942  
FXUS61 KPHI 071651  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
1251 PM EDT TUE JUL 7 2020  
   
SYNOPSIS
 
 
A SUMMER-LIKE PATTERN WILL PERSIST THROUGHOUT THE WEEK WITH  
SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED MOST DAYS ALONG  
WITH ABOVE AVERAGE TEMPERATURES. A COASTAL STORM WILL IMPACT THE  
REGION FRIDAY THROUGH SATURDAY AS IT MOVES NORTH FROM THE  
CAROLINAS. A COLD FRONT WILL FOLLOW THE COASTAL STORM OVER THE  
WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A FEW THUNDERSTORMS ARE MAKING THEIR WAY NORTH AND EAST FROM  
THE DELAWARE BEACHES TO CAPE MAY COUNTY. OTHERWISE, THE  
ATMOSPHERE IS BEHAVING MUCH BETTER THIS AFTERNOON. INCREASED  
CLOUD COVER THROUGH THE MORNING THAT CONTINUES TO LINGER IN MANY  
PLACES LOOKS TO HAVE INHIBITED MORNING SURFACE HEATING CRUCIAL  
TO TODAY'S CONVECTIVE POTENTIAL. MANY LOCATIONS STILL REMAIN A  
FEW DEGREES BELOW THEIR RESPECTIVE CONVECTIVE TEMPERATURES (MID  
TO UPPER 80S).  
 
THE MAIN PROBLEM FOR TODAY WILL BE JUST HOW MUCH THE ATMOSPHERE  
CAN REBOUND FROM BEING SO WORKED OVER YESTERDAY. MODEL  
SOUNDINGS SHOW INCREASING INSTABILITY AS WE HEAD TOWARDS THIS  
AFTERNOON AND SOME OF THE CAMS HAVE SCATTERED TO WIDESPREAD  
CONVECTION DEVELOPING OVER OUR FORECAST AREA. ONE ISSUE IS THE  
CLOUD COVER AND HOW FAST IT GIVES WAY TO SUNNY SKIES. WE ALSO  
LACK A SOURCE OF EXTRA LIFT ACROSS THE REGION AS WEAK RIDGING IS  
PRESENT ALOFT AND NO SHORTWAVES ROTATE THROUGH THE FLOW INTO  
OUR AREA TODAY. ONE PLUS IS THAT WE HAVE DECENTLY HIGH CAPE  
VALUES (1500-2000 J/KG) SO THE INSTABILITY WILL BE THERE. ONCE  
AGAIN, WE HAVE VERY WEAK STEERING FLOW ACROSS THE REGION SO NOT  
MUCH HELP IN KEEPING THINGS MOVING SHOULD THEY DEVELOP. WITH  
PWATS STILL AROUND 1.5-2.0", HEAVY, TORRENTIAL RAINS WILL BE  
POSSIBLE AND THE GREATEST CONCERN WILL CERTAINLY BE IN THOSE  
AREAS THAT SAW ABUNDANT RAIN YESTERDAY. SO WHILE THE SEVERE  
THREAT IS LESS THE FLOODING THREAT REMAINS PRETTY HIGH. THE  
WORDED FORECAST MAY BE MORE PESSIMISTIC THAN IT ACTUALLY APPEARS  
AS MAJORITY OF ANYTHING THAT DOES GET GOING WILL LIKELY BE  
LATER IN THE DAY AND MAY BE MORE ISOLATED TO SCATTERED.  
 
WITH PLENTY OF MOISTURE ACROSS THE REGION AND HIGHS RISING INTO  
THE MID TO UPPER 80S TODAY, IT WILL FEEL HUMID AND  
UNCOMFORTABLE. WINDS WILL BE GENERALLY OUT OF THE SOUTH TO  
SOUTHEAST THROUGH THE DAY TODAY AND MAINLY AROUND 10 TO 15 MPH  
BUT UNFORTUNATELY MIGHT NOT PROVIDE MUCH RELIEF FROM THE HEAT  
AND HUMIDITY.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/
 
 
CONVECTION IS EXPECTED TO DWINDLE INTO THIS EVENING AND THEN  
DISSIPATE OVERNIGHT. A FEW ISOLATED SHOWERS MAY CONTINUE ACROSS  
OUR NORTHERN ZONES AFTER MIDNIGHT BUT FOR THE MOST PART WE  
SHOULD HAVE DRY CONDITIONS ACROSS THE FORECAST AREA.  
 
CONDITIONS WILL REMAIN WARM AND MUGGY AS THE FLOW REMAINS OUT  
OF THE SOUTH/SOUTHEAST. WITH CONTINUED LOW LEVEL MOISTURE, WE  
WILL ONCE AGAIN SEE SOME PATCHY FOG DEVELOP BUT CONFIDENCE IS  
LOW AS TO EXACTLY WHERE IT WILL BE SINCE IT MAY BE LARGELY  
DEPENDENT ON WHERE THE RAIN FALLS. OVERNIGHT LOWS WILL BE IN THE  
UPPER 60S TO LOWER 70S.  
 

 
   
LONG TERM /THURSDAY THROUGH MONDAY/
 
 
THE EXTENDED APPEARS TO BE FAIRLY ACTIVE WITH SEVERAL EVENTS TO  
NOTE. WEDNESDAY STARTS OFF QUIET FROM A SENSIBLE WEATHER  
PERSPECTIVE AS A MID LEVEL RIDGE SITS OVER THE REGION. MAX TEMPS  
WILL AGAIN START TO PUSH BACK INTO THE LOW 90S AS MODEST WARM  
AIR ADVECTION RETURNS.  
 
WHILE THE MID-ATLANTIC IS BRIEFLY QUIET, OUR ATTENTION TURNS FURTHER  
SOUTH TO THE POTENTIAL DEVELOPMENT OF A SYMMETRIC WARM CORE LOW  
PRESSURE SYSTEM THAT IS EXPECTED TO DEVELOP SOMEWHERE BETWEEN  
GEORGIA AND THE CAROLINAS. THE 12Z AND 18Z GUIDANCE DEVELOPED A WEAK  
LOW PRESSURE SYSTEM THAT TAKES ON TROPICAL CHARACTERISTICS AS  
IT MOVES EASTWARD TO THE ATLANTIC. ONCE THE SYSTEM REACHES THE  
ATLANTIC, THE BERMUDA HIGH SHOULD START TO PUSH THE SYSTEM  
TOWARDS THE NORTH UP THE ALTANTIC COASTLINE FRIDAY INTO  
SATURDAY. BASED ON THIS GUIDANCE, THE NATIONAL HURRICANE CENTER  
HAS UPGRADED THE TROPICAL WEATHER OUTLOOK TO INDICATE A 40%  
CHANCE OF TROPICAL DEVELOPMENT WITHIN THE NEXT 5 DAYS. THE 00Z  
GUIDANCE THIS MORNING OFFERS A SLIGHTLY DIFFERENT SOLUTION AS  
THE LOW PRESSURE SYSTEM STARTS OFF SYMMETRIC WARM CORE, BUT  
QUICKLY UNDERGOES EXTRA-TROPICAL TRANSITION BECOMING A COLD CORE  
ASYMMETRIC SYSTEM BASED ON ANALYSIS OF CYCLONE PHASE SPACE  
DIAGRAMS AVAILABLE AT MOE.MET.FSU.EDU/CYCLONEPHASE  
 
TIME WILL TELL ON HOW THE SYSTEM DEVELOPS AND/OR HOW IT WILL  
IMPACT THE AREA. HOWEVER THE IDEA THAT WE COULD SEE A COASTAL  
LOW PRESSURE SYSTEM MOVING UP THE COAST THURSDAY NIGHT INTO  
FRIDAY APPEARS FAIRLY LIKELY. THIS WILL HAVE THE POTENTIAL TO  
CAUSE AN INCREASE IN COASTAL TIDAL HEIGHTS AND THE POSSIBILITY  
FOR MODERATE TO HEAVY RAIN DEPENDING ON WHERE THE CENTER OF THE  
LOW ACTUALLY TRACKS.  
 
AS THE LOW TRACKS TO THE NORTH, IT QUICKLY GETS PUSHED OUT OF THE  
REGION BY A DEEPENING MID LEVEL TROUGH DROPPING OUT OF THE GREAT  
LAKES. THIS WILL BRING ANOTHER ROUND OF WIDESPREAD RAINFALL WITH  
SCATTERED THUNDERSTORMS ACROSS THE REGION. HEIGHT FALLS ARE  
FAIRLY STRONG WITH THE COLD FRONT AND ALMOST ALL OF THE MEDIUM  
RANGED GUIDANCE INDICATES THAT WE'LL BE SITTING IN THE RIGHT  
REAR ENTRANCE REGION OF A 250MB JET. SO THERE SHOULD BE  
SUBSTANTIAL SYNOPTIC LIFT AVAILABLE AND WHEN CONSIDERING TEMPS  
WILL AGAIN BE PUSHING INTO THE UPPER 80'S TO LOW 90S WITH DEW  
POINTS ABOVE 70F WE'LL LIKELY SEE FAIRLY WIDESPREAD THUNDERSTORMS  
AS EQ'S ARE PROGGED TO BE IN EXCESS OF 30KFT WITH TEMPS OF -35C.  
OF COURSE THIS IS ALL BASED ON TRENDS IN THE LATEST SUITE OF  
MEDIUM RANGED GUIDANCE AND SUBTLE CHANGES TO THE LOCATION OF THE  
UPPER LEVEL JET/MID LEVEL TROUGH/HEIGHT FALLS WILL ALL HAVE  
SIGNIFICANT IMPACTS ON THE POTENTIAL FOR POTENT THUNDERSTORMS.  
 
COMING OUT OF THE WEEKEND THE LOW PRESSURE SYSTEM THAT SHOULD TRACK  
THROUGH OUR AREA ON SATURDAY WILL RUN INTO A ROAD BLOCK IN THE FORM  
OF A BROAD ATLANTIC HIGH PRESSURE SYSTEM. THE HIGH WILL FORCE  
THE LOW NORTH AND MAY BRING AN ELONGATED LOW PRESSURE SYSTEM  
BACK ONSHORE CAUSING ANOTHER ROUND OF SHOWERS AND POTENTIAL  
THUNDERSTORMS BUT AT THIS RATE, I DONT HAVE A SIGNIFICANT AMOUNT  
OF CONFIDENCE IN WHAT WILL HAPPEN BEYOND THE FRONTAL PASSAGE  
OVER THE WEEKEND BASED ON TRENDS IN GUIDANCE.  
 

 
   
AVIATION /18Z TUESDAY THROUGH SUNDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE,  
KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...THERE IS ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS  
AFTER 18Z. HOWEVER, IT IS DIFFICULT TO DETERMINE WHICH TAF SITES  
WILL BE IMPACTED AT THIS POINT SO HAVE MAINLY INCLUDED VCTS FOR  
THE AFTERNOON HOURS AT THIS TIME. MOSTLY SOUTH WINDS AROUND 10  
KNOTS OR LESS OUTSIDE OF STORMS. MODERATE CONFIDENCE, BUT LOW  
CONFIDENCE ON THE POTENTIAL FOR AND LOCATION OF AFTERNOON  
THUNDERSTORMS.  
 
TONIGHT...VFR CONDITIONS EXPECTED WITH POSSIBLE MVFR CONDITIONS,  
MAINLY NORTH AND WEST OF KPHL. LIGHT SOUTHERLY WINDS. MODERATE  
CONFIDENCE WITH LOW CONFIDENCE ON LOWER CONDITIONS.  
 
OUTLOOK...  
 
WEDNESDAY THROUGH THURSDAY...PREVAILING VFR EXPECTED, HOWEVER  
SCATTERED SHOWERS AND THUNDERSTORMS, GENERALLY BETWEEN 18Z AND  
06Z EACH DAY, MAY LOCALLY LOWER RESTRICTIONS. WINDS WILL BE  
GENERALLY SOUTHERLY BECOMING SOUTHEASTERLY AROUND 10 KTS.  
MODERATE CONFIDENCE.  
 
FRIDAY...MVFR/IFR CEILINGS PROBABLE WITH SOUTHEASTERLY TO  
EASTERLY WINDS AROUND 10 KTS. SCATTERED MODERATE TO LOCALLY  
HEAVY SHOWERS WITH EMBEDDED THUNDERSTORMS WILL LOWER VISIBILITY  
AND CEILING RESTRICTIONS LOCALLY. LOW TO MODERATE CONFIDENCE.  
 
SATURDAY...MAINLY VFR EXPECTED WITH RAPIDLY LOWERING FLIGHT  
CONDITIONS IN SHOWERS AND THUNDERSTORMS. MODERATE CONFIDENCE.  
 

 
   
MARINE
 
 
SUB-ADVISORY CONDITIONS ARE EXPECTED TO CONTINUE ON THE AREA  
WATERS THROUGH TUESDAY. SOUTH TO SOUTHEAST WINDS AROUND 10 TO 15  
KNOTS WITH SOME GUSTS AROUND 20 KNOTS. WINDS WILL DROP DOWN TO  
AROUND 5 TO 10 KNOTS OVERNIGHT. SEAS WILL BE AROUND 2 TO 3 FEET  
ON THE OCEAN WATERS.  
 
OUTLOOK...  
 
WEDNESDAY THROUGH THURSDAY: EXPECT SUB-SCA CONDITIONS WITH  
GUSTS UP TO 15 KTS AND WINDS INITIALLY STARTING SOUTHERLY  
BECOMING SOUTHEASTERLY BY THURSDAY AFTERNOON. SEAS WILL BE  
GENERALLY 2-3 FEET. AFTERNOON AND EVENING SHOWERS AND  
THUNDERSTORMS ARE POSSIBLE TUESDAY THROUGH THURSDAY, WHICH MAY  
LOCALLY INCREASE WINDS AND SEAS.  
 
FRIDAY THROUGH SATURDAY: SCA CONDITIONS ANTICIPATED BEGINNING  
FRIDAY AS SEAS BUILD TO 7 FEET ON EASTERLY FLOW WITH GUSTS UP TO  
20 KTS. THIS CONTINUES ON SATURDAY WITH SEAS ANTICIPATED TO BE  
5 TO 7 FEET DURING THE DAY WITH THE FLOW BECOMING WEST TO  
SOUTHWEST BEHIND A COASTAL LOW. SHOWERS AND THUNDERSTORMS  
CERTAINLY REMAIN POSSIBLE WHICH MAY LOCALLY INCREASE WINDS AND  
AND SEAS.  
 
RIP CURRENTS...  
 
THERE IS A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS AND LIFE  
THREATENING RIP CURRENTS THROUGH THURSDAY DUE TO THE COMBINATION  
OF SHORTER PERIOD SWELLS AND RELATIVELY LOW SURF HEIGHTS.  
 
HOWEVER HEADING INTO FRIDAY, WE ANTICIPATE THE RISK FOR  
DANGEROUS RIP CURRENTS TO INCREASE SUBSTANTIALLY. AS SEAS BUILD  
OVER THE REGION, AND WE GO THROUGH A PROLONGED PERIOD OF LONGER  
PERIOD ONSHORE SWELL, THE RISK FOR DANGEROUS, LIFE THREATENING  
RIP CURRENTS WILL INCREASE TO AT LEAST MODERATE AND POSSIBLY  
HIGH ESPECIALLY FOR THE JERSEY COASTLINE. THOSE WITH BEACH  
INTERESTS SHOULD MONITOR CONDITIONS CLOSELY AS THE DEVELOPMENT  
OF DANGEROUS RIP CURRENTS SEEMS QUITE LIKELY BASED ON LATEST  
TRENDS IN THE FORECAST.  
 

 
   
EQUIPMENT
 
 
THERE IS AN ISSUE WITH THE OBSERVATION EQUIPMENT AT READING,  
KRDG. TECHNICIANS WILL BE TAKING A LOOK AT THE EQUIPMENT ON  
TUESDAY.  
 
THE NOAA WEATHER RADIO ALL HAZARDS BROADCAST FROM HIBERNIA  
PARK, PA (WNG704) REMAINS OFF THE AIR UNTIL FURTHER NOTICE DUE  
TO DAMAGE TO THE ANTENNA DURING THE JUNE 3 DERECHO.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...DEAL  
NEAR TERM...DAVIS/MEOLA  
SHORT TERM...MEOLA  
LONG TERM...DEAL  
AVIATION...DAVIS/DEAL/MEOLA  
MARINE...DEAL/MEOLA  
EQUIPMENT...WFO PHI  
 
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