Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 200754 AFDOKX Area Forecast Discussion National Weather Service New York NY 354 AM EDT Fri Oct 20 2017 .SYNOPSIS... Mild high pressure dominates through Monday. A slow moving frontal system will then approach the area Tuesday into Tuesday night with a cold frontal passage by early Wednesday. The front is slow to depart farther away with a wave of low pressure developing along it and approaching the area mid into late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Weak cold front pushes south of Long Island early this morning with deep layered ridging building in from the west. NW flow develops in the wake of the front with perhaps some gusts in the upper teens late this morning and aftn. With no real change in airmass and mostly clear skies, highs will be similar to yesterday, mainly upper 60s to lower 70s except mid 70s in the NY/NJ metro area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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Ridging continues to build into the region with weak WAA through the short term providing dry and unseasonably warm conditions. Even though optimal conditions will exist for radiational cooling tonight, clear skies and light/calm winds, the WAA will limit its impact. 925mb temps at 12z this morning are progged to be between 10C and 12C, and increase to 15-16C by 12Z Sat. Sunny conditions expected on Sat with just few-sct cirrus. Highs will remain above normal ranging in the mid to upper 70s except on the twin forks of LI and SE coastal CT.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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Warm weather continues through Monday as the jet stream remains north of the region with upper level ridging. At the surface, the dominant feature will be high pressure eventually moving offshore and the resulting S-SW flow. Mainly clear sky conditions are expected to continue through Sunday. Clouds increase Monday into Monday night ahead of the next frontal system. The next chance of rain showers arrives late Monday night into Tuesday, when a deep upper level trough approaches from the west. The trough further deepens Tuesday along the eastern seaboard with increasing meridional flow. This will give plentiful moisture to a developing frontal system at the surface. The frontal system will be approaching the region Tuesday into Tuesday night with the region being in the warm sector to the east of the low with strengthening southerly flow, thereby increasing warm air advection. Precipitable water increases to near 1.5 inches from the moisture advection. This is much above normal for this time of year. According to OKX sounding climatology, it would be above the 90th percentile. Some moderate to heavy rainfall will be possible. The cold front moves across Wednesday morning, with a substantial decrease in precipitable water thereafter to less than 1 inch. The front slows down and is slow to depart away from the region. The numerical forecast models show weak low pressure development along it and the low approaching the region mid into late next week, with rain shower chances continuing. Temperatures are expected to be well above normal this weekend through Tuesday with a gradual decline thereafter. Highs this weekend through Tuesday are forecast to be well into the 70s with lows trending to be well into the 50s and near 60 for some locations along the coast and NYC. The highs are forecast to be more in the 60s for next Wednesday and next Thursday.
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&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/... VFR as a weak cold front approaches passes through prior to daybreak shifting winds to NW. High pressure then builds in from the west. Good confidence in the wind forecast with typical 20 degrees of variability either side of forecast through the day. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .Saturday-Monday...VFR. .Tuesday...MVFR possible in showers. S wind G20-25 kt. LLWS possible. && .MARINE...
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NW flow today as high pressure builds in with some near shore gusts to 20 KT. Otherwise, tranquil conditions are forecast through Monday. Winds, as well as seas on the ocean, increase on Tuesday ahead of a cold front with Small Craft Advisory conditions likely.
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&& .FIRE WEATHER...
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The special weather statement will be continued for today for the entire region due to enhanced fire danger. Min RH values are expected to drop to 30 to 35 percent, except in the NY/NJ metro area where they could drop into the upper 20s. Wind gusts of 20 to 25 mph are also expected, especially late this morning into the afternoon.
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&& .HYDROLOGY... No hydrologic problems are expected through Monday night. For Tuesday through early Wednesday, heavy rain will be possible at times with potential areas of 1 inch or higher. There is much uncertainty with exact rainfall amounts. Urban and poor drainage flooding will be possible. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...None.
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&& $$

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