Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210123 AFDOKX Area Forecast Discussion National Weather Service New York NY 923 PM EDT Fri Oct 20 2017 .SYNOPSIS... High pressure will be in control through the weekend before moving offshore Sunday night through Monday night. A strong cold approaches on Tuesday and moves across by early Wednesday. The front slows down its eastward progress, staying close to the region Wednesday into Thursday as weak low pressure develops along the front. The front moves farther east away from the region later Thursday into next Friday with weak high pressure returning to the region. && .NEAR TERM /THROUGH SATURDAY/...
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The forecast is on track with no changes made with this update. A dry atmosphere in place with no clouds in sight amidst high pressure will create favorable radiational cooling conditions tonight as the winds subside. Despite radiational cooling, above normal temperatures will continue with lows in the 40s across most areas and closer to the low to mid 50s in urban areas and closer to the coast.
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&& .SHORT TERM /SATURDAY NIGHT/... High pressure continues into Saturday with a subtle return flow/weak WAA allowing unseasonable warmth. Highs will generally be in the 70s, and may approach 80 degrees in northern NJ. Skies will remain clear into the night, once again allowing radiational cooling as winds relax. Temperatures and moisture will be slightly higher than Friday night in a light onshore flow. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The jet stream will remain well north of the region with upper level ridging Sunday through Monday. Clouds will be minimal until Monday when an upper level trough will dig to the west of the region and become amplified. There will be an increase in meridional flow across the region. At the surface, high pressure continues to move offshore during this period, increasing warm and moist air advection. Low levels look to become moist enough late Monday night into early Tuesday for the development of patchy fog. The upper level trough and jet stream dive toward the Southeast during this time. The meridional flow increases further across the region. For Tuesday, rain showers will expand and develop ahead of the cold front. The southerly flow will increase to near 20 to 25 mph with higher gusts to near 30 to 35 mph possible. The precipitable waters grow to near 1.8 inches according to the GFS, which is slightly higher than what this model was showing yesterday. This would be well above the 90th percentile according to OKX sounding climatology. With parallel flow from low to high levels, training of showers and thunderstorms will be possible with potential for heavy rain. The thunderstorms are only a slight chance with surface CAPE only a few hundred J/kg so expecting these to materialize as a few embedded thunderstorms within the heavy showers. The cold front moves across Wednesday morning, with a substantial decrease in precipitable water thereafter to much below 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 approaching the region Wednesday into Thursday, with rain shower chances continuing, highest for Southeast CT and Eastern Long Island. Chances for rain showers lower Thursday into Friday as the front pushes farther east of the region. Did not trend down too fast in case subsequent model runs are stronger with the low along the front and trend closer to the region with the front. Weak high pressure moves in Thursday into Friday next week. Temperatures are expected to be well above normal Sunday through Tuesday with a little decline thereafter to values closer to normal. Highs Sunday through Tuesday are forecast to be well into the 70s with lows trending to be well into the 50s to lower 60s for some locations along the coast and NYC. The highs are forecast to be more in the 60s for Wednesday through Friday next week. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
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VFR through the TAF period as high pressure builds in from the west overnight, then begins to move offshore Saturday. Light NW winds overnight shift to the N, or become nearly calm. In the morning, light and variable winds shift to the S/SW under 10 kt in the afternoon. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .Saturday night-Sunday...VFR. .Sunday night-Monday...MVFR/IFR possible in stratus and fog. .Tuesday...MVFR possible in showers. S wind G20-25 KT at coast. LLWS possible. .Wednesday...VFR. A chance of showers with areas of MVFR, especially early.
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&& .MARINE... NW wind gusts will continue subsiding this evening as high pressure builds over the waters. The high will remain in control through the late weekend, maintaining tranquil conditions across the waters. Conditions stay below SCA Monday into Monday night. Then southerly flow and fetch increase ahead of the cold front Tuesday. SCA conditions more probable for all waters Tuesday into Tuesday night, lingering for the ocean Wednesday into Wednesday night with non- ocean waters trending below SCA as cold front lingers offshore. && .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... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MD/JM NEAR TERM...MD/DS SHORT TERM...MD LONG TERM...JM AVIATION...PW MARINE...MD/JM HYDROLOGY...MD/JM

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