054  
FXUS61 KOKX 232143  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
543 PM EDT SUN JUL 23 2017  
   
SYNOPSIS
 
 
A FRONTAL BOUNDARY REMAINS TO OUR SOUTH TONIGHT. LOW PRESSURE THEN  
MOVES ALONG THE FRONT, TRACKING OFF THE MID-ATLANTIC COAST  
MONDAY. HIGH PRESSURE BUILDS OVER THE NORTHEAST LATE TUESDAY  
THROUGH WEDNESDAY, THEN DRIFTS OFF THE COAST WEDNESDAY NIGHT.  
ANOTHER WAVE OF LOW PRESSURE FOLLOWS FOR THURSDAY INTO SATURDAY.  
HIGH PRESSURE RETURNS SUNDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
 
 
A STATIONARY FRONT WILL REMAIN TO THE SOUTH OF THE CWA TONIGHT.  
A WEAK AREA OF LOW PRESSURE DEVELOPS ALONG THIS FRONTAL  
BOUNDARY AND SLOWLY TRACKS NORTHEAST, SITUATED NEAR THE NEW  
YORK CITY METRO AREA LATE TONIGHT INTO EARLY MONDAY MORNING.  
THIS WILL BE THE FOCUS FOR SHOWERS TO START OFF WITH, BUT A MORE  
WIDESPREAD RAIN WILL DEVELOP AS THE LOW APPROACHES. THERE IS A  
PERIOD OF HEAVY RAINFALL POSSIBLE, GENERALLY FROM 2 AM TO 8 AM  
FOR NEW YORK CITY AND POINTS WEST AND FROM 4 AM TO 10 AM FOR  
POINTS EAST. ALL THE DETERMINISTIC MODELS HAVE INCREASED QPF  
FROM THEIR PREVIOUS RUNS, AND IN PARTICULAR, THE 12Z GFS HAD  
TWICE AS MUCH QPF FROM 2 AM TO 8 AM MONDAY. THERE IS ALSO THE  
POSSIBILITY OF 1 TO 2 INCH RAINFALL RATES IN THE METRO AREA AS  
PER THE NCAR ENSEMBLE, WHICH SHOWS A 50-70% CHANCE OF SEEING  
RAINFALL RATES GREATER THAN 1" AT SOME POINT OVERNIGHT, FROM 4  
AM TO 6 AM, JUST BEFORE THE MORNING RUSH. THEREAFTER, A PERIOD  
OF MODERATE RAIN IS STILL POSSIBLE. ALSO OF NOTE, THE 12Z ECMWF  
HAD A BULLS EYE OF OVER 2" OF RAINFALL JUST NORTH OF THE CITY.  
THEREFORE, A FLASH FLOOD WATCH WAS ISSUED FOR ALL OF NEW YORK  
CITY, WESTERN LONG ISLAND, NORTHEAST NEW JERSEY, AND PORTIONS OF  
THE LOWER HUDSON VALLEY. THE REST OF THE CWA HAS A CHANCE OF  
SEEING FLASH FLOODING, HOWEVER, THERE IS MORE UNCERTAINTY WITH  
WHERE THE AXIS OF HEAVY RAIN WILL BE FOR THESE AREAS, SO DID NOT  
ISSUE A WATCH FOR THESE AREAS. THIS WILL NEED TO BE LOOKED AT  
OVERNIGHT.  
 
SPC HAS PLACED PORTIONS OF NEW YORK CITY AND NORTHEAST NEW  
JERSEY IN A MARGINAL RISK FOR SEVERE THUNDERSTORM THROUGH 8 AM  
MONDAY. HOWEVER, STABILITY DOES NOT LOOK IMPRESSIVE WITH THIS  
LOW, AND DID NOT MENTION ANY SEVERE, THOUGH AN ISOLATED SEVERE  
IS NOT OUT OF THE QUESTION.  
 
THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF RIP CURRENTS AT  
OCEAN BEACHES THROUGH THIS EVENING.  
 

 
   
SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/
 
 
LOW PRESSURE WILL PULL AWAY FROM THE AREA MONDAY AFTERNOON. THIS  
WILL ALLOW RAINFALL TO TAPER OFF FROM WEST TO EAST FROM MONDAY  
MORNING INTO THE AFTERNOON. HOWEVER, CHANCES FOR RAIN CONTINUE AS  
THE UPPER LEVEL TROUGH REMAINS OVER THE AREA THROUGH MONDAY  
NIGHT, WITH JUST A SLIGHT CHANCE FOR THE ENTIRE AREA FROM 3 AM  
ONWARD MONDAY NIGHT. RAINFALL AMOUNTS WILL NOT BE NEARLY AS HIGH  
AS FOR MONDAY MORNING.  
 
SPC HAS PLACED MUCH OF THE CWA, EXCEPT SOUTHWEST CONNECTICUT IN  
A MARGINAL RISK FOR SEVERE THUNDERSTORM MONDAY INTO MONDAY NIGHT.  
HOWEVER, STABILITY DOES NOT LOOK IMPRESSIVE WITH THIS LOW, AND  
DID NOT MENTION ANY SEVERE, THOUGH AN ISOLATED SEVERE IS NOT OUT  
OF THE QUESTION.  
 
THERE IS A HIGH RISK FOR THE DEVELOPMENT OF RIP CURRENTS AT  
OCEAN BEACHES MONDAY.  
 

 
   
LONG TERM /TUESDAY THROUGH SUNDAY/
 
 
THE EXTENDED FORECAST MAINLY REMAINS CONSISTENT WITH THE PREVIOUS  
FORECAST WITH THE EXCEPTION THAT PRECIPITATION IS EXPECTED REMAIN  
INTO SATURDAY AS WAS HINTED AT BY THE ECMWF LATE SATURDAY, AS AN  
UPPER TROUGH IS SLOWER TO MOVE EAST.  
 
THE NORTHERN STREAM FLOW ALONG THE US/CANADIAN BORDER REMAINS  
NEARLY ZONAL AND PROGRESSIVE WITH EMBEDDED SHORTWAVES MOVING  
THROUGH THE FLOW.  
 
ONE SHORTWAVE WILL BE EXITING THE NORTHEASTERN COAST, ALONG WITH  
THE ACCOMPANYING SURFACE LOW, TUESDAY. CAPE AND INSTABILITY  
REMAIN LIMITED SO WILL CONTINUE WITH SHOWERS.  
 
A WEAK RIDGE AXIS BUILDS INTO SOUTHERN CANADA FROM THE SOUTHERN  
RIDGE OVER THE SOUTHWEST AND MOVING INTO THE PLAIN STATES MID WEEK.  
 
ANOTHER SHORTWAVE WAS COMING ONSHORE OF THE CANADIAN PACIFIC  
COAST AS SEEM ON THE UPPER LEVEL WATER VAPOR LOOP. AND THESE  
SYSTEM HAS BEEN PICKED UP BY THE MODELS. THIS SHORTWAVE OPEN AND  
TRACKS QUICKLY ACROSS SOUTHERN CANADA THEN DIGS AND LARGE TROUGH  
ALONG THE EASTERN UNITED STATES LATE IN THE WEEK INTO THE WEEKEND  
AS A WESTERN NORTH ATLANTIC RIDGE BUILDS AND BLOCKS THE EASTERN  
TROUGH. THIS WILL KEEP WAVES OF LOW PRESSURE TRACKING ALONG A  
FRONTAL BOUNDARY THURSDAY INTO SATURDAY BEFORE THE LAST ONE EXITS  
LATER SATURDAY. SO NOW HAVE CHANCES OF PRECIPITATION THROUGH  
FRIDAY INTO SATURDAY.  
 
THE UPPER TROUGH WEAKENS SUNDAY AS SURFACE HIGH PRESSURE BUILDS  
TO THE NORTH RESULTING IN A DRY SUNDAY.  
 
TEMPERATURES THROUGH THE EXTENDED PERIOD WILL BE NEAR SEASONAL  
NORMALS, EXCEPT FOR BEING BELOW NORMAL TUESDAY.  
 

 
   
AVIATION /22Z SUNDAY THROUGH FRIDAY/
 
 
A STATIONARY FRONT WILL REMAIN TO OUR SOUTH INTO MONDAY MORNING,  
WITH A WAVE OF LOW PRESSURE MOVING ALONG IT TOWARDS THE REGION  
TONIGHT, THEN PASSES TO THE SOUTH INTO MONDAY AFTERNOON.  
 
CONDITIONS BECOME MVFR AT ALL TERMINALS BY LATE EVENING/EARLY  
MORNING. SHOWERS ALSO OVERSPREAD THE AREA, MAINLY AFTER MIDNIGHT.  
IN ADDITION, AN ISOLATED RUMBLE OF THUNDER CANNOT BE RULED OUT  
DURING THE OVERNIGHT HOURS AS WELL, WITH THE BEST CHANCE FROM THE  
CITY TERMINALS ON N/W. IFR CONDITIONS ARE PROBABLE BY AROUND  
SUNRISE, THEN SHOULD IMPROVE BACK TO MVFR BY MID MORNING.  
 
WINDS BECOME E THROUGHOUT BY EARLY MORNING AT AROUND 10-15KT.  
GUSTS TO AROUND 15-20KT ARE PROBABLE OVERNIGHT FOR CT/LONG ISLAND  
TERMINALS/KLGA AND BRIEFLY AT KJFK. WIDESPREAD 15-20KT GUSTS ARE  
PROBABLE THROUGHOUT BY MID MONDAY MORNING, AS THE WINDS BACK TO  
THE NE.  
   
OUTLOOK FOR 18Z MONDAY THROUGH THURSDAY
 
   
MONDAY AFTERNOON-TUESDAY
 
MVFR LIKELY. IFR, NE-E WINDS G15-25KT  
AND ISOLATED-SCATTERED SHOWERS ARE POSSIBLE.   
TUESDAY NIGHT
 
MVFR LIKELY. IFR AND NE WINDS G15-25KT ARE POSSIBLE.   
WEDNESDAY-THURSDAY
 
VFR. THERE IS A CHANCE OF SHOWERS AND POSSIBLY  
A THUNDERSTORM MAINLY TO THE N/W OF CITY TERMINALS THURSDAY  
AFTERNOON.   
THURSDAY NIGHT-FRIDAY
 
MVFR OR LOWER CONDITIONS AND ISOLATED TO  
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE.  
 

 
   
MARINE
 
 
SCA WAVES OF 5 FT ARE POSSIBLE OVER THE OCEAN WATERS TONIGHT,  
GENERALLY AFTER 10 PM AS A PERSISTENT EASTERLY FLOW ALLOWS WAVES  
TO BUILD. WINDS GUST OF UP TO 30 KT ARE POSSIBLE OVER THE OCEAN  
AFTER 2 AM, AND THE SOUND, PECONIC BAY, AND GARDINER'S BAYS AFTER  
7 AM MONDAY MORNING AS A WEAK AREA OF LOW PRESSURE DEVELOPS OVER A  
STALLED FRONTAL BOUNDARY AND HEADS NORTHEAST, PASSING SOUTH AND  
EAST OF LONG ISLAND INTO MONDAY MORNING. WINDS SHOULD DIMINISH  
BELOW 25 KT OVER MOST WATERS BY THE AFTERNOON, EXCEPT FOR EASTERN  
AREAS, WHICH MAY REMAIN ABOVE 25 KT THROUGH THE DAY MONDAY. WAVES  
REMAIN ABOVE 5 FT THROUGH MONDAY NIGHT.  
 
A PERSISTENT EASTERLY FLOW WILL BE ON GOING TUESDAY, WITH WINDS  
AND GUSTS BELOW SMALL CRAFT ADVISORY LEVELS. HOWEVER, OCEAN SEAS  
WILL BE AT SMALL CRAFT LEVELS. THE EASTERLY FLOW CONTINUES INTO  
WEDNESDAY AND THEN GRADUALLY DIMINISHES AND BECOMES SOUTHEASTERLY  
AS HIGH PRESSURE MOVES WELL EAST OF THE FORECAST WATERS. OCEAN  
SEAS ARE EXPECTED TO SUBSIDE BELOW 5 FEET DURING WEDNESDAY. THEN  
WINDS AND SEAS REMAIN BELOW SMALL CRAFT LEVELS WEDNESDAY NIGHT  
INTO FRIDAY.  
 

 
   
HYDROLOGY
 
 
HEAVY RAINFALL IS POSSIBLE LATE TONIGHT INTO MONDAY MORNING FOR  
THE ENTIRE AREA. GENERALLY, 1 TO 1.5 INCHES IS FORECAST, WITH  
LOCALLY HIGHER AMOUNTS POSSIBLE IN ANY THUNDERSTORMS. A FLASH  
FLOOD WATCH HAS BEEN ISSUED FOR PORTIONS OF THE AREA (SEE ABOVE)  
FOR THIS THREAT. IN PARTICULAR, THE NEW YORK CITY AREA COULD SEE  
A PERIOD OF HEAVY RAINFALL LATE TONIGHT INTO EARLY MONDAY  
MORNING, LEADING TO URBAN FLOODING.  
 
ADDITIONAL RAINFALL IS POSSIBLE THURSDAY THROUGH FRIDAY NIGHT.  
HYDROLOGIC IMPACTS ARE NOT EXPECTED AT THIS TIME.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WITH THE NEW PHASE OF THE MOON TODAY, TIDES ARE RUNNING HIGH.  
POSITIVE TIDAL DEPARTURES OF 1/2 TO 1 FT ARE NEEDED FOR MINOR  
FLOODING DURING THE NIGHT TIME HIGH TIDE. WITH A SE TO E FLOW  
EXPECTED, AND LOOKING AT WHAT OCCURRED LAST NIGHT AND WITH THIS  
MORNINGS HIGH TIDE, HAVE CONTINUED THE COASTAL FLOOD ADVISORY FOR  
WESTERN LI SOUND, THE SOUTH SHORE BAYS OF LI, AND LOWER NY HARBOR  
FOR THE EVENING AND NIGHT TIME HIGH TIDES (WILL ADD E UNION WITH  
THIS UPDATE). A FEW LOCATIONS COULD REACH OR SLIGHTLY EXCEED  
MODERATE BENCHMARKS ACROSS THE SOUTH SHORE BAYS OF NASSAU AND  
QUEENS.  
 
THE THREAT FOR MINOR FLOODING COULD CONTINUE INTO MONDAY (POSSIBLY  
THE MORNING AND LIKELY THE NIGHT TIME HIGH TIDE), WITH E/NE FLOW  
PROGGED TO CONTINUE.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...COASTAL FLOOD ADVISORY FROM 11 PM THIS EVENING TO 2 AM EDT  
MONDAY FOR CTZ009.  
NY...FLASH FLOOD WATCH FROM MIDNIGHT EDT TONIGHT THROUGH MONDAY  
MORNING FOR NYZ067-069-071>075-078-080-176>179.  
COASTAL FLOOD ADVISORY FROM 11 PM THIS EVENING TO 2 AM EDT  
MONDAY FOR NYZ071-073-176-177.  
HIGH RIP CURRENT RISK FROM MONDAY MORNING THROUGH MONDAY  
EVENING FOR NYZ075-080-081-178-179.  
COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR NYZ074-  
075-178-179.  
NJ...FLASH FLOOD WATCH FROM MIDNIGHT EDT TONIGHT THROUGH MONDAY  
MORNING FOR NJZ002-004-006-103>108.  
COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR NJZ108.  
MARINE...SMALL CRAFT ADVISORY FROM 7 AM TO 2 PM EDT MONDAY FOR ANZ330-  
335-340.  
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 PM EDT  
MONDAY FOR ANZ350-353-355.  
 

 
 

 
SYNOPSIS...JP/MET  
NEAR TERM...JP  
SHORT TERM...JP  
LONG TERM...MET  
AVIATION...MALOIT  
MARINE...JP/MET  
HYDROLOGY...JP/MET  
TIDES/COASTAL FLOODING...  
 
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