Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241143 AFDOKX Area Forecast Discussion National Weather Service New York NY 743 AM EDT Mon Oct 24 2016 .SYNOPSIS... High pressure gradually builds across the region through Wednesday night. A frontal system will approach from the west on Thursday and move across Thursday night into early Friday, followed by weak high pressure later Friday into Saturday. A series of weak frontal systems will then approach Saturday night into Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Some minor adjustments were made to temperatures, dewpoints and POPs. A fast clipper type low will move across the region early this morning. High pressure will be slow to build in behind the front. The center of the high will be moving from South Central Canada into the Midwest to Western Great Lakes. Meanwhile, a persistent strong parent low in Quebec will gradually fill in while moving southeast today. Expecting some decrease in clouds with more sun late this morning but clouds will tend to increase this afternoon. This will be due to diurnal instability with cyclonic flow aloft allowing for stratocumulus to develop. With cold air advection expected through the day on a gusty NW flow, went with cooler guidance of EKD and MAV. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Still enough of a pressure gradient tonight to allow for steady winds and wind gusts. Rural locations and other locations away from the coast will have lighter winds and with mostly clear conditions anticipated, there will be some radiational cooling. Min temperatures were taken from a blend of MAV/MET guidance which yields a range from just above freezing to the lower 40s. Rural locations with the lighter winds and generally across the interior is where frost can be expected. However, frost coverage is only expected to be patchy. For Tuesday, there will be continued cold air advection and another breezy day with a steep pressure gradient between low pressure to the northeast of the region and high pressure to the northwest of the region. Cyclonic flow aloft remains. The airmass will trend drier with a continued northwest flow. Highs again were taken from the relatively cooler guidance, MAV, and will be several degrees cooler than max temperatures of the previous day. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... High pressure builds into the region Tuesday night and Wednesday. Expect a dry, cool period as temperatures Tuesday night fall into the 30s. Wednesday will be sunny with highs in the middle and upper 40s. The high pressure system moves offshore Wednesday night. There should be enough radiational cooling during the first half of the night to allow temperatures to fall into the 30s, possibly even some upper 20s, far north and west of NYC. However, during the second half of the night, clouds increase as a frontal system approaches from the west. This could limit how cold temperatures get. There remains some uncertainty with respect to timing of the precipitation. Some of the models want to bring the precipitation in between 09z-12z. If this occurs, temperatures should be cold enough for some wintry precipitation north and west of NYC. For now, will carry slight chance/chance pops during the morning, with likely pops by afternoon. Any wintry precipitation that falls, should quickly change over to rain after 8am or 9am as temperatures quickly warm. Most of the precipitation that falls with this system falls Thursday night. If the system moves through as quickly as latest guidance suggest, Friday could be dry throughout, but will continue to keep chance pops in for eastern Long Island and SE CT. Forecast certainty diminishes after Friday, with big timing differences noted with a series of frontal systems moving through. Have only a broad-brush slight chance PoP from Sat night into Sunday, and this could change as the more likely time periods for rain come into focus in later forecast cycles. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... High pressure builds in behind a departing cold front. VFR. Winds increase this morning and are more likely to prevail north of 310 magnetic for most of the day. Occasional gusts to 30 KT possible in the city terminals this afternoon. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Winds should prevail north of 310 magnetic, but could go south of it at times before 14z, and again from approx 18- 21z. KLGA TAF Comments: Winds should prevail north of 310 magnetic, but could go south of it at times before 14z, and again from approx 18- 21z. KEWR TAF Comments: Winds prevailing south of 310 magnetic until around 14-15z, then north of it thereafter. There is a chance that winds are frequently south of 310 magnetic through the afternoon. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Occasional gusts 24-29 kt possible this afternoon. KHPN TAF Comments: Occasional gusts 26-30 kt possible this afternoon. KISP TAF Comments: Occasional gusts 26-30 kt possible this afternoon. .Outlook for 12Z Tuesday through Friday... .Tuesday...VFR. NW winds G25-30 kt, diminishing Tuesday night. .Wednesday...VFR. NW-NNW G20 kt possible near the coast. .Thursday...MVFR or lower possible Thursday and Thurs night in rain. .Friday...Chc MVFR early, otherwise VFR with NW gusts around 25 kt. && .MARINE... SCA in effect on all waters through Tuesday with a steep pressure gradient remaining between a weakening parent low across Southeast Canada and strong high pressure building into the Midwest. SCA conditions continue on the waters Tuesday night but late at night will be primarily on the ocean and the eastern Sound, and this could linger possibly into Wed morning. Sub- SCA conditions are then expected from Wednesday afternoon through much of Thursday. SW flow increasing to 15-20 kt Thursday night ahead of a frontal system should push ocean seas up to 5-6 ft Thu night. Post- frontal WNW flow could gust up to 25 kt on the ocean on Fri as well. && .HYDROLOGY... No widespread significant precipitation is expected through Wednesday. Thursday and Thursday night, QPF from a passing frontal system is expected to produce anywhere from 1/2 to 3/4 of an inch of rainfall. local amounts over an inch are possible. No hydrologic impacts expected at this time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ330-335-338- 340-345-350-353-355. && $$ SYNOPSIS...BC/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...BC AVIATION...JC MARINE...BC/JM HYDROLOGY...BC/JM is the U.S. government's official web portal to all federal, state and local government web resources and services.