623
FXUS61 KCTP 170035
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
735 PM EST THU JAN 16 2025
SYNOPSIS
A POTENT UPPER LEVEL SHORTWAVE AND ASSOCIATED SURFACE TROUGH
WILL MOVE ACROSS PENNSYLVANIA LATE TODAY ACCOMPANIED BY PERIODS
OF SNOW, THAT WILL BE LIGHT IN MOST PLACES.
HIGH PRESSURE WILL BUILD INTO THE REGION FRIDAY, THEN A COLD
FRONT WILL PUSH THROUGH THE STATE LATE SATURDAY. A DEEP UPPER
LEVEL TROUGH WILL PIVOT EASTWARD INTO PENNSYLVANIA SUNDAY INTO
THE FIRST HALF OF NEXT WEEK, LEADING TO BITTERLY COLD WEATHER
FOR SEVERAL DAYS.
NEAR TERM /THROUGH FRIDAY/
RELATIVELY WEAK LOW-MID LEVEL ISENT LIFT FROM THE WEST-SOUTHWEST
WAS OCCURRING ACROSS PA AND POINTS UPSTREAM OVER LAKES ERIE AND
SE LOWER MICHIGAN WHERE WE'RE SEEING VARYING REFLECTIVITY
INTENSITIES ON DUAL POL AND TEXTURED/DEEPER CLOUD COVER ON
VISIBLE SAT LOOP.
THE STRONGEST UPSLOPE COMPONENT AND ISENTROPIC LIFT FROM THE
SWRLY SFC WIND AND MEAN 925-850 MB WSW FLOW WILL RESIDE OVER THE
WESTERN MTNS OF PA AND THE LAUREL HIGHLANDS WHERE WINTER
WEATHER ADVISORIES (AND A WINTER STORM WARNING FOR SOMERSET
COUNTY) WILL REMAIN IN EFFECT THROUGH THE REST OF THE DAY AND
TONIGHT (ENDING AT 12Z FRIDAY).
THE LLVL DOWNSLOPE COMPONENT TO THE WIND AND TRANSIENT PULSES OF
ISENT LIFT ELSEWHERE ACROSS CENTRAL PA AND THE SUSQ VALLEY HAS
KEPT THE SNOW INTENSITY ALMOST ENTIRELY IN THE LIGHT CATEGORY
WITH SOME BRIEF VSBY DROPS BELOW 1SM, BUT PREDOMINANT VSBYS OF
2-4SM AND SNOWFALL RATES 0.25 INCH/HR OR LESS WILL OCCUR THROUGH
THIS EVENING, BEFORE THE SNOW TAPERS TO JUST SOME FLURRIES LATER
TONIGHT OVER THE CENTRAL RIDGE AND VALLEY REGION IN THE WAKE OF
A RATHER WEAK COLD FRONT.
TEMPS FOR THE REST OF THE DAYLIGHT HOURS WILL RANGE FROM THE LOW
20S ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST TO THE MID
AND UPPER 20S RESPECTIVELY THROUGHOUT THE CENTRAL AND SOUTHERN
VALLEYS.
NEAR NEUTRAL LLVL TEMP ADVECTION FROM THE WEST AND PLENTY OF
CLOUD COVER THRU MOST OF THE NIGHT TONIGHT WILL LIMIT TEMPS FROM
FALLING BELOW THE UPPER TEENS NE, AND M20S IN THE SOUTH-
CENTRAL MTNS (0-10F ABOVE NORMALS).
SHORT TERM /FRIDAY NIGHT/
LAKE EFFECT (NW MTNS) AND OROGRAPHIC SNOW (LAURELS) WILL END
QUITE QUICKLY BY NOON FRIDAY AS A SFC RIDGE BUILDS OVERHEAD AND
THE SUBSIDENCE INVERSION CRASHES TO 3KFT AGL, AND LOWER IN THE
AFTERNOON.
CLEARING TO THE SE OF THE MTNS WILL HELP TEMPS CLIMB TO NEAR
40F FOR A HIGH FRIDAY AFTERNOON, BUT READINGS WILL BE CAPPED OFF
IN THE UPPER 20S OVER THE NW MTNS (WITHIN 3F EITHER SIDE OF
DAILY NORMALS). ANY LINGERING LES SNOW BANDS SHOULD LIFT N OF
THE NY STATE LINE BY EARLY AFTN, AND EVEN SOME SUNSHINE IS
LIKELY ACROSS THE LAUREL HIGHLANDS AND NW MTNS DURING THE MID TO
LATE AFTERNOON AS THE STRATOCU DISSIPATES PRIOR TO THE HIGHER
CLOUD COVER IN ADVANCE OF THE NEXT WEATHER MAKER THICKENING UP.
LONG TERM /SATURDAY THROUGH THURSDAY/
THE EXTENDED PERIOD WILL BEGIN WITH AN UPPER LEVEL RIDGE
PUSHING OFF THE EAST COAST. THE RIDGE WILL BE REPLACED BY UPPER
LEVEL TROUGHING THAT WILL PERSIST OVER THE EASTERN UNITED STATES
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK.
SATURDAY WILL FEATURE (RELATIVELY) MILD TEMPERATURES AS A COLD
FRONT CROSSES THE COMMONWEALTH, ACCOMPANIED BY LIGHT SNOW
ACROSS NORTHERN PA AND LIGHT RAIN OR SNOW (OR EVEN A BIT OF
FREEZING RAIN) ACROSS THE SOUTH. HIGHS WILL RANGE FROM THE LOW
TO MID 30S ACROSS THE NORTHERN MOUNTAINS TO THE LOW 40S
SOUTHEAST OF THE MOUNTAINS.
THE FRONT WILL PULL TO OUR EAST SATURDAY NIGHT INTO SUNDAY,
ALTHOUGH ITS FORWARD PROGRESS WILL SLOW. WE WILL HAVE TO WATCH
FOR THE POTENTIAL FOR AN AREA OF LOW PRESSURE TO DEVELOP OFF
THE CAROLINA COAST AND PUSH SOME LIGHT SNOW NORTHWARD INTO
SOUTHEASTERN PENNSYLVANIA ON SUNDAY.
COLDER AIR WILL BEGIN TO FILTER INTO THE REGION SATURDAY NIGHT
INTO SUNDAY AS WELL, WITH A REINFORCING SHOT OF BITTERLY COLD
AIR ARRIVING SUNDAY NIGHT INTO MONDAY. TEMPERATURES WILL BOTTOM
OUT TUESDAY, WITH HIGHS RUNNING 20 TO 30 DEGREE BELOW AVERAGE.
CONSIDERING THAT LATE JANUARY IS THE CLIMATOLOGICAL COLDEST TIME
OF THE YEAR, HIGHS THAT FAR BELOW AVERAGE MEANS THAT WE ARE IN
FOR A SIGNIFICANT BOUT OF ARCTIC AIR.
THE UPPER-LEVEL TROUGH WILL BEGIN TO LIFT OUT OF THE AREA BY
LATE NEXT WEEK, WHICH SHOULD RESULT IN SLOWLY MODERATING
TEMPERATURES.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
THE MAIN AVIATION CONCERN OVERNIGHT WILL BE ACROSS THE W MTNS,
WHERE RESIDUAL MOISTURE BEHIND EXITING LOW PRESSURE WILL PRODUCE
LOW CIGS AND LINGERING LIGHT SNOW. UPSTREAM OBSERVATIONS AND
MODEL SOUNDINGS SUPPORT PREDOMINANTLY IFR CONDITIONS FROM KBFD
SOUTH THROUGH KJST OVERNIGHT.
ELSEWHERE, LIGHT SNOW OVER THE EASTERN HALF OF PA WILL TAPER
OFF THIS EVENING, AS AN ASSOCIATED WEAK LOW PRESSURE SYSTEM
PASSES OFF OF THE DELMARVA PENINSULA. RADAR TRENDS INDICATE
TEMPO MVFR CONDITIONS CAN BE EXPECTED FROM KIPT SOUTH THROUGH
KMDT/KLNS UNTIL AROUND 04Z, WITH A HIGH CONFIDENCE IN VFR
THEREAFTER. FURTHER WEST, MODEL SOUNDINGS INDICATE LINGERING
MVFR CIGS ARE LIKELY AT KUNV/KAOO THROUGH THE NIGHT.
A RIDGE OF HIGH PRESSURE BUILDING INTO PA FROM THE OHIO VALLEY
WILL BRING IMPROVING FLYING CONDITIONS FRIDAY, WITH LIGHT WINDS
ACROSS THE ENTIRE REGION. FORECAST SOUNDINGS INDICATE CIGS
ACROSS THE W MTNS SHOULD LIFT TO MVFR BY AROUND 15Z FOLLOWED BY BREAKING
CLOUDS LATE IN THE DAY. IMPROVEMENT SHOULD ARRIVE EARLIER
DOWNWIND (EAST) OF THE ALLEGHENIES, WITH WIDESPREAD VFR
ANTICIPATED BY 16Z.
INCREASING SOUTHWEST WINDS ALOFT, COMBINED WITH RELATIVELY LIGHT
SURFACE WINDS, COULD POTENTIALLY RESULT IN LLWS CRITERIA FRIDAY
EVENING ACROSS THE NW MTNS (KBFD).
OUTLOOK...
SAT...LIGHT SNOW/LOW CIGS LIKELY, MAINLY N AND W MTNS. EVENING
FOG POSSIBLE SOUTHEAST PA. EARLY AM LLWS ALSO POSSIBLE, MAINLY
NW MTNS.
SUN...AM LOW CIGS POSSIBLE W MTNS AND SOUTHEAST PA. SNOW
POSSIBLE SOUTHERN PA LATER IN THE DAY.
MON...LIGHT SNOW/VIS REDUCTIONS POSSIBLE W MTNS, MAINLY AM.
TUE...NO SIG WX EXPECTED.
CTP WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR PAZ004-005-
010-017-024.
WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR PAZ033.
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...FITZGERALD/EVANEGO
AVIATION...FITZGERALD
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