110  
FXUS61 KPHI 230520  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
120 AM EDT SAT SEP 23 2017  
   
SYNOPSIS
 
 
POST-TROPICAL CYCLONE JOSE WILL CONTINUE TO WEAKEN AND DRIFT  
SOUTHEAST OF NEW ENGLAND BEFORE DISSIPATING LATE THIS WEEKEND.  
HIGH PRESSURE STRETCHED FROM NEW ENGLAND TO THE CENTRAL  
APPALACHIANS WILL HOLD FIRM INTO EARLY NEXT WEEK. HURRICANE  
MARIA WILL BE MOVING NORTHWARD IN THE OFFSHORE ATLANTIC WATERS,  
OFF THE EAST COAST NEXT WEEK. A COLD FRONT PASSING THROUGH THE  
MID ATLANTIC STATES SHOULD TURN MARIA EASTWARD AND FAR OUT TO  
SEA LATER THURSDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
QUIET NIGHT ACROSS THE AREA, AS RESILIENT BUT DECAYING JOSE  
CHURNS WELL OFFSHORE. ENOUGH OF A PRESSURE GRADIENT EXISTS TO  
THE WEST OF JOSE TO ESTABLISH A LIGHT NORTHERLY FLOW ACROSS THE  
AREA TONIGHT, BUT THE FOG-PRONE VALLEY LOCATIONS IN EASTERN PA  
AND NORTHERN NJ HAVE NEARLY CALM WINDS AND RAPIDLY FALLING  
TEMPERATURES. THINK SOME PATCHY FOG IS A GOOD BET IN THE FAVORED  
LOCATIONS (K12N, KFWN, KPTW, KMQS) AS WELL AS EAST OF CHESAPEAKE  
BAY (WHERE DEW POINTS ARE A LITTLE HIGHER). HAVE KEPT/ADDED  
MENTION IN THE GRIDS WITH THE 1230 AM UPDATE.  
 
MODIFIED TEMPERATURES QUITE A BIT WITH THIS UPDATE, AS  
STATISTICAL GUIDANCE IS DOING A POOR JOB WITH HOURLY  
TEMPERATURES BOTH FOR THE COLD VALLEYS AND THE WARM URBAN  
CORRIDOR. THE PROPOSED AMENDMENTS MAY NOT BE ENOUGH, AS READINGS  
ARE RUNNING ABOUT 3-7 DEGREES HIGHER THAN PROGGED SO FAR IN THE  
PHILLY METRO AREA. ADDITIONALLY, WITH DEW POINTS ERRONEOUSLY  
HIGH NORTHWEST OF THE FALL LINE, OVERNIGHT LOWS MAY STILL BE  
TOO WARM IN THE SOUTHERN POCONOS AND VICINITY. ADJUSTED THESE  
DOWNWARD, BUT WOULD NOT BE SURPRISED IF THESE WERE STILL TOO  
HIGH BY A DEGREE OR TWO.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/
 
 
1230 AM UPDATE: SENT PRELIMINARY GRIDS OUT WITH THIS UPDATE, BUT  
WILL LIKELY CHANGE THE SKY COVER AND TEMPS A BIT MORE WITH THE  
330 AM PACKAGE. MAIN CHANGES WERE TO INCORPORATE MORE OF THE  
HIGH-RESOLUTION 2-M TEMPERATURES, WHICH SEEMED TO CAPTURE THE  
EXPECTED BOUNDARY-LAYER MIXING MORE REALISTICALLY (ESPECIALLY  
WHEN ANALYZING PROJECTED 900- AND 850-MB TEMPERATURES). THIS  
RESULTED IN AN INCREASE IN TEMPERATURES BY ABOUT 1-2 DEGREES IN  
MOST LOCATIONS. UNUSUALLY WARM DAY ON TAP.  
 
PREVIOUS DISCUSSION...  
 
THE MID-LEVEL RIDGE CONTINUES TO DRIFT EASTWARD TOMORROW. H5 HEIGHTS  
CLIMB TO AT LEAST 588 DM. H8 TEMPS CLIMB TO ABOUT 30 DEG C. AS A  
RESULT, ANOTHER WARM DAY IS IN STORE FOR THE DELAWARE VALLEY AND  
ADJACENT LOCALES. JUST ABOUT EVERYONE SHOULD HIT AT LEAST 80. THE  
EXCEPTIONS COULD BE THE HIGHER TERRAIN IN THE POCONOS AND NW NJ AND  
AT THE BEACHES.  
 
NO RAIN IS FORECAST. EXPECT LOTS OF BLUE SKY, ESPECIALLY BY LATE  
MORNING. WINDS WILL BE OUT OF THE NORTH AND SLACKEN DURING THE  
AFTERNOON HOURS. WITH THE GRADIENT WEAKENING, A SEA BREEZE  
SHOULD DEVELOP.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
 
 
SUNDAY THROUGH MONDAY...SURFACE HIGH SETTLES IN OVER THE REGION. AS  
A RESULT EXPECT CONTINUED DRY AND VERY WARM WEATHER. WE COULD GET  
CLOSE TO RECORD HIGHS BOTH DAYS AT INLAND LOCATIONS (SEE CLIMATE  
SECTION FOR THE CURRENT RECORD HIGHS FOR THOSE DAYS). A LIGHT  
ONSHORE FLOW COULD TEMPER THE WARMING TREND AT COASTAL LOCATIONS.  
 
TUESDAY AND WEDNESDAY...SURFACE HIGH WEAKENS. AS IT DOES SO, WE  
COULD HAVE SOME SHOWERS DEVELOP, PRIMARILY DIURNALLY DRIVEN (RAIN  
ASSOCIATED WITH THE LOW OVER EASTERN CANADA WILL STAY WELL TO OUR  
NORTHWEST, AND AT THIS POINT IT DOESN'T LOOK LIKE MARIA WILL GET  
CLOSE ENOUGH THAT WE WILL SEE ANY OF THE OUTER RAIN BANDS). AS FOR  
MARIA, IT IS EXPECTED TO STAY WELL TO OUR SOUTH (BY A FEW HUNDRED  
MILES) THROUGH THIS PERIOD. PLEASE SEE THE FORECAST DISCUSSION FROM  
THE NATIONAL HURRICANE CENTER FOR THE LATEST INFORMATION ON THE  
TRACK.  
 
THURSDAY...THERE ARE TWO THINGS TO WATCH THROUGH THIS PERIOD. FIRST,  
THE COLD FRONT STILL LOOKS ON TRACK TO PROPAGATE THROUGH OUR REGION  
LATE WEDNESDAY NIGHT INTO THURSDAY. THAT WILL BRING US BACK TO NEAR  
NORMAL TEMPERATURES (ALTHOUGH DEPENDING ON HOW QUICKLY IT MOVES  
THROUGH, WE MAY NOT NOTICE IT UNTIL FRIDAY). THE OTHER THING WE WILL  
BE WATCHING IS THE EVENTUAL TRACK OF MARIA. THIS IS BEYOND THE 5  
DAYS OF THE OFFICIAL HURRICANE TRACK FORECAST, SO THERE IS  
CONSIDERABLE UNCERTAINTY, BUT AT THIS POINT, ALMOST ALL GUIDANCE  
SHOWS THE STORM TAKING A RIGHT TURN, FURTHER OUT TO SEA,  
THROUGH THIS PERIOD. IF THIS DOES OCCUR, WE WILL SEE VERY LITTLE  
IN THE WAY OF IMPACTS ASIDE FROM THE SWELLS AND HIGH SURF.  
 
FRIDAY...COOLER AND DRIER AIR SHOULD SETTLE IN OVER THE REGION. IT  
WILL BE QUITE A BIT COOLER THAN THE EARLY WEEK PERIODS, BUT ONLY  
NEAR NORMAL FOR LATE SEPTEMBER.  
 

 
   
AVIATION /05Z SATURDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
FOR THE 06Z TAFS...VFR THROUGH THE PERIOD. LIGHT/VARIABLE WINDS  
BECOMING NORTHERLY AROUND OR BELOW 10 KTS DURING THE DAY. SCT-  
BKN DECK AROUND 5000-6000 FEET NEAR/EAST OF THE DELAWARE RIVER  
WILL DISSIPATE DURING THE DAY, WITH FEW OR NO CLOUDS THEREAFTER.  
 
OUTLOOK...  
 
SUNDAY AND MONDAY...MOSTLY VFR CONDITIONS ARE EXPECTED.  
 
TUESDAY AND WEDNESDAY...MOSTLY VFR CONDITIONS EXPECTED. THERE  
IS A SLIGHT CHANCE FOR SHOWERS BOTH DAYS. NORTHEASTERLY WIND UP  
TO 10 KT POSSIBLE.  
 

 
   
MARINE
 
 
TONIGHT...  
SCA SEAS CONTINUES. THE NORTH WINDS ARE EXPECTED TO CONTINUE  
THROUGH THE PERIOD. SPEEDS WILL MAINLY BE IN THE 10 TO 15 KT  
RANGE ON THE OCEAN. THE DOMINANT LONG PERIOD EASTERLY SWELL  
WILL CONTINUE. SEAS WILL RANGE IN THE 4 TO 7 FOOT RANGE ON THE  
OCEAN OVERNIGHT; MAINLY IN THE 1 TO 2 FOOT RANGE ON DELAWARE  
BAY.  
 
SATURDAY...THE SCA ADVISORY WILL REMAIN POSTED ON THE ATLANTIC  
WATERS. SATURDAY CONDITIONS WILL BE VERY MUCH LIKE TONIGHT WITH  
NORTHERLY WINDS OCCASIONALLY GUSTING UP TO 20 KT, A LARGE  
EASTERLY SWELL, AND SEAS IN THE 4 TO 6 FOOT RANGE.  
 
OUTLOOK...  
SATURDAY NIGHT AND SUNDAY...ELEVATED SEAS ON THE ATLANTIC COASTAL  
WATERS ARE EXPECTED TO CONTINUE THROUGH AT LEAST PART OF THE  
NIGHT SATURDAY NIGHT. HOWEVER, WE ARE EXPECTING A LULL IN  
ELEVATED SEAS BEFORE THE SWELLS FROM HURRICANE MARIA ARRIVE.  
SOME GUIDANCE HAS SEAS INCREASING BY MID DAY, BUT TRENDS WITH  
RECENT STORMS HAVE GUIDANCE SHOWING SWELLS ARRIVING TOO QUICKLY.  
IF THIS TREND CONTINUES, WE MAY SEE A LULL IN ELEVATED SEAS FOR  
MUCH OF THE DAY.  
 
MONDAY THROUGH WEDNESDAY...SWELLS FROM HURRICANE MARIA ARE EXPECTED  
TO RESULT IN A PROLONGED PERIOD OF HAZARDOUS SEAS ON THE ATLANTIC  
COASTAL WATERS. A FEW GUSTS NEAR 25 KT ARE POSSIBLE ESPECIALLY  
WEDNESDAY, BUT IN GENERAL, WINDS SHOULD STAY BELOW SCA CRITERIA  
THROUGH THIS PERIOD.  
 
RIP CURRENTS...  
 
SATURDAY...LOOKS TO BE SOMEWHAT OF A TRANSITION DAY AS THE BEACHES  
SEE LEFTOVER NE SWELLS OF AROUND 4 OR 5 FEET FROM JOSE AT 9 SECOND  
INTERVALS AND THE INTRODUCTION OF 2-3 FOOT SE SWELLS OF 15 SECOND  
INTERVALS FROM MARIA. MARIA'S SWELLS WILL GROW WITH TIME NEXT  
WEEK. MORE ABOUT THAT IN THE OUTLOOK. THE SURF ZONE MAY BE A  
BIT CHAOTIC AS SWELLS FROM DIFFERING DIRECTIONS AND ENERGY  
COLLIDE. SO WHILE THE SURF HEIGHT WILL BE LESS, IT STILL LOOKS  
TROUBLINGLY DIFFICULT TO SAFELY ENJOY THE SURF ZONE SWIMMING.  
FOR NOW WE'VE ISSUED A MODERATE RISK BUT THAT MAY NEED TO BE  
RAISED TO A HIGH RISK PENDING OVERNIGHT SWELL TRENDS FROM  
DECAYING JOSE.  
 
OUTLOOK...  
 
SUNDAY...THERE MAY BE A BRIEF LULL IN THE LARGER SWELLS BUT FOR  
NOW...A SE SWELL OF 4-5 FEET IS MODELED AT 15 SECOND INTERVALS  
FROM MARIA. THATS A STRONG MODERATE RISK IF NOT A HIGH RISK FOR  
THE FORMATION OF DANGEROUS RIP CURRENTS.  
 
MONDAY...A 5 OR 6 FOOT SE SWELL OF 15 SECONDS IS EXPECTED TO BE  
DOMINANT AND RESULT IN A HIGH RISK.  
 
TUESDAY...AN 8 FOOT 15 SECOND SWELL SHOULD BE DOMINANT BY THAT  
TIME...LOTS OF ENERGY AND A SOLID HIGH RISK.  
 
WEDNESDAY...AROUND AN 11 TO 13 FOOT SE SWELL AT 15 SECONDS. EVEN  
HIGHER RISK AND IF THIS MATERIALIZES AS CONSTANTLY MODELED...WE'D  
NEED A HIGH SURF ADVISORY AS WELL, ALLOWING 70 PERCENT FOR  
BREAKING WAVES AT THE BEACH (8 TO 9 FOOT).  
 
THURSDAY THE 28TH...STILL A 10 FOOT SE SWELL AT 14 SECONDS.  
HIGH RISK.  
 
FRIDAY...MAYBE DOWN TO 5 OR 6 FEET AND A MDT OR HIGH RISK.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WE ARE STILL FEELING THE EFFECTS FROM POST-TROPICAL CYCLONE JOSE AND  
THE NEW MOON. THE COASTAL FLOOD ADVISORY EXPIRED AT 3 PM. MINOR  
FLOODING OCCURRED UP AND DOWN THE DE/NJ COASTS...MORE SPOTTY ACROSS  
NORTHERN NJ AND MORE WIDESPREAD ACROSS SOUTHERN NJ AND SUSSEX COUNTY  
DE.  
 
FOR THIS EVENING'S HIGH TIDE, SPOTTY MINOR FLOODING IS EXPECTED  
ALONG THE NJ AND DE COASTS. THIS EVENING'S HIGH TIDE IS THE LOWER OF  
THE TWO TODAY BY ABOUT 1/2 FOOT. AS A RESULT, WE DON'T THINK THE  
FLOODING WILL BE WIDESPREAD ENOUGH TO ISSUE ANOTHER ADVISORY.  
 

 
   
CLIMATE
 
 
WITH HIGH TEMPERATURES MAKING A RUN AT 90 SUNDAY AND MONDAY  
ACROSS THE REGION, SOME RECORD HIGH TEMPERATURES MAY BE TIED OR  
BROKEN. THE HIGHEST CHANCES ARE ON MONDAY WHERE ALL LOCATIONS  
BUT GEORGETOWN ARE EXPECTED TO BE WITHIN THREE DEGREES OF A  
RECORD.  
 
HERE ARE THE RECORDS FOR BOTH DAYS.  
 
SUNDAY  
 
ACY-92(2010)  
PHL 95(1970)  
ILG-92(2010)  
ABE-92(1970)  
TTN-92(1970)  
GED-97(2010)  
RDG-95(1970)  
MPO-85(2010)  
 
MONDAY  
 
ACY-91(1970)  
PHL-92(1970)  
ILG-93(1970)  
ABE-92(1970)  
TTN-92(1970)  
GED-92(2010 AND 1970)  
RDG-92(1970)  
MPO-85(1970)  
 
MONTHLY CLIMATE: DEPENDING ON WHETHER THERE IS ANY RAIN AT KILG,  
IF NONE FOR THE REMAINDER OF THE MONTH, THE CURRENT MONTHLY  
TOTAL OF 1.12 INCHES WOULD RANK 12TH DRIEST IN THE PERIOD OF  
RECORD.  
 
SEPTEMBER TEMPS: PHL IS PROJECTING A 71.7 AVERAGE OR 2.6 DEGREES  
ABOVE AVERAGE, WHICH WOULD MAKE IT THE 13TH WARMEST SEPTEMBER  
IN THE PHL PERIOD OF RECORD. ABE IS PROJECTING A 68 DEGREE AVG  
OR 4.1 DEGREES ABOVE NORMAL WHICH WOULD BE 9TH WARMEST SEPTEMBER  
IN THE ABE PERIOD OF RECORD.  
 
THESE PROJECTIONS TOOK INTO ACCOUNT TODAYS HIGH/LOW, THE PHI  
330 PM FORECAST THROUGH THE 29TH AND A NORMAL HIGH/LOW FOR THE  
30TH.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT SUNDAY  
FOR ANZ450>455.  
 

 
 

 
SYNOPSIS...DRAG/JOHNSON  
NEAR TERM...CMS  
SHORT TERM...CMS/KRUZDLO  
LONG TERM...JOHNSON  
AVIATION...CMS/JOHNSON  
MARINE...DRAG/JOHNSON  
TIDES/COASTAL FLOODING...STAFF  
CLIMATE...DRAG  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab PA Page
The Nexlab NJ Page
The Nexlab DE Page
The Nexlab MD Page Main Text Page