Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 232308 AFDOKX Area Forecast Discussion National Weather Service New York NY 708 PM EDT MON MAY 23 2016 .SYNOPSIS... An area of low pressure will slowly track from off the Mid- Atlantic coast tonight to near Nova Scotia by late Tuesday night. High pressure briefly builds across the area Wednesday ahead of cold front approaching from the northwest, the front then briefly passes through the area Thursday morning before returning northward as a warm front. High pressure then remains over the western Atlantic through the weekend with an inland thermal trough each afternoon. A backdoor cold front drops across the area Sunday night into Monday morning. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Area of showers/earlier thunderstorms NW of NYC is dissipating. Next area offshore pivoting northward. Scattered to Likely showers tonight as a cutoff low slowly tracks up the Mid-Atlantic Coast. Early this evening, instability is waning, so no mention of thunder initially. Overnight, as the cold pool with the cutoff moves in, have sufficient low level instability to warrant slight chance mention for thunderstorm in the forecast throughout the area. A blend of MAV/MET/ECS guidance and NAM 2-meter temperatures were used for lows Tonight, with values slightly above normal. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Showers will become more scattered to isolated in nature as the day progresses on the cutoff low moves to the east. However, its cold pool will still be near enough to warrant a slight chance of thunderstorms throughout the area through the day. For highs on Tuesday, a blend of ECS/MET/MAV guidance, NAM 2-meter temperatures and a mix down from 950-925 hPa per BUFKIT soundings was used. Highs should be near to slightly below normal. Any lingering showers over far eastern zones should come to an end early Tuesday evening as the cutoff low exits to the northeast. There should also be some partial clearing as the night progresses. Lows Tuesday night were based on a blend of MET/MAV/ECS guidance and NAM 2-meter temperatures, with readings forecast to be up to 5 degrees above normal. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The main emphasis this period will be building heights as an upper ridge establishes itself across the eastern third of the country. This will result in considerably warmer and more humid conditions as the sub-tropical ridge set up across the western Atlantic. The unknowns continue to be with the amount of short wave energy emerging from the western trough and rounding the upper ridge across eastern Canada. A day ago there was some consensus in dropping a cold front across the area Friday morning with a low-level easterly flow undercutting the warm ridging aloft. This very much put in question high temps for Fri with cooler air moving in off the Atlantic. Now, 24 hours later, both the 12Z operational ECMWF and GFS take a cold front across the area Wed night into Thu morning and then quickly return it northward as the upper ridge axis passes to the east. Thereafter, the upper ridge continues to amplify across the east ahead of an upper trough lifting north across the plains and upper midwest. A backdoor cold front then comes into question Sun into Mon, with the ECMWF about 24 hours earlier. It bring the front through Sun morning. while the GFS is Mon morning. Once again,this all hinges on the magnitude of the short wave energy rounding the top of the eastern ridge as well as with the interaction of a northern branch trough moving eastern Canada. For the time, will side with a consensus forecast and keep the boundary north of the area Sun. This could potentially throw a wrinkle into the forecast Sun with cooler conditions. As for rainfall, it mainly appears to be diurnal in nature with aft/early evening convection. The best chances will be across the interior due to instability from higher temps. The possible cold frontal passage Thu morning looks to be mainly dry with limited moisture and instability. Depending how fast the warm front lifts north on Thu, this could serve as a focus for convection. Confidence is low for any significant precipitation. Before the upper ridge amplifies further Fri into Sat, the southern edge of the westerlies always need to be watched for a possible MCS. Highs during this period will be unseasonably warm with portions of NYC and the interior in the low to mid 80s and coastal sections generally in the 70s. This is above normal by about 10 degrees. && .AVIATION /23Z MONDAY THROUGH SATURDAY/... Low pressure off the Delmarva moves slowly NNE through Tuesday. Southerly flow will continue into the evening before becoming light and variable after 00Z as the sea breeze circulation weakens. NNW winds develop on Tuesday, shifting to the WSW Tuesday evening. Mainly VFR thru this evening. Scattered showers over the Hudson Valley and northeast NJ will continue to move to the southwest through this evening. An isolated thunderstorm cannot be ruled out in this area, but all activity should remain west of NYC. MVFR or lower conditions then develop in rain after 04Z, with MVFR ceilings lingering into Tuesday afternoon. ...NY Metro Enhanced Aviation Weather Support... Detailed information...including hourly TAF wind component fcsts can be found at: http:/ KJFK TAF Comments: Chance of an isolated shower or thunderstorm this evening. KLGA TAF Comments: Chance of an isolated shower or thunderstorm this evening. KEWR TAF Comments: Low prob of a thunderstorm this evening. KTEB TAF Comments: Low prob of a thunderstorm this evening. KHPN TAF Comments: Low prob of a thunderstorm this evening. KISP TAF Comments: No unscheduled amendments expected. .OUTLOOK FOR 18Z Tuesday through Saturday... .Tuesday afternoon/evening...periods of MVFR in showers and/or tstms. .Late Tuesday night-Thursday...VFR. .Thursday night...low chance of MVFR in showers. .Friday-Saturday...MVFR possible in tstms. && .MARINE... A relaxed pressure gradient over the waters around Long Island will keep winds at 10 kt or less and seas less than 5 ft tonight through Tuesday night. Sub-sca conditions will prevail Wednesday through Saturday as well, with the lack of a strong pressure gradient or significant swell. The flow will generally be southerly in nature and looks to be strongest on Wed with gusts up to 20 kt during the aft/eve hours on the ocean waters ahead of an approaching cold front. && .HYDROLOGY... Showers with possibly embedded thunderstorms should produce from around 1/3 to 2/3 of an inch of rain through Tuesday afternoon, with locally higher amounts possible in areas experiencing any stronger convection. Areas that do receive locally heavy rainfall could experience some localized ponding of water on roadways. Widespread significant rainfall is not expected from Tuesday Night through Saturday. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Maloit/DW NEAR TERM...Maloit/PW SHORT TERM...Maloit LONG TERM...DW AVIATION...FEB MARINE...Maloit/DW/PW HYDROLOGY...Maloit/DW is the U.S. government's official web portal to all federal, state and local government web resources and services.