Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 041133 AFDOKX Area Forecast Discussion National Weather Service New York NY 633 AM EST Sun Dec 4 2016 .SYNOPSIS... High pressure approaches from the west today and passes east of the area late tonight. A weak frontal system will then move through on Monday. High pressure briefly returns for Monday night into early Tuesday, before giving way to low pressure passing well south of our region Tuesday night into Wednesday. A rather strong cold front passes through on Thursday bringing unseasonably cold weather for Friday into the weekend a well as strong gusty winds. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Ridging both aloft and at the surface approaches from the west today with plenty of sun and a gradually diminishing NW flow. Highs will top out in the lower to mid 40s, which is a few degrees below normal. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/... A fast moving, nearly zonal flow across the northern half of the country will send an upper trough over the Upper Midwest across the Great Lakes tonight and then up into eastern Canada and northern New England on Monday. Large scale warm advection ahead of this system and preceding a surface warm front will result in a quick shot of light overrunning precipitation late tonight into Monday morning. Vertical temperature profiles support mainly light snow inland and a rain/snow mix initially at the coast. A weak return flow should result in the boundary layer warming with a quick changeover to all rain at the coast by daybreak, and by late morning inland. Only looking for about a tenth of an inch of liquid with temperatures generally above freezing at the coast, and around freezing across the interior. About an inch of snow is possible well inland, with perhaps a a tenth of two across coastal locations outside of the NYC metro. Some limiting factors for this event are a dry sub cloud layer at the onset, and then drying aloft in the snow growth region as the low-levels moisten. Be alert for some slippery road conditions during the Monday morning rush for interior locations. Conditions will quickly dry out by early Monday afternoon with clearing from west to east by early evening. Highs will be seasonable in the 40s. High pressure then briefly returns for Monday night. && .LONG TERM /TUESDAY THROUGH SATURDAY/... A rather complex period upcoming with two more systems. 1. First system is from the upper low currently over the Gulf of California. The upper low will weaken dramatically into a minor shortwave that passes the region Tuesday evening. NWP has uncertainty in timing. The 00z NAM still appears too fast compared to the GEFS and deterministic runs. Have maintained low chances for rain Tuesday afternoon. Light PCPN becomes likely Tuesday Night...but QPF is < 0.1". Have kept PCPN all liquid based on profile analysis which has the freezing level up at 6000` over the interior. 2. Next is the Gulf of Alaska low. The feature deepens the midwest upper trof on Wednesday and eventually drives a cold front through the local region on Thursday. There is uncertainty in how strong the cyclogenesis is over the Atlantic/Maritimes on Friday and the resultant strength of the CAA and pressure gradient. For now, have gone with highs near MOS (which may be too warm) and wind gusts of 25-35 mph (which may be too low). Wind chills get down into the teens Friday night and stay in the 20s most of Saturday. Showers on Thursday diminishes in the evening. Flurries for Friday. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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High pressure remains in control through this evening. A weak front approaches early Monday morning. VFR through around 06z with conditions lowering to MVFR towards daybreak Monday in a light rain/snow mix near the coast and light snow inland. NW winds will continue through the day before veer to the NNW-N this evening. Wind direction at the city terminals will remain to the right of 310 magnetic. Winds speeds around 10-12 kt will slowly diminish into the afternoon and early evening. Light winds are forecast overnight. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday...Light snow inland with rain at coast early. MVFR and local IFR possible in the morning, then VFR. .Tuesday...VFR early, then MVFR possible with a chance of light rain. .Tuesday night-Wednesday...IFR in drizzle and light rain. .Thursday...MVFR possible with a chance of rain.
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&& .MARINE... With high pressure over the waters today into tonight, and with a weak frontal system moving through Monday winds and seas will be sub small craft. Relatively tranquil conditions on the local waters for Monday night into Thursday. A cold front passing through on Thursday and will set the stage for potential Gales for all waters on Friday into Saturday. Outlook has been issued. && .HYDROLOGY... No hydrologic impacts are anticipated the next 7 days. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...DW NEAR TERM...DW SHORT TERM...DW LONG TERM...Tongue/DW AVIATION...DS MARINE...Tongue/DW HYDROLOGY...Tongue/DW

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