Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 232028 AFDOKX Area Forecast Discussion National Weather Service New York NY 328 PM EST Thu Feb 23 2017 .SYNOPSIS... A weak cold front approaches tonight and then retreats back to the north as a warm front on Friday. High pressure will remain steady over the western Atlantic through Friday night. A frontal system approaches Saturday and crosses the region Saturday Night. High pressure builds over the area during the early part of next week. A warm front moves through Tuesday, with the attendant low and cold front moving through by mid to late week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... The only stratus that remains is across the south coast of eastern Long Island and southeast Connecticut. Temperatures have warmed well into the 60s across the NYC metro, Lower Hudson Valley, and portions of interior Connecticut. A few 70 degree readings have also been observed in Orange County. Main concern tonight is the potential redevelopment/expansion of low stratus and fog. An unseasonably warm and moist airmass will remain in place. Light southerly flow will continue tonight and soundings continue to hint at moisture becoming trapped beneath an inversion. Overall, the setup is similar to last night/this morning so think fog will occur. However, the uncertainty lies in the timing and coverage. The best chance at dense fog is across Long Island and coastal Connecticut. Have held off on issuing a dense fog advisory at this time until trends this evening can be assessed. One factor that may inhibit widespread fog is the approaching shortwave and weak front. Some middle and high level clouds may stream across the region, which may lend to more of a low stratus situation than fog. This shortwave and weak boundary could spark a few isolated to scattered showers, mainly inland as there is some weak elevated instability present in model forecast soundings. Temps will be well above normal in middle 40s to near 50 degrees. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Weak frontal boundary retreats to the north as a warm front during the day on Friday. Models have come into better agreement with this scenario, which is reasonable given a stronger southerly flow developing ahead of system strong shortwave across the central states. Low stratus and areas of fog will start the day with potential for dense fog during the morning commute, especially near the coast. The forecast uncertainly lies with how quickly the low stratus and fog erode. As was the case on Thursday, it will likely erode away north and west of the coast by early afternoon and could linger near the coast into much of the afternoon. This will play a role in high temperatures. With anomalously warm air in place, highs should have no trouble reaching the middle and upper 60s north and west of the NYC metro. These numbers could be higher dependent on how quickly clouds erode. Further east, temperatures will likely be held down in the upper 50s and lower 60s due to onshore flow and longer duration of clouds/fog. Stratus and fog are once again possible Friday night with conditions remaining unseasonably warm. Some light rain or drizzle is also possible as a stronger onshore flow develops ahead of approaching cold front from the west. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Persistent low-level warm/moist advection will maintain a chance of stratus, patchy fog and drizzle beneath the inversion through Saturday morning. High temperatures will once again be close to 10 to 20 degrees above climatological normals, though perhaps a few degrees colder than Friday closer to the coast due to onshore flow. By Saturday evening, a potent vort max and attendant cold front approach the region. At this time it appears a narrow line of showers and perhaps a few thunderstorms will move through ahead of the front with a quick 0.25-0.50 inches of rain possible. A few stronger gusts may mix to the surface as the front passes, given wind speeds 30-40 kt just above the surface. Temperatures and dew points will slowly fall Saturday night, though will still remain above normal as winds remain strong and gusty through the night. The stronger winds will continue through Sunday, with high temperatures closer to climatological normals. High pressure will pass to the south Sunday night into Monday, with increased cloud cover between the high and an approaching area of low pressure to the west maintaining mild temperatures across the region. Thereafter, confidence decreases rapidly, though general consensus indicates a warm frontal passage Tuesday followed by increasing chances of precipitation ahead of the associated slowly approaching low pressure and attendant cold front. However, model differences are very large, as the systems for early to late week are still over the data sparse areas of the Pacific, and are not yet initialized well. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... High pressure will continue to drift eastward off the Mid Atlantic Coast during the day. A cold front approaches overnight tonight into Friday morning, before pushing north as a warm front on Friday. Stratus deck has eroded around the city terminals as of 19Z, and will eventually erode over the next hour or so across Long Island and CT terminals. MVFR and IFR conditions return tonight as fog and low stratus redevelop across the region. In addition, areas of drizzle or light rain showers are possible overnight. S-SW winds through the afternoon generally 10 KT or less. Winds then become light and variable again outside of the city tonight. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments:Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. KLGA TAF Comments: Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. KEWR TAF Comments:Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. KTEB TAF Comments:Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. KHPN TAF Comments:Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. KISP TAF Comments:Uncertainty with timing regarding lowering of ceilings and visibility this evening through overnight. .OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... .Friday-Saturday...MVFR to IFR in stratus and fog with periods of light rain and drizzle Friday morning. Conditions could improve to VFR for a period during the day on Friday before lowering again Friday night. .Saturday night...MVFR likely with rain. .Sunday...VFR. .Monday...VFR early...becoming MVFR. Chance of rain or snow. .Tuesday...Possible MVFR in showers. && .MARINE... Main hazard on the local waters through Friday night is potential for dense fog. Similar conditions to Wednesday night /Thursday morning are expected tonight with potential for dense fog to become widespread. Have held off on issuing an advisory at this time, but there is a possibility of one for overnight into Friday morning. Otherwise, high pressure over the western Atlantic brings a persistent southerly flow through Friday night, but winds and seas will fall below small craft levels. Winds and seas will increase to Small Craft Advisory levels Saturday ahead of a cold front, and likely remain elevated through Sunday following the frontal passage. Winds and waves will gradually subside Sunday night into Monday as high pressure moves south of the area. The next chance of Small Craft Advisory conditions will be Monday night into Tuesday as winds strengthen following a warm frontal passage. Winds and seas may remain at or near Small Craft Advisory conditions through late week ahead of a cold front. && .HYDROLOGY... A quarter to one half of an inch of rain is likely Saturday. No hydrologic impacts are expected through the next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MD/DS NEAR TERM...DS SHORT TERM...DS LONG TERM...MD AVIATION...CB MARINE...MD/DS HYDROLOGY...MD/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.