027  
FXUS61 KOKX 270623  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
223 AM EDT THU APR 27 2017  
   
SYNOPSIS
 
 
WEAK LOW PRESSURE SLOWLY DEPARTS TONIGHT AND DISSIPATES ON  
THURSDAY WITH WEAK HIGH PRESSURE BUILDING IN. 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 THIS MORNING/
 
 
AREAS OF DENSE FOG WERE PRIMARILY CONFINED ACROSS SE CT AND  
EASTERN LI. THERE AREAS REMAIN UNDER A DENSE FOG ADVISORY.  
ELSEWHERE, THE FOG IS MORE PATCHY IN NATURE AND NOT AS A DENSE.  
IT'S POSSIBLE WITH THE NEARLY SATURATED LOW-LEVELS THAT THE  
DENSE FOG COULD EXPAND ELSEWHERE. THERE SEEMS TO BE A LOT OF  
VARIABILITY FROM HOUR TO HOUR.  
 
THE UPPER LEVEL LOW AND SURFACE LOW BOTH TRANSLATE EAST OF THE  
REGION, GETTING INTO THE VICINITY OF COASTAL NEW ENGLAND BY  
MORNING.  
 
OVERNIGHT LOWS WILL BE MILD IN THE 50S.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM 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 /06Z THURSDAY THROUGH MONDAY/
 
 
LOW PRESSURE WEAKENS AS IT DRIFTS TOWARDS THE GULF OF MAINE THIS  
MORNING. A WEAKENING COLD FRONT THEN APPROACHES FROM THE WEST  
INTO TONIGHT.  
 
BECOMING IFR OR LOWER AT ALL TERMINALS EARLY THIS MORNING.  
CONDITIONS IMPROVE TO MVFR AROUND MIDDAY, EXCEPT AT KGON WHERE  
SHOULD IMPROVE TO NO BETTER THAN IFR. VFR POSSIBLE THIS  
AFTERNOON AT KEWR/KTEB/KHPN/KSWF FOR A FEW HOURS. RETURN TO IFR  
OR LOWER THROUGHOUT THIS EVENING.  
 
LIGHT AND VARIABLE WINDS BECOME SSE-SE AT UNDER 10 KT INLAND  
AND AROUND 10KT AT COASTAL TERMINALS FROM MID MORNING INTO EARLY  
AFTERNOON. WINDS BECOME LIGHT AND VARIABLE AGAIN THIS EVENING.  
   
OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY
 
   
LATE TONIGHT/FRIDAY MORNING
 
IFR OR LOWER PROBABLE. ISOLATED-  
SCATTERED SHOWERS POSSIBLE WITH MAYBE A RUMBLE OF THUNDER. LLWS  
POSSIBLE LATE TONIGHT AT SOUTHERN TERMINALS.   
FRIDAY AFTERNOON-SUNDAY
 
MOST LIKELY VFR.   
SUNDAY NIGHT-MONDAY
 
MVFR OR LOWER POSSIBLE.  
 

 
   
MARINE
 
 
NO CHANGES TO CURRENT FORECAST. DENSE FOG ADVSY IS IN EFFECT  
FOR ALL WATERS THROUGH 14Z THU DUE TO A WEAK PRESSURE GRADIENT  
AND ABUNDANT LOW LEVEL MOISTURE. 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.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR CTZ008-012.  
NY...DENSE FOG ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NYZ079-081.  
NJ...NONE.  
MARINE...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR ANZ330-335-  
338-340-345-350-353-355.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY  
FOR ANZ350-353-355.  
 

 
 

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