913
FXUS61 KCTP 170805
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
305 AM EST TUE DEC 17 2024
SYNOPSIS
MILDER AND MOIST AIR OVERRUNNING THE COLD, DENSE AIRMASS
ENTRENCHED IN THE CENTRAL VALLEYS WILL LEAD TO PERIODS OF RAIN
THROUGH EARLY TONIGHT, BEFORE GRADUALLY TAPERING OFF FROM WEST
TO EAST DURING THE PREDAWN HOURS OF TUESDAY.
MILDER TEMPERATURES WILL ACCOMPANY HIGH PRESSURE AS IT BUILDS
INTO THE REGION TUESDAY, THEN A WEAK AREA OF LOW PRESSURE
LIFTING OUT OF THE OHIO VALLEY IS LIKELY TO PUSH INTO
PENNSYLVANIA BY LATE WEDNESDAY WITH ANOTHER PERIOD OF RAIN
POSSIBLY ENDING AS SNOW.
NEAR TERM /UNTIL 7 AM THIS MORNING/
WE HAD AN UNUSUALLY SHORT TIME GAP BETWEEN PRECIP PRODUCING
SYSTEMS YESTERDAY INTO EARLY THIS MORNING, AND THE CURRENT
ROUND(S) OF (LIQUID) PRECIP (IN THE FORM OF LIGHT RAIN AND
DRIZZLE) WHICH IS RACING EAST ACROSS THE CWA AND SUPPORTED BY A
FEW SLUGS OF LOW TO MID LEVEL WARM ADVECTION VIA A 50-55 KT
WSWRLY LLJS (OVER NORTHERN PA AND NORTHERN OHIO) AND THE
SOUTHERN EDGE OF A 115 KT UPPER LEVEL JET.
THE FIRST BATCH OF RAIN IS OVER THE LOWER SUSQ VALLEY AND POINTS
EAST, WHILE A SECOND AREA IS NESTLED WITHIN THE AXIS OF PWATS
AROUND 0.90 OF AN INCH JUST AHEAD OF A COLD FRONT.
SW TO WESTERLY WINDS WILL KICK UP (INTO THE 25 TO 30 MPH RANGE)
ABOUT 3 HOURS EITHER SIDE OF THE CFROPA THAT WILL OCCUR
OVERNIGHT.
MRMS HAS CONFIRMED OUR RAINFALL FORECAST AND DISTRIBUTION OF
HEAVIER AMOUNTS ACROSS THE NRN 1/2 OF THE CWA.
ENSEMBLE MEAN RAINFALL BY THE PREDAWN HOURS OF TUESDAY WILL BE
THE GREATEST BETWEEN ROUTE 6 AND I-80 IN NORTHERN PA WHERE
BETWEEN 0.25 AND 0.40 INCH IS EXPECTED WHILE THE LEAST WILL
FALL ACROSS THE SOUTHERN VALLEYS WITH GENERALLY 0.1 - 0.2 OF AN
INCH.
MIN TEMPERATURES IN THE MID 30S TO LOW 40S HAVE OCCURRED (OR
WILL OCCUR SHORTLY IN A FEW SPOTS, WITH THE MERCURY RISING VERY
SLOWLY (ABOUT 2-4 DEG F) OVERNIGHT. LOOK FOR TEMPS TO RANGE FROM
THE UPPER 30S TO MID 40S BY DAYBREAK TUESDAY.
SHORT TERM /7 AM THIS MORNING THROUGH 6 PM WEDNESDAY/
AFTER THE RAIN EXITS TO THE EAST OF THE FORECAST AREA EARLY
TUESDAY, THERE WILL BE A LIGHT TO MODERATE WESTERLY FLOW WITH
GUSTS IN THE MID TEENS TO AROUND 20 MPH. STRATUS DECK MAY BE
STUBBORN TO BREAK ONCE AGAIN, BUT THE CLOUD LAYER WILL BE ABOUT
HALF AS THICK AS TODAY, AND THE WESTERLY LLVL FLOW AND
ASSOCIATED ADIABATIC WARMING/DRYING SHOULD ALLOW SOME BREAKS OF
SUN/BLUE SKY.
HIGH PRESSURE BRIEFLY ATTEMPTS TO BUILD IN BEHIND A COLD FRONT
TUESDAY NIGHT INTO THE FIRST HALF OF WEDNESDAY, WHICH WILL KEEP
THE REGION MAINLY DRY. TUESDAY WILL BE THE WARMEST DAY OF THE
PERIOD WITH HIGHS IN THE 40S AND 50S.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
WET SYSTEM ON WED WILL LIKELY PRODUCE SN FOR THE NW HALF OF THE
CWA WITH RAIN ELSEWHERE. PROBABLY NOT QUITE 0.50" OF QPF, AND
JUST AN INCH OR TWO OF SNOW OVER THE NW. DRYING OUT AND GUSTY
ON THURS.
CLIPPER MOVING ACROSS THE GREAT LAKES ON FRI SHOULD PRODUCE A
LITTLE LIGHT SNOW, BUT DOES NOT LOOK LIKE A SIGNIFICANT
SNOWFALL. HOWEVER, THE GFS HAS THE SHARPEST PART OF THE UPPER
TROUGH PASSING OVERHEAD LATE FRI/EARLY FRI NIGHT. TEMPS ARE
ALREADY COLD, BUT DEPENDING ON TIMING, SNSQ ARE POSSIBLE, ESP IF
THE FORCING ARRIVES MID-AFTN. THE AIR MASS BEHIND THE CLIPPER
SYSTEM IS VERY COLD, AND WE HAVE MADE SURE TO STAY ON THE LOW
SIDE OF GUIDANCE FOR TEMPS SAT- SUN NIGHT. SUN NIGHT MAY BE THE
COLDEST AS THE SFC RIDGE WILL BE CRESTING OVERHEAD AND LAKE
EFFECT CLOUDS WILL BE GOING AWAY.
AVIATION /08Z TUESDAY THROUGH SATURDAY/
LOW CIGS WITH IFR/LIFR CONDITIONS CONTINUE THROUGH THE
SUSQUEHANNA VALLEY AS A DEEP LAYER OF SFC MOISTURE RESIDES
BENEATH A STRENGTHENING LOW LEVEL INVERSION. THESE LOW CIGS ARE
EXPECTED TO STICK AROUND THROUGH 12Z BEFORE A COLD FRONT
APPROACHES.
A WEAK COLD FRONT APPROACHING FROM THE WEST WILL BRING A BROKEN
LINE OF SHOWERS THAT WILL WEAKEN EVEN MORE AS IT PUSHES
EASTWARD. BEHIND THE FRONT, LOWER DEWPOINT AIR WILL HELP TO
SCOUR OUT LOW CIGS MAINLY ACROSS WESTERN AIRFIELDS BETWEEN 08Z
AND 10Z, HOWEVER BKN MVFR CIGS ARE LIKELY TO REDEVELOP BEFORE
SUNRISE. THE FRONT WILL MAKE IT TO THE LOWER SUSQ VALLEY AROUND
12Z.
IMPROVEMENT CONTINUES WITH ALL TERMINALS EXCEPT BFD LIKELY
RISING OUT OF IFC WITHIN A COUPLE OF HOURS OF SUNRISE.
LLWS IS OCCURRING AND AND IS NEAR PEAK. 40-45KT ARE EXPECTED
NEAR THE TOP OF THE LAYER, AS THE HIGHEST 925-850MB WIND SURGES
THROUGH.
OUTLOOK...
WED-THU...FOG POSSIBLE WED MORNING, THEN RAIN MOVES IN DURING
THE AFTERNOON AND CONTINUES INTO THURSDAY, BEFORE PARTIAL
CLEARING LATER THURSDAY.
FRI...IFR POSSIBLE IN SNOW NW & RAIN SE.
SAT...MVFR CIGS NW.
CLIMATE
ASTRONOMICAL WINTER (SOLSTICE) BEGINS ON SATURDAY, DECEMBER 21ST
AT 4:19 A.M. EST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/COLBERT
LONG TERM...LAMBERT/DANGELO/BAUCO
AVIATION...DANGELO/COLBERT
CLIMATE...STEINBUGL
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