Area Forecast Discussion
Issued by NWS Upton, NY

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507 FXUS61 KOKX 281139 AFDOKX Area Forecast Discussion National Weather Service New York NY 739 AM EDT Tue Mar 28 2017 .SYNOPSIS... A frontal system will approach today, and pass early Wednesday. High pressure will build in for Thursday, and drift offshore Thursday night. A low pressure system will impact the region Thursday night into Saturday. High pressure builds in Sunday and Monday. && .NEAR TERM /THROUGH TONIGHT/... Satellite indicates the main upper level system was moving over eastern Kentucky into West Virginia. Elevated instability was increasing across the forecast area evidenced by showers and thunderstorms. These should continue to develop per the NAM which appears to have a very good handle on the activity thus far. Fog was widespread, however, visibilities were generally 2 to 4 miles, with areas 1 to 2 miles. As the main system approaches this afternoon and evening, more showers can be expected. Some embedded thunderstorms cannot be ruled out until the instability axis exits, leaving remnant stratiform light rain. The models were in good agreement so a blend was used for temperatures through tonight. && .SHORT TERM /WEDNESDAY/... Dry weather with a northwesterly breeze. Despite a cooler airmass in place, temperatures will actually be warmer than Tuesday because of deep mixing. Mostly sunny skies are progged, although some fair weather convective clouds will be possible if they are able to overcome the subsidence. A blend of the guidance was used for temperatures. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The extended period will feature a split flow across the continental United States with systems moving through active northern and southern streams. As a result, even through there are similarities in the longwave and overall solutions, the details of the forecast have become more uncertain, and inconsistencies from run to run have increased. Currently there is now little to no phasing of systems impacting the east, and in particular the region, Thursday night into Saturday, and yet another system Monday night into Tuesday. There are now more uncertainties as to the depth of the lows, timing, and tracks. For late Thursday night through Saturday night have long period of probabilities, and even likely probabilities from Friday into Saturday. This is likely too long a period however, with the uncertainties wanted to maintain some consistency with prior forecasts. Both the ECMWF and GFS have some lingering cold air across the northern portions of the CWA Thursday night before warm advection increases. So have kept a mix of snow and rain inland. Canadian high pressure builds in for late Saturday night into Monday, and possibly Tuesday if ridging remains as per the GFS. The ECMWF is quicker to weaken and shift the ridge off shore Tuesday. Have introduced a low chance of precipitation for Tuesday. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... A front remains just south of the terminals and attempts to push back north as a warm front on Tuesday. Light ENE winds for Tuesday morning with areas of rain and low ceilings. LIFR conditions at times this morning, otherwise areas of rain this morning will result in IFR conditions at times, and then back down to LIFR when the rain lightens or stops. Another area of rainfall will arrive later in the day and for the evening. There is a thunderstorm chance with this next area of rainfall for the city terminals, but not confident enough to put in TAFS at this time. IFR to LIFR conditions are expected to prevail until about 6z late tonight, with improving conditions thereafter from west to east. 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: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. KLGA TAF Comments: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. KEWR TAF Comments: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. KHPN TAF Comments: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. KISP TAF Comments: Timing of next area of rain may be off by +/- 2 hours this afternoon. There is a thunderstorm chance late today but confidence is low. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .Wednesday...VFR. N-NW gusts 15-20KT. .Thursday...VFR. .Friday...A wintry mix possible early north and west with IFR conditions possible before a change to rain, otherwise sub VFR conditions with rain elsewhere. .Friday night and Saturday...Chance of rain with MVFR or lower conditions. E winds G20-25KT at coastal terminals for Saturday. && .MARINE... Winds and seas will remain below Small Craft Advisory levels through tonight. Patchy fog may limit visibilities to less than 1 NM at times today, but it is no longer expected to be widespread. The Dense Fog Advisory was therefore cancelled. Marginal Small Craft Advisory level winds are possible on Wednesday after the frontal passage. Small craft advisory conditions will be likely across the ocean forecast waters Wednesday night into Thursday, with strong and gusty northwest winds, as high pressure builds in behind a cold. Ocean seas will build Wednesday nigh into early Thursday and may be around small craft levels. In addition, occasional gusts across eastern Long Island Sound, and the eastern bays may be near small craft levels Wednesday night. Northwesterly winds will develop behind the cold front and then increase into Wednesday and Wednesday night as high pressure builds to the north. Minimal SCA conditions are possible across the ocean waters Wednesday night into early Thursday. Sub advisory conditions are expected late Thursday into Friday as high pressure moves across the waters. The next chance of small craft conditions will be late Friday through Saturday night as southerly winds increase ahead of a low pressure system. && .HYDROLOGY... Basin average rainfall of a half inch or less can be expected through tonight. Locally heavier amounts can be expected however in any thunderstorms that develop. Additional rainfall of 1/2 inch to 1 inch will be possible Thursday night through Saturday. No hydrologic concerns are anticipated. && .TIDES/COASTAL FLOODING... Astronomical tides remain high due to a recent new moon. Water levels may approach minor flood thresholds during the high tide cycles Thursday night, with minor flooding possible Friday night as a low pressure system approaches. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...12/MET NEAR TERM...12/MET SHORT TERM...12 LONG TERM...MET AVIATION...JC/JE MARINE...12/MET HYDROLOGY...12/MET TIDES/COASTAL FLOODING...

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