Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211159 AFDOKX Area Forecast Discussion National Weather Service New York NY 759 AM EDT Wed Jun 21 2017 .SYNOPSIS...
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A series of frontal systems will impact the area through early next week. The first will approach this afternoon and move through this evening, followed by another from Friday afternoon into Saturday, and then another late Sunday into Sunday night. Low pressure will pass off to the southeast Monday into Monday night, possibly followed by yet another weak frontal passage on Tuesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A frontal boundary remains stalled through the area, marked by dewpoints in the 60s to the east and 50s to the west. This boundary should push through this morning and dissipate as another cold front approaches from the west. For near term update, increased PoP through the evening for some areas based on latest high resolution guidance including the HRRR/RAP/SUNY Stony Brook WRF. Convective activity should take place mainly after 18Z, with scattered tstms as a mid level shortwave trough approaches aloft with the front. Strong deep shear and steepening low level lapse rates could produce a few isold strong to even severe tstms. Concur with SPC marginal risk given steep low level lapse rates, inverted-V look to fcst soundings, and deep layer shear. WINDEX (dry microburst wind index) values reach 50-55 kt late this afternoon, and even MDPI (wet microburst day potential index) values increase to 0.75 across Long Island per RAP toward 00Z, supporting the wind threat with stronger storms. Will mention in HWO. Temps will be seasonable in the 80s. There is a high risk for rip current development at the Suffolk County ocean beaches, and a moderate risk for the NYC and Nassau county ocean beaches through this evening.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
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Convection should still be ongoing across NYC metro and Long Island through about sunset, then convective threat should wane with the loss of heating and with the front pushing through. Not much in the way of an air mass change tonight and Thursday despite the fropa. H8 temps remain right around 12-14C next 24 hours, with a WAA pattern developing thereafter. Dry weather will prevail with rising heights.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... An active northern branch of the polar jet will remain across the northern tier of the country, with the mean upper trough residing over the Northern Plains through Friday, then extending into the Northeast this weekend and early next week. This will allow for several frontal systems to impact the area during the time, the first Friday into Saturday, and then another late Sunday into Sunday night. After a warm frontal passage Friday morning, temps should warm up well into the 80s and lower 90s, with dewpoints increasing to the upper 60s. A few tstms are possible in the warm sector, but timing/areal coverage are in question, as models generally indicate better instability from late morning into early afternoon, and disagree on timing of the approach of a southern branch mid level shortwave trough well in advance of the remnants of Tropical Storm Cindy to produce lift. Any storms that do develop would have potential to be strong to locally severe, with MLCAPE over 1000 J/kg and mid level flow up to 35 kt, along with some veering with height. This first front looks to stall over the area, with another chance for showers/tstms on Saturday. Areal coverage will depend on the northward extent of any residual energy from the remnants of Cindy to provide lift. If this forcing remains suppressed per ECMWF, areal coverage would be isolated at most, but could end up more widespread per farther north/slower GFS. Instability looks more limited with the second frontal passage on Sunday, and moisture will be more lacking, so have only mentioned isolated showers. ECMWF amplifies the mean upper trough more than the GFS over the weekend, enough to induce somewhat stronger low development along the frontal boundary to the south that would track closer to the area. As a result have mentioned chance for showers from Mon into Mon night. Temps should be several degrees above average through the weekend, then return to near average early next week. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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A weak front moves through the region this afternoon. VFR. Scattered shra/tsra activity expected late this afternoon/early evening. Wind gusts of 35 to 40 kt possible with any activity. WSW-SW flow increases through the morning...with gusts to 25 kt by this afternoon. Isolated gusts to 30 kt. Afternoon S/SSW seabreeze development expected for south coastal terminals...with sustained 20 kt possible for KJFK. Winds subside after 23 to 01z. ...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: SW winds gusts to 25 kt expected to develop after 15-16z. S seabreeze of 20G25kt likely to develop after 19-20z. Low probability of a shower/tsra between 20z and 00z...with accompanying potential for westerly G35-40 kt. KLGA TAF Comments: W gusts to 25 kt expected to develop after 15-16z. Low probability of a shower/tsra between 20z and 00z...with accompanying potential for westerly G35-40 kt. KEWR TAF Comments: W gusts to 25 kt expected to develop after 15-16z. Low probability of a shower/tsra between 20z and 00z...with accompanying potential for westerly G35-40 kt. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: W gusts to 25 kt expected to develop after 15-16z. Low probability of a shower/tsra between 20z and 00z...with accompanying potential for westerly G35-40 kt. KHPN TAF Comments: W gusts to 25 kt expected to develop after 15-16z. Low probability of a shower/tsra between 20z and 00z...with accompanying potential for westerly G35-40 kt. KISP TAF Comments: SW winds gusts to 25 kt expected to develop after 15-16z. SSW seabreeze likely after 19-20z. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SUNDAY... .Thursday...VFR. Afternoon coastal sea breezes. .Friday...Chance of mainly aftn showers/tstms with MVFR or lower conds. SW gusts around 20 kt. .Saturday...CHC early -shra/MVFR, otherwise VFR. NW gusts 20-25 kt. .Sunday...VFR.
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&& .MARINE... Seas remain right around 5 ft on the ocean waters east of Fire Island inlet early this morning. While the seas are expected to drop below sca levels around 12z...near shore winds will begin to increase after sunrise...reaching SCA levels this afternoon. A moderate SW flow could also bring seas back up to marginal levels later this aftn and eve so have extended the SCA through 06z tonight. Elsewhere...with the exception of eastern Long Island Sound...where confidence isn`t as high...near shore gusts around 25 kt are SCA conditions will be possible on the ocean Friday into Saturday as S-SW flow increases to near/just over 15 kt with the approach of a cold front, building seas to near 5 ft. && .HYDROLOGY... Any tstms that develop today should be fast moving. No flooding impacts are anticipated through Sunday. && .TIDES/COASTAL FLOODING... With the approach of a new moon, occurring Friday evening, astronomical tides will be running very high, especially during the high tide cycles Thursday, Friday, Saturday evening. Less than 1 ft of surge is needed for minor flooding...and in some cases less then 1/2 ft...during these evening high tide cycles. The expected S/SW flow is not favorable for surge build-up, but southerly swells and a running anomaly will likely be enough for minor coastal flooding along the south shore back bays of Nassau with each evening tidal cycle. Brief and localized minor coastal flooding will also be possible in Jamaica Bay and Western Long Island Sound during this time. && .EQUIPMENT... KOKX weather radar is scheduled for maintenance starting this Friday June 23rd for a period of 3 days. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...High Rip Current Risk through this evening for NYZ080-081. NJ...None. MARINE...Small Craft Advisory from noon today to 8 PM EDT this evening for ANZ335-338-340-345-355. Small Craft Advisory until 2 AM EDT Thursday for ANZ350-353. && $$ SYNOPSIS...Goodman/24 NEAR TERM...24 SHORT TERM...24 LONG TERM...Goodman AVIATION...NV MARINE...Goodman/24 HYDROLOGY...Goodman/24 TIDES/COASTAL FLOODING... EQUIPMENT...

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