Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 220901 AFDOKX Area Forecast Discussion National Weather Service New York NY 401 AM EST Mon Jan 22 2018 .SYNOPSIS... A warm front stalls across the area today, before shifting northward tonight into Tuesday morning. A cold front quickly follows for Tuesday evening. High pressure builds during the mid and late week period. The high moves east next weekend ahead of a cold front that likely passes sometime Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Weak isentropic lift ahead of the approaching warm front has led to the development of some light showers and patchy drizzle across the area this morning. Model forecasts indicate the potential for minimal drier air above the surface to advect eastward in westerly flow later this morning into the early afternoon, which may help at least decrease the coverage of showers, though patchy drizzle will remain possible at times. Temperatures will largely by the most difficult portion of the forecast today. In general, above normal temperatures will continue in subtle warm advection, though daytime highs are expected to be cooler than over the weekend. Highs will depend on the northward progression of the warm front, which typically ends up stalling across Long Island. Cold air damming to the north of the front, primarily across the Lower Hudson Valley and Connecticut in combination with the overcast skies and light drizzle will likely keep temperatures a few degrees below guidance. Farther south across northeastern NJ, the NYC metro and Long Island, there is some potential for temperatures to be higher than guidance/forecast if the warm front progresses northward faster. Trends will be closely monitored. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Well above normal temperatures are expected for tonight as overcast skies and warm advection prevail. A non-diurnal trend will occur as the warm front begins to shift northward through the area. Similar to the uncertainties of Monday, low temperatures will largely depend on the speed in which the warm front passes to the north, while highs will be around 10-15 degrees above climatological normals as the front moves through. After the passage of the front, low-level mass response to the potent upper short wave will allow for quick moisture advection, with southwest flow just above the surface ranging from 50-70 kt. Deep layer moisture represented by precipitable water values around 1-1.20 inches will be potentially close to a climatological maximum for this time of year, setting the stage for periods of moderate to locally rainfall. With strong warm advection in the low- levels and cooling temperatures aloft with the approaching upper short wave, there will be a period of at least marginal elevated instability, which will support thunderstorms and locally heavy rainfall. Should temperatures rise enough at the surface to lead to a weakened inversion, there is potential for the stronger winds above the surface to mix down in any thunderstorms. Regardless, a tight pressure gradient will lead to strong winds across the area through the day. With deep-layer flow strongly veered initially, expect heavy showers to be scattered in nature. As the front approaches, low- level flow will veer, creating a more unidirectional deep- layer profile oriented along the boundary that may support the development of a line of showers and thunderstorms. Thereafter, precipitation will rapidly decrease from west to east following the frontal passage. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The main question among available guidance is speed of downstream trough as is passes across the country. The GFS not surprisingly remains on the faster side of the guidance. ECMWF is trending quicker, while ensemble guidance suggests a slightly slower progression east. This obviously impacts surface features and associated cold front as well. Overall, dry weather prevails Tuesday night through early Saturday, and quite possibly through Saturday night. Any lingering rain with the cold front Tuesday evening quickly ends. Upper shortwave passes across the northeast, and is followed by another weak upper level shortwave Wednesday night, with little fanfare with this second shortwave. Then ridge builds ahead of aforementioned trough next weekend. Dry forecast until Saturday night/Sunday. Capped pops at high chance Sunday due to timing uncertainty. Temperatures return to near normal as CAA ensues behind the cold front. It may take some time for the colder air to settle in, which likely happens behind sfc trough associated with second shortwave, so readings may eclipse seasonal norms Wednesday before falling back closer to seasonal norms Wednesday night through Friday. Then temps rebound to above climo in return flow ahead of trough, cold front next weekend. Due to this warmup, plain rain is expected with the next system. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... A warm front will likely remain fairly stationary across the NYC metro and LI terminals today, moving slowly through the region tonight. Exact timing and placement are uncertain, but it appears the front will likely stall south of KTEB, KLGA and northern terminals through this evening. MVFR conditions develop early this morning with drizzle, light rain, and fog. Conditions likely lower to IFR for the terminals mentioned north of the front during or just after the morning push, and likely continue through the evening push. Meanwhile the terminals south of the front (KJFK, KEWR, KISP) likely remain MVFR and possibly briefly improve to VFR in the aft/eve. Winds will be light se for terminals to the south of the warm front, and light ne to the north. ...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: Light SE winds likely, with MVFR conditions possible for morning and evening push. The afternoon KJFK haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KLGA TAF Comments: Light NE winds and MVFR conditions likely for morning and evening push. Low probability for IFR conds for evening push. The afternoon KLGA haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KEWR TAF Comments: Light SE winds likely, with MVFR conditions possible for morning and evening push. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: MVFR conds possible for morning push. Light ne winds and MVFR conditions likely for evening push. KHPN TAF Comments: MVFR conditions likely for morning push, with IFR conditions possible. IFR conds likely for evening push. Light e/ne winds through the period. KISP TAF Comments: Light SE winds likely, with MVFR conditions possible for morning and evening push. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Late Tonight...IFR. LLWS developing toward 12Z. Showers become likely. .Tuesday...IFR/LIFR in SHRA, isolated TSTM possible. LLWS. S winds G25-30KT. 30 to 35 kt possible for KISP/KGON. .Tuesday Night into Wednesday...VFR. WNW G25-30KT. .Thursday-Friday...VFR. && .MARINE... With light flow across the area as the warm front approaches, expect seas to remain tranquil through much of the day. A rapid shift in conditions will then occur later tonight as the warm front slowly moves north of the waters. South- southwest flow will rapidly strengthen, with at least SCA-level winds developing late tonight. Depending on the strength of the inversion, there is potential for strong low-level jet winds to mix to the surface, with at least isolated gale-force winds on Tuesday. Gale-force winds will also be possible in any thunderstorms that can develop. A gale watch remains in effect. Seas will rapidly build in response to the strengthened flow, remaining elevated even as the cold front moves through Tuesday evening. Winds may briefly drop off as the front moves through, before rapidly strengthening again following its passage. A wind shift to the west occurs behind the cold front Tuesday night, and SCA level winds in the 25 to 30 kt range are expected. A few gale force gusts are possible, but not too confident in this happening. By Wednesday, gusty westerly winds persist as the pressure gradient remains rather tight. A trough moves through Wednesday evening, and winds shift to the NW, and remain gusty through Thursday. High pressure finally approaches from the west, and winds should diminish as the high draws closer Thursday night and Friday. Rough ocean seas Tuesday night and Wednesday gradually subside Wednesday night and Thursday, but likely do not subside below 4 ft until the winds diminish Thursday night and Friday. In fact, seas are expected to be rather tranquil Friday. For the non ocean waters, choppy waves/seas subside Thursday and Friday as the high approaches. && .HYDROLOGY... Total rain Monday night through Tuesday is expected to range mostly 1/2 to 1 inch, with locally 1 to 2 inches possible. No significant hydrologic issues are anticipated at this time. No hydrologic impacts are anticipated Wednesday through early next weekend. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 6 AM to 6 PM EST Tuesday for ANZ335- 338. Gale Watch from Tuesday morning through Tuesday afternoon for ANZ330-340-345-350-353-355. && $$ SYNOPSIS...MD/PW NEAR TERM...MD SHORT TERM...MD LONG TERM...PW AVIATION...NV MARINE...MD/PW HYDROLOGY...MD/PW EQUIPMENT...

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