE LOWER SINGLE DIGITS ACROSS THE LOWER SUSQUEHANNA
VALLEY. THIS CYCLE, HAVE DECIDED TO RIDE THE EXTREME COLD WATCH
GIVEN SOME MARGINALITY IN TEMPERATURES; HOWEVER, SOMERSET AND
CAMBRIA COUNTIES WILL BE THE FIRST COUNTIES IN CONSIDERATION FOR
EXTREME COLD WARNINGS, BUT CONFIDENCE REMAINS TOO LOW AT THIS
TIME.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
THE MAIN STORY FOR THE LONG TERM WILL BE THE BITTER COLD THAT WE
WILL EXPERIENCE THROUGH THE MIDDLE OF THE WEEK. PERSISTENT
UPPER LEVEL TROUGHING WILL KEEP IT QUITE COLD ACROSS MUCH OF THE
EASTERN UNITED STATES.
FOR CENTRAL PA, HIGH TEMPERATURES MON-WED WILL RUN 20-30 DEGREES
BELOW AVERAGE. CONSIDERING THAT LATE JANUARY IS CLIMATOLOGICALLY
THE COLDEST TIME OF THE YEAR, THIS WILL BE A SIGNIFICANT ARCTIC
OUTBREAK. AN EXTREME COLD WATCH REMAINS IN EFFECT FOR THE
NORTHERN AND WESTERN HIGHLANDS, WHERE WIND CHILLS WILL DIP WELL
BELOW ZERO AND COULD APPROACH OR EXCEED -20F TUES NIGHT AND WED
NIGHT.
LINGERING SNOW SHOWERS ARE POSSIBLE INTO MONDAY ACROSS THE
WESTERN HIGHLANDS. OTHERWISE, IT WILL BE COLD AND DRY INTO
TUESDAY.
A WAVE OF LOW PRESSURE PASSING WELL TO OUR SOUTH COULD BRUSH
SOUTHEASTERN PA WITH SOME LIGHT SNOW TUES EVE/NIGHT. AFTER A
VERY COLD WED, TEMPERATURES WILL MODERATE A BIT THURS INTO FRI.
A REINFORCING SHOT OF COLD AIR (NOT QUITE AS COLD AS EARLIER IN
THE WEEK) COULD BE ACCOMPANIED BY SOME SNOW SHOWERS ACROSS N/W
PA LATE FRIDAY OR EARLY SATURDAY.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
SNOW SHOWERS CONTINUE TO PRODUCE LIFR CONDITIONS AT JST AS OF
05Z. ELSEWHERE, IFR CEILINGS ARE BEING OBSERVED AT BFD WHILE
MVFR/VFR CEILINGS CAN BE FOUND AT THE OTHER TAF SITES. SOME
PATCHY FOG HAS DEVELOPED ACROSS THE LOWER SUSQUEHANNA VALLEY AND
WILL CONTINUE TO PRODUCE MVFR VISIBILITIES THROUGH MUCH OF THE
NIGHT BEFORE GRADUALLY IMPROVING INTO THE MORNING.
A COASTAL LOW WILL BRING A ROUND OF SNOW INTO THE AREA ON
SUNDAY. THE SNOW WILL OVERSPREAD THE AREA FROM SOUTH TO NORTH
THROUGH THE MORNING AND EARLY AFTERNOON HOURS. ONCE THE SNOW
BEGINS, CONDS SHOULD QUICKLY DROP TO IFR. MOST GUIDANCE SUGGESTS
THAT A PERIOD OF HEAVY SNOW IS LIKELY AT MDT AND LNS IN THE
18Z-00Z TIMEFRAME AND VISIBILITIES AS LOW AS 1/4SM WILL BE
POSSIBLE FOR THOSE AIRFIELDS.
THE STEADY SNOW WILL PULL EAST OF THE REGION SUNDAY EVENING
INTO SUNDAY NIGHT, ALTHOUGH LINGERING LIGHT UPSLOPE
PRECIPITATION REMAINS POSSIBLE ACROSS THE WESTERN HIGHLANDS
SUNDAY NIGHT. AS THE SNOW EXITS THE REGION, CEILINGS GRADUALLY
RISE TO VFR EAST OF UNV, WHILE MVFR CEILINGS PERSIST TO THE
WEST.
OUTLOOK...
MON...MVFR TO IFR CONDS IN SNOW SHOWERS ACROSS MAINLY
NORTHWESTERN PA; COLDER AREAWIDE WITH GUSTY WEST WINDS.
TUE...NO SIG WX EXPECTED; VERY COLD.
TUES NIGHT-WED...SCATTERED SNOW SHOWERS POSSIBLE, BRINGING
LOCALIZED RESTRICTIONS; VERY COLD.
THU...NO SIG WX EXPECTED; CONTINUED COLD.
CTP WATCHES/WARNINGS/ADVISORIES
EXTREME COLD WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING
FOR PAZ004>006-010>012-017-018-024-033-037-041-042.
WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 10 PM
EST THIS EVENING FOR PAZ019-024>028-033>035-042-045-046-
049>052.
WINTER STORM WARNING FROM 4 AM EARLY THIS MORNING TO 10 PM EST
THIS EVENING FOR PAZ036-053-056>059-063>066.
SYNOPSIS...NPB
NEAR TERM...DANGELO/NPB
SHORT TERM...DANGELO/NPB
LONG TERM...MARTIN/EVANEGO
AVIATION...EVANEGO/BAUCO
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