424
FXUS61 KCTP 230407
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1107 PM EST WED JAN 22 2025
SYNOPSIS
*A WEAK CLIPPER TRACKING NORTH OF PA WILL BRING INCREASING
CLOUD COVER TO THE COMMONWEALTH THIS EVENING AND INTO THURSDAY.
*LAKE EFFECT AND UPSLOPE SNOW SHOWERS POSSIBLE BEGINNING LATE
THURSDAY AND INTO FRIDAY, BRINING GENERALLY LIGHT ACCUMULATIONS
TOPPING OUT ACROSS NORTHWESTERN PENNSYLVANIA.
*TEMPERATURES TREND TOWARDS AVERAGE THIS WEEKEND AND INTO THE
BEGINNING OF NEXT WEEK.
NEAR TERM /UNTIL 7 AM THURSDAY MORNING/
SURFACE RIDGING ALONG THE MID ATLANTIC COAST WILL PROVIDE
CENTRAL PA WITH FAIR AND COLD CONDITIONS TONIGHT. EXPECT VARYING
AMOUNTS OF MID LEVEL CLOUDINESS ASSOCIATED WARM ADVECTION
PRECEDING A PAIR OF MID LEVEL VORT MAXES LIFTING THROUGH AN
UPSTREAM TROUGH.
MOSTLY CLEAR SKIES, LIGHT WIND AND FRESH SNOW COVER WILL RESULT
IN THE MOST EFFICIENT RADIATIONAL COOLING ACROSS SOUTHEAST PA,
WHERE WE HAVE NUDGED MIN TEMPS A BIT BELOW NBM GUIDANCE. MORE
PERSISTENT CLOUDINESS AND A MORE ACTIVE SOUTHERLY BREEZE SHOULD
HOLD READINGS UP A BIT ACROSS THE N MTNS. EXPECT MIN TEMPS IN
THE LOWER SINGLE DIGITS ACROSS MUCH OF THE FORECAST AREA, BUT
THE COLDEST RURAL VALLEYS OF SOUTH-CENTRAL PA ARE LIKELY TO DIP
INTO THE 5-10 BELOW ZERO RANGE.
SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
A MARKED WARMUP IS ANTICIPATED THURSDAY, AS A SOUTHWEST FLOW
DEVELOPS BETWEEN THE SURFACE RIDGE OFF OF THE EAST COAST AND AN
UPSTREAM COLD FRONT OVER THE GRT LKS. SEE NO REASON TO DEVIATE
FROM NBM MAX TEMPS, WHICH ARE IN THE 20S.
THE BULK OF MODEL GUIDANCE POINTS TO MOSTLY SUNNY SKIES FOR MUCH
OF CENTRAL PA THURSDAY, AS THE STRONGEST MID LEVEL WARM
ADVECTION LIFTS NORTH OF THE PA/NY BORDER. RH TIMESECTIONS
THEN INDICATE CLOUDS ARRIVING FROM WEST TO EAST LATE IN THE DAY
AHEAD OF THE APPROACHING COLD FRONT. MODEL SOUNDINGS INDICATE
THE RETURN MOISTURE AHEAD OF THE FRONT WILL BE SHALLOW, BUT
COULD SUPPORT A BIT OF VERY LIGHT SNOW WHERE THE WSW FLOW IS
FORCED TO ASCEND THE ALLEGHENY PLATEAU THURSDAY EVENING.
LARGE SCALE SUBSIDENCE BEHIND THE EXITING COLD FRONT SHOULD
RESULT IN MAINLY DRY CONDITIONS FRIDAY. HOWEVER, VEERING
BOUNDARY LAYER FLOW SHOULD RESULT IN SCATTERED LAKE EFFECT SNOW
SHOWERS OVER THE NW MTNS. LOW INVERSION HEIGHTS AND A MAINLY
FROZEN LK ERIE SHOULD KEEP ACCUMULATIONS MINIMAL. MODEL QPF
SUPPORTS TOTAL SNOWFALL THURSDAY PM THROUGH FRIDAY RANGING FROM
A DUSTING OVER MOST OF THE ALLEGHENY PLATEAU, TO PERHAPS 2
INCHES IN THE SNOWBELT OF NORTHWEST WARREN COUNTY. ANY SNOW
SHOWERS SHOULD END FRIDAY NIGHT, AS SURFACE RIDGING BUILDS INTO
THE STATE AND BOUNDARY LAYER FLOW SHIFTS TO THE SOUTHWEST.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
MEDIUM RANGE GUIDANCE SUPPORTS MAINLY DRY AND SEASONABLY COLD
WEATHER THIS WEEKEND INTO EARLY NEXT WEEK, AS UPPER LEVEL
TROUGHING REMAINS OVER THE REGION DESPITE THE DEPARTURE OF THE
ANOMALOUS COLD. THE 18Z EPS INDICATES A SERIES OF WEAK,
MOISTURE-STARVED SHORTWAVES WILL TRAVERSE THE REGION IN THE
NORTHWEST FLOW. THE PASSAGE OF EACH OF THESE SYSTEMS WILL BRING
THE CHANCE OF A BIT OF VERY LIGHT SNOW OVER THE NW MTNS,
FOLLOWED BY SCATTERED LAKE-ENHANCED OROGRAPHIC SNOW SHOWERS OVER
THE ALLEGHENIES. HOWEVER, A LARGELY FROZEN LK ERIE SHOULD
RESULT IN MINIMAL ACCUMULATIONS.
A FEW ENSEMBLE MEMBERS ARE A BIT DEEPER WITH A PAIR OF
SHORTWAVES EARLY NEXT WEEK, RESULTING IN A WAVE OF LOW PRESSURE
PASSING SOUTH OF PA. THIS SCENARIO WOULD RESULT IN A PERIOD OF
SNOW OVER PRIMARILY SOUTHERN PA. HOWEVER, THIS APPEARS A LOW
PROBABILITY, WITH THE BULK OF GUIDANCE CURRENTLY SUPPORTING DRY
WEATHER OUTSIDE OF SOME VERY LIGHT LAKE-ENHANCED OROGRAPHIC SNOW
OVER THE N AND W MTNS.
AVIATION /04Z THURSDAY THROUGH MONDAY/
SCATTERED TO BROKEN CLOUDS ARE CONTINUING TO STREAM IN FROM THE
WEST AS OF 0Z. VFR CONDITIONS ARE EXPECTED TO CONTINUE FOR THE
REST OF TONIGHT AND THROUGH THE DAY TOMORROW. MID AND HIGH
CLOUDS WILL INCREASE IN COVERAGE DURING THE EVENING AS WARM
ADVECTION INCREASES AHEAD OF A MOISTURE- STARVED DISTURBANCE
APPROACHING FROM THE WEST. MODEL SOUNDINGS SUGGEST THAT MUCH OF
THIS CLOUD COVER WILL DISSIPATE DURING THE DAY ON THURSDAY AND
PARTLY CLOUDY TO MAINLY CLEAR SKIES ARE EXPECTED AFTER 12Z.
WINDS WILL SHIFT TO THE WEST-SOUTHWEST THURSDAY AFTERNOON WHICH
WILL LEAD TO CLOUDS DEVELOPING AT BFD AND JST. MOISTURE WILL BE
VERY LIMITED, AT LEAST INITIALLY, SO NOT EXPECTING ANY SNOW
SHOWERS PRIOR TO 18Z. MODEL RH PROFILES DO SUGGEST THAT LOWER
CEILINGS DEVELOP DURING THE LATE AFTERNOON AND A FEW LAKE EFFECT
AND UPSLOPE SNOW SHOWERS COULD LEAD TO VISIBILITY RESTRICTIONS
AT BFD AND JST INTO THE EVENING. A MENTION OF PROB30 SNOW
SHOWERS HAS BEEN INCLUDED FOR BFD BETWEEN 19Z AND 21Z WITH
LIGHT SNOW AND LOWER CEILINGS LIKELY TOWARDS THE END OF THIS
FORECAST PERIOD.
OUTLOOK...
THU NIGHT...RESTRICTIONS POSSIBLE AT BFD AND JST WITH -SHSN.
FRI...MVFR/IFR CONDITIONS POSSIBLE WITH -SHSN IN NORTHERN &
WESTERN PA MAINLY DURING THE DAY.
SAT...VFR/NO SIG WX.
SUN-MON...MVFR IN -SHSN POSSIBLE IN NORTHERN & WESTERN PA.
CLIMATE
A RECORD LOW TEMPERATURE OF -11 DEGREES WAS SET AT ALTOONA, PA
LAST NIGHT. THE OLD RECORD WAS -5 DEGREES SET IN 1984.
A RECORD LOW TEMPERATURE OF -11 DEGREES WAS SET AT JOHNSTOWN,
PA LAST NIGHT. THE OLD RECORD WAS -9 DEGREES SET IN 1984.
A RECORD LOW TEMPERATURE OF -18 DEGREES WAS TIED AT BRADFORD,
PA LAST NIGHT. THE PREVIOUS RECORD LOW TEMPERATURE DATE WAS
2022.
RECORD LOW MAXIMUM TEMPERATURES FOR JANUARY 22:
HARRISBURG 14F IN 2014
WILLIAMSPORT 14F IN 1961
ALTOONA 10F IN 2014
BRADFORD 6F IN 2014
STATE COLLEGE 7F IN 1936
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...NPB
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD/NPB
LONG TERM...FITZGERALD
AVIATION...BAUCO/BOWEN
CLIMATE...STEINBUGL
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