912  
FXUS61 KOKX 281153  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
753 AM EDT THU SEP 28 2023  
   
SYNOPSIS  
 
HIGH PRESSURE TO THE NORTH TODAY WILL GIVE WAY TO AN INVERTED  
SURFACE TROUGH AND WEAK LOW MOVING NORTHWARD ALONG THE COAST  
TONIGHT INTO FRIDAY. THE LOW WILL MOVE SLOWLY STRENGTHEN AND  
MOVE EAST FRIDAY NIGHT INTO SATURDAY, WITH HIGH PRESSURE  
BUILDING IN ITS WAKE AND REMAINING DOMINANT INTO NEXT WEEK.  
 
 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/  
 
UPPER RIDGING OVER NEW ENGLAND SLOWLY SLIDES EAST TODAY AS A  
CLOSED UPPER LOW OVER THE GREAT LAKES SLOWLY SLIDES EAST TOWARDS  
THE AREA. AT THE SURFACE, AN INVERTED TROUGH OFF THE MID  
ATLANTIC COAST GRADUALLY EXTENDS NORTH THIS AFT/EVE AS CANADIAN  
HIGH PRESSURE SLIDES OFF NEW ENGLAND.  
 
RIVER VALLEY FOG EARLY THIS MORNING WILL GIVE WAY TO STRATUS  
DEVELOPMENT ACROSS SOUTHERN AND WESTERN PORTIONS OF THE AREA  
DUE TO AN INCREASINGLY MOIST ONSHORE FLOW UNDER AN 850MB  
SUBSIDENCE INVERSION. THE STRATUS DECK WILL GRADUALLY WORKING  
N/NE THRU THE AFT. ADDITIONALLY, THE APPROACHING CLOSED LOW,  
STRENGTHENING LLJ AND THETA-E ADVECTION WILL BRING INCREASING  
CHANCES FOR LIGHT SHOWERS ACROSS NE NJ/NYC AND LI THIS  
AFTERNOON, GRADUALLY WORKING N THROUGH THIS EVENING. TIMING AND  
N/NE EXTENT OF SHOWERS IS A BIT UNCERTAIN WITH SUBSIDENCE AND  
DRY AIR TO CONTEND WITH.  
 
ONSHORE FLOW AND CLOUD COVER WILL KEEP TEMPS SEVERAL DEGREES BELOW  
SEASONABLE TODAY (MID 60S), WARMEST ACROSS SE CT WITH MORE IN  
THE WAY OF SUNSHINE.  
 
 
   
SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/  
 
MODELS IN GOOD AGREEMENT WITH CLOSED UPPER LOW CONTINUING TO  
APPROACH TONIGHT INTO FRIDAY, GRADUALLY SLIDING ACROSS THE AREA  
FRIDAY NIGHT INTO SATURDAY. AT THE SURFACE, SPRAWLING HIGH  
PRESSURE REMAINS OVER NEW ENGLAND, ALTHOUGH WITH ITS CENTER  
MOVING OFFSHORE. THIS WILL ALLOW AN INVERTED TROUGH/SURFACE LOW  
SITTING OFF THE MID ATLANTIC COAST TO SLIDE TOWARDS THE REGION  
FRIDAY AND THEN GRADUALLY SLIDING SOUTHEAST OF THE AREA FRIDAY  
NIGHT/SATURDAY.  
 
GOOD GENERAL AGREEMENT WITH INCREASING DEEP LAYERED LIFT FROM  
APPROACHING UPPER LOW AND RIGHT FRONT QUAD OF ULJ, COMBINED  
WITH A STRENGTHENING SE/E LLJ TONIGHT/FRI, TRANSPORTING A SUB-  
TROPICAL AIRMASS (+1-1.5 STD PWATS) INTO THE REGION, CONVERGING  
IN THE VICINITY OF AN INVERTED TROUGH/COASTAL FRONT (WITH  
POSSIBLE DEFORMATION ZONE AND OROGRAPHIC ENHANCEMENT) FOR A  
6-12 HR PERIOD ACROSS PORTIONS OF THE AREA LATE TONIGHT THRU  
FRIDAY. ALSO CAN RULE OUT A BIT OF ELEVATED INSTABILITY ACROSS  
SOUTHERN AND WESTERN PORTIONS OF THE TRI-STATE WITH APPROACH OF  
UPPER LOW ON FRIDAY, INCREASING DEEP CONVECTION. THE SIGNAL FOR  
AN AXIS OF HEAVY RAIN IN THE VICINITY OF THE AREA IS STRONG,  
BUT MODEL SPREAD BETWEEN ENSEMBLE, DETERMINISTIC AND HIGH RES  
MODEL SOLUTIONS EXISTS IN THE EXACT LOCATION AND DURATION OF  
THIS MESOSCALE CONVERGENCE ZONE WHERE HEAVIEST RAIN WILL FALL.  
 
AS FAR AS ENSEMBLES, PROB OF 2" RAIN IN 24 HRS (MAINLY FRIDAY)  
RANGES FROM HIGH (60-70% GEPS PROB FOR NYC AND PTS EAST), HIGH  
(70-80% ECE PROB FOR EASTERN PORTIONS OF THE REGION), TO LOW  
(10-20% GEFS PROB FOR EASTERN PORTIONS OF THE REGION). NBM HAS  
A 30-40% PROB OF 2"/24 HRS, 15% PROB OF 3"/24 HR FOR FRIDAY ACROSS  
NYC/NJ METRO, LOWER HUD, SW CT AND LI. NOTE: THIS IS A  
CONSIDERABLE UPWARD TREND IN 2" PROBS FROM SINGLE DIGIT PROBS  
OVER THE LAST 24 HRS.  
 
AS FAR AS HIGH RES SOLUTION GUIDANCE, 00Z HREF, WHICH IS JUST NOW  
COVERING THE FRIDAY DAY PERIOD HAS A BROAD 10% ENSEMBLE PROB OF  
3"/3HR ACROSS NYC, NJ, AND LOWER HUD, WITH A BULLSEYE OF 30%  
ENSEMBLE PROB OF 3"/3HR ACROSS NE NJ. THIS 30% 3"/3HR TENDS TO  
BE AN ELEVATED SIGNAL FOR FLASH FLOODING POTENTIAL (W/ TYPICAL  
LOCATION UNCERTAINTY), IF THIS HEAVY RAIN AXIS ENDS UP OVER THE  
URBAN AND FLASHY RIVER BASINS IN THIS AREA. HEADWATER GUIDANCE  
FOR SEVERAL OF THE FLASHY STREAMS IN NE NJ IS AROUND 2- 2 1/2"  
IN 6HR FOR MINOR, AND 2 1/2 TO 3 1/2 IN 6 HR FOR MODERATE  
FLOODING, WHICH IS A BIT CONCERNING IF THIS ALL COMES TOGETHER  
ACROSS THIS REGION (HREF 6 HR PMM IS SIGNALING POTENTIAL FOR  
3-5" IN 6HR FRI MORNING IN AFTERNOON WEST OF THE HUDSON R.).  
 
SO NEEDLESS TO SAY, A GOOD SIGNAL FOR A HEAVY RAIN AXIS  
PRESENTING A URBAN AND POOR DRAINAGE AND FLASHY RIVER BASIN  
FLOOD THREAT, WITH A CONDITIONAL LOCALIZED TO SCATTERED FLASH  
FLOOD POTENTIAL, BUT LOW CONFIDENCE ON LOCATION. WITH THIS  
LOCATION/DURATION UNCERTAINTY, LACK OF MODEL TO MODEL AND RUN TO  
RUN CONSISTENCY, AND THIS BEING THE FIRST CYCLE OF HREF  
RESOLVING THIS TIME PERIOD, WILL HOLD OFF ON FLOOD WATCH AT THIS  
TIME. BUT IF THE HEAVIER QPF SOLUTIONS REMAIN CONSISTENT, A  
FLOOD WATCH WILL LIKELY BE NEEDED FOR PORTIONS OF THE AREA,  
PARTICULARLY IF THE HEAVY RAIN AXIS IS EXPECTED OVER NYC, NE NJ,  
LOWER HUD, AND SW CT.  
 
AS THE CLOSED LOW MOVES OVERHEAD AND LOW PRESSURE BECOMES MORE  
DEVELOPED FRI NIGHT INTO SATURDAY AND GRADUALLY SLIDES EAST,  
THE INVERTED TROUGH/CONVERGENCE AXIS SHOULD BREAK DOWN AND SLIDE  
EAST WITH A MORE GENERAL DEFORMATION RAIN ON THE NW SIDE OF THE  
LOW CONTINUING FRIDAY NIGHT INTO SATURDAY MORNING, GRADUALLY  
TAPERING FROM W TO E.  
 
IN ADDITION TO THE RAIN, NE WINDS OF 15-20G25-30MPH LIKELY ALONG THE  
COAST FRI AM THROUGH SAT AM. A FEW PEAK GUSTS TO 35 MPH POSSIBLE.  
LIGHTER WINDS FOR THE INTERIOR.  
 
HIGH TEMPS WILL RUN SEVERAL DEGREES BELOW SEASONABLE IN RAIN  
AND ONSHORE FLOW, AND NEAR SEASONABLE FOR OVERNIGHT LOWS.  
 
 
   
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/  
 
A HIGH AMPLITUDE UPPER LEVEL RIDGE OVER THE MISSISSIPPI VALLEY WILL  
TRANSLATE EAST DURING THE PERIOD. THIS WILL RESULT IN A DRY,  
UNSEASONABLY WARM PERIOD. A WEAKENING BACKDOOR COLD FRONT SLIPS  
THROUGH SUNDAY NIGHT INTO MONDAY MORNING WITH LITTLE IF ANY CHANGE  
IN AIRMASS. SURFACE HIGH PRESSURE BUILDS IN FROM THE WEST THROUGH  
TUESDAY AND THEN OFFSHORE BY MID WEEK.  
 
HIGH TEMPERATURES DURING THE TIME WILL GENERALLY BE IN THE 70S, EVEN  
APPROACHING 80 ACROSS THE NYC METRO AND INLAND AREAS. THE WARMEST  
DAYS AT THIS TIME LOOK TO BE TUE AND WED WITH 85H TEMPS AROUND 15C,  
POSSIBLY A BIT HIGHER. LOWS WILL GENERALLY BE 55 TO 60. ON AVERAGE,  
DEPARTURES LOOK TO BE ABOUT 5 DEGREES ABOVE NORMAL.  
 
 
   
AVIATION /11Z THURSDAY THROUGH MONDAY/  
 
HIGH PRESSURE REMAINS ACROSS EASTERN CANADA AND THE NORTHEAST  
THROUGH THE END OF THE WEEK. HOWEVER, AN OFFSHORE INVERTED TROUGH  
WORKS TOWARD THE AREA TODAY AND ACROSS THE AREA TONIGHT INTO FRIDAY.  
 
MVFR CEILINGS WILL DEVELOP ACROSS THE NYC TERMINALS THIS MORNING,  
POSSIBLY SOME OF THE OUTLYING TERMINALS AS WELL. VFR CONDITIONS MAY  
PREVAIL THROUGH MUCH OF THE DAY ELSEWHERE. EVEN THOSE LOCATIONS THAT  
GO MVFR COULD SEE OCCASIONAL VFR CEILINGS. CEILINGS WILL THEN LOWER  
TONIGHT AS STEADY RAIN MOVES IN OFF THE ATLANTIC. THE LOWEST  
CONDITIONS WILL BE ACROSS THE NYC AND LOWER HUDSON VALLEY  
TERMINALS WHERE IFR CEILINGS ARE FORECAST TO DEVELOP AFTER 06Z  
WITH THE LIKELIHOOD OF HEAVY SHOWERS. FOR THE EASTERN TERMINALS,  
LOWER CEILINGS LOOK TO BE LATER AS THE HEAVIEST RAIN AT THIS  
TIME LOOKS TO BE WEST.  
 
THE BEST CHANCE FOR RAIN WILL BE TONIGHT, BUT A FEW SHOWERS ARE  
POSSIBLE IN THE AFTERNOON, MAINLY AT THE COASTAL TERMINALS.  
CONFIDENCE IS TOO LOW AT THIS TIME TO MENTION IN THE TAFS.  
EMBEDDED THUNDERSTORMS ARE POSSIBLE FRIDAY.  
 
NE WINDS 10KT OR LESS EARLY WILL VEER A BIT, INCREASING TO  
10-15 KT. GUSTS DEVELOP TO AROUND 20 KT AT THE COASTAL TERMINALS  
LATE TONIGHT.  
 
...NY METRO (KEWR/KLGA/KJFK/KTEB) TAF UNCERTAINTY...  
 
THE AFTERNOON HAZE POTENTIAL FORECAST IS YELLOW...WHICH IMPLIES  
SLANT RANGE VISIBILITY 4-6SM OUTSIDE OF CLOUD.  
 
TIMING OF MVFR ONSET MAY BE OFF BY A COUPLE OF HOURS. A SPOTTY  
SHOWER CANNOT BE RULED OUT THIS AFTERNOON.  
 
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...  
 
FRIDAY: IFR AND RAIN. ENE WINDS G15-25 KT, HIGHEST AT THE COASTAL  
TERMINALS.  
 
SATURDAY: MVFR/IFR AND RAIN IN THE MORNING, IMPROVING TO VFR BY  
LATE. NE WINDS G15-20KT MAINLY AT THE COASTAL TERMINALS.  
 
SUNDAY AND MONDAY: VFR.  
 
DETAILED INFORMATION, INCLUDING HOURLY TAF WIND COMPONENT FORECASTS,  
CAN BE FOUND AT: HTTPS:/WWW.WEATHER.GOV/ZNY/N90  
 
 
   
MARINE  
 
AN EXTENDED PERIOD OF SCA CONDS IS LIKELY FOR THE OCEAN INTO EARLY  
NEXT WEEK. SCA GUSTS ARE LIKELY LATE TONIGHT INTO SAT AM, WITH SEAS  
ELEVATING TO 6 TO 8 FT ON E/SE WIND SWELLS, AS WELL AS BACKGROUND SE  
SWELLS FROM A DEVELOPING OFFSHORE LOW AND DISTANT TROPICAL SYSTEMS  
IMPACT THE COASTAL WATERS. MARGINAL SCA GUSTS POSSIBLE ON THE  
NEARSHORE WATERS LATE TONIGHT INTO SAT AM, BUT OTHERWISE  
EXPECTED TO BE BELOW SCA.  
 
WINDS AND SEAS WILL GRADUALLY SUBSIDE SATURDAY AFT THROUGH  
MONDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST WITH DIMINISHING  
WINDS AND DECREASING SEAS. SCA SEAS LIKELY REMAIN ON THE OCEAN  
WATERS DURING THIS TIME, SUBSIDING TO AROUND 5 FT BY MONDAY.  
 
 
   
HYDROLOGY  
 
POTENTIAL IS INCREASING FOR A WIDESPREAD 2-3" OF RAIN ACROSS  
THE REGION TONIGHT INTO SATURDAY MORNING. HIGH-RES GUIDANCE  
INDICATING POTENTIAL FOR A LOCALIZED SWATH OF 3-5"+ IN 6 HR FRI  
AM/PM (10-30% PROB OF 3"/3HR, WITH SPOTTY 10-20% PROB OF  
1"/HR), BUT LOW CONFIDENCE ON DEVELOPMENT OR LOCATION OF THIS  
TYPE OF RAINFALL AXIS AT THIS TIME. BASED ON THIS CONDITIONAL  
THREAT, A SLIGHT RISK OF FLASH FLOODING HAS BEEN COORDINATED  
WITH WPC FOR THE REGION.  
 
WITH RECENT RAINS, HEADWATER GUIDANCE FOR SEVERAL OF THE FLASHY  
STREAMS IN NE NJ IS AROUND 2-2 1/2" IN 6HR FOR MINOR FLOODING,  
AND 2 1/2 TO 3 1/2" IN 6 HR FOR MODERATE FLOODING, WHICH IS A  
BIT CONCERNING IF THIS ALL COMES TOGETHER ACROSS THIS REGION.  
 
ANOTHER CONSIDERATION IS THAT THE PERIOD OF HEAVIEST RAIN FRI AM  
INTO PM WILL COINCIDE WITH TWO HIGH TIDAL CYCLES WHERE MINOR  
FLOOD THRESHOLDS ARE EXPECTED TO BE REACHED. THIS WILL LIMIT  
STORM DRAINAGE CAPACITY FOR COASTAL LOCATIONS DURING THESE  
TIMES AND EXACERBATE FLASH FLOOD THREAT IN THESE AREAS DURING  
THESE TIMES.  
 
SO, A GOOD SIGNAL FOR A MINOR URBAN AND POOR DRAINAGE AND  
FLASHY RIVER BASIN FLOOD THREAT, WITH A CONDITIONAL LOCALIZED TO  
SCATTERED FLASH FLOOD POTENTIAL IF/WHERE HEAVY RAINFALL AXIS  
MATERIALIZES, BUT LOW CONFIDENCE ON LOCATION. WITH THIS  
LOCATION/DURATION UNCERTAINTY, LACK OF MODEL TO MODEL AND RUN TO  
RUN CONSISTENCY, AND THIS BEING THE FIRST CYCLE OF HREF  
RESOLVING THIS TIME PERIOD, WILL HOLD OFF ON FLOOD WATCH AT THIS  
TIME. BUT IF THE HEAVIER QPF SOLUTIONS REMAIN CONSISTENT, A  
FLOOD WATCH WILL LIKELY BE NEEDED FOR PORTIONS OF THE AREA,  
PARTICULARLY IF THE HEAVY RAIN AXIS IS EXPECTED OVER NYC, NE NJ,  
LOWER HUD, AND SW CT.  
 
 
   
TIDES/COASTAL FLOODING  
 
LOCALIZED MINOR COASTAL FLOODING POSSIBLE MAINLY IN THE MOST  
VULNERABLE SOUTH SHORE BAYS OF NASSAU LOCATIONS THIS MORNING.  
 
THEREAFTER, AN APPROACHING FULL MOON WILL HAVE RISING  
ASTRONOMICAL TIDES (AS LOW AS 1/4-1/2 FT NEEDED TO REACH MINOR  
THRESHOLDS), COMBINED WITH A PERSISTENT AND SLIGHTLY  
STRENGTHENING E-NE FLOW AND E WIND WAVE/SWELL TODAY INTO SAT AM  
WILL HAVE WATER LEVELS SOLIDLY AT MINOR FLOOD LEVELS (UP TO 1  
1/2 FT INUNDATION) FOR VULNERABLE NY/NJ HARBOR, JAMAICA BAY,  
WESTERN GREAT SOUTH BAY, AND COASTAL WESTCHESTER/FAIRFIELD  
COMMUNITIES, WITH LOCALIZED MINOR ELSEWHERE ACROSS LI AND NYC  
FOR TONIGHT, FRI AM, FRI PM AND LIKELY THE SAT AM HIGH TIDAL  
CYCLES.  
 
A BIT MORE UNCERTAINTY ON HOW WIDESPREAD THE MINOR COASTAL  
FLOODING WILL BE WITH THE SAT PM INTO SUN HIGH TIDAL CYCLES AS  
ASTRONOMICAL TIDES WILL PEAK, BUT WINDS WILL TURN MORE TO THE  
N/NE AND GRADUALLY SUBSIDE. HIGHEST CONFIDENCE IN ADDITIONAL  
CYCLES OF WIDESPREAD MINOR FLOODING ARE FOR THE SOUTHERN BAYS  
OF NASSAU AND QUEENS DUE TO RESTRICTED TIDAL DRAINAGE, WITH  
PERHAPS MORE LOCALIZED MINOR FLOODING ELSEWHERE.  
 
IN ADDITION, CONTINUED BEACH EROSION/ESCARPMENT WILL CONTINUE  
THROUGH AT LEAST SATURDAY DUE TO ELEVATED WATER LEVELS, 4 TO 7  
FT BREAKING SURF, AND A STRONG E TO W LONG SHORE CURRENT. DUNE  
EROSION POTENTIAL LOOKS TO BE LOCALIZED, WITH OVERWASHES NOT  
EXPECTED.  
 
ALTHOUGH OUR SURF ZONE FORECAST SEASON IN OVER, THE RISK FOR  
DANGEROUS RIP CURRENT WILL CONTINUE INTO AT LEAST EARLY NEXT  
WEEK BASED ON THE WAVE CONDITIONS.  
 
NOTE: THE PECONIC RIVER AT RIVERHEAD TIDAL GAUGE IS OUT OF  
SERVICE (HAD BEEN READING TOO HIGH). THE GAUGE IS BEING LOOKED  
INTO BY OUR PARTNERS AT THE USGS.  
 
 
   
OKX WATCHES/WARNINGS/ADVISORIES  
 
CT...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 1 AM EDT  
FRIDAY FOR CTZ009.  
COASTAL FLOOD ADVISORY FROM 10 AM TO 1 PM EDT FRIDAY FOR  
CTZ009.  
COASTAL FLOOD ADVISORY FROM 10 PM FRIDAY TO 2 AM EDT SATURDAY  
FOR CTZ009.  
NY...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 1 AM EDT  
FRIDAY FOR NYZ071.  
COASTAL FLOOD ADVISORY FROM 10 AM TO 1 PM EDT FRIDAY FOR  
NYZ071.  
COASTAL FLOOD ADVISORY FROM 10 PM FRIDAY TO 2 AM EDT SATURDAY  
FOR NYZ071.  
COASTAL FLOOD ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT EDT  
TONIGHT FOR NYZ178-179.  
COASTAL FLOOD ADVISORY FROM 7 AM TO 1 PM EDT FRIDAY FOR NYZ178-  
179.  
COASTAL FLOOD ADVISORY FROM 7 PM FRIDAY TO 2 AM EDT SATURDAY  
FOR NYZ178-179.  
NJ...COASTAL FLOOD ADVISORY FROM 6 PM TO 10 PM EDT THIS EVENING FOR  
NJZ006-106-108.  
COASTAL FLOOD ADVISORY FROM 7 AM TO 11 AM EDT FRIDAY FOR  
NJZ006-106-108.  
COASTAL FLOOD ADVISORY FROM 7 PM FRIDAY TO MIDNIGHT EDT FRIDAY  
NIGHT FOR NJZ006-106-108.  
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT SATURDAY FOR ANZ350-353-  
355.  
 
 
 
 
 
SYNOPSIS...NV/DW  
NEAR TERM...NV  
SHORT TERM...NV  
LONG TERM...DW  
AVIATION...DW  
MARINE...NV/DW  
HYDROLOGY...NV/DW  
TIDES/COASTAL FLOODING...NV  
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