770  
FXUS61 KOKX 262034  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
434 PM EDT WED APR 26 2017  
   
SYNOPSIS
 
 
WEAK LOW PRESSURE MOVES INTO COASTAL NEW ENGLAND TONIGHT INTO  
THURSDAY. THE LOW EVENTUALLY DISSIPATES ALTOGETHER, LEAVING THE  
REGION WITH WEAK HIGH PRESSURE BRIEFLY THURSDAY AFTERNOON INTO  
THURSDAY EVENING. A COLD FRONT APPROACHES LATE THURSDAY NIGHT  
AND MOVES INTO THE REGION FRIDAY BUT WILL ALSO WEAKEN WITH TIME.  
A COLD FRONT WILL SLOWLY APPROACH FROM THE NORTH LATE FRIDAY  
NIGHT INTO SATURDAY, AND PASS THROUGH SATURDAY EVENING. HIGH  
PRESSURE WILL BRIEFLY BUILD IN ITS WAKE FROM SOUTHEAST CANADA ON  
SUNDAY. A WARM FRONT WILL APPROACH SUNDAY NIGHT AND LIFT NORTH  
ON MONDAY, FOLLOWED BY A TRAILING COLD FRONT LATE MONDAY IN TO  
MONDAY NIGHT. WEAK HIGH PRESSURE WILL PASS TO THE SOUTH FROM  
TUESDAY INTO WEDNESDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
THE MAIN STORY TONIGHT WILL BE THE LOW CLOUDS AND FOG. THE UPPER  
LEVEL LOW AND SURFACE LOW BOTH TRANSLATE EAST OF THE REGION,  
GETTING INTO THE VICINITY OF COASTAL NEW ENGLAND BY EARLY  
THURSDAY. WITH ATMOSPHERIC FLOW STAYING BELOW 15KT BELOW 10KFT  
AND A LOW LEVEL INVERSION AT AROUND 1-2 KFT, THE LOW LEVEL  
MOISTURE STAYS IN PLACE. THERE COULD BE SOME DRIZZLE OR VERY  
LIGHT SHOWERS BUT MOST MOISTURE PROBABLY IS MANIFESTED AS FOG.  
MOST SUSCEPTIBLE AREAS WILL BE WHERE RELATIVELY MORE RAIN HAS  
FALLEN, EASTERN LONG ISLAND AND SOUTHEAST CONNECTICUT WHERE JUST  
A LITTLE COOLING THIS EVENING WITH LIGHT EASTERLY FLOW WILL  
HELP ADVECT AND FURTHER DEVELOP THE FOG, AND IT WILL EVENTUALLY  
BECOME DENSE. DENSE FOG ADVISORY FOR EASTERN LONG ISLAND AND NEW  
LONDON COUNTY CONNECTICUT WAS ISSUED FOR LATE THIS EVENING INTO  
EARLY THURSDAY MORNING. OTHER AREAS FARTHER WEST WILL ALSO GET  
FOG BUT NOT AS MUCH DENSE FOG. TOOK RELATIVELY WARMER MAV  
GUIDANCE FOR LOWS, UPPER 40S TO UPPER 50S.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/
 
 
FOG BURNS OFF IN THE MORNING WITH DAYTIME HEATING AND AS MORE  
WESTERLY FLOW DEVELOPS IN THE ATMOSPHERE. THE UPPER LEVEL LOW  
MOVES FARTHER EAST OF THE REGION AS A SURFACE LOW DISSIPATES.  
MORE OF A RETURN W-SW FLOW DEVELOPS IN THE REGION THEREAFTER.  
MODELS AGREE ON A SUBSTANTIALLY WARMER DAY THURSDAY, GETTING  
WELL INTO THE 60S FOR A MAJORITY OF THE REGION FOR HIGHS. WEAK  
HIGH PRESSURE WILL BRIEFLY RESIDE IN THE REGION WITH DRY  
CONDITIONS DURING THE DAY AND THROUGH THE FIRST HALF OF THURSDAY  
NIGHT.  
 
THE NEXT LOW PRESSURE SYSTEM AND ASSOCIATED UPPER LEVEL TROUGH  
WILL BE APPROACHING LATE THURSDAY NIGHT.THE UPPER LEVEL FLOW  
REMAINS SW AND THE PARENT LOW WITH THE SYSTEM MOVES NORTHWARD  
FRIDAY WITHIN SOUTHEAST CANADA WHILE ITS COLD FRONT MOVES IN AND  
DISSIPATES WITH TIME. THERE WILL INITIALLY BE ENOUGH VERTICAL  
LIFT LATE THURSDAY NIGHT INTO EARLY FRIDAY ALONG WITH SOME  
ELEVATED INSTABILITY TO GIVE THE REGION SOME SHOWERS AND  
THUNDERSTORMS. HOWEVER, THIS LOOKS TO BE BRIEF WITHOUT PRODUCING  
MUCH RAIN. OUTSIDE OF THE RAIN WITH THE FLOW AHEAD OF THE COLD  
FRONT TURNING MORE SOUTHERLY, THE REGION WILL SEE A RETURN OF AT  
LEAST PATCHY FOG THURSDAY NIGHT INTO EARLY FRIDAY WITH MORE  
ONSHORE FLOW AND INHERENT MOISTURE ADVECTION. DRY CONDITIONS  
RETURN LATER FRIDAY.  
 
THE OVERALL SHIFT WILL BE ONE OF A GRADUALLY WARMING AIRMASS.  
TEMPERATURES TREND SEVERAL DEGREES WARMER FOR BOTH LOWS  
THURSDAY NIGHT AND HIGHS ON FRIDAY.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
 
 
BIG PICTURE SHOWS AN AMPLIFIED PATTER DEVELOPING OVER THE EASTERN  
HALF OF THE LOWER 48, WITH A BUILDING UPPER RIDGE OVER THE EAST AND  
A CLOSED LOW MOVING FROM THE PLAINS STATES THROUGH THE MIDWEST AND  
INTO SOUTHEAST CANADA. AT FIRST THE AREA WILL BE UNDER ZONAL FLOW  
ALOFT BETWEEN THE RIDGE TO THE SOUTH AND AN UPPER TROUGH MOVING  
ACROSS SOUTHEAST CANADA, THAT WILL SEND A BACK DOOR COLD FRONT  
TOWARD THE AREA LATE FRIDAY NIGHT INTO SATURDAY. A SHORTWAVE  
EMBEDDED IN THE FLOW ALOFT COULD TRIGGER A SHOWER OR TSTM LATE FRI  
NIGHT OR EARLY SAT MORNING, THEN SAT SHOULD BE A PARTLY SUNNY TO  
MOSTLY CLOUDY DAY WITH TEMPS ON THE WARM SIDE, WITH HIGHS 80-85 FROM  
NYC NORTH/WEST AND IN THE 70S ACROSS LONG ISLAND AND SOUTHERN CT.  
LOW LEVELS LOOK CAPPED JUST ABOVE THE BOUNDARY LAYER UNTIL LATE DAY  
SAT, SO DO NOT EXPECT ANY PRECIP UNTIL LATE DAY SAT WITH THE COLD  
FROPA, AND ONLY AND ISOLATED SHOWER OR TSTM AT MOST.  
 
COOLER AIR RETURNS FOR SAT NIGHT INTO SUNDAY NIGHT, WITH LOWS IN THE  
40S AND 50S, AND HIGHS IN THE 60S TO NEAR 70. AS THE FLOW ALOFT  
AMPLIFIES, A LEADING WARM FRONT WELL IN ADVANCE OF THE SURFACE LOW  
OVER THE MIDWEST WILL APPROACH, AND MOVE THROUGH SOME TIME ON  
MONDAY, THE FRONT SHOULD LIFT THROUGH NYC METRO AND POINTS  
NORTH/WEST BY AFTERNOON, NUT COULD TAKE LONGER ACROSS LONG ISLAND  
AND SOUTHERN CT. THEN AS UPPER RIDGING MOVES EAST, COLD FRONT  
SHOULD PASS THROUGH LATE DAY MONDAY INTO MONDAY NIGHT, WITH SHOWERS  
AND A FEW TSTMS. DO NOT EXPECT STRONG CONVECTION WITH THE COLD FROPA  
ATTM, BUT A FASTER TIMING PER 12Z ECMWF COULD YIELD A BRIEF WINDOW  
FOR THIS TO OCCUR LATE DAY MONDAY FROM NYC NORTH/WEST.  
 
DRY WX WITH NEAR TO SLIGHTLY ABOVE SEASONABLE TEMPS EXPECTED FOR TUE  
INTO WED, WITH THE WEAKENING LOW PASSING WELL NORTH, WEAK SURFACE  
HIGH PRESSURE PASSING TO THE SOUTH. ZONAL FLOW ALOFT WILL ALSO  
BECOME RE-ESTABLISHED BY WED, THAT COULD LEAD TO LATE WEEK PRECIP  
CHANCES JUST BEYOND THE FORECAST PERIOD.  
 

 
   
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
 
 
LOW PRESSURE APPROX 50 MILES SSE OF KJFK WILL SLOWLY SHIFT EAST THIS  
AFTERNOON AND EVENING.  
 
CIGS MOSTLY 600-1200 FT THIS AFTERNOON, LOWERING TONIGHT. A STRAY  
BRIEF SHOWER OR TWO / DRIZZLE STILL POSSIBLE THIS AFTN.  
 
NE-N WINDS AROUND 10 KT BECOMING A LITTLE LIGHTER LATE THIS  
AFTN. WINDS EVENTUALLY BCMG LIGHT AND VARIABLE THIS EVENING.  
 
NY METRO ENHANCED AVIATION WEATHER SUPPORT...  
 
DETAILED INFORMATION, INCLUDING HOURLY TAF WIND COMPONENT FORECASTS,  
CAN BE FOUND AT: HTTP:/WWW.WEATHER.GOV/ZNY/N90  
 
KJFK TAF COMMENTS: TIMING OF VSBYS LOWERING BELOW 1SM MIGHT BE OFF  
BY AN HOUR OR TWO, OR MAY NOT HAPPEN AT ALL.  
 
KLGA TAF COMMENTS: TIMING OF VSBYS LOWERING BELOW 1SM MIGHT BE OFF  
BY AN HOUR OR TWO, OR MAY NOT HAPPEN AT ALL.  
 
KEWR TAF COMMENTS: TEMPO OR PREVAILING IFR CIGS STILL POSSIBLE  
THIS AFTN. TIMING OF RETURN TO PREVAILING IFR MAY BE OFF BY AN  
HOUR OR TWO.  
 
KTEB TAF COMMENTS: TEMPO OR PREVAILING IFR CIGS STILL POSSIBLE THIS  
AFTN. TIMING OF RETURN TO PREVAILING IFR MAY BE OFF BY AN HOUR OR  
TWO.  
 
KHPN TAF COMMENTS: TIMING OF VSBYS LOWERING BELOW 1SM MIGHT BE OFF  
BY AN HOUR OR TWO, OR MAY NOT HAPPEN AT ALL.  
 
KISP TAF COMMENTS: TIMING OF VSBY DROPPING BELOW 3/4SM MAY BE  
OFF BY A COUPLE OF HOURS OR POTENTIALLY MIGHT NOT HAPPEN AT ALL  
TONIGHT.  
   
OUTLOOK FOR 18Z THURSDAY THROUGH SUNDAY
 
   
THURSDAY AFTN
 
MVFR.   
THURSDAY NIGHT
 
MVFR WITH CHC IFR.   
FRIDAY
 
CHANCE SHOWERS/THUNDERSTORMS/MVFR AM, VFR PM.   
SATURDAY
 
MAINLY VFR.   
SUNDAY
 
MAINLY VFR.  
 

 
   
MARINE
 
 
WITHOUT MUCH OF A PRESSURE GRADIENT OVERALL, LIGHT RESIDUAL  
EASTERLY FLOW GOING INTO TONIGHT WILL RESULT IN THE FOG  
SPREADING FARTHER WEST ACROSS THE WATERS. THE FOG TONIGHT ACROSS  
THE WATERS IS EXPECTED TO BE DENSE. THE MARINE DENSE FOG WILL  
QUICKLY RETURN THIS EVENING FOR EASTERN WATERS AND WILL DEVELOP  
EVENTUALLY FOR MORE WESTERN WATERS LATE THIS EVENING. THE DENSE  
FOG CONTINUES INTO EARLY THURSDAY. THE FOG IS EXPECTED TO  
GRADUALLY DISSIPATE THURSDAY MID TO LATE MORNING BEFORE  
RETURNING AGAIN THURSDAY NIGHT INTO EARLY FRIDAY.  
 
WINDS WILL STAY BELOW SCA THROUGH FRIDAY BUT THE HIGHER OCEAN  
SEAS WILL REMAIN THROUGH THURSDAY NIGHT AND PERHAPS INTO FRIDAY  
AS WELL. NON-OCEAN WATERS STAY BELOW SCA. OCEAN SEAS ARE MORE  
MARGINAL FOR SCA FRIDAY, AT NEAR 5 FT, SO LEFT END TIME OF 6AM  
FRIDAY FOR SCA FOR HAZARDOUS SEAS ON THE OCEAN.  
 
OCEAN SEAS ABOVE 5 FT SHOULD LINGER INTO FRI NIGHT, AND PERHAPS INTO  
PART OF SAT INTO SAT NIGHT, DEPENDING PARTLY ON THE STRENGTH OF SW  
FLOW AHEAD OF A BACK DOOR COLD FRONT THAT LOOKS TO MOVE THROUGH SAT  
NIGHT.  
 
ADVY LEVEL CONDITIONS ARE ALSO POSSIBLE ON THE OCEAN MON AFTERNOON  
AND NIGHT AFTER A WARM FRONTAL PASSAGE AND BEFORE/JUST AFTER A COLD  
FRONTAL PASSAGE, WITH S-SW FLOW GUSTING UP TO 25 KT AND SEAS  
BUILDING TO 5-7 FT PER COMBO OF WAVEWATCH AND WIND/WAVE  
CLIMATOLOGY.  
 

 
   
HYDROLOGY
 
 
NO SIGNIFICANT RAINFALL EXPECTED THROUGH FRIDAY. RAIN AMOUNTS  
THROUGH FRIDAY ARE GENERALLY EXPECTED TO REMAIN BELOW A QUARTER  
OF AN INCH. HOWEVER, THERE MAY BE ISOLATED BRIEF HEAVY  
DOWNPOURS IN ANY THUNDERSTORMS THAT DEVELOP.  
 
COMBO OF A WARM FRONTAL PASSAGE LATE SUNDAY NIGHT INTO MON MORNING,  
AND A COLD FRONTAL PASSAGE LATE DAY MON INTO MON NIGHT, COULD BRING  
PRECIP AMOUNTS OF 1/2 TO 1 INCH, HIGHEST NW OF NYC. LOCALIZED HIGHER  
AMTS POSSIBLE THAT COULD CAUSE TYPICAL NUISANCE PONDING.  
 

 
   
TIDES/COASTAL FLOODING
 
 
DUE TO HIGH ASTRONOMICAL TIDES AND AN EASTERLY SWELL THE NEXT  
COUPLE OF DAYS, WATER LEVELS MAY APPROACH MINOR COASTAL FLOOD  
BENCHMARKS, IN PARTICULAR ACROSS THE SOUTH SHORE BACK BAYS OF  
WESTERN LI. ONLY 1/3 TO 3/4 OF A FOOT OF SURGE IS NEEDED FOR  
MINOR FLOODING. A COASTAL FLOOD STATEMENT HAS BEEN ISSUED FOR  
THIS EVENING'S HIGH TIDE CYCLE FOR THESE LOCATIONS.  
 
IN ADDITION, THE ELEVATED WATER LEVELS COMBINED WITH A PROLONGED  
PERIOD OF 5-9 FT BREAKING SURF TONIGHT INTO THU WILL RESULT IN  
BEACH EROSION ISSUES AND MAY CAUSE SOME LOCALIZED DUNE TOE  
EROSION DURING THE HIGH TIDES.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...DENSE FOG ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT THURSDAY  
FOR CTZ008-012.  
NY...DENSE FOG ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT THURSDAY  
FOR NYZ079-081.  
NJ...NONE.  
MARINE...DENSE FOG ADVISORY FROM 10 PM THIS EVENING TO 10 AM EDT  
THURSDAY FOR ANZ335-338-345-353-355.  
DENSE FOG ADVISORY UNTIL 10 AM EDT THURSDAY FOR ANZ330-340-350.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY  
FOR ANZ350-353-355.  
 

 
 

 
SYNOPSIS...GOODMAN/JM  
NEAR TERM...JM  
SHORT TERM...JM  
LONG TERM...GOODMAN  
AVIATION...JC  
MARINE...GOODMAN/JM  
HYDROLOGY...GOODMAN/JM  
TIDES/COASTAL FLOODING...  
 
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