Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 231813 AFDOKX Area Forecast Discussion National Weather Service New York NY 213 PM EDT Fri Jun 23 2017 .SYNOPSIS...
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A warm front remains well north of the region this afternoon. A cold front approaches tonight and moves across the area Saturday. A series of frontal boundaries will move across the Tri-State area Sunday through Tuesday. A large area of high pressure builds in thereafter.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A warm front is located well north of the region with a pre- frontal trough developing in the lee of the Appalachians. The local region is in the warm sector with a warm and humid airmass in place. Temperatures range from upper 70s to mid 80s this afternoon although much of the region will be in the upper 70s to lower 80s. Dewpoints are in the lower 70s. Showers are located near and north of NYC with overall shower activity expected to be isolated in coverage but by late afternoon expecting scattered showers as well as thunderstorms. These will be mostly north and west of NYC. The clouds have been abundant so this has limited the surface based CAPE and instability. There is some shear that increases towards the evening as winds at 3kft increase to near 30kt. This will allow for convection to become more organized. The moderate risk of rip current development continues through this afternoon, due to building southerly winds waves and a 2 ft long period SE swell.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Northern stream longwave trough continues to deepen into the Upper Mississippi River Valley and Great lakes through the period...with the shortwave remnants of Cindy shearing northeast towards the region late tonight into Saturday morning. At the surface...a cold front over the Great Lakes will slide east towards the region tonight...with the remnant circulation of Cindy riding NE towards the region along the front. Leading edge of southern stream shortwave energy and pre- frontal trough approach the region this evening. Will have to watch for convection developing over Central/Eastern PA this afternoon...and whether line segments can translate east in the moderate mid- level flow into the Lower Hudson Valley/NE NJ before instability begins to wane. A conditional low threat for severe winds gusts exists mainly NW & W of NYC if this activity survives. The parade of shortwaves late evening into the overnight and tropical airmass will keep a threat for iso convection with heavy downpours overnight. Coastal stratus/fog development possible with high dewpoint airmass advecting across E LI/SE CT late today/this evening. Main concern during this period will be approach of cold front and remnant low of Cindy late tonight/Saturday morning. Environment presents a threat for flash flooding along and just to the south of the path of this low...with PWATS in excess of 2+ inches and Corfidi vectors indicating potential for slow moving or back building convective elements. Also can`t rule out an isolated severe wind/tornado threat if any MCS type activity develops in a weak instability but high shear/helicity and low- LCL environment. 745am Update...06z guidance is indicating that this feature may track to the south of the region. If 12z guidance continues with this theme...the above mentioned severe/flash flood threat may end up south of the region. Drying conditions in the wake of the cold front and Cindy circulation Saturday afternoon...with highs in the mid to upper 80s. A high risk of rip current is likely Saturday with building southerly swells and wind waves. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... NWP is in agreement that a broad upper level trough will remain east of the Rockies into early next week. The H5 flow then flattens from west to east as a cutoff low pres system moves through the western Canadian provinces...eventually consolidating with a vortex over northern Quebec. This will sharpen the trough with its axis passing through Tue night followed by weak ridging for the remainder of the forecast period. In terms of sensible weather...not a whole lot to talk about. A few cool frontal boundaries will pass through the local area...the first Sunday aftn/eve with just a chance of isold showers. Mid level warming will keep instability in check so no tstms in the forecast. The second boundary approaches on Monday and is very slow to move through the area. It may become hung up...before pushing east Tue night. Despite a decent shortwave and being in the RRQ of a 120+ kt upper jet...moisture looks very meager...thus have kept the forecast dry. Moisture is still limited on Tue...but there could be enough for isold showers/tstms in the aftn. Dry and seasonable weather then returns for the remainder of the forecast period. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Low pressure tracks through eastern Canada this afternoon into Saturday morning with an associated cold front approaching this evening and moving through the terminals 12Z to 16Z Saturday. Winds will be generally from the southwest 220 true, with gusts to around 20 kt. Sea breeze influence will keep the winds more southerly along the coastal areas this afternoon. With the passage of the cold front winds shift to west to northwest, to the left of 310 true, and become gusty Saturday morning. Generally VFR with occasional MVFR ceilings this afternoon. Restrictions in fog and showers develops after 06Z, isolated to scattered thunder is possible late this afternoon and this evening. Another round of showers develops late tonight with the chance of heavy rain and IFR visibilities. 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: Amendments possible late this afternoon and this evening for developing thunderstorms. KLGA TAF Comments: Amendments possible late this afternoon and this evening for developing thunderstorms. KEWR TAF Comments: Amendments possible late this afternoon and this evening for developing thunderstorms. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility greater than 6SM outside of cloud. KTEB TAF Comments: Amendments possible late this afternoon and this evening for developing thunderstorms. KHPN TAF Comments: Amendments possible late this afternoon and this evening for developing thunderstorms. KISP TAF Comments: Amendments possible late this afternoon and this evening for developing thunderstorms. The chance of thunder is less likely east of the NYC terminals. .OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY... .Saturday...VFR. WNW winds gusting around 20 kt. .Saturday night-Sunday Night...VFR. .Monday-Tuesday...VFR. A chance of shra/tsra Monday afternoon into Tuesday. .Wednesday...VFR.
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&& .MARINE...
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Ocean seas have increased to 3 ft with gusts near 20 kt that have developed. The wind gusts will further increase to 25 kt late this afternoon. Southerly winds at SCA levels likely continues into tonight. Occasional gusts to 25 kt possible on nearshore waters this afternoon. Ocean seas likely building to SCA levels late this afternoon...and to 4 to 7 ft tonight. Winds subside and Saturday...but southerly swells are expected to keep ocean seas at 4 to 7 ft on Sat. The other hazards for mariners will be rounds of showers/thunderstorms this today into Saturday morning, and potential for dense fog development on the ocean waters and eastern LI nearshore waters this afternoon and continuing into tonight. Seas begin to subside Sat night...but could take until Sun morning to drop below SCA levels east of Moriches Inlet. A weak pressure field is then expected to prevail through Tue...keeping conds at sub- advsy levels.
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&& .HYDROLOGY... Localized minor urban and poor drainage flooding is possible with showers and thunderstorm activity this afternoon into the first half of tonight. There is a threat for flash flooding late tonight through Saturday morning from a likely complex of showers and thunderstorm associated with a frontal wave (remnants of Cindy) moving through the areas. Uncertainty exists on the exact track of this wave...which could be from the Northern Mid- Atlantic to Southern New England. 745am Update...06z guidance is indicating that this feature may track to the south of the region. If 12z guidance continues with this theme...the above mentioned flash flood threat may end up south of the region. Otherwise, no other hydrologic concerns. && .TIDES/COASTAL FLOODING... Astronomical tides are running very high, especially during the evening high tide cycles today and Saturday. Less than 1 ft of surge is needed during these evening high tide cycles for minor flooding, and in some cases less then 1/2 ft. The expected S/SW flow is not favorable for surge, but a background anomaly will likely be enough for minor coastal flooding of the most vulnerable coastal locales along the south shore bays of Western Long Island, along Jamaica Bay, and along western Long Island Sound during this time. && .EQUIPMENT... KOKX weather radar is scheduled for maintenance starting today June 23rd for a period of 3 days. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 2 AM EDT Sunday for ANZ350-353-355. && $$ SYNOPSIS...24/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...24 AVIATION...MET MARINE...24/JM/NV HYDROLOGY...24/NV TIDES/COASTAL FLOODING... EQUIPMENT...

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