Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221144 AFDOKX Area Forecast Discussion National Weather Service New York NY 744 AM EDT Mon May 22 2017 .SYNOPSIS... High pressure moves east of the area today ahead of a cold front approaching from the west. The front moves through tonight followed by brief high pressure for tomorrow ahead of an area of low pressure that will pass to the south Tuesday night. Another low and frontal system approaches Wednesday and Thursday, and passes to the east late in the week and into the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Rain moving east across the area early this morning. Expect a brief break northern zones this morning before more rain moves in from the south this afternoon. Precipitation may be moderate at times through the afternoon as a short wave moves through the area and warm/moist advection increases. Forecast soundings indicate minimal elevated instability in the temperature range supportive of charge separation, so an isolated thunderstorm is possible. Outside of the afternoon, model sounding profiles generally lean more towards a stratus/drizzle profile which should help to reduce overall rainfall amounts. Additionally, deterministic and ensemble models have trended southward with the heaviest rainfall, which may now skirt south of Long Island. Have reduced total QPF values to reflect these trends, with rainfall totals now expected to be around 1 to 1 and 1/2 over a broad period from today through Tuesday morning. Minor urban flooding of low lying poor drainage areas is possible, primarily associated with any locally heavier downpours that may occur with isolated thunderstorms. As southeast winds continue blowing off the cool Atlantic Ocean, day time temperatures will range 60-65 degrees. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... By evening, rainfall will gradually decrease from west to east. There may be a brief period of fog as moisture remains beneath the inversion until the cold front moves through leading to drier conditions overnight. Low temperatures will be closer to climatological normals due to cloud cover and initially strong winds that will gradually decrease through the morning. Although a short wave is progged to move through the region Tuesday afternoon, forecast upper divergence appears supportive of a more southerly track of a developing surface low, which should limit overall rainfall totals across the area. Much of the day may remain dry through the day. Temperatures will be warmer due to offshore flow, with highs closer to or slightly below climatological normals. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Still note some differences in upper level pattern, with regard to handling large midwest trough that eventually ejects to the east, kicked by upstream low. This trough/closed low passes overhead by Friday, then moves east next weekend. Weak ridge builds behind. For the Tuesday night-Wednesday time frame, shortwave embedded in broad southwest flow passes Tuesday night into early Wednesday. A wave of low pressure at the surface passes to the south, and the local area could get clipped with rain, with best chance along the coast, and less of a chance as you head north and west. NWP suite is now tracking this low similarly. Dry air in the lower levels, along with best lift to the south may preclude much in the way of rain for our area. Once that wave passes, dry weather should return briefly, although cannot rule out an isolated shower Wednesday. Then, the next chance arrives Thursday as the upper trough tracks east, approaching the area. Surface low and front approach, and showers will be likely Thursday into Thursday night based on latest model timing. Warm front likely remains just south of the area Thursday, with sfc low and occluded front passing Thursday night. Weak instability noted, so will maintain thunder mention. Depending on how this trough evolves, there could be lingering instability showers/thunderstorms Friday as the system moves across the northeast. Much uncertainty next weekend, but dry weather should prevail Saturday for the most part, with Sunday less clear due to model differences in timing of next upstream shortwave/sfc warm front. ECMWF still the more progressive model with this feature Sunday. Daytime highs will be near or just below normal mid week, then warm a few degrees closer to normal levels late in the week into next weekend. At night, lows will run around 5 degrees above normal late in the week and through the weekend. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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A weak frontal system will move across the area the next 24 hours. Ceilings will gradually lower to IFR through late morning into early this afternoon and then remain through most of tonight. There is uncertainty with the timing of lowering conditions as well with the rain. SE winds 5-10 kt gradually increase, generally 8 to 13 kt. Occasional gusts up 15-18 kt possible today. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http:/ KJFK TAF Comments: Onset of IFR conditions could vary by several hours. Winds may back more easterly. KLGA TAF Comments: Onset of IFR conditions could vary by several hours. Winds may remains more east. KEWR TAF Comments: Onset of IFR conditions could vary by several hours. Winds may back to the E/NE in the late afternoon. The afternoon KEWR haze potential forecast is YELLOW, which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Onset of IFR conditions could vary by several hours. Winds may back to the E/NE in the late afternoon. KHPN TAF Comments: Onset of IFR conditions could vary by several hours. KISP TAF Comments: Onset of IFR conditions could vary by several hours. Winds may remain more easterly. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .TUESDAY...Becoming VFR in the morning. Possible late day rain near the coast. .WEDNESDAY...VFR. .THURSDAY...Possible IFR conditions in rain. Slight chance of thunderstorms Thursday evening. .FRIDAY...MVFR or lower possible in showers.
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&& .MARINE... A warm front approaches today, followed by a cold or occluded front tonight. SE winds should remain below 25 kt or SCA thresholds. These winds shift to the S, then shift all the way around to the NW or N late tonight. A wave of low pressure passes south of the waters Tuesday night into Wednesday. Then a warm front approaches Wednesday night and Thursday. Low pressure tracks across the waters Thursday night and moves east by Friday. Shifting winds are anticipated through the period in this somewhat active pattern, but speeds should remain below SCA thresholds. Seas on the other hand may remain elevated across the ocean waters on the backside of the first low Wednesday, and again behind the second stronger low Friday. Otherwise, seas remain rather tranquil through the mid to late week period. && .HYDROLOGY... Rainfall accumulations of a half inch to one and a half inches is possible from today through Tuesday morning. Minor urban flooding of low lying poor drainage areas is possible. Unsettled weather is expected mid to late week, but no hydrologic impacts are anticipated at this time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MD NEAR TERM...MD/PW SHORT TERM...MD LONG TERM...PW AVIATION...DW MARINE...MD/PW HYDROLOGY...MD/PW is the U.S. government's official web portal to all federal, state and local government web resources and services.