Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221423 AFDOKX Area Forecast Discussion National Weather Service New York NY 1023 AM EDT Sun Apr 22 2018 .SYNOPSIS... High pressure will be in control through Tuesday, then give way to a coastal low pressure Tuesday Night into Wednesday Night. Another low pressure systems may affect the region Friday or Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The forecast is on track with only minor adjustments made to the hourly forecast for a few elements. Mean upper troughing lingers today, with trough axis crossing the region this evening. At the surface, a surface trough develops across the region this afternoon, pushing southeast through the region this evening. Mostly sunny, tranquil and seasonable Spring conditions today. With airmass moderating about 1 to 2 degrees from yesterday, and continued deep mixing, expect temps to be a degree or two higher than yesterday. Highs generally in the lower 60s along the coast and interior, although temps will likely drop back into the 50s along the south coasts late this afternoon with sea breeze development. While for NE NJ, NYC metro and surrounding suburbs, temps should be able to rise into the mid 60s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... Trough axis slides offshore tonight, with shortwave ridging building into the region through Monday Night and then offshore on Tuesday. Meanwhile, an upper low over the southern Mississippi River Valley today will slowly works northeast towards the Central Appalachians through Tuesday. At the surface, high pressure will build overhead tonight, and then gradually slide offshore Monday into Tuesday. Meanwhile, southern low pressure begins to lift NE towards the Mid Atlantic on Tuesday. A clear and chilly night once again tonight. Areas of frost likely across outlying areas with good radiational cooling to around freezing. Elsewhere lows generally in lower 40s to mid 40s. A continued moderation in airmass and moisture Monday Night, should have temps slightly warmer, with a more patchy threat for frost across far outlying areas. Mostly sunny, tranquil and seasonable Spring conditions continue Monday. With continued moderation of airmass and developing return flow, temps across the interior should continue to moderate into the mid to upper 60s. Meanwhile, along the coast, temps will likely hold in the lower 60s with onshore flow and early sea breeze development. Even NYC/NJ metro will sea breeze in this flow regime, which should hold temps in the lower to mid 60s. The influence of offshore high pressure should maintain another dry day Tuesday. NAM is likely too aggressive with stratus development during the day, but increasing late afternoon/evening cloud cover seems likely. Despite mostly sunny conditions to start, greater influence of a Canadian Maritime airmass on Tuesday and continued onshore flow should have temps dropping back to near or slightly below seasonable levels for much of the region. Lower to mid 60s NW Interior, lower 60s NYC/NJ metro to upper 50s across coastal areas. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Models continue in good agreement with the southern closed upper low over the Tennessee River Valley Tuesday, opening and lifting into the NE US through Wednesday in response to northern stream shortwave energy moving into the upper Midwest/Great Lakes. At the surface, resultant low pressure lifts towards the region Tuesday Night into Wednesday, and then into New England Wed Night. A soaking rain with breezy E/SE winds is expected to develop across the area Tuesday night and continue into Wednesday morning. Can`t rule out an isolated thunderstorm Wed morning into early afternoon along/ahead of warm front with weak elevated instability and forcing from approaching shortwave energy and 50-60 kt llj. Best forcing/moisture move NE Wed afternoon, with lingering showers late Wed into Wed Eve. Thereafter, models still have some spread in the evolution of the above mentioned Upper Midwest/Great Lakes trough, as its energy splits N/S during the late week period. This is further complicated by differences in evolution of the next northern stream shortwave diving into the Great Lakes and Mississippi River Valley for late week. The interaction between these two energies will determine sensible weather for Fri into the weekend. At this point, it appears there is potential for one or two progressive low pressure systems to affect the region during this time, but predictability on details is low. Will continue with low chance of showers in the forecast during this time to denote the potential. 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 /14Z SUNDAY THROUGH THURSDAY/...
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VFR conditions continue as high pressure remains over the region through the TAF period. NW-N winds 5-10 kt this morning will back to the W-SW this afternoon with sea breeze development likely along the coast. Timing of the sea breeze may be off 1-2 hours from forecast, but winds at should back to the S-SSW once it passes. Highest confidence with sea breeze passage is at KJFK, KLGA, KBDR, KGON, and KISP, with lower confidence at KEWR, KTEB, KHPN. KSWF will remain with NW flow. Winds become light and variable tonight. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday-Tuesday...VFR. Local enhancement to winds late Monday afternoon at KJFK with SE winds 10-15 KT gusts near 20KT. SE gusts near 20 KT for Tuesday afternoon. .Tuesday Night-Wednesday...MVFR or lower increasingly likely with rain. SE gusts near 20 KT Tuesday evening. E gusts 20 KT on Wednesday. Gusts subside by late Wednesday afternoon. .Thursday...Chance of showers with MVFR possible. SW-W gusts to 20 KT possible.
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&& .MARINE... Sub-SCA conditions expected through Tuesday with high pressure in control and a weak pressure gradient. Although there is potential for 15 to 20 kt gusts in late day sea breezes across NY Bight and surrounding nearshore waters late this afternoon and perhaps late Monday afternoon. Low pressure moving up the eastern seaboard Tuesday into Wednesday will result in strengthening easterly winds and building seas Tuesday Night, with SCA conditions likely to returning late Tuesday Night into Wednesday morning. Winds likely subside below SCA late Wed into Wed Eve as low pressure moves over and then NE of the region, but ocean seas may remain elevated a SCA levels into late week from residual SE swells. && .HYDROLOGY... Dry conditions are expected through Tuesday. A widespread 1/2 to 1 inch of rain is expected Tuesday Night into Wednesday, but no hydrologic issues are anticipated 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...JC/NV SHORT TERM...NV LONG TERM...NV AVIATION...JM/DS MARINE...NV HYDROLOGY...NV EQUIPMENT...

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