493  
FXUS61 KPHI 180925  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
525 AM EDT THU OCT 18 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD FROM THE OHIO VALLEY INTO THE MIDDLE  
ATLANTIC REGION THROUGH FRIDAY NIGHT. LOW PRESSURE WILL THEN TRACK  
TO OUR NORTH OVER SOUTHERN CANADA DRAGGING A COLD FRONT ACROSS OUR  
REGION SATURDAY. HIGH PRESSURE WILL THEN BUILD INTO THE AREA INTO  
THE START OF NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
TEMPERATURES IN THE POCONOS AND NW NJ HAVE INCREASED SLIGHTLY  
OVER THE PAST 2 HOURS. THEREFORE, CANCELLED THE FREEZE WARNING  
FOR THIS MORNING AS ALL SITES ARE ABOVE FREEZING. THE FREEZE  
WARNING FOR TONIGHT/FRIDAY MORNING REMAINS IN EFFECT.  
 
SURFACE HIGH WILL CONTINUE TO BUILD TOWARDS THE REGION THROUGH THE  
DAY TODAY. IN THE MID AND UPPER LEVELS, THE TROUGH WILL SHIFT  
FURTHER OFF SHORE WITH HEIGHTS BEGINNING TO GRADUALLY BUILD OVER OUR  
REGION THROUGH THE DAY.  
 
THE PRESSURE GRADIENT IS EXPECTED TO GRADUALLY DIMINISH, ESPECIALLY  
THIS AFTERNOON. THEREFORE, NOT EXPECTING AS BREEZY OF A DAY  
YESTERDAY. HOWEVER, TEMPERATURE WISE, THIS COULD BE THE COLDEST DAY  
OF THE SEASON SO FAR WITH HIGHS ONLY IN THE 40S AND 50S ACROSS THE  
REGION.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/
 
 
WE SHOULD HAVE ALL THE INGREDIENTS NEEDED TONIGHT FOR A WIDESPREAD  
FREEZE AND FROST FOR MUCH OF THE AREA OVERNIGHT. SURFACE HIGH WILL  
CONTINUE TO BUILD CLOSER. WINDS SHOULD BE LIGHT AND SKIES SHOULD BE  
CLEAR. CONSEQUENTLY HAVE ISSUED A FREEZE WARNING FOR EAST CENTRAL PA  
AND NW NJ.  
 
FOR BERKS, WESTERN CHESTER, AND UPPER MONTGOMERY COUNTIES, HAVE GONE  
WITH A FROST ADVISORY FOR NOW, THOUGH WOULD NOT BE SURPRISED IF THE  
HIGHER ELEVATIONS, ESPECIALLY IN BERKS COUNTY ARE ABLE TO GET TO  
FREEZING.  
 
THE OTHER LOCATION OF CONCERN IS THE PINE BARRENS OF SOUTH JERSEY.  
GUIDANCE CONSISTENTLY HAS A WARM BIAS IN SCENARIOS LIKE THIS, SO I  
HAVE UNDERCUT GUIDANCE MINS IN THESE LOCATIONS. EXPECT A WIDESPREAD  
FROST, THOUGH AT THIS POINT, I THINK TEMPERATURES MAY STAY JUST  
ABOVE FREEZING, SO WILL GO WITH A FROST ADVISORY.  
 
THE URBAN CORRIDOR FROM WILMINGTON TO TRENTON SHOULD STAY IN THE  
UPPER 30S THANKS IN LARGE PART TO THE URBAN HEAT ISLAND EFFECT, SO  
NOT EXPECTING A WIDESPREAD FROST HERE (THOUGH LOCATIONS IN MERCER  
COUNTY OUTSIDE OF TRENTON WILL LIKELY SEE FROST).  
 
FOR DELMARVA, PATCHY FROST IS POSSIBLE IN INTERIOR SECTIONS, BUT NOT  
SURE IT WILL BE WIDESPREAD, SO WILL HOLD OFF ON ISSUING A FROST  
ADVISORY FOR THESE LOCATIONS.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
FRIDAY...INCREASING CLOUDS WITH SLIGHTLY BELOW NORMAL  
TEMPERATURES. HIGH PRESSURE WILL BE MOVING OFFSHORE AND AN  
APPROACHING LOW/FRONT WILL BRING ADDED MOISTURE TO WRN AREAS BY  
LATE IN THE DAY.  
 
FRIDAY NIGHT/SATURDAY...LOW PRESSURE MOVES NORTH OF THE AREA  
WHILE AN ASSOCIATED FRONT CROSSES THE AREA. MOSTLY HIGH CHC /LOW  
LIKELY POPS FOR THE PERIOD. TEMPERATURES A LITTLE ABOVE NORMAL,  
PRIOR TO FROPA.  
 
SATURDAY NIGHT THRU WEDNESDAY...HIGH PRESSURE ACROSS THE AREA  
MUCH OF THE TIME SO MOSTLY FAIR WEATHER EXPECTED. A FEW SHOWERS  
POSSIBLE N/NW TUE. TEMPERATURES WELL BELOW NORMAL SUN/MON, THEN  
CLOSER TO NORMAL TUE. MUCH TO BELOW NORMAL WED.  
 
NORMALS: MPO/PHL/GED -- HIGHS: 55/63/65 LOWS: 34/46/43 .  
 

 
   
AVIATION /10Z THURSDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR CONDITIONS EXPECTED. NORTHWESTERLY WINDS MAY AT TIMES  
GUST TO NEAR 20 KT, BUT SHOULD GRADUALLY DIMINISH THROUGH THE DAY.  
HIGH CONFIDENCE.  
 
TONIGHT...VFR CONDITIONS EXPECTED. LIGHT NORTHWESTERLY WINDS WILL  
SHIFT TO SOUTHWESTERLY OVERNIGHT. HIGH CONFIDENCE.  
 
OUTLOOK...  
 
FRIDAY...VFR EXPECTED WITH INCREASING CLOUDS.  
FRI NIGHT/SATURDAY...SUB-VFR POSSIBLE WITH SCATTERED SHOWERS.  
SAT NIGHT THRU MONDAY...VFR. GUSTY WINDS SUNDAY.  
 

 
   
MARINE
 
 
WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE DAY. THE ONLY  
SITE STILL REACHING GALE GUSTS IS AT BRANDYWINE SHOAL, SO WILL  
KEEP THE GALE WARNING GOING FOR THE LOWER DELAWARE BAY THROUGH  
LATE THIS MORNING. OTHERWISE, THE REST OF THE WATERS HAVE A SMALL  
CRAFT ADVISORY. ON THE UPPER DELAWARE BAY, WINDS SHOULD DROP  
BELOW SCA THRESHOLDS BY LATE THIS MORNING. FOR THE REST OF THE  
WATERS, SCA CONDITIONS ARE EXPECTED TO CONTINUE THROUGH EARLY  
THIS EVENING.  
 
OUTLOOK...  
FRIDAY...SUB-SCA. FAIR. INCREASING WINDS/SEAS LATE.  
FRI NIGHT/SATURDAY...SCA FLAG EXPECTED. SHOWERS.  
SAT NIGHT THRU SUN NIGHT...SCA. LOW END GALE POSSIBLE SAT NIGHT. FAIR.  
MONDAY/MONDAY NIGHT...SUB-SCA. FAIR.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...FREEZE WARNING FROM 1 AM TO 9 AM EDT FRIDAY FOR PAZ054-055-061-  
062-105.  
FROST ADVISORY FROM 1 AM TO 9 AM EDT FRIDAY FOR PAZ060-101-103.  
NJ...FREEZE WARNING FROM 1 AM TO 9 AM EDT FRIDAY FOR NJZ001-007>010.  
FROST ADVISORY FROM 1 AM TO 9 AM EDT FRIDAY FOR NJZ012-013-  
015>022-027.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR  
ANZ450>455.  
SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR ANZ430.  
GALE WARNING UNTIL 10 AM EDT THIS MORNING FOR ANZ431.  
 

 
 

 
SYNOPSIS...DAVIS/O'HARA  
NEAR TERM...JOHNSON  
SHORT TERM...JOHNSON  
LONG TERM...O'HARA  
AVIATION...JOHNSON/O'HARA  
MARINE...JOHNSON/O'HARA  
 
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