313  
FXUS61 KCTP 040227  
AFDCTP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE STATE COLLEGE PA  
1027 PM EDT THU OCT 3 2024  
   
SYNOPSIS  
 
* VALLEY FOG REDEVELOPS OVERNIGHT; CLOUDS AND A STRAY SHOWER  
POSSIBLE OVER EAST-CENTRAL PA LATER FRIDAY AND FRIDAY NIGHT  
* A GREAT START TO THE FIRST WEEKEND OF OCTOBER; RAIN SHOWERS  
RETURN FROM NW->SE LATER SUNDAY THROUGH SUNDAY NIGHT  
* DRYING OUT AND COOLING DOWN NEXT WEEK WITH FROST RISK  
 
 
   
NEAR TERM /UNTIL 8 AM FRIDAY MORNING/  
 
FOG HAS BEGUN TO FILL IN THE WEST BRANCH AND TRIBS N OF UNV.  
THE VALLEY FOG SHOULD CONTINUE TO EXPAND. THUS FAR, NOT BAD OR  
WIDESPREAD ENOUGH FOR A FOG ADVY. LOWER CLOUDS MOVING UP FROM  
THE S ARE NOT SOLID AS OF YET. 00Z NAM CONTINUES TO BE THE MOST  
AGGRESSIVE MODEL AT CLOUD COVERAGE/SPREAD NORTHWARD. THUS FAR,  
IT'S TOO AGGRESSIVE. WE'LL KEEP WITH THE GOING FCST OF OVERCAST  
NOT QUITE GETTING UP TO I-80 BY SUNRISE.  
 
SEG THE COLD SPOT AT 51F AT 02Z. LOW TEMPS WILL RANGE FROM  
MID/UPPER 40S IN THE NORTHERN TIER TO MID 50S ALONG THE MD  
BORDER (+5-10F ABOVE THE HISTORICAL AVERAGE FOR EARLY OCTOBER).  
WHEN CLOUDS ARRIVE/DEVELOP IN THE S, THEY MIGHT HELP TEMPS GO UP  
A COUPLE DEGS, AND ALMOST CERTAINLY LEVEL THEM OFF.  
 
 
   
SHORT TERM /8 AM FRIDAY MORNING THROUGH SUNDAY/  
 
VALLEY FOG AND LOW CLOUDS TO START THE DAY ON FRIDAY. MODEL  
GUIDANCE INDICATES A SHORTWAVE TROUGH ROTATING THROUGH THE LOWER  
GREAT LAKES TOMORROW AFTERNOON/EVENING COINCIDING WITH A SURGE  
OF LOW LEVEL MOISTURE IN ADVANCE OF A WEAK SFC COLD FRONT. THESE  
FEATURES WILL COMBINE TO DRIVE LOW POPS OVER THE NORTHERN AND  
EASTERN PORTIONS OF THE CWA THROUGH FRIDAY NIGHT.  
 
WARM ADVECTION PRECEDING THE COLD FRONT SHOULD PUSH TEMPS INTO  
THE LOW TO MID 70S FRIDAY AFTERNOON WITH THE LARGEST ANOMALIES  
OVER THE ALLEGHENY PLATEAU, WHERE THE MOST SUNSHINE IS EXPECTED.  
 
HIGH PRESSURE AND AN ASSOCIATED LOW-PWAT AIRMASS IS PROGGED TO  
BUILD SOUTHEAST INTO PA SATURDAY, PROVIDING THE REGION WITH  
MOSTLY SUNNY SKIES. ENSEMBLE MEAN 850MB TEMPS IN THE 7-9C RANGE  
SUPPORT HIGHS RANGING FROM THE MID 60S OVER THE N MTNS, TO THE  
MID 70S IN THE LOWER SUSQ VALLEY. HAVE UNDERCUT NBM DEWPOINTS  
SAT AFTERNOON BASED ON MODEL SOUNDINGS, WHICH SHOW VERY DRY AIR  
ABOVE A WEAK INVERSION.  
 
FAIR AND SEASONABLE WEATHER APPEARS LIKELY INTO THE SECOND HALF  
OF THIS WEEKEND, AS SURFACE HIGH PRESSURE BUILDS ACROSS THE  
STATE. WE'LL CONTINUE TO SLIGHTLY UNDERCUT NBM MIN TEMPS  
SATURDAY NIGHT, WHEN CONDITIONS FAVOR EFFICIENT RADIATIONAL  
COOLING DIRECTLY UNDER THE SURFACE HIGH. THIS WILL ALSO BE  
FAVORABLE FOR MORNING FOG ACROSS TYPICAL FOG PRONE AREAS ACROSS  
THE COMMONWEALTH THROUGH THE WEEKEND.  
 
 
   
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/  
 
INCREASING CLOUDS AHEAD OF THE NEXT CHANCE OF SHOWERS ARE  
EXPECTED SUNDAY NIGHT AS A COLD FRONT APPROACHES CENTRAL  
PENNSYLVANIA. THIS FORECAST CONTINUES TO OUTLINE THE BEST  
CHANCES FOR RAINFALL IN THE OVERNIGHT PERIOD INTO MONDAY MORNING  
ACROSS THE NORTHERN TIER AND THE LAUREL HIGHLANDS. RAINFALL IS  
EXPECTED TO CONTINUE WITH A EAST/NORTHEASTERLY PROGRESSION  
THROUGHOUT THE MONDAY MORNING HOURS. INSTABILITY CONTINUES TO  
LOOK FAIRLY LIMITED TO THE EARLIEST HOURS SUNDAY NIGHT ACROSS  
THE WESTERN HIGHLANDS ALONG WITH THE LOWER SUSQUEHANNA VALLEY,  
SO HAVE RETAINED SCHC OF THUNDERSTORMS IN THIS PERIOD. STORM  
CHANCES DECREASE CLOSER TO DAYBREAK ON MONDAY, SO HAVE LIMITED  
PRECIPITATION MENTIONS TO JUST SHOWERS THIS FORECAST CYCLE.  
 
ENHANCED WESTERLY FLOW IN THE WAKE OF THE COLD FRONT WILL ALLOW  
FOR LINGERING SHOWERS ACROSS MAINLY NW PA THROUGHOUT THE DAY ON  
MONDAY. GUIDANCE DOES OUTLINE HIGH PRESSURE BEGINNING TO BUILD  
INTO THE AREA LATE MONDAY AND INTO THE MID-WEEK ALLOWING FOR  
DRIER CONDITIONS TO PREVAIL FOR THE BULK OF CENTRAL PA ALTHOUGH  
HAVE RETAINED LOW-END SCHC POPS ACROSS NW PA ON WEDNESDAY WITH  
ENHANCED WESTERLY FLOW CONTINUING THROUGHOUT THE PERIOD.  
 
HIGH PRESSURE INFLUENCING THE AREA WILL ALLOW FOR CLEAR/MOSTLY  
CLEAR SKIES WHICH DOES PROMOTE UNDERCUTTING NBM MINTS TUESDAY  
AND WEDNESDAY NIGHTS. THE COMBINATION OF CLEAR SKIES, LIGHT  
WINDS,AND COOLER TEMPERATURES START TO BRING THE FIRST CONCERNS  
OF FROST INTO THE FORECAST ACROSS N PA. HAVE INTRODUCED FROST  
MENTIONS ON TUESDAY NIGHT GIVEN A SLIGHTLY MORE FAVORABLE SET-  
UP FOR FROST FORMATION WHILE LIMITING MENTIONS ON WEDNESDAY  
NIGHT DUE TO MORE UNCERTAINTY, BUT GIVEN SIMILAR ENVIRONMENTAL  
SET-UP, SUBSEQUENT FORECAST PACKAGES MAY NEED TO INTRODUCE  
FROST MENTIONS FOR THIS PERIOD.  
 
 
   
AVIATION /02Z FRIDAY THROUGH TUESDAY/  
 
MAINLY CLEAR SKIES WITH CALM WINDS AND PREVAILING VFR CONDITIONS  
ARE PRESENT OVER THE AIRSPACE FOR THE START OF THE 00Z TAF  
PACKAGE. THE AREA HAD THE CHANCE TO DRY OUT SOME TODAY WITH  
PLENTY OF SUNSHINE THROUGHOUT THE DAY, SO FOG WILL NOT BE AS  
QUICK TO FORM AS LAST NIGHT.  
 
AFTER 06Z FRIDAY, FOG CONCERNS BEGIN ENTERING THE FORECAST  
AREA AGAIN, WITH THE HIGHEST PROBABILITIES IN HREF GUIDANCE  
LIGHTING UP AT AOO (09-13Z FRIDAY) AND UNV (10-13Z FRIDAY) WITH  
LOWER- LEVEL CLOUD DECKS BEING THE MAIN CONCERN. THERE IS SOME  
SPREAD IN MODEL GUIDANCE WITH GLAMP BEING LESS KEEN ON ANY  
RESTRICTIONS THROUGHOUT THE PERIOD; HOWEVER, GIVEN A COMBINATION  
OF PREVIOUS GLAMP MODEL CYCLES, RAP MODEL SOUNDINGS, AND HREF  
PROBS, HAVE OUTLINED A PERIOD OF MVFR/IFR CONDITIONS THROUGHOUT  
THIS TIMEFRAME. THERE IS MODERATE (40-50%) CONFIDENCE IN  
RESTRICTIONS AT AOO/UNV WITH LOWER CONFIDENCE ON LOW-LEVEL  
MOISTURE MANIFESTING FURTHER EAST AT IPT/MDT/LNS OVERNIGHT.  
 
ANY VALLEY FOG FORMATION BEGINS TO MIX OUT ~14Z FRIDAY WITH VFR  
CONDITIONS EXPECTED OUTSIDE OF THE LOWER SUSQUEHANNA VALLEY  
THROUGH 18Z FRIDAY WITH MODERATE (~60%) CONFIDENCE. GUIDANCE  
DOES SUGGEST A LOWER-LEVEL (~2-4KFT) CLOUD DECK MAKING WAY INTO  
LNS/MDT FOR A PERIOD OF MVFR CEILINGS EARLY IN THE DAY BEFORE  
SCATTERING BACK TOWARDS VFR IN THE 18-20Z FRIDAY TIMEFRAME.  
 
OUTLOOK...  
 
SAT-SUN PM...PATCHY AM VALLEY FOG; OTHERWISE, VFR PREVAILS.  
 
SUN PM-MON...SHRA MOVES IN WEST-TO-EAST, SOME TSRA POSSIBLE.  
 
TUE-WED...VFR, NO SIG WX.  
 
 
   
CLIMATE  
 
TOTAL PRECIPITATION FOR THE MONTH OF SEPTEMBER WAS 1.11 INCHES  
AT WILLIAMSPORT (-3.65" BELOW AVERAGE) WHICH RANKS AS THE 11TH  
DRIEST ON RECORD.  
 
THE AVERAGE TEMPERATURE FOR THE MONTH OF SEPTEMBER WAS 63.1  
DEGREES AT BRADFORD (+4.2F ABOVE AVERAGE) WHICH RANKS AS THE  
WARMEST SEPTEMBER ON RECORD.  
 
HARRISBURG (MDT) CONSECUTIVE DAYS STREAK OF MEASURABLE RAIN  
ENDS AT 9 WITH ONLY A TRACE RECORDED YESTERDAY 10/2. THIS TIES  
THE RECORD FOR LONGEST SUCH STRETCH SET FROM APRIL 7-15, 1893  
AND MATCHED MAY 15-23, 1893 AND JULY 28-AUGUST 5, 1971.  
 
 
   
CTP WATCHES/WARNINGS/ADVISORIES  
 
NONE.  
 
 
 
 
 
SYNOPSIS...STEINBUGL  
NEAR TERM...DANGELO/STEINBUGL  
SHORT TERM...FITZGERALD/STEINBUGL  
LONG TERM...NPB/BOWEN  
AVIATION...NPB/BOWEN  
CLIMATE...STEINBUGL/BANGHOFF  
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