157  
FXUS61 KCTP 170059  
AFDCTP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE STATE COLLEGE PA  
759 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/  
 
THE NEXT SYSTEM WILL BE MORE ENERGETIC WITH RAIN RETURNING TO  
THE FORECAST WEDNESDAY AFTERNOON OR EVENING, AS A DEVELOPING  
SURFACE LOW TRACKS OVER OR JUST EAST OF PENNSYLVANIA AND A  
PERIOD OF STRONG ISENT LIFT SPREADS ACROSS THE REGION IN  
ASSOCIATION WITH THE PASSAGE OF A SOUTHWESTERLY LLJ OF 55-65  
KTS. PRECIP WILL START OFF AS RAIN, BUT THE LATEST OPER MODELS  
AND ENSEMBLES SUGGEST ENOUGH COULD AIR SHOULD MOVE IN FROM THE  
WEST TO ALLOW FOR THE RAIN TO MIX WITH OR FULLY TRANSITION TO  
SNOW FOR AREAS WEST OF THE ALLEGHENY FRONT. NORTHWESTERLY FLOW  
BEHIND THIS SYSTEM SHOULD ALLOW FOR SOME LAKE EFFECT SNOW  
SHOWERS TO CONTINUE INTO THURSDAY.  
 
GUIDANCE IS BEGINNING TO COME INTO BETTER AGREEMENT IN REGARD TO  
THE SYSTEM THAT WILL MOVE THROUGH IN THE FRIDAY/SATURDAY  
TIMEFRAME. A WEAKENING SURFACE LOW WILL TRACK NEAR THE REGION ON  
SATURDAY AND WHILE MOISTURE LOOKS FAIRLY LIMITED, MOST OF THE  
REGION WILL LIKELY SEE LIGHT SNOW. UPSLOPE AND LAKE EFFECT SNOW  
SHOWERS LINGER THROUGH THE DAY ON SATURDAY BEFORE HIGH PRESSURE  
BUILDS IN FOR THE SECOND HALF OF THE WEEKEND AND INTO THE  
BEGINNING OF NEXT WEEK.  
 
TEMPERATURES WILL BE ON A DOWNWARD TREND THROUGH THE EXTENDED  
PERIOD, WITH MUCH COLDER AIR WORKING INTO CENTRAL PA BY SUNDAY.  
HIGH TEMPERATURES WILL BE IN THE 20S AND LOWS WILL BE IN THE  
SINGLE DIGITS AND TEENS.  
 
 
   
AVIATION /01Z TUESDAY THROUGH SATURDAY/  
 
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 AS THE WEST WIND DRIES THINGS OUT A BIT.  
 
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/BAUCO  
AVIATION...LAMBERT/DANGELO  
CLIMATE...STEINBUGL  
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