Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211655 AFDOKX Area Forecast Discussion National Weather Service New York NY 1155 AM EST Sun Jan 21 2018 .SYNOPSIS... Weak high pressure will move east through the region today. A warm front will approach the region tonight, slowly working north through the region late Monday into Monday Night. A strong frontal system will cross the region on Tuesday, with high pressure returning for the remainder of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Updated the forecast mostly for sky cover and high temps. Broken to overcast cirrus will exit east this afternoon, meanwhile lower stratus will slowly shift in from the west late in the day, reaching some of the western zones. High temps were bumped up a couple of degrees for most spots outside of the Lower Hudson Valley and adjacent areas. Highs will average 10-15 degrees above normal for most spots.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Models in good agreement with the amplifying trough over the SW states interacting with subtropical jet energy today. The resultant deep closed upper low is then expected to track NE across the Central Plains and Mid Mississippi valley tonight through Mon. A large resultant low pressure system will take similar track through the Central US. Meanwhile the local region will remain under slight ridging, with PAC/Polar jet confluence well to the north. At the surface, weak high pressure moves offshore tonight, with a warm front developing to the south of the region. Stratus and light precip/drizzle appears likely to work into the region tonight into Monday morning with strong theta-e advection ahead of the approaching Central US system. Models have trended slightly warmer with low-level temps tonight into Monday, with polar air staying locked across northern New England. This has reduced the threat for widespread freezing temps and icing across the interior, but still potential for interior valley areas of the Lower Hudson Valley and Southern CT to have temps hang around freezing, resulting in a localized glaze of icing threat. CT River valley is most vulnerable. On Monday, the warm front will likely have trouble moving north through the region until the llj works into the region Monday Night. This based on position of the surface low well west of the Appalachians on Monday and high-res models signaling a weak cold air damming signal from high pressure nosing down the coastal plain from SE Canada. This will spell chilly conditions with stratus, drizzle, and light rain showers continuing Mon into Mon eve. Patchy freezing rain/drizzle may linger across interior through Monday morning, particularly in the CT River Valley due to cold air drainage. Highs on Monday will likely hold in the upper 30s interior to lower 40s city/coast. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Models continue in strong agreement with the closed upper low tracking through the Great lakes Monday Night into Tuesday before beginning to phase with northern stream energy as it swings into the NE US Tuesday Night. At the surface, primary low pressure tracks through the Great Lakes Monday Night into Tuesday, while secondary low pressure develops in vicinity of the region Tuesday and lifts into New England Tuesday Night. Model-to-model and run-to-run consistency continues for a quick moving moderate to heavy rain event for late Monday night into Tuesday, in response to strong deep layered lift (region under of nose of 65-70 kt LLJ and left front quad of a 125+ kt jet streak in difluent upper flow) of a positive 2-3 STD above normal PWAT moisture plume over the region, focused ahead of the cold front/surface wave. Embedded thunder possible as well with the strong forcing and weak elevated instability. Based on SREF/GEFS ensemble model spread, a general 1/2 to 1 inches of rain is likely across the region late tonight through Tuesday, with locally 1 to 2 inches. Highest rain amounts will likely be in path of surface wave and across interior hills due to orographic enhancement. Despite a low level inversion, a period of 30 to 40 mph gusts appears likely for LI/SE CT Tue morn/aft ahead of cold front as a 60-70 kt 950mb llj works over this region, with a low prob for a few gusts of 40 to 50 mph being mixed down with convection/heavy rain. The frontal system pushes through by late Tuesday with drying conditions Tuesday evening. A breezy NW flow will usher in a cold and dry airmass for mid to late week, with Canadian high pressure building in for the late week and east for the weekend. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... High pressure remains centered to the south through today. A warm front approaches from the south tonight. Initially VFR conditions will gradually lowering to MVFR tonight with the approach of the warm front. IFR conditions will likely develop towards Monday morning as the warm front stalls across the area. Winds will generally be light WNW (left of 310) today, gradually backing to the W-SW in the afternoon. Winds will then become light and variable tonight as the warm front approaches, remaining light and at times variable through at least Monday afternoon. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... Monday...MVFR/IFR likely. Chance of -RA. -FZRA possible at SWF early Monday morning. .Tuesday...IFR/LIFR in -RA. LLWS. S winds G25KT morning, WSW winds G30-35KT possible near the coast in the afternoon. .Wednesday...VFR. WNW G25-30KT. .Thursday...VFR. NW winds G20KT. && .MARINE... Winds and seas will remain tranquil through today as weak high pressure shifts northeastward. A warm front then approaches tonight and slowly moves through Monday, keeping winds light and seas tranquil. As the warm front moves through Monday night into Tuesday, southerly flow will rapidly strengthen, with at least SCA-level winds on the waters. A strong low-level jet will lead to the possibility of at least isolated gale-force winds on Tuesday, despite an inversion that may hinder the strongest winds from reaching the waters. Seas will rapidly build in response to the strengthened flow. Winds may then briefly decrease Tuesday evening as the cold front moves through, before strengthening into Tuesday night in strong cold advection. Expect SCA-level gusts Tuesday night into Thursday, with seas remaining elevated on the ocean waters. High pressure then begins to build across the area for the late week, with winds decreasing and seas gradually subsiding. && .HYDROLOGY... A frontal system passing through late tonight through Tuesday is likely to produce a widespread 1/2 to 1 inch of rain, with locally 1 to 2 inches possible. No significant hydrologic issues are anticipated at this time. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...NV NEAR TERM...JC/NV SHORT TERM...NV LONG TERM...NV AVIATION...BC/MD MARINE...MD HYDROLOGY...NV EQUIPMENT...

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