868  
FXUS61 KOKX 191147  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
747 AM EDT THU APR 19 2018  
   
SYNOPSIS
 
 
LOW PRESSURE PASSES TO SOUTH, THEN SOUTHEAST OF LONG ISLAND  
TODAY, THEN QUICKLY EXITS INTO THE CANADIAN MARITIMES TONIGHT  
THROUGH FRIDAY AS IT DEEPENS. HIGH PRESSURE SLOWLY BUILDS IN  
FROM THE GREAT LAKES FRIDAY NIGHT THROUGH SUNDAY NIGHT, THEN  
GRADUALLY SLIDES OFFSHORE FROM MONDAY THROUGH TUESDAY NIGHT. A  
COASTAL LOW APPROACHES FROM THE SOUTHEASTERN SEABOARD ON  
WEDNESDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
MADE MINOR CHANGES THIS UPDATE TO REFLECT THE LATEST TRENDS IN  
OBSERVATIONS AND GUIDANCE. THE FORECAST APPEARS ON TRACK.  
 
A PERSISTENT UPPER LEVEL LOW WILL REMAIN IN THE NORTHEAST, WITH  
THE MAIN UPPER LEVEL JET WILL BE SOUTH OF THE REGION. THE MID  
LEVELS CONVEY A FLATTENED MID LEVEL RIDGE MOVING EAST OF THE  
REGION WITH AN APPROACHING SHORTWAVE TROUGH.  
 
LOW LEVEL WARM AIR ADVECTION HAS BEEN OCCURRING WITH SOME  
ISENTROPIC LIFT AS WELL. THIS WILL BE A SETUP FOR OVERRUNNING  
RAIN THAT WILL BE MAIN WEATHER THEME OF THE DAY. GOING INTO THIS  
MORNING, HIGHER TERRAIN ACROSS THE INTERIOR COULD HAVE THE  
PRECIPITATION AS A RAIN/SNOW MIX OR EVEN SOME SNOW. LITTLE TO NO  
SNOW ACCUMULATION IS EXPECTED, EXCEPT FOR POSSIBLY UP TO AROUND  
1" OVER THE HIGHER ELEVATIONS ACROSS NORTHERN PORTIONS OF THE  
LOWER HUDSON VALLEY AND S CT.  
 
EXPECTING A DAMP COOL DAY AS TEMPERATURES WILL NOT RISE MUCH  
FROM EARLY MORNING VALUES.  
 
CONTINUOUS RAIN EXPECTED ON A LIGHT NORTHERLY FLOW TO START BUT THAT  
FLOW WILL INCREASE TOWARDS MID TO LATE AFTERNOON AS PRESSURE  
GRADIENT BECOMES TIGHTER BETWEEN THE LOW AND STRONG HIGH PRESSURE  
STILL WELL OUT WEST INTO THE CENTRAL PLAINS.  
 
EXPECTING COOLER THAN NORMAL TEMPERATURE WITH THE NORTHERLY FLOW AND  
RAIN THROUGH THE DAY. USED THE COOLER MET GUIDANCE FOR HIGHS.  
INCREASED ONE DEGREE ALONG THE COAST FOR HIGHS.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/
 
 
THE MAIN UPPER LEVEL JET WILL REMAIN SOUTH OF THE REGION THROUGH  
FRIDAY.  
 
FOR THURSDAY NIGHT:  
 
TWO MORE SHORTWAVES PIVOT ACROSS THE REGION IN THE MID LEVELS. SO  
DESPITE THE SURFACE LOW MOVING FARTHER AWAY TO THE SOUTH OF NOVA  
SCOTIA, THE REGION WILL REMAIN IN CYCLONIC FLOW ALOFT. THE CHANCES  
FOR PRECIPITATION WHILE LOWER THAN EARLIER IN THE DAY, WILL BE  
STILL BE PRESENT MAINLY DURING THE EVENING. COLD AIR ADVECTION  
ON THE BACKSIDE COULD RESULT IN A LIGHT RAIN/SNOW MIX ACROSS  
SOME PARTS OF THE INTERIOR, ESPECIALLY HIGHER TERRAIN. NO  
SNOW ACCUMULATION IS EXPECTED. OTHERWISE, THE PRECIPITATION  
WILL END AS RAIN.  
 
FOR OVERNIGHT, MORE DRYING TAKES OVER WITH THE PERSISTENT NW  
FLOW.  
 
WITH THE ABUNDANT CLOUDS, USED A BLEND OF GUIDANCE IN TERMS OF  
TEMPERATURES INCLUDING THE PREVIOUS FORECAST. THERE WILL BE  
SOME COLD AIR ADVECTION BUT WITHOUT IDEAL RADIATIONAL COOLING.  
WINDS STAY UP SO DESPITE TEMPERATURES IN THE MID 30S FOR THOSE  
PARTS OF THE REGION IN THE GROWING SEASON, NOT EXPECTING FROST  
FORMATION.  
 
FOR FRIDAY:  
 
IN THE MID LEVELS, THE MID LOW WILL BE MOVING EAST OF THE REGION,  
ALLOWING FOR HEIGHTS TO BUILD AS RIDGING COMMENCES FROM WELL TO THE  
WEST.  
 
THE SAME PRESSURE GRADIENT REMAINS FOR FRIDAY SO THAT WILL MEAN MORE  
GUSTY NW FLOW. AT THE SURFACE, THE LOW WILL BE MOVING NEAR  
NEWFOUNDLAND WHILE THE HIGH WILL BE MOVING INTO THE GREAT LAKES AND  
INTO THE WEST OF THE APPALACHIANS.  
 
NW FLOW CONTINUES SO DRY CONDITIONS WILL REMAIN. STILL EXPECTING  
ABUNDANT CLOUDS THOUGH, SO WILL SIDE WITH A BLEND FOR HIGH  
TEMPERATURES INCLUDING THE PREVIOUS FORECAST.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
 
 
NW FLOW ALOFT FRIDAY NIGHT. WITH NO SHORTWAVE EMBEDDED IN THE FLOW  
PROGGED TO IMPACT THE REGION, HAVE CONTINUED WITH THE DRY FORECAST.  
LOWS FRIDAY NIGHT SHOULD BE AROUND 5-10 DEGREES BELOW NORMAL.  
 
A COUPLE OF NORTHERN STREAM 700-500 HPA SHORTWAVES PUSH THROUGH THE  
AREA SATURDAY AND SATURDAY NIGHT AS THE ROTATE AROUND THE BASE OF A  
CLOSED LOW OVER THE CANADIAN MARITIMES. WITH RELATIVE DRY LOW LEVELS  
AND DOWNSLOPING BOUNDARY LAYER FLOW, THE SHORTWAVES SHOULD PASS  
THROUGH DRY. HIGHS ON SATURDAY AND LOW SATURDAY NIGHT SHOULD BE  
AROUND 5-10 DEGREES BELOW NORMAL.  
 
DEEP LAYERED RIDGING THEN BEGINS TO BUILDS IN SUNDAY AND CONTINUES  
TO RIDGE OVER THE AREA THROUGH TUESDAY. SUBSIDENCE ASSOCIATED WITH  
THE RIDGE SHOULD KEEP THINGS DRY AND RELATIVELY (IF NOT TOTALLY)  
CLOUD FREE DURING THIS TIME FRAME. HIGHS SUNDAY-TUESDAY RUN A FEW  
DEGREES BELOW NORMAL AND LOWS DURING THIS TIME FRAME RUN 5-10  
DEGREES BELOW NORMAL.  
 
NOTING THAT 1) THE GFS HAS A KNOWN PROGRESSIVE BIAS IN THE LONG TERM  
AND 2) THAT THE UPPER LEVEL PATTERN FEATURES CLOSED LOWS AND FAIRLY  
SHARP RIDGES - BOTH OF WHICH SUPPORT A LESS PROGRESSIVE PATTERN -  
FAVOR THE SLOWER LIFTING OF THE RIDGE AXIS TO THE NE AND ARRIVAL OF  
THE NEXT SYSTEM IN THE ECMWF/CMC GLOBAL THAN THE MORE PROGRESSIVE GFS  
HANDLING OF BOTH FEATURES. THE FORECAST TUESDAY NIGHT-WEDNESDAY IS  
BASED ON A BLEND OF THE ECMWF/CMC GLOBAL AS A RESULT.  
 
TUESDAY NIGHT SHOULD BE DRY AS THE DEEP LAYERED RIDGE AXIS LIFTS TO  
THE NORTHEAST. MOST OF WEDNESDAY SHOULD PROBABLY BE DRY AS WELL, BUT  
TO KEEP THINGS SIMPLE, GIVEN THE INHERENT UNCERTAINTY THIS FAR OUT,  
HAVE RUN CHANCE POPS THE ENTIRE PERIOD FOR SOME WARM ADVECTION  
INDUCED RAINS. LOWS TUESDAY NIGHT SHOULD BE NEAR TO SLIGHTLY ABOVE  
NORMAL AND HIGHS ON WEDNESDAY A FEW DEGREES BELOW NORMAL.  
 

 
   
AVIATION /12Z THURSDAY THROUGH MONDAY/
 
 
LOW PRESSURE PASSES TO THE SOUTH TODAY.  
 
VFR BCMG MOSTLY MVFR BY LATE MORNING. -SHRA RETURNS AROUND NOON.  
VFR THEN RETURNS LATE AFTN WITH -SHRA ENDING. NE-N WINDS AROUND  
10 KT BCMG NW AND INCREASING TO 10-20KT WITH GUSTS 20-30KT THIS  
AFTN. GUSTS CONTINUE INTO 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 FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS. WINDS PREVAIL NORTH OF 310 MAGNETIC THIS  
AFTERNOON INTO EARLY EVENING.  
 
THE AFTERNOON KJFK HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES  
SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD.  
 
KLGA TAF COMMENTS: TIMING OF FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS. WINDS PREVAIL NORTH OF 310 MAGNETIC THIS  
AFTERNOON INTO EARLY EVENING.  
 
THE AFTERNOON KLGA HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES  
SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD.  
 
KEWR TAF COMMENTS: TIMING OF FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS. WINDS PREVAIL NORTH OF 310 MAGNETIC THIS  
AFTERNOON BUT COULD BE SOUTH OF IT AT TIMES EARLY EVENING.  
 
THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES  
SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD.  
 
KTEB TAF COMMENTS: TIMING OF FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS.  
 
KHPN TAF COMMENTS: TIMING OF FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS. CHC IFR CIGS DO NOT OCCUR.  
 
KISP TAF COMMENTS: TIMING OF FLIGHT CATEGORY CHANGES MAY BE OFF  
BY 2-3 HOURS.  
   
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY
 
   
FRIDAY
 
VFR. NW WINDS G20-30KT.   
SATURDAY-MONDAY
 
VFR.  
 

 
   
MARINE
 
 
MADE MINOR CHANGES THIS UPDATE TO REFLECT THE LATEST TRENDS IN  
OBSERVATIONS AND GUIDANCE. THE FORECAST APPEARS ON TRACK.  
 
SUB-SCA CONDITIONS WILL BE IN PLACE TODAY, BUT WINDS AND SEAS  
WILL BEGIN INCREASING. SCA THRESHOLDS ARE FORECAST TO BE MET  
ACROSS THE WATERS TONIGHT THROUGH FRIDAY MORNING WITH THE OCEAN  
EAST OF MORICHES INLET LIKELY GETTING SCA CONDITIONS TONIGHT THROUGH  
ALL OF THE DAY FRIDAY.  
 
A RELATIVELY STRONG PRESSURE GRADIENT OVER THE REGION FRIDAY NIGHT,  
SHOULD ALLOW FOR GUSTS TO AROUND 25 KT TO PERSIST OVER THE COASTAL  
OCEAN ZONES AND GUSTS TO AROUND 20 KT ON THE NON-OCEAN ZONES.  
 
THE PRESSURE GRADIENT BEGINS TO SLACKEN ON SATURDAY, WITH ALL WATERS  
FALLING TO BELOW SMALL CRAFT ADVISORY THRESHOLDS BY SATURDAY  
MORNING. WINDS SATURDAY-MONDAY NIGHT WILL BE LIMITED TO 10 KT OR  
LESS ON THE NON-OCEAN WATERS. THE COASTAL OCEAN ZONES WILL BE  
SIMILARLY LIMITED SATURDAY-MONDAY NIGHT, EXCEPT FOR WINDS UP TO 15 KT  
ARE PROBABLE SATURDAY MORNING.  
 

 
   
HYDROLOGY
 
 
LESS THAN A HALF INCH OF RAIN EXPECTED THROUGH THIS EVENING WITH  
DRY CONDITIONS FOR LATE TONIGHT THROUGH FRIDAY. NO HYDROLOGIC  
IMPACTS EXPECTED.  
 
IT SHOULD BE DRY FRIDAY NIGHT-TUESDAY NIGHT, WITH LIGHT RAIN  
EXPECTED WEDNESDAY. NO SIGNIFICANT HYDROLOGIC IMPACTS ARE EXPECTED  
FRIDAY NIGHT-WEDNESDAY AS A RESULT.  
 

 
   
EQUIPMENT
 
 
NYC NOAA WEATHER RADIO STATION KWO-35 (162.55 MHZ) REMAINS OFF  
THE AIR.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
NY...NONE.  
NJ...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO NOON EDT FRIDAY  
FOR ANZ330-335-338-340-345-353-355.  
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EDT FRIDAY  
FOR ANZ350.  
 

 
 

 
 
SYNOPSIS...MALOIT/JM  
NEAR TERM...MALOIT/JM  
SHORT TERM...JM  
LONG TERM...MALOIT  
AVIATION...JC  
MARINE...MALOIT/JM  
HYDROLOGY...MALOIT/JM  
EQUIPMENT...  
 
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