180
FXUS61 KCTP 170349
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1049 PM EST MON DEC 16 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 AFTER
MIDNIGHT.
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 TUESDAY MORNING/
WE HAD AN UNUSUALLY SHORT TIME GAP BETWEEN PRECIP PRODUCING
SYSTEMS YESTERDAY INTO EARLY THIS MORNING, AND THE CURRENT
ROUND OF (LIQUID) PRECIP WHICH IS RACING EAST ACROSS THE CWA
AND SUPPORTED BY A SLUG OF LOW TO MID LEVEL WARM ADVECTION VIA
A 50-55 KT WSWRLY LLJ AND THE SOUTHERN EDGE OF A 115 KT UPPER
LEVEL JET.
MUCH OF THE STEADIER RAIN WILL BE ON THE FRONT END OF THE
SYSTEM EARLY THIS EVENING WHEN ISENTROPIC ASCENT AND MOISTURE
TRANSPORT ARE STRONGEST, WHILE ANY LINGERING RAIN AFTER MIDNIGHT
WILL LIKELY COME IN THE FORM OF SCATTERED SHOWERS.
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 WILL OCCUR EARLY TONIGHT 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 TUESDAY MORNING THROUGH TUESDAY NIGHT/
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 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 /04Z TUESDAY THROUGH SATURDAY/
TROUGH AXIS IS ALMOST INTO THE CWA. THE BACK EDGE OF THE PRECIP
OVER ERI-YNG IS LIKELY THE END OF ANY ACCUMULATING RAIN TONIGHT.
THE TIMING STILL LOOKS LIKE A 04-07Z PASSAGE ACROSS THE CWA.
AFTERWARD, DRIZZLE MAY LINGER, BUT SOME LOWERING OF SFC TD
SHOULD OCCUR BY MORNING.
PREV...
STRONG SHORTWAVE TROUGH ALOFT IS HELPING TO BRING WARM AIR UP
AND INTO PA. AN AREA OF RAIN ON TOP OF A WARM FRONT WILL CROSS
THE AIRSPACE IN JUST 3-4HRS. AFTER THIS MAIN SLUG OF RAIN MOVES
THROUGH, SOME ISOLD SHRA WILL PUSH THRU FROM WEST TO EAST
SHORTLY AFTER MIDNIGHT. PATCHY DRIZZLE/LIGHT RAIN WILL LINGER
FOR A FEW MORE HOURS. WIDESPREAD IFR AND LIFR CURRENTLY WILL
IMPROVE AFTER MIDNIGHT.
LLWS IS OCCURRING AND AND IS NEAR PEAK OVER THE WEST (JST/BFD)
AND SHOULD PEAK SHORTLY IN AOO-UNV-IPT. 40-45KT ARE EXPECTED
NEAR THE TOP OF THE LAYER, AS THE HIGHEST 925-850MB WIND SURGES
THROUGH.
IMPROVEMENT CONTINUES WITH ALL TERMINALS EXCEPT BFD AND JST
RISING OUT OF IFC WITHIN A COUPLE OF HOURS OF SUNRISE. EVEN
THOSE TWO HAVE <30PCT CHC OF STAYING IFR PAST 14Z, AND JST
MAY EVEN CLEAR OUT (VFR/SKC) BY MID-MORNING. BFD IS LIKELY
(70PCT) TO STAY MVFR THRU THE DAY.
TEMPS STAY MILD OVERNIGHT AND RISE WELL INTO THE 40S AND 50S
(SE) ON TUES. THE MELTING SNOW WILL MAKE SOME SHALLOW FOG, AND
IT SHOULD GET FOGGY AGAIN FOR WED AM AS THE AIR CALMS DOWN.
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...LAMBERT/DANGELO
CLIMATE...STEINBUGL
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