Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 041756 AFDOKX Area Forecast Discussion National Weather Service New York NY 1256 PM EST Sun Dec 4 2016 .SYNOPSIS... High pressure moves across the region from the west today through 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/...
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Forecast on Track as of 1730Z - A slight increase in temperatures was made based on trends. 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.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
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Latest NWP as of 1730Z supports current forecast. Basically no snow accumulation along the coastal plain. 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.
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&& .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 /18Z SUNDAY THROUGH FRIDAY/...
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High pressure remains in control through this evening. A weak front approaches early Monday morning. VFR through around 06Z before conditions lower to MVFR as light precipitation overspreads the area before daybreak Monday. Expecting primarily rain across the city and coastal terminals. Farther inland, precipitation at KSWF should remain all snow while KHPN may start as a rain/snow mix before transitioning to all rain. NW winds will continue through the day before veering to the NNW-N this evening. An occasional gust to 15-20 kt is not out of the question this afternoon, but should diminish by sunset. Light winds overnight will shift to the SE by Monday morning and SW Monday afternoon at around 10 kt. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... .Monday afternoon...Becoming VFR. .Tuesday...VFR early, then MVFR possible with a chance of light rain or drizzle. .Tuesday night-Wednesday...IFR in drizzle and light rain. .Thursday...MVFR possible with a chance of rain. .Friday...VFR
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&& .MARINE...
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Forecast on Track as of 1730Z - no changes at this time. High pressure moves over the waters today into tonight. A weak frontal system moves through Monday. Winds and seas remain 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 for Gales on Friday remains in effect.
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&& .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...Tongue/DW SHORT TERM...DW LONG TERM...Tongue/DW AVIATION...FEB MARINE...Tongue/DW HYDROLOGY...Tongue/DW

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