Area Forecast Discussion
Issued by NWS Upton, NY

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075 FXUS61 KOKX 261119 AFDOKX Area Forecast Discussion National Weather Service New York NY 719 AM EDT Wed Oct 26 2016 .SYNOPSIS... High pressure briefly builds down from Southeast Canada today through much of tonight. A frontal system approaches Thursday and moves across Thursday night with the attached low deepening towards Friday morning. High pressure then builds back in on Friday and lasts into Saturday. A weak cold front moves through Saturday night, followed by a weak low passage to our south Sunday night. High pressure then returns for Monday and Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Region under the influence of high pressure with light winds and clearing conditions, allowing for good radiational cooling going into daybreak. Freeze warning continues across the interior with the forecast on track. There will be some ridging aloft but the core of an upper level NW jet streak remains above the region today. High pressure at the surface builds down from Southeast Canada allowing for a weaker pressure gradient. Dry weather is expected today with a cool day expected. The vertical mixing will be less with less gusty winds. The remaining cyclonic flow aloft will keep a cooler than normal airmass in place. Highs were taken using a blend of MAV and MET guidance, with a range from the upper 40s to lower 50s. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... The jet streak exits tonight into Thursday but another one moves in Thursday night and the local region will be right in the left front quad of that upper level jet streak. The mid levels become more zonal tonight into Thursday before an amplifying shortwave trough approaches Thursday night. These features, with the left front quad and approaching shortwave, will enhance synoptic lift. Expecting dry weather to continue through much of tonight and then widespread precipitation moves across ahead of a frontal system for Thursday through Thursday Night, mainly in the form of rain. The aforementioned synoptic forcing will allow for periods of moderate rain and perhaps locally heavy rain at times. Thursday night is when the models are conveying some elevated instability, so added in isolated thunderstorms along with the rain. Uncertainty at the onset Thursday with regards to timing and precip type across the interior. Soundings seem more of a rain/snow scenario versus freezing rain. Made freezing rain just a chance. The forcing initially Thursday will be the warm air advection aloft evident with the isentropic lift. However, the model soundings are not showing much of a warm nose around 5kft above the surface. The temperatures gets to near or just above freezing near 5kft, with surface temperatures right near to just below freezing Thursday morning. This portends to more of a snow and sleet scenario without complete melting of falling ice crystals as there will be a greater area below freezing within the boundary layer. Snow accumulations across parts of the interior including portions of Northeast NJ, the Lower Hudson Valley and SW Connecticut could reach 1 to possibly 2 inches of snow. The soundings are actually showing sufficient icing with moist vertical profiles in between the -10 to -30 degree C levels. This is portraying the moisture coming in first tonight as mid and high levels clouds tonight and then gradually lowering and thickening towards early Thursday with increasing low level moisture thereafter through much of Thursday night. Cooler than normal temperatures continue tonight and Thursday. The rain and clouds Thursday night will keep temperatures a smaller range across the region and a little above normal. && .LONG TERM /FRIDAY THROUGH TUESDAY/... High pressure builds in during Friday with breezy conditions. The shortwave aloft will already be to the east and moisture will be limited, so not expecting any instability showers and will continue with a dry forecast. High temperatures will be slightly below normal. The high pressure ridge shifts through the region early Saturday morning. Looks like clouds will increase ahead of an approaching cold front, but it still could be at least partly sunny for a good amount of the day. Will keep in a slight chance of an afternoon shower well north and west, but it looks like moisture is lacking and wouldn`t be surprised if it turns out to be dry all day there. High temps slightly above normal. The cold front passes through Saturday night with weak ridging behind it on Sunday. ECMWF has trended toward GFS during this period in that only a weak low is progged to approach us, eventually passing us to the south Sunday night. Some lift will be provided with a shortwave aloft, so will still at least go with a slight of showers Sunday/Sunday night. High pressure builds in Monday, lingers into Tuesday, then is followed by an approaching cold front late Tuesday night. Once again, moisture is lacking, so will keep this entire period dry. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... High pressure slowly builds into the region today. A frontal boundary approaches tonight. VFR through midnight. Winds will generally be from the Northwest today (310-340) around 10 kt. Will continue to carry gusts into the middle and upper teens, however the gusts may be more occasional that frequent today. Gusts diminish late in the day, and speeds fall to 10 kt or less overnight. Clouds increase and lower after midnight. Precipitation overspreads the region from west to east after 09z. Mainly rain everywhere, except far north and west of NYC where the precipitation is expected to start as light snow at KSWF. The snow will become a rain/snow mix after sunrise, and then all rain by mid to late morning. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. KLGA TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. KEWR TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. KHPN TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. KISP TAF Comments: Wind gusts may be more occasional than frequent today. High confidence VFR. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thursday...MVFR or lower possible in rain. Potential for a wintry mix across the interior before 15Z. Southerly winds. .Friday...VFR with strong northwest flow behind a cold front. Gusts to at least 25 kt are expected at this time. .Saturday and Sunday...VFR with southwest flow possible. && .MARINE... SCA conditions linger on the ocean and eastern waters into early this morning, due to wind gusts. Thereafter, the gusts will be on a downward trend with decreasing winds in the boundary layer as the pressure gradient lowers. High pressure builds down from Southeast Canada this afternoon through tonight. The sub SCA conditions remain through early Thursday and then increase again ahead of a frontal system Thursday afternoon with possible SCA conditions late. SCA becomes more probable Thursday night as the frontal system moves through and the low with this system deepens towards Friday morning, increasing the pressure gradient and therefore the winds. The pressure gradient tightens as high pressure builds in behind the departing storm. Looks like gales will be possible on the ocean and at least over the eastern Sound and Bays as well. In any case, at least a SCA will likely be needed eventually. Winds and seas then diminish Friday night into Saturday as the high pressure ridge moves in. Looks like sub-SCA conditions will be on all waters by Saturday morning. The rest of the forecast period likely remains under advisory criteria, however there is chance of gusts around 25 kt on the ocean Saturday afternoon and evening as the pressure gradient tightens ahead of an approaching cold front. && .HYDROLOGY... Weather remains dry through tonight and then widespread precipitation, mostly rain is expected Thursday through Thursday night. This will amount to around 1 to 1.25 inch. Locally higher amounts will be possible. So there will be possible localized minor flooding and ponding of water but no other hydrologic problems are anticipated. Widespread significant precipitation is not expected for the rest of the forecast period. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Freeze Warning until 9 AM EDT this morning for CTZ005>008. NY...Freeze Warning until 9 AM EDT this morning for NYZ068>070. NJ...Freeze Warning until 9 AM EDT this morning for NJZ002-004-103- 105-107. MARINE...Small Craft Advisory until 8 AM EDT this morning for ANZ350- 353-355. && $$ SYNOPSIS...JM NEAR TERM...JM SHORT TERM...JM LONG TERM...JC AVIATION...BC MARINE...JC/JM HYDROLOGY...JC/JM is the U.S. government's official web portal to all federal, state and local government web resources and services.