Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 231546 AFDOKX Area Forecast Discussion National Weather Service New York NY 1146 AM EDT MON MAY 23 2016 .SYNOPSIS... Low pressure off the Mid Atlantic coast moves slowly north through tonight, then drifts northeast Tuesday and Tuesday night, remaining offshore and passing south and east of the region. High pressure will then briefly follow for Wednesday through Thursday morning, then a cold front stalls in the vicinity Thursday afternoon and night. The front returns north as a warm front on Friday...followed by high pressure building in from the south through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Latest radar and high resolution model trends support a dry forecast through at least the remainder of this morning, so have adjusted the current forecast accordingly. The main question for this afternoon is will generally a few hundred J/kg of CAPE mainly to the W/N of NYC Metro be sufficient to fire convection along an area of surface convergence stretching from SE CT back towards NE NJ. This line should push slowly to the N/W during the afternoon. For now, other than slowing the onset of convection...did not make any changes to forecast for isolated thunderstorms. However, if current trends hold, can foresee removing mention of thunder especially over Long Island, and possibly NYC proper for the next update. Temperatures initially this morning have been running higher than forecast, but a look at 12z KALY and KOKX soundings suggest that previously forecast high temperatures appear on track, so no changes there. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... The surface low continues to drift north and northeast tonight through Tuesday night, remaining offshore, as the mid and upper cutoff low also drifts along the coast. With the low a little closer to the coast tonight and additional energy rotating through, there will be a better, likely, chance of showers. There may be isolated thunder early, however, cape and instability will be decreasing. Not all areas will see precipitation, and will be dependent on where the low and upper low drift. Once again, Tuesday afternoon thunderstorms will be possible as a surface trough develops and the low drifts east of the region. Precipitation ends during Tuesday evening as the upper low begins to fill and open, moving farther to the east, and height will be rising at all levels after 03z Wednesday. Could be a rather sharp end to the precipitation. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Ridging aloft on Wednesday will help slow down a cold front sinking south across the Northeast. Insufficient moisture and lift should therefore keep the CWA dry. Mixing to 850 mb, where temps are forecast to rise to around 13C, along with a mostly sunny sky and SW winds will bring high temps about 10-15 degrees above normal across the entire area. The cold front weakens and stalls over us on Thursday as ridging aloft continues. Chance of afternoon tstms from around the city and points west where better instability will reside. Subsidence will limit mixing more than on Wednesday, so expecting high temps to be a couple of degrees cooler on average versus Wednesday. Friday and Saturday look to be similar days with ridging aloft and a weak SE-S wind flow. This will probably limit chances of showers/thunderstorms to inland sections both days, and chances don`t appear to be very high due to limited moisture and/or capping from ridging aloft. Models however hint at the possibility of an Mesoscale Convective System moving through late Thursday night into early Friday morning, so a more widespread rainfall is still a possibility. High temps both days still averaging above normals in spite of a limited mixing profile. It appears that Sunday could feature deeper mixing,and along with rising temps aloft, high temps could end up a few degrees warmer than currently forecast. Didn`t want to stray too far from WPC guidance this far out in time, which is warmer than Superblend. Highs well into the 80s for some inland spots. Once again, limited chances of showers/storms focused inland. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... Low pressure off the Delmarva moves slowly NNE through Tuesday. Sea breeze flow is expected to take over by early afternoon. Winds then become light and variable tonight as the sea breeze circulation weakens. Northwest winds develop during the day on Tuesday. Mainly VFR thru this evening, although some scattered showers are possible after 17-18Z, primarily north and west of NYC. Isolated tstms cannot be ruled out...particularly from the city into the Hudson Valley and northeastern NJ. For tonight...MVFR or lower in rain after 4Z. ...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 afternoon. KLGA TAF Comments: Chance of an isolated shower or thunderstorm this afternoon. KEWR TAF Comments: Low prob of a thunderstorm this afternoon. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Low prob of a thunderstorm this afternoon. KHPN TAF Comments: A tempo may be needed for tstms this afternoon...mainly aft 18z. KISP TAF Comments: No unscheduled amendments expected. .OUTLOOK FOR 12Z Tuesday through Friday... .Tuesday...periods of mvfr in -shra and/or tstms. .Wednesday-Thursday...vfr. .Thursday night...low chance of mvfr -shra. .Friday...mvfr possible in tstms. && .MARINE... Seas have fallen below 5 ft on the coastal ocean waters, so will be dropping the SCA for Hazardous Seas there with this issuance. Otherwise, a rather weak pressure gradient force will be across the waters today through Tuesday night as a weak low off the North Carolina coast moves north today and tonight, and northeast Tuesday and Tuesday night. Winds will remain below small craft levels today through Tuesday night. And seas on the ocean waters will remain below small craft once the seas subside this morning. Sub-sca conditions will prevail for the rest of the forecast period with the lack of a strong pressure gradient or significant swell. && .HYDROLOGY... A long period of generally light precipitation is expected today through Tuesday evening with 1/3 to 2/3 of an inch expected. Locally higher amounts are possible if any thunderstorms develop this afternoon and Tuesday afternoon. Widespread significant rainfall is not expected for the rest of the week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/MET NEAR TERM...Maloit/MET SHORT TERM...MET LONG TERM...JC AVIATION...FEB/JMC MARINE...JC/Maloit/MET HYDROLOGY...JC/MET is the U.S. government's official web portal to all federal, state and local government web resources and services.