Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 190806 AFDOKX Area Forecast Discussion National Weather Service New York NY 406 AM EDT Wed Jul 19 2017 .SYNOPSIS...
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A weak trough of low pressure remains nearly stationary in the vicinity of the coastal waters through this evening. A weak cold front moves southeast stalling across the area Thursday through Saturday. It returns north as a warm front Sunday, followed by a cold front Monday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... Stratus clouds and light fog across portions of SE CT and the east end of Long Island will gradually spread west across the coast, mainly east of NYC overnight. Otherwise, a very warm humid maritime tropical air mass will continue overnight, making it feel quite uncomfortable. Other than an isolated shower, no additional convection is forecast overnight. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Little change is expected as high pressure remains over the western Atlantic and a surface trough remains inland. Wednesday will be a little more humid and warmer as the airmass remains in place. Convection will again be diurnally driven with the best low chance probabilities inland, and slight chances along the coastal areas. CAPE and instability will again be marginal. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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An active near zonal flow will exist late week through the weekend as a anomalously strong polar low tracks through Northern Ontario/Quebec. This will be followed by an approaching PAC shortwave and troughing for early next week. A weak cold front approaches Thursday Night as the first in a series of shortwaves tracks through the NE in the developing zonal flow. Models are signaling potential for an MCS to track into the region late Thu Night into Friday morning with shortwave energy rounding periphery of southern ridge...but low predictability on details at this point. Otherwise...the weak cold front appears to push through the region Friday, but subsidence in deep wnw flow Friday will likely result in hot and dry conditions. The region will lie in an active zonal flow this weekend between polar low to the north and broad southern ridging, while a frontal boundary resides near the region. Models in decent agreement with the front pushing south Fri Night and remaining to the south through Saturday. This would keep the region mainly dry on Saturday with the axis of convective activity farther south...but will have to watch for any MCS activity. As PAC shortwave energy begins to dig towards the Great lakes Sat Night into Sun Night...associated low pressure/s will begin to push the stationary front through the region as a warm front Sat Night into Sunday NIght. The presence of shortwave energy moving through aloft, and a surface boundary interacting with an increasingly moist and unstable airmass, will bring an increased threat for shower and thunderstorm activity during this time. Uncertainty on how quickly this front moves north as this time. Good agreement on the shortwave trough over the Great Lakes continuing to approach the region Monday and then across the region Tuesday. The associated frontal system slowly moves through the region Monday into Monday Night with shower and thunderstorm activity. Thereafter...a cooler and drier Canadian airmass appears poised to advect into the region behind the front. Temperatures through Sat should be above normal (well into the 80 to lower 90s). This could be the 4th consecutive day of 90 degree temps for the urban corridor, although slightly lower dewpoints may make for marginal heat advisory conditions of 95 degrees. Lower confidence on temp forecast for Sun and Mon based on frontal placement and convection, but near to above seasonable temps appear likely. Temps on Tuesday may fall to below seasonable levels in a cool Canadian airmass behind the cold front.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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High pressure remains over the western Atlantic as a trough of low pressure sits over the area today. Mainly VFR. Some patchy fog and stratus has developed, however the only terminal impacted is KGON, where conditions have fallen to sub- IFR. Unsure just how far west these lower conditions get. Will leave the lower conditions out of the KISP/KBDR TAFs for now. Any morning stratus and fog burns off after 13-15Z, with VFR expected during the late morning and afternoon hours outside of any showers or thunderstorms. Best chance for showers and thunderstorms NW of NYC. Light South/Southwest winds increase today with 10-15 kt sustained, gusting to near 20 kt. ...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: Medium to high confidence forecast. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Medium to high confidence forecast. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Medium to high confidence forecast. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Medium to high confidence forecast. KHPN TAF Comments: Medium to high confidence forecast. KISP TAF Comments: Low chance of showers and thunderstorms this afternoon between 16-18Z as storms develop along the seabreeze. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Wednesday night...Any showers and thunderstorms diminishing in the evening. VFR. .Thursday-Friday...VFR. .Saturday...MVFR or lower possible with a chance of showers and thunderstorms. .Sunday...MVFR or lower possible with a chance of showers and thunderstorms.
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&& .MARINE...
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With a warm and humid airmass across the waters this evening and tonight, visibilities will lower as fog develops, especially late tonight. At this time will not bring visibilities below 1 nautical mile, however, this will be possible late overnight. Otherwise, a weak pressure gradient over the region will keep winds 10-15 kt or less, and keep seas below SCA levels through Saturday. Southerly swells should begin to increase Sunday into Monday ahead of an approaching frontal system, with a low probability for SCA conditions on the ocean by Monday.
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&& .HYDROLOGY...
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No flood impacts are expected through Friday. There is a low chance for flooding during the Saturday Night into Monday Night period as a slow moving frontal system interacting with a moist and unstable airmass brings a threat for periods of heavy showers and thunderstorms.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Heat Advisory from 11 AM this morning to 6 PM EDT Thursday for NYZ069>075-176>179. NJ...Heat Advisory from 11 AM this morning to 6 PM EDT Thursday for NJZ004-006-103>108. MARINE...None.
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&& $$ SYNOPSIS...GC/NV NEAR TERM...GC SHORT TERM...GC LONG TERM...NV AVIATION...BC MARINE...GC/NV HYDROLOGY...GC/NV

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