251
FXUS61 KCTP 201707
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1207 PM EST MON JAN 20 2025
SYNOPSIS
* SNOW SHOWERS DISSIPATE IN THE LAUREL HIGHLANDS TODAY
* ARCTIC BLAST DELIVERS FRIGID/EXTREME COLD THROUGH WEDNESDAY
* DEEP FREEZE ENDS LATE WEEK WITH MORE SEASONABLE TEMPERATURES
FORECAST INTO THE UPCOMING WEEKEND
NEAR TERM /THROUGH TONIGHT/
930 AM UPDATE... WINTER STORM WARNING (SOMERSET) AND WINTER
WEATHER ADVISORY (CAMBRIA) WERE ALLOWED TO EXPIRE ON SCHEDULE,
AS OF 9 AM.
OVERALL, A VERY COLD AND FAIRLY DRY AIR MASS CONTINUES TO
DESCEND ON THE COMMONWEALTH THIS MORNING. THE COMBINATION OF A
DRY BOUNDARY LAYER ENVIRONMENT AND GRADUALLY BACKING LOW-LEVEL
FLOW INTO THE WSW SHOULD REDUCE UPSTREAM LAKE FETCH AND ALLOW
PRESENT SNOW SHOWERS TO CONTINUE TO SCATTER OUT AND REDUCE TO
FLURRIES ACROSS NW PA AND THE ALLEGHENIES. ALTHOUGH SNOWFLAKES
WILL BE IN THE AIR OVER THESE AREAS FROM TIME TO TIME,
ADDITIONAL ACCUMULATIONS LOOK MINIMAL FOR THE REMAINDER OF THE
DAY.
FARTHER EAST INTO THE MIDDLE AND LOWER SUSQUEHANNA VALLEYS,
DOWNSLOPING FLOW AND SHALLOW MOISTURE TO BEGIN WITH SHOULD BRING
PARTLY TO MOSTLY SUNNY SKIES.
HOWEVER, THE BITING ARCTIC COLD WILL BE EVER-PRESENT. AFTERNOON
HIGHS WILL HAVE A TOUGH TIME MAKING IT MUCH ABOVE 20 DEGREES IN
THE SUSQUEHANNA VALLEY AND OUT OF THE SINGLE DIGITS ACROSS THE
ALLEGHENIES. BRISK WINDS WILL MAKE IT FEEL COLDER, WITH APPARENT
TEMPERATURES GENERALLY IN THE PLUS OR MINUS SINGLE DIGITS, WITH
-10 TO -15 IN THE LAURELS, WHERE AN EXTREME COLD ADVISORY IS
STILL IN EFFECT.
PREVIOUS DISCUSSION... PERSISTENT LAKE STREAMER BANDS WILL
CONTINUE TO BRING SNOW TO THE LAUREL HIGHLANDS THIS MORNING.
MRMS RADAR TRENDS FAVOR THE BULK OF ADDITIONAL SNOW ACCUMULATION
MAINLY TO THE SOUTH OF US-22 AND ALONG THE WEST-FACING SLOPES
AND SUMMITS ON LAUREL MTN (SOMERSET/WESTMORELAND BORDER). FCST
SOUNDINGS SHOW FALLING INVERSION HEIGHTS INTO MIDDAY WITH SFC
RIDGE AXIS BUILDING TO THE EAST NORTHEAST THROUGH THE OHIO
VALLEY. THIS PATTERN FAVORS A GRADUAL DIMINISHING/ENDING TO THE
SNOW SHOWER ACTIVITY OVER THE LAURELS, BUT HIRES MODEL DATA DOES
SHOW SOME LIGHT SNOW SHOWERS REDEVELOPING OVER THE NW
ALLEGHENIES LATER THIS AFTERNOON. WINTER WEATHER HEADLINES
SHOULD BE ALLOWED TO EXPIRE AT 9AM.
BREAKS IN THE CLOUDS AND LIGHT/CALM WINDS HAS ALLOWED FOR
SIGNIFICANT RADIATIONAL COOLING IN PARTS OF EAST-CENTRAL PA.
WITH HELP FROM FRESH SNOW COVER, KSEG AND KTHV AIR TEMPS HAVE
PLUMMETED TO -2F AND -1F AS OF 09Z!
FRIGID ARCTIC AIR WILL CONTINUE TO SPILL INTO THE AREA THROUGH
TONIGHT. HIGHS TODAY IN THE 10-20F RANGE ARE 15 TO 25 DEGREES
BELOW THE HISTORICAL AVERAGE FOR LATE JANUARY. THE DEPARTURES
ARE EVEN MORE IMPRESSIVE WHEN YOU PUT INTO PERSPECTIVE THAT THIS
IS TYPICALLY THE COLDEST TIME OF THE YEAR! WE EXPANDED THE COLD
WEATHER ADVY TO COVER THE ENTIRE CWA TONIGHT WITH MINIMUM WIND
CHILLS BETWEEN 5 AND 25 DEGREES BELOW ZERO INTO EARLY TUESDAY
MORNING.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
BITTER TO EXTREME COLD CONDITIONS LAST THROUGH MIDWEEK WITH COLD
WX ADVISORY AND EXTREME COLD WARNINGS IN EFFECT. TUESDAY NIGHT
LOOKS LIKE THE COLDEST WITH LOWS FROM AROUND 0F TO -15F AND
WIND CHILLS FROM 10 TO 25 BELOW ZERO.
REINFORCING UPPER LEVEL TROUGH AND ARCTIC FRONT SHOULD GENERATE
SNOW SHOWERS AND FLURRIES ON TUESDAY OVER THE ALLEGHENIES AND
WE KEEN TO RAISE POPS OVER THE BONE DRY NBM. SNSQ PARAMETER
SUGGEST SOME LOCALLY HEAVIER SNOW BURSTS ARE POSSIBLE MAINLY
OVER FAR WESTERN PA.
WEDNESDAY NIGHT LOOKS LIKE THE LAST VERY COLD AND FRIGID NIGHT
BEFORE TEMPS BEGIN TO MODERATE INTO LATE WEEK.
LONG TERM /THURSDAY THROUGH SUNDAY/
SOME MODERATION IN TEMPERATURES IS EXPECTED THURSDAY INTO THE
WEEKEND, AND WE MAY FINALLY SEE TEMPERATURES CLOSER TO AVERAGE
BY SUNDAY.
AN APPROACHING SHORTWAVE COULD REINVIGORATE SNOW SHOWER ACTIVITY
ACROSS WESTERN PA ON FRIDAY, WITH THE NEXT WAVE BRINGING A
CHANCE OF SNOW SHOWERS (PERHAPS MIXED WITH RAIN SOUTH) BY SUNDAY.
AVIATION /18Z MONDAY THROUGH SATURDAY/
18Z UPDATE... ALTHOUGH PERIODIC MVFR-FUEL ALTERNATE RESTRICTIONS
CAN BE EXPECTED THIS AFTERNOON ACROSS THE ALLEGHENIES (KBFD AND
KJST TERMINAL SITES) IN BLOWING SNOW AND LIGHT SNOW
SHOWERS/FLURRIES, THERE IS HIGH CONFIDENCE (80-90%) THAT
VFR/UNRESTRICTED WILL PREVAIL ACROSS CENTRAL PA THROUGH MIDDAY
TUESDAY. ALTHOUGH THE AIR WILL BE COLD, IT IS ALSO FAIRLY DRY,
AND THAT DRY AIR IS WHAT IS EXPECTED TO KEEP VFR CONDITIONS
LARGELY IN PLACE.
SURFACE WINDS WILL BE GUSTY THIS AFTERNOON ACROSS ALL OF CENTRAL
PA (GUSTS INTO THE 25-30 KT RANGE), AND INTO THE EARLY EVENING
OVER THE LOWER SUSQUEHANNA VALLEY (KMDT AND KLNS TERMINAL
SITES). WINDS SHOULD BECOME LESS GUSTY LATER TONIGHT AND TUESDAY
MORNING, AND ALSO BACK INTO A WEST-SOUTHWESTERLY DIRECTION.
OUTLOOK...
WED-SAT...PRIMARILY VFR ANTICIPATED.
CTP WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL NOON EST WEDNESDAY FOR PAZ004>006-
010>012-017-018-037-041-042.
COLD WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
WEDNESDAY FOR PAZ019-025>028-034>036-045-046-049>053-056>059-
063>066.
COLD WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ024-
033.
EXTREME COLD WARNING FROM 7 PM THIS EVENING TO NOON EST
WEDNESDAY FOR PAZ024-033.
SYNOPSIS...STEINBUGL
NEAR TERM...JUREWICZ/STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...MARTIN/EVANEGO
AVIATION...JUREWICZ
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