557  
FXUS61 KOKX 210138  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
938 PM EDT SUN AUG 20 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE BUILDING INTO THE REGION THROUGH MONDAY MORNING  
WILL SETTLE TO THE SOUTH AND EAST MONDAY AFTERNOON, ALLOWING A  
WEAK WARM FRONT TO APPROACH MONDAY NIGHT. AFTER A HOT AND HUMID  
TUESDAY, A COLD FRONTAL PASSAGE ON WEDNESDAY WILL PRODUCE A  
DRASTIC COOL DOWN FOR THE END OF THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
 
 
NO CHANGES MADE TO THE FORECAST TONIGHT. DAYTIME CUMULUS HAVE  
DIMINISHED. WEAK RIDGING ALOFT WITH HIGH PRESSURE BUILDING IN  
WILL LEAD TO MOSTLY CLEAR SKIES FOR THE REST OF THE NIGHT.  
THIS ALONG WITH DIMINISHING WINDS SHOULD ALLOW TEMPS TO DROP TO  
THE 50S AND 60S IN MOST AREAS, WITH ONLY NYC REMAINING ABOVE 70  
OVERNIGHT.  
 

 
   
SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/
 
 
SKY COVER COULD BE TRICKY IN SPOTS FOR THE PARTIAL SOLAR  
ECLIPSE, WHICH SHOULD RUN FROM ABOUT 120 PM TO 400 PM IN NYC  
AND PEAK AT 244 PM. DO EXPECT SOME SCT HIGH CLOUDS AND ALSO SOME  
SCT CU, POSSIBLY A NARROW BAND OF BROKEN CU WITH THE SEA BREEZE  
CLOSER TO THE NORTH SHORE OF LONG ISLAND AND IN SOUTHERN CT.  
SOUTH FACING COASTLINES MAY BE BETTER VIEWING LOCATIONS AS ANY  
LOWER CLOUDS THAT FORM INLAND WITH THE SEA BREEZE.  
 
TEMPS SHOULD RISE QUICKLY INTO EARLY AFTERNOON, AND PER 15Z RUN  
OF THE HRRRX WHICH HAS BEEN MODIFIED TO INCORPORATE IMPACT ON  
INCOMING SOLAR RADIATION DUE TO THE ECLIPSE, MAY ACTUALLY DROP A  
COUPLE OF DEGREES BETWEEN 2-4 PM, THEN REBOUND. OVERALL TEMPS  
SHOULD STILL REACH THE MID/UPPER 80S, POSSIBLY 90 IN PARTS OF  
URBAN NE NJ.  
 
THE APPROACHING WARM FRONT COULD SPARK AN ISOLATED SHOWER OR  
TSTM TOWARD SUNSET WELL WEST OF NYC, WITH SLIGHT CHANCES  
OVERSPREADING NEARLY ALL THE AREA LATER MON NIGHT. LOWS SHOULD  
BE IN THE UPPER 60S/LOWER 70S, AND IT WILL BECOME MUGGY AS  
DEWPOINTS ALSO INCREASE INTO THAT RANGE.  
 
THERE IS A MODERATE RISK OF RIP CURRENTS AT ATLANTIC BEACHES ON  
MONDAY.  
 

 
   
LONG TERM /TUESDAY THROUGH SUNDAY/
 
 
A COLD FRONT WILL REACH THE AREA ON WEDNESDAY PER THE 12Z SUITE OF  
MODEL GUIDANCE, WHICH WAS IN GOOD AGREEMENT. THIS MEANS THAT TUE IS  
SETTING UP TO BE HOT AND HUMID. WINDS PROGGED AROUND 200 DEGREES  
WILL PUMP LOTS OF HUMIDITY INTO THE AREA, AND ACROSS THE ERN HALF OF  
THE CWA KEEP ACTUAL TEMPS SLIGHTLY SUPPRESSED DESPITE H85  
WARMING TOWARDS 20C. THE HUMIDITY WILL COMPENSATE FOR ANY LACK  
OF HEAT, WITH JUST ABOUT ALL AREAS LIKELY AOA 90 FOR A HEAT  
INDEX. ACROSS THE NORMALLY HOTTEST AREAS LIKE NJ ZONES, THE  
HEAT INDEX ATTM LOOKS TO REACH ABOUT 100. THERE COULD BE A FEW  
AFTN AND EVE TSTMS, PARTICULARLY N AND W OF NYC, BUT THERE WILL  
AT LEAST BE AN INCREASE IN DENSE CIRRUS FROM UPSTREAM  
CONVECTIVE DEBRIS. AS A RESULT THE FCST GOES MOSTLY CLOUDY BY  
TUE EVE. SHWRS AND TSTMS AHEAD OF THE FRONT TUE NGT AND WED,  
THEN THE AREA DRIES OUT FOR THE REMAINDER OF THE FCST PERIOD.  
THE COLD FRONT WILL BE DRIVEN BY A 100-KT H3 JET, SO TSTMS WILL  
BE EASIER TO SUSTAIN OR INITIATE AT NGT. IF THE TIMING ENDS UP  
SLIGHTLY SLOWER, A SVR OUTBREAK IS POSSIBLE ON WED AS CAPE COULD  
SOAR TO 3000 J/KG OR MORE. EVEN WITH THE PROGGED FASTER TIMING  
HOWEVER, THERE COULD STILL BE SVR AT ANY TIME AHEAD OF THE FRONT  
WITH THE JET ACTING ON MUCAPE AROUND 1500-2000 J/KG. MUCH COOLER  
WEATHER WILL THEN SETTLE IN FOR THU-SUN, WITH TEMPS AVERAGING  
BLW CLIMO.  
 

 
   
AVIATION /02Z MONDAY THROUGH FRIDAY/
 
 
VFR THROUGH THE TAF PERIOD AS HIGH PRESSURE REMAINS IN CONTROL  
THROUGH MONDAY.  
 
NW WINDS WILL DIMINISH THIS EVENING TO AROUND 5 KT AT CITY  
TERMINALS AND BECOME LIGHT AND VARIABLE ELSEWHERE. WINDS WILL  
INCREASE LATE MONDAY MORNING INTO THE AFTERNOON OUT OF THE SW  
AND BACK TOWARDS THE SOUTH AT COASTAL TERMINALS. SEA BREEZE  
ENHANCEMENT MAY ALLOW FOR GUSTS IN THE UPPER TEENS AT KJFK AND  
KISP IN THE AFTERNOON.  
   
OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY
 
   
MONDAY NIGHT
 
MAINLY VFR, WITH LOW CHANCE MVFR OR LOWER AT  
MAINLY LONG ISLAND TERMINALS.    
TUESDAY-WEDNESDAY
 
A CHANCE OF SHOWERS AND THUNDERSTORMS WITH  
BRIEF PERIODS OF MVFR OR LOWER POSSIBLE. SW WINDS G15-20KT  
TUESDAY AFTERNOON.    
WEDNESDAY NIGHT-FRIDAY
 
VFR.  
 

 
   
MARINE
 
 
HIGH PRESSURE OVER THE WATERS WILL LEAD TO SUB-SCA CONDITIONS  
THROUGH MONDAY NIGHT. A FEW GUSTS UP TO 20 KT ARE POSSIBLE ON  
THE WATERS WEST OF FIRE ISLAND INLET IN THE AFTERNOON DUE TO SEA  
BREEZE ENHANCEMENT.  
 
WINDS AND SEAS WILL RAMP UP ON TUE, WITH SCA CONDITIONS  
DEVELOPING ON ALL WATERS. WINDS WILL DECREASE AFTER A COLD  
FRONTAL PASSAGE, BRINGING WINDS THE PROTECTED WATERS BLW SCA  
LVLS BY WED EVE. ON THE OCEAN, SEAS SHOULD LINGER AROUND 5 FT  
INTO WED NGT. WINDS AND SEAS ARE THEN PROGGED TO REMAIN, IN THE  
ABSENCE OF ANY INCREASED SWELL, BLW SCA LVLS THRU THE WEEKEND.  
 

 
   
HYDROLOGY
 
 
NO WIDESPREAD HYDROLOGIC IMPACTS ARE FORECAST THROUGH THE WEEK.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
NY...NONE.  
NJ...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...JMC/GOODMAN  
NEAR TERM...GOODMAN/DS  
SHORT TERM...GOODMAN  
LONG TERM...JMC  
AVIATION...DS  
MARINE...JMC/GOODMAN  
HYDROLOGY...JMC/GOODMAN  
 
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