Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 230227 AFDOKX Area Forecast Discussion National Weather Service New York NY 1027 PM EDT Thu Oct 22 2020 .SYNOPSIS... A mild, humid airmass will remain in place through the end of the week. A cold front will move through on Saturday, followed by high pressure building to the north Saturday night into Sunday. A frontal system will then impact the area through the middle of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... High pressure along the New England coast will keep the area under a light, moist southerly flow. Areas of fog, and possibly drizzle, along the coast will expand north and west across the interior overnight. Because guidance is mixed in supporting the development of widespread 1/4sm vis or less, a dense fog advy has not been issued. This does not rule out the potential for dense fog to develop tngt, along with the need for a possible short fused advy. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... A drier llvl airmass will attempt to gather across ME tngt, then advect swwd into or close to the fcst area thru Fri. The latest progs suggests it may at least reach the far ern portion of the cwa. Confidence is low however with this amount of precision. The modeling then indicates that even this wedge of dry air will be overcome by the continual moist onshore flow Fri ngt. Therefore, fog and dz is expected late into Fri mrng, then some sprinkles or patchy dz for the rest of the day west of this dry air slug. Fog and dz is then expected to expand again Fri ngt across the entire area. Time heights indicate a little subsidence Fri ngt, so this may have some impact on the coverage of fog and dz. As a result, went only with patchy in the fcst for now. For temps, if we were to mix down from h85 highs would be near 80. But this is not the case, and despite the warm temps aloft, highs in the mid 60s are expected. The NBM was used with the typical local adjustments thru the period. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Little overall change in the upper air pattern as the mean upper trough across the Northern Plains and Upper Midwest gradually translates slowly east through the period. This will mean above normal heights and ridging across the western Atlantic and eastern seaboard. Global models are generally pointing to a pattern change toward the end of period as the upper trough works into the northeast quarter of the country. The biggest change in the extended is the handling of the frontal system that impacts the area late Sunday night through mid week. There is had been good agreement in the prior days runs with a cold frontal passage on Tuesday, followed by high pressure for the second half of the week. Both the 12Z ECMWF and GFS now stall the front across area Tuesday with the potential for multiple frontal waves traversing the region with rain Tuesday night into Wednesday. The ECMWF is much quicker in sending the front southward on Wednesday and drying conditions out, while the GFS continues to load up with southern branch energy as a closed upper moving into to the Lower Mississippi shears out to the northeast. Complex interaction between northern branch shortwave energy dropping into the mean trough and the interaction with the aforementioned closed upper low emerging from the Southern Plains will likely result in several different solutions in coming days until the guidance locks onto a solution. The GGEM is completely at odds with the both the GFS and ECMWF, but does interestingly stall another boundary mid week. Bottom line, forecast is more of a consensus of the ECMWF and GFS. Thus, looking at inclement weather with a chance of showers/rain late Sunday night through middle of the week. Timing will be better resolved as the event approaches. Prior to then, a dry cold frontal passage on Saturday will be followed a quick shot of cool air on Sunday before moderating back to just above seasonable levels for much of the period. Unseasonably cold air looks to arrive late next week. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... High pressure will remain over the terminals through Friday morning, and drift east Friday afternoon as a cold front approaches. IFR to LIFR will remain through the overnight hours into early Friday morning. Conditions will be improving slowly to MVFR Friday morning, then remain MVFR through the remainder of the forecast. Winds remain light and variable to near calm until Friday morning when a light SE flow develops. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Uncertainty with the timing and flight category changes through Friday. Amendments for fluctuations in flight categories through Friday. Low confidence forecast. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday night...MVFR with IFR at times. .Saturday...MVFR becoming VFR in the afternoon. .Sunday...VFR. N winds G15-20kt AM push. .Sunday night-Tuesday...Chance of showers with MVFR possible. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 && .MARINE... A dense fog advisory has been issued for all waters as moist S winds traverse the cooler waters with fog forecast to expand through the night. Swells from Epsilon have arrived and a SCA remains in effect thru Saturday night on the ocean. Areas of fog will result in low vis at times thru Fri ngt on all waters. Long period swells will be highest Friday night through Saturday night, then gradually subsiding Sunday through Tuesday. There will be gusts up to 20 kt on the ocean waters late Saturday night through Sunday as strong high pressure passes to the north and low pressure approaches from the southwest. Please refer to National Hurricane Center products for further details on Epsilon. && .HYDROLOGY... No hydrologic impacts are expected thru the forecast period. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Dense Fog Advisory until 10 AM EDT Friday for ANZ330-335-338- 340-345. Dense Fog Advisory until 10 AM EDT Friday for ANZ350-353-355. Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355. && $$

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