Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 151102 AFDOKX Area Forecast Discussion National Weather Service New York NY 702 AM EDT Wed Aug 15 2018 .SYNOPSIS... Weak high pressure will be over the region through Thursday. A warm front passes Friday, followed by a cold front Friday night. The front settles just south of the area as waves of low pressure ride along it through the weekend. High pressure briefly builds Monday before another frontal system approaches from the Plains states Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... An upper ridge and surface high build in from the west today. Mostly sunny, and with a westerly flow plus 850mb temps around 17C, highs in the upper 80s to lower 90s. MAV/MET MOS guidance for this afternoon`s surface dewpoints has trended lower since yesterday`s guidance as expected. The westerly flow combined with progged dewpoints through the mixed layer will allow for surface dewpoints to mix out from this morning`s values. Thinking is that even in spite of relatively wetter grounds, a blend of the MOS is still not mixing out surface dewpoints enough, so have gone slightly below a blend. Even with this however, there`s still enough coverage of 95+ degree heat indices to go with a heat advisory for the city and the adjacent suburbs. There is a moderate risk of rip current development at the ocean beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Upper ridge flattens as its axis shifts into the region late Thursday. Weak high pressure remains in place, and it should remain rain-free across the entire area through Thursday afternoon. Low temperatures for tonight will be above normal. 850mb temperatures rise slightly, so expecting Thursday`s highs to be slightly warmer than today`s. Winds this time will be more SW with slightly higher dewpoints through the mixed layer. Surface dewpoints therefore should be a little higher than yesterday, more so for coastal areas, but drier grounds could help dewpoints drop a little more than anticipated elsewhere. It appears that 95+ degree heat indices will be more widespread, and a heat advisory could eventually be needed for more locations across the tri-state area on Thursday depending on whether or not Friday sees similar coverage. There is a low risk of rip current development at the ocean beaches on Thursday. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Upper ridge Thursday night will give way to lowering heights as a shortwave approaches and settles over the northeast this weekend. Models remain in general agreement. Then ridge builds early next week as upstream shortwave, then longwave trough extending from central Canada approaches Tuesday. At the sfc, a warm front lifts to the north Thursday night and Friday as low pressure passes to the north across New England by Friday. A prefrontal trough develops to the Lee of the Appalachians, and the main cold front approaches Friday night into Saturday. The front passes just offshore as waves of low pressure ride along it through the weekend. High pressure builds to the north during this time frame. The front will finally depart by Monday as the ridge remains in place. Then the next frontal system approaches and could impact the area as early as Tuesday. Dry conditions Thursday night give way to an increasing amount of clouds, and shower/thunderstorm chances increase Friday. Some of these showers could produce heavy rain as PW values are progged to increase to over two inches. Low level SW flow prevails by this time ahead of the trough. This weekend looks to be unsettled, but do not anticipate a washout by any means at this time. Models differ in shower development/coverage Saturday as the area sits to the north of the front, and upper trough passes. Cannot rule out a passing shower or thunderstorm. A similar scenario exists for Sunday, but will keep rain chances low at this time this weekend. Dry weather is forecast Monday, then shower/thunderstorm chances increase yet again by Tuesday. Warm/hot temps continue Friday, and relatively high humidity should result in heat indices in the 90s most locations. Behind the front, temps cool off closer to normal this weekend. Sunday looks to be the coolest day thanks to northeast/east breezes. Near normal temps are anticipated early next week. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... Weak high pres builds in today. Mainly vfr thru the taf period. Patchy mvfr cigs e of the city arpts will dissipate by 13z. W winds today with gusts up to 20kt. Winds lighten tngt, then remain generally aob 10kt Thu. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: No unscheduled amendments are expected. The afternoon KJFK haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KLGA TAF Comments: No unscheduled amendments are expected. The afternoon KLGA haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KEWR TAF Comments: No unscheduled amendments are expected. The afternoon KEWR haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KTEB TAF Comments: No unscheduled amendments are expected. KHPN TAF Comments: No unscheduled amendments are expected. KISP TAF Comments: No unscheduled amendments are expected. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thursday...VFR with winds backing to the sw. .Friday...MVFR or lower conditions possible in late day/evening showers and tstms. S flow 15-25 kt. .Saturday and Sunday...MVFR or lower at times. Shwrs and tstms possible. W flow becoming n. && .MARINE... Conditions will be just below advisory criteria across the ocean today, with the rest of the waters also below SCA criteria. Winds become lighter tonight and Thursday, allowing for waves/seas to diminish as well. Southerly flow Thursday night will increase Friday ahead of an approaching cold front. Generally expect winds for all waters and ocean seas to remain below SCA thresholds. Winds will shift to the west Friday night, then eventually veer to the north/northeast this weekend as a cold front passes. Speeds increase by Sunday as waves of low pressure ride along the stalled frontal boundary to the south and east. High pressure builds to the north. Ocean seas may build close to 5 ft Sunday, otherwise winds and seas remain below SCA thresholds across the remainder of the waters. && .HYDROLOGY... Showers and thunderstorms ahead of a frontal boundary Friday will likely produce heavy rain in spots, mainly during the afternoon and evening hours. Deep layer SW flow nearly parallel to the approaching frontal boundary will increase moisture over the region with PW expected to reach over 2 inches. As a result, there is potential for heavy rain and thus flooding with individual cells and also training of cells, mainly from the NYC metro area north/west. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Heat Advisory from noon today to 6 PM EDT Thursday for NYZ071>075-176>179. NJ...Heat Advisory from noon today to 6 PM EDT Thursday for NJZ006- 104-106>108. MARINE...None. && $$ SYNOPSIS...JC/PW NEAR TERM...JC/PW SHORT TERM...JC LONG TERM...PW AVIATION...JMC MARINE...JC/PW HYDROLOGY...JC/PW EQUIPMENT...

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