Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210540 AFDOKX Area Forecast Discussion National Weather Service New York NY 140 AM EDT Wed Aug 21 2019 .SYNOPSIS... High pressure across the region will shift east tonight. A warm front will then move north of the area on Wednesday followed by an approaching cold front late Wednesday night. A cold front will slowly move through the area Thursday into Friday, followed by high pressure into the weekend. Unsettled weather may return early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... High pressure across the area will shift east tonight as a warm front approaches from the south. Both moisture and PoPs will increase through the night, with short term model trends continuing to indicate that the best chances of precipitation will be after midnight, although even then shower/thunderstorm coverage may be limited. Adjusted temperatures and dewpoints to better capture current trends, with overnight lows ranging from the upper 60s to mid 70s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... As a warm front pushes north across the area on Wednesday, a very humid airmass will usher in across the area with dewpoints rising into the lower 70s in southerly flow. A weak shortwave will interact with the warm front as it lifts north, which could spark a few morning showers and thunderstorms. Given the moist airmass, any thunderstorms will have the potential for gusty winds and local downpours, especially north across of our CWA. Thunderstorms will continue through Wednesday afternoon as an upper trough over the Great Lakes sends a cold front towards the area. Upper level jet support combined with mid level shortwave energy will initiate convective development during the afternoon. Forecast soundings showing >2000 J/kg of CAPE into the afternoon along with increasing shear with the incoming trough. With a favorable storm environment, the Storm Prediction Center has placed the area under a slight risk. Southwesterly flow will advect in precipitable water of near 2 inches, therefore heavy downpours are likely in any storm. Showers will continue through Wednesday night as the cold front approaches the area from the west. Temperatures on Wednesday will be in the mid to upper 80s to near 90. The combination of heat and increasing dewpoints will result in heat indices in the low to mid 90s with the exception of eastern Long Island and southeastern coastal Connecticut. Wednesday night lows will be in the upper 60s to lower 70s. There is a moderate risk of rip current development at ocean beaches for Wednesday. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Cold front slowly pushes through the area Thu into Thu night. Both GFS and NAM soundings are indicating a capping inversion around H8 which would limit shower/tstm activity. This inversion may weaken late in the afternoon and into the evening so have highest pops during this time, although only chc appear warranted at this time. The low chc showers continues Thu night as the front moves through. It should clear the area by Fri morning and appears to be far enough south to keep any pcpn associated with weak waves of low pres riding along it to the south as well. The heat and humidity will vanish as well as a Cp airmass is ushered in behind the front. Upper trough will remain over the Northeast into the weekend, although increasing subsidence from strong sfc high pres traversing eastern Canada will result in dry and pleasant conditions. Have maintained a dry forecast into early next week although an increasing easterly flow Sun/Mon could lead to low clouds and perhaps some drizzle or light rain at the coast. The 12z EC is also less progressive with the upper flow and is now cutting off the flow at H5 over the northeast. GFS does this as well but over the Northern Atlantic. If the former pans out, then there could be more shower activity around between Sun and Tue as it is slow to depart. Temperatures are expected to be below normal levels Fri through Mon, then near normal on Tue. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... A warm front passes this morning. A trough of low pressure develops this afternoon ahead of an approaching cold front, with showers and thunderstorms becoming likely. Mainly VFR this morning, except in possible patchy stratus, or with an isolated shower or thunderstorm. Coverage of showers and thunderstorms will increase this afternoon, with MVFR or IFR possible in any thunderstorm. Thunderstorm chances diminish later this evening. Southerly winds will be less than 10 kt early this morning, with winds light and variable at the outlying terminals. Winds increase to 10 to around 15 kt late this morning, with gusts to around 20 kt possible at the NYC terminals during the afternoon. Winds lighten from the SW this evening. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .Late tonight-Thursday night...Mainly VFR, MVFR or lower is possible in showers and thunderstorms. .Friday-Sunday...VFR. && .MARINE... Winds and seas will remain below SCA criteria through Wednesday with seas increasing to SCA criteria by Wednesday night ahead of a cold front. Winds and seas on the ocean waters may reach marginal SCA levels Sun into Mon due to an increasing easterly flow. Otherwise, sub-advsy conds are expected through the remainder of the period. && .HYDROLOGY... Locally heavy rainfall is possible with thunderstorms that develop Wednesday, which may result in localized flooding for urban and poor drainage areas. No hydrologic impacts are expected Thu through Tue. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off the air. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Fig/24 NEAR TERM...FEB/Fig SHORT TERM...Fig LONG TERM...24 AVIATION...PW MARINE...Fig/24 HYDROLOGY... EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.