Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 032058 AFDOKX Area Forecast Discussion National Weather Service New York NY 358 PM EST Sat Dec 3 2016 .SYNOPSIS...
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High pressure builds slowly over the area tonight and Sunday. The high drifts east Sunday night as a weak low approaches Sunday night and moves through the region Monday. High pressure Monday night into early Tuesday quickly gives way to to low pressure passing well south of our region on Wednesday. A rather strong cold front pass through on Thursday bring unseasonably cold weather for Friday into the weekend a well as strong gusty winds.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Surface high pressure builds into the area from the west tonight as low pressure departs to the east. Winds will be slowly subsiding as the pressure gradient force weakens. An upper ridge builds toward the area tonight with rising heights and increasing subsidence. The combination of drier air, subsidence, loss of daytime heating, clouds will be dissipating this evening.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
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The upper ridge builds over the area through Sunday then quickly weakens as a northern stream shortwave and vort max rotate into the region. Much of the energy and lift with this trough will remain to the north of the area, through upstate New York and New England. As the ridge weakens limited moisture will be moving into the area. Lift will be increasing in response to the onset of weak warm advection. The atmosphere will be cold enough across much of the area for light snow with a mix of rain and snow along the coast. Snow becomes increasing likely as the snow growth region becomes saturated Sunday night and then the mid and lower levels cool as the result of precipitation evaporating. Even along the coast the lower levels will cool and much of the column will be below freezing that the precipitation types are expected to be dominated by snow and possibly rain along the immediate coast. Have increased probabilities to likely late Sunday night and into Monday as the shortwave moves through the area. Warmer air does begin to move in Monday morning, however this may take longer than models are indicating, and will keep snow until late in the morning. Minor accumulations are possible Monday, 1 1/2 inches across the lower Hudson Valley and a few tenths along the coast. As the wave passes Monday and height builds the precipitation ends.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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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. 12Z NAM appears too fast compared to the 12Z GEFS and the 12Z Deterministic runs for the International Centers. Have gone with a very low POP for Tuesday AFTN as a result of this thinking. 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 that appears initialized in the the NWP models a little south of actuality based on Water Vapor imagery. 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 example the 00Z EC and 12Z EC differed by 20mb (the more recent is weaker). 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.
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&& .AVIATION /21Z SATURDAY THROUGH THURSDAY/...
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VFR conditions and NW flow through the TAF period as high pressure builds into the area. Any BKN 4-5 kft ceilings late this afternoon become SCT this evening. Wind gusts will begin to decrease to around 20-25 kt as the sun sets this evening before diminishing entirely by around 00Z. NW winds remain around 10 kt through the overnight period at the city terminals, slightly lower at outlying locations. NW flow continues through the day on Sunday at around 10 kt before diminishing toward evening. Wind direction at the city terminals will remain to the right of 310 magnetic through the period. .OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... .Sunday...VFR. .Sunday night...MVFR possible after midnight in chance of light snow. .Monday...Rain/snow mix possible early with MVFR possible in the morning. .Tuesday...MVFR possible with a chance of rain. .Tuesday night-Wednesday...IFR in drizzle and light rain. .Thursday...MVFR possible with a chance of rain.
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&& .MARINE...
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A strong pressure gradient force remains across the waters into this evening as low pressure continues to move east through the Northern Atlantic Ocean and high pressure builds to the west. Small craft gusty winds will continue across the waters until late this evening and on the ocean waters through most of tonight. Winds will be diminishing as the high builds east and wind gusts on the ocean may fall below small craft levels before Sunday morning. Small craft seas on the ocean will be subsiding late tonight and very early Sunday morning. Seas were marginal small craft at this time. With high pressure over the waters Sunday and into Sunday night, and with a weak low 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 will set the stage for potential Gales for all waters on Friday into Saturday.
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&& .HYDROLOGY...
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No hydrologic impacts are anticipated the next 7 days.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ330- 335-338-340-345. Small Craft Advisory until 7 AM EST Sunday for ANZ350-353-355. && $$ SYNOPSIS...MET/Tongue NEAR TERM...MET SHORT TERM...MET LONG TERM...Tongue AVIATION...FEB MARINE...MET/Tongue HYDROLOGY...Tongue

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