000 FXUS61 KOKX 200633 AFDOKX Area Forecast Discussion National Weather Service New York NY 233 AM EDT Tue Apr 20 2021 .SYNOPSIS... Shortwave ridging builds overhead through today. A strong cold front approaches from the west tonight. Low pressure develops along the front into Wednesday as it passes across the region. low pressure system Tuesday night into Wednesday. High pressure builds in behind the system, then another low may impact the area over the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A mid level shortwave trough will slide further offshore overnight, with weak ridging and subsidence building in from the west into the overnight. With light winds and some good radiational cooling, some locally patchy fog is not out of the question overnight, especially across Long Island and coastal CT. Have left fog out of the grids, however, as it's not expected to be widespread and confidence is low. Low temps will be in the 40s across the area, with lower 50s across the NYC metro. Based on latest trends went with more of a GLAMP blend with minimums. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... The upper ridge axis settles to the east of the area on Tuesday as high pressure builds in from the west. Deep southwesterly flow results, as a deeper trough takes shape over the Great Lakes. The day should remain mostly cloud free. West/southwest winds and a deep mixed layer will keep the region dry, gusty and warm during the day. Winds will be gusty--15-20mph by the afternoon. NBM deterministic max temperatures were again below the interquartile range for most locations, so adjusted up to near the 50th-75th percentile, which gives highs in the low 70s for the urban areas, and in the mid to upper 60s elsewhere. This approach has worked well this spring for this kind of regime when the deterministic NBM temps are on the low end of the ensemble envelope. By Tuesday night, the upper trough and attendant cold front begin to push east through central PA. Cloud cover will be on the increase as the frontal system approaches, with precipitation chances increasing somewhat toward daybreak. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Two lows to look at in the extended. The first develops along a strong cold front near the Oh Valley on Tue. This low deepens as it passes thru the area on Wed. The GFS/ECMWF/NAM all take the low on basically same track thru the Hudson Valley. This track puts the area in the warm sector with chances for some convection invof the low passage. Ern areas will be much more stable in the llvls than wrn areas, which will have the best chance for tstms. Areas most at risk for tstms are NJ, all of NY outside of LI, and Fairfield county in CT. The main threat for svr is damaging winds with 40-50kt of wind already availhance of rain. S-SW gusts near 15 kt.able in the low to mid lvls. Strong caa Wed ngt. Low temps in the 30s for all areas, with perhaps a few 20s across the nwrn interior. The cold airmass produces highs about 5-10 degrees blw normal for Thu. With h85 winds progged blw 50kt attm, did not go advy strength in the grids attm. However, winds can often overperform this time of year with deep mixing so it is something to watch. Fair wx Fri into Sat, then low pres develops over the sern conus and tracks offshore for the 2nd half of the weekend. This would be a rainstorm. This far out, there is still some uncertainty wrt the track and intensity. Nonetheless, NBM likely pops were used for the fcst due to the current model consensus. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Weak high pressure across the area will give way to a cold front approaching from the Great Lakes today. The front stalls near or just north of the Lower Hudson Valley terminals early this evening. Mainly VFR conditions are expected through the TAF period. There is a low chance for some low clouds and patchy fog for eastern terminals through daybreak, but confidence remains too low to include in TAFs. Light and variable winds become W-SW later this morning, increasing through the late morning and early afternoon to 10-15 kt, with gusts 20-25 kt. Seabreeze enhancement at KJFK will likely produce sustained winds 15 to 20 kt in the afternoon. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Amendments not anticipated through much of overnight, with maybe the exception of some patchy fog for a few of the eastern terminals late. Gusts may occur 1 to 2 hours earlier than indicated in TAFs. .OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY.... .Late Tuesday night...Mainly VFR. MVFR possible late at night. LLWS possible late with SW winds of 40 kt at 2kft. .Wednesday...MVFR or lower possible. LLWS likely at the coastal terminals with SW winds of 40-45 kt at 2kft. Showers with a chance of thunder. S gusts 20-25kt, becoming W to NW going into the evening. .Thursday...VFR. WNW gusts 25-30kt. .Friday...VFR. WNW gusts 20-25kt. .Saturday...Mainly VFR, chance of MVFR in rain at night. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 && .MARINE... Winds and seas will remain below SCA levels through Today with a weak pressure gradient in place. With southwesterly flow increasing by Tuesday afternoon, and a prefrontal trough approaching by late Tuesday night, occasional gusts of 20-25 kt are possible, especially over the ocean waters. An sca will likely be needed on Wed as low pres passes n of the waters. As the low pulls away, increasing wly winds will approach gale force Wed ngt and Thu. Lingering sca conditions possible on Fri, especially on the ocean with elevated seas. All areas briefly blw sca lvls on Sat before a coastal low impacts the area Sat ngt and Sun. && .HYDROLOGY... No hydrologic impacts are expected through the week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JMC/DBR NEAR TERM...JE/DBR SHORT TERM...DBR LONG TERM...JMC AVIATION...DW MARINE...JMC/DBR HYDROLOGY...JMC/DBR