474  
FXUS61 KCTP 170413  
AFDCTP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE STATE COLLEGE PA  
1113 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 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 TUESDAY 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 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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