Area Forecast Discussion
Issued by NWS Upton, NY

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430 FXUS61 KOKX 211140 AFDOKX Area Forecast Discussion National Weather Service New York NY 740 AM EDT Sat Apr 21 2018 .SYNOPSIS... High pressure builds in from the west through the weekend, and remains over the region into Monday. A coastal low will affect the region the middle of next week, possibly lingering into late week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Deep closed low continues to lift north of New Foundland, with mean troughing continuing over the NE US in its wake. At the surface, high pressure builds into the region from the west. Although a weak backside shortwave will have a surface trough moving through the region in the afternoon/evening. Continued W/NW flow today with afternoon gustiness, but weaker than Friday. A gradual moderation in airmass and deep mixing should allow temps to rise into the mid to upper 50s. Late day seabreeze possible along the immediate south coasts. Mostly sunny skies expected, just few-sct afternoon CU across NE portions of the region with late day shortwave/trough passage. Otherwise just a few wisps of cirrus. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... Tranquil period with mean troughing in control of the NE US through the weekend, then giving way to shortwave ridging Sunday night into Monday. At the surface, high pressure will continue to build in from the west Sunday and overhead on Monday. Although, a weak front will move through the region late Sunday in response to one final kicker shortwave moving through the region. A couple of clear and chilly nights tonight and Sunday Night. Areas of frost expected across outlying areas with good radiational cooling into the upper 20s to lower 30s. Elsewhere lows generally in upper 30s to lower 40s, and slightly milder NYC/Nj metro. Otherwise, mostly sunny, tranquil and seasonable Spring conditions Sunday and Monday. Highs generally in the upper 50s to lower 60s on Sunday, with cooler temps along the south coasts with afternoon sea breeze development. A bit warmer conditions likely Monday (lower to mid 60s) , especially NYC/NJ metro and interior, with continued moderation of airmass and developing return flow. Along the coast, temps will likely hold in the upper 50s to lower 60s with return flow and sea breezes developing in the afternoon. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Upper air pattern will very much resemble early springtime as an upper low over the Mississippi Valley this weekend slowly works east on the heels of the departing trough over the Northeast. Models in good agreement with this energy and associated low pressure system lifting northward towards the region Tuesday into Wednesday in response to northern stream shortwave energy moving into the upper Midwest and Great Lakes. Overrunning rains are likely to develop across the area Tuesday night and continue through Wednesday, possibly Wed night. Thereafter, models diverge in the amplification of this shortwave energy over the the Upper Midwest and Great Lakes region during the midweek period. This is further complicated by differences in the amplification the next northern stream shortwave diving into the Great Lakes and Mississippi River Valley for late week. The evolution of these two troughs will determine the details for the next low pressure system/s affecting the region Thu thru Sat. A chance of showers remain in the forecast during this time to denote the potential. So uncertainty in the guidance for the end of the week continues, however, the global models continue to point to some degree of troughing reestablishing itself across the Northeast for next weekend. As for temperatures, much of the period will feature seasonable temperatures with the exception of Wednesday, where onshore flow will keep highs several degrees below normal. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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High pressure will build in through the TAF period. VFR conditions are expected. Winds will be near 10 kt or less through much of the TAF period mainly from a W to NW direction. A late day sea breeze is possible for KJFK. The winds will initially be NW and then back to a more westerly direction during the afternoon with some SW flow as a sea breeze for some terminals. Also for this afternoon into early evening, there will be some wind gusts to 15-20 kt, which could be occasional. The timing and duration of any sea breezes is uncertain with wind direction possibly varying about 20-40 degrees comparing observed to forecast at times this afternoon. The timing of the SW flow could also be 2-3 hours off from forecast. .OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY... .Sunday through Tuesday...VFR. .Tuesday night through Wednesday...MVFR or lower conditions increasingly likely with rain. E winds near 10 kt gusting near 15-20 kt Wednesday.
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&& .MARINE... Tranquil conditions expected this weekend through next Tuesday with high pressure in control and a weak pressure gradient. Low pressure moving up the eastern seaboard Tuesday into Wednesday will result in increasing winds and building seas with SCA conditions likely to return by Wednesday morning. && .HYDROLOGY... Dry conditions are expected through Tuesday, with area rivers and streams gradually receding. A widespread rainfall is expected for the middle of next week with the possibility of moderate to heavy rain. Predictability is low on rainfall amounts and hydrologic impacts at this time. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...NV NEAR TERM...NV SHORT TERM...NV LONG TERM...NV/DW AVIATION...JM MARINE...NV/DW HYDROLOGY...NV/DW EQUIPMENT...

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