Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 070522 AFDOKX Area Forecast Discussion National Weather Service New York NY 1222 AM EST Wed Dec 7 2016 .SYNOPSIS... A low pressure center passes to our south overnight into Wednesday morning while a trough of low pressure moves through the tri-state area, this is followed by weak high pressure building in late Wednesday. Several re-enforcing cold fronts will cross the area from Thursday into Friday night, followed by high pressure building in Saturday and Saturday night. High pressure slowly retreats to the east early next week as a warm front approaches from the south Sunday and Sunday night, then lifts to the north Monday followed by a cold front pushing through Monday night. Another cold front approaches from the northwest on Tuesday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Main area of precipitation moving east. More spotty light precip expected for the remainder of the overnight. Shortwave and trough aloft passing through. At the surface, low pressure center has emerged off the Del-Mar-Va Peninsula and shifts east out to sea. Meanwhile, a low pressure trough shifts through the tri state area overnight. Snow confined to NW zones, and a report of 3.3 inches was observed in Orange county. Lift weakens and mid levels are beginning to dry out. The loss of ice nucleation aloft therefore makes it more difficult for snow formation during this period with light rain or possibly even drizzle becoming more likely wherever there is a wintry mix. Looks like just about all spots will be above freezing by the time this happens. These sfc temps will need to be monitored. Winter Wx adv remains in effect for Orange county. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... Plenty of low level moisture lingers into early afternoon, but lift is weak...maybe just some large scale lift from an approaching jet streak. Low chances of light rain or drizzle, primarily during the morning. Clouds then diminish somewhat late in the day or early evening before increasing once again late at night. A blend of MOS guidance looked good for temperatures in the short term. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... A northern stream 850-500 hPa closed low tracks across Southeastern Canada Thursday through Friday bringing successive shots of re-enforcing cold air as shortwaves rotate around it through the region. The combination of strong low level cold advection and favorable low level flow from the Great Lakes will produce mainly isolated mainly rain showers (rain/snow showers far NW Orange County) Thursday, then a transition to mainly isolated snow showers from NW to SE Thursday night and continuing on Friday. Little or no accumulation is expected outside of higher elevations, where isolated 1-2 inch amounts are possible in any stronger convective bands which set up and linger over a given area. Note that higher elevations experiencing multiple prolonged convective snow bands could receive 1-2 inches per band experienced and not just 1-2 inches of snow total. At this time, it is too early to specify if and/or when and where any of these bands might occur, if they do at all. What is more certain Thursday-Friday is that much colder air will move into the region on gusty NW winds. Highs on Thursday will occur mainly in the morning, reaching the lower-mid 40s, with falling temperatures in the afternoon. Lows Thursday night should fall mainly into the 20s (lower-mid 30s Twin Forks of Long Island) with wind chills into the teens and lower 20s towards sunrise Friday morning. Highs on Friday will struggle to reach the mid 30s to around 40 over most of the region. A northern stream shortwave ridge should transit the area Friday night, bringing an end to any snow showers, followed by a brief period of zonal flow on Saturday - which also should be dry. A northern stream short wave passes Saturday night, but dry low levels should keep things dry. Northern stream ridging crosses the area Sunday, but could see strong enough low level warm advection by late Sunday to bring some light snow to far northern zones - for now lift does not appear strong enough over the remainder of the area for any precipitation Sunday afternoon. As is typical, there are differences between the models in how fast the warm front lifts to the north. The ECMWF and its idea of a slow warm frontal passage late Sunday night, is consistent with climatology which suggests that warm fronts very rarely lift north of Long Island at night, except maybe towards sunrise - so leaned towards the ECMWF Sunday night. As a result have a chance of snow across the interior and a chance of rain elsewhere for now Sunday night. This will be refined as exact extent of any cold air damming becomes better resolved with time (ECMWF currently hints at this at 12z Monday with kink in isobars to the S of Long Island - suggestive of at least a coastal front to the S if not a warm front). The region should become solidly in the warm sector Monday morning ahead of an approaching northern stream trough that passes to the east Monday night, bringing any showers to an end. Tuesday should be dry as northern stream ridging transits the area. Temperatures Friday night-Tuesday were based on the Superblend. They should run around 10 degrees below normal on Saturday, moderate to a few degrees above normal by Monday and then return to being below normal on Tuesday. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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Low pressure off the Delmarva coast will pass to the south today. Expect IFR conds overnight into the morning at KTEB/KHPN/KSWF, and MVFR cigs at the remaining terminals with potential for a couple of hours of IFR cigs toward daybreak and into the early daylight hours. Precip type overnight should be mainly light rain or drizzle, but there could be a prolonged period of freezing drizzle as steady snow has ended and temps remain at freezing for the rest of the night. From late morning into the afternoon expect mainly MVFR cigs, with some improvement to BKN035 possible late in the afternoon at KEWR/KTEB/KLGA as winds become light NW. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Late Wednesday night...VFR. .Thursday-Friday...Isolated rain/snow showers could result in brief MVFR/IFR conditions. Gusty W-NW flow 10-20KT with G25-30KT, highest Thursday night and Friday. .Friday night...VFR. NW winds 15-20KT. G25KT in the evening. .Saturday-Sunday...VFR.
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&& .MARINE... The pressure gradient increases as low pressure passes to the south of the waters overnight. Winds and seas have increased, with SCA conditions observed on the ocean waters. This should last into Wednesday morning, so will leave the SCA on the ocean unchanged. Looks like NY Harbor will fall short of criteria, so have dropped the SCA here. Relatively tranquil conditions then follow Wednesday afternoon and night. Small craft conditions are likely from Thursday into Saturday due to strong low level cold advection with Gales possible Friday and Friday night. The risk of gales will be highlighted in the HWO. Conditions should fall below SCA levels on all waters by late Saturday and remain below into Sunday. Small craft advisory conditions are possible again by late Sunday on the coastal ocean waters. && .HYDROLOGY... A half inch or less of liquid equivalent precipitation is expected through tonight, then no significant widespread precipitation is expected Wednesday-Sunday. There is a chance of a widespread 1/2 inch or more of precipitation from Sunday night through Monday. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Winter Weather Advisory until 6 AM EST early this morning for NYZ067. NJ...None. MARINE...Small Craft Advisory until noon EST today for ANZ350-353-355.
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&& $$ SYNOPSIS...JC NEAR TERM...JC/Fig/PW SHORT TERM...JC LONG TERM...Maloit AVIATION...Goodman MARINE...JC/Fig/Maloit HYDROLOGY...JC/Maloit

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