Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221913 AFDOKX Area Forecast Discussion National Weather Service New York NY 313 PM EDT Sun Apr 22 2018 .SYNOPSIS... High pressure will be in control through Tuesday. Low pressure then approaches Tuesday night and passes to the northeast Wednesday. Another low pressure system may impact the region Friday or Saturday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Deep-layered ridging with a surface high axis over us will result in clear conditions with light to calm winds. Areas of frost will be likely with these good radiational cooling conditions, mainly across eastern Long Island and the northernmost suburbs. A MAV/NAM MOS blend was used for low temps. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... High pressure slowly shifts east of the region Monday into Monday night, but ridging remains aloft. Mostly clear conditions through the period along with seasonable temperatures, although some areas west of the Hudson and away from a SE flow will have highs in the upper 60s. Some frost should return late at night across eastern Long Island, SE CT, and parts of the Lower Hudson Valley. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Complex pattern this time frame, with several features to watch. Initial shortwave lifts slowly northeast, with sfc low along the coast tracking northeast toward the area Tuesday and Tuesday night. General model agreement noted with this mid week system. Clouds will be on the increase Tuesday with dry weather through much of the day. Then rain moves in Tuesday night and continues into Wednesday as the low draws near, and warm front lifts toward the area. Northern stream shortwave dives out of Canada, phasing with the trough over the northeast Wednesday. The sfc low lifts northeast Wednesday, and drier air should advect east across the area behind the system as the shortwave and low pulls further to the northeast Wed night into Thursday. Then, next southern stream shortwave passes across the southeast states, with downstream northern stream shortwave moving quickly east Thursday and into Friday. The question is how these two features interact late in the week. If they phase, could see a larger trough developing late in the week and into next weekend. The sfc low likely will deepen as it lifts northward, dragging a cold front through. But, not all model/ensemble members show this scenario, which leads to forecast uncertainty, especially with exact details during the late week and weekend time frame. In general, wet weather Tue night/Wednesday, followed by drier conditions Wed night and Thursday. Unsettled thereafter (except mainly dry Thu night into Friday), and will maintain slight chance or chance pops given the uncertainty and timing of strength of the aforementioned upper features. Seasonable temperatures are anticipated for much of the period, except Wednesday. This would be the cooler day due to clouds, rain and gusty onshore flow ahead of the low. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... VFR conditions through the TAF period with high pressure in control. Sea breeze continues to slowly progress inland this afternoon. Winds at KLGA will vary under 10 kt this afternoon. Timing of sea breeze passage at KLGA may be off 1-2 hours. Confidence the sea breeze will pass across KEWR and KTEB is lower and it may not pass until early evening when winds diminish. KSWF will remain with NW flow and this is possible across KHPN as well. Winds become light and variable tonight before becoming SE 5-10 kt Monday morning and early afternoon. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... .Monday Afternoon-Tuesday...VFR. SE gusts 20 kt possible near the coast on Tuesday. .Tuesday Night-Wednesday...IFR becoming likely with rain. SE gusts near 20 KT Tuesday night. E gusts 20-25 KT on Wednesday morning. .Thursday-Friday...Mainly VFR. Shower Possible. && .MARINE... Sub-SCA conditions expected through Tuesday with high pressure in control and a weak pressure gradient. There is, however, a potential for 15 to 20 kt gusts in sea breezes across NY Bight and surrounding nearshore waters early this evening and late day/early evening Monday. Low pressure moves up the eastern seaboard Tuesday into Wednesday. Strengthening easterly winds and building seas are forecast across the waters Tuesday night into Wednesday morning. Winds likely subside below SCA late Wednesday as low pressure moves over and then NE of the region. However, ocean seas remain elevated a SCA levels into late week from residual SE swells. && .HYDROLOGY... A widespread 1/2 to 1 inch of rain with locally higher amounts, is expected Tuesday night into Wednesday. No hydrologic issues are anticipated at this time. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/PW NEAR TERM...JC SHORT TERM...JC LONG TERM...PW AVIATION...DS MARINE...JC/PW HYDROLOGY...JC/PW EQUIPMENT...

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