Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 242011 AFDOKX Area Forecast Discussion National Weather Service New York NY 411 PM EDT Tue Apr 24 2018 .SYNOPSIS... Low pressure over the Southeast states will move northeast toward the area tonight into Wednesday, then pass over the area Wednesday night, with a trailing cold front also passing through. Weak high pressure will briefly build in on Thursday, then give way to another low late Friday into Friday night. A cold front will move through on Saturday, followed by high pressure Sunday through Tuesday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Ridge axis aloft is passing east, with clouds lowering and thickening from NYC metro south/west. Steady rains are still well to the southwest over central/eastern Maryland, and are not likely to arrive in the NYC metro area until about 11 PM, though a few spits of light rain are possible here and there beforehand this evening in the onshore flow between the approaching low and departing offshore high pressure. Low temps are a blend of GFS/NAM MOS and 2m raw temps, with lower 50s in NYC metro and western Long Island, and mid/upper 40s elsewhere. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Combo of a decent shot of Atlantic inflow and elevated instability ahead of the approaching surface low will lead to rain, heavy at times, along with chance of thunder as TT increases to near 50 and Showalter indices decrease to near of below 0C. This area should lift NE and off the eastern New England Coast Wed night, leaving the area in a col for most of the night with light rain and patchy fog developing. NWP guidance shows some phasing of northern/southern branches of the jet stream late Wed night, and as this takes place the southern stream low and mid level shortwave trough should pass through late Wed night, along with a cold frontal passage associated with the northern branch of the jet stream and a surface low well to our north. Elevated convection could be reinvigorated by this cold front, and so have kept slight chance mention of thunder in the forecast for Wed night. Temps will be below seasonal norms but certainly not unusual for a springtime rain event, with not much diurnal changes. Highs Wed will be in the 50s, and lows Wed night in the upper 40s and lower 50s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... During the Thursday through Saturday time frame, features to watch include departing shortwave over the northeast, southern stream shortwave traversing across the southeast states ahead of vigorous northern stream shortwave that moves out of the upper midwest toward the east coast by Saturday. Any lingering rain should end early Thu morning with weak ridging and dry weather returning through Thu night. Meanwhile, the aforementioned southern stream shortwave will lift northeast as the downstream trough amplifies, with deep SW flow setting up. There are some differences aloft, the American models track the shortwave further west than the EC/CMC/UKMET, leading to higher rain amounts on Fri. Will need to fine tune this in the coming days, but for now have increased CHC PoPs a bit. During the Saturday night through Monday timeframe, upper trough pushes east, and there is the potential for additional showers associated with a weak cold front late Saturday into Saturday night, although probabilities do not appear to be high at this time. Greater likelihood would be NW of the area as trough closes off north of the Great Lakes region. Upper trough lingers Sunday but gives way to building ridge as sfc high builds by Monday. Temperatures remain right around seasonal norms, with Sunday perhaps a few degrees cooler behind the cold front. Temperatures warm early next week. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... High pressure off the northeast coast weakens through this evening as low pressure approaches from the southwest. The center of the low pressure system moves along the mid Atlantic coast through Wednesday. VFR until around 02Z, then ceilings and visibilities lower to MVFR as light rain develops. Conditions continue to lower to IFR later tonight, around 06Z. Then IFR conditions continue through the remainder of the forecast. A period of moderate to heavy rain is possible, along with embedded thunderstorms, from 10Z to 16Z. Southerly winds 10-15KT, with gusts to around 20 KT, back to the SE then E through this afternoon. Winds will then remain E to SE. A period of gusty winds, up to 20 KT, is possible Wednesday morning, mainly along the coast. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. Occasional gusts may continue a couple hours passed 22Z. KLGA TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. Occasional gusts may continue a couple hours passed 22Z. KEWR TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. Occasional gusts may continue a couple hours passed 22Z. KTEB TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. Occasional gusts to around 20 KT possible through 23Z. KHPN TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. KISP TAF Comments: No unscheduled amendments are expected until early this evening as rain develops. .OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY... .Wednesday...Rain with IFR conditions. Conditions improve Wednesday night as rain begins to taper off. .Thursday...VFR. .Friday-Saturday...VFR. A chance of showers with areas of MVFR conditions. .Sunday...VFR. W wind 10-15KT, G20-25KT. && .MARINE... The weak pressure gradient will keep conditions well below SCA thresholds today. Tonight, with the continuance of onshore flow, expecting ocean seas to eventually build to 5-6 ft late. Then as the pressure gradient tightens ahead of the approaching sfc low, expect wind gusts gusts of 25-30 kt mainly during the first half of Wed. Seas on the ocean waters should remain AOA 5 ft into Sat before subsiding from W to E as the pressure gradient weakens. && .HYDROLOGY... A widespread 1.00-1.50" of rain likely late tonight into Wednesday. Heavy rain at times could cause minor urban and poor drainage flooding, especially if the higher end of the expected rainfall range is realized. Expecting the bulk of the rain to fall between 2 AM and 2 PM Wednesday, perhaps lingering into late afternoon across SE CT. && .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...Small Craft Advisory from 6 AM to noon EDT Wednesday for ANZ330-335-338-340-345. Small Craft Advisory from 2 AM Wednesday to 6 AM EDT Thursday for ANZ350-353-355. && $$ SYNOPSIS...Goodman/24 NEAR TERM...Goodman SHORT TERM...Goodman LONG TERM...24 AVIATION...MET MARINE...Goodman/24 HYDROLOGY...Goodman/24 EQUIPMENT...

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