Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 160145 AFDOKX Area Forecast Discussion National Weather Service New York NY 845 PM EST Thu Feb 15 2018 .SYNOPSIS... A warm front stalls to the north tonight, then pushes back south as a cold front late tonight and Friday morning. A second cold front races to our south Friday afternoon and evening, followed by high pressure building in Friday night. Quick moving low pressure passes south and east late Saturday and Saturday night. High pressure then returns Sunday into early Monday. A warm front moves through late Monday followed by a slowly approaching cold front through midweek. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Cloud cover broken to overcast across much of the forecast area with warm front pushing into the region. Therefore adjusted temperatures upward. Dew points were also increasing or holding steady, so also raised dew pints through early this evening. Used a blend of previous forecast and higher res guidance to adjust model catch up to short term persistence / past performance. Most of higher res guidance has patchy and area of fog coming back quickly this evening, more so for CT and Eastern LI into this evening. This fog could become locally dense, for these areas which is something that will have to be watched early tonight before the rain sets in. Adjusted, slowed, the onset of rain by a few hours, as area of precipitation remains to the west with the better frontal forcing. It will be a quick slug of 700mb dynamics with a good chunk of the area seeing moderate rainfall from the 4z to 9z time period. Lift is briefly impressive and cannot totally rule out a rumble of thunder across NE New Jersey with LIs approaching 0 here, but not confident enough to officially mention. With a series of 700 hPa shortwaves crossing the area late tonight into early Friday morning triggering periods of light to moderate rainfall did not try to time multiple periods of moderate rain, although the rain will pulse a bit while getting on the edge of enhanced stratiform, slantwise convective activity. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... The cold front will push through during Friday morning, with timing for now 14-16z for the city. Some lingering jet dynamics and with pulses of energy just south of the region through the early afternoon decided to trend down with rain probabilities through the morning, with complete shut off by early afternoon across Eastern LI. Clouds will persist through much of the day, but with airmass change and improved CAA behind a second cold front the more discernible clearing will wait until late in the day and into Friday evening. Turning noticeably colder after midnight into Saturday morning as temperatures return closer to normal for this time of the year. && .LONG TERM /SATURDAY THROUGH THURSDAY/... A progressive flow across the continental United States prevails through this time frame, with amplification by early next week as east coast ridge builds. This ridge could very well bring record warmth to the area next week. Prior to that, a fast moving low is the focus. Looking at the passing low Saturday night, latest analysis of model runs shows a deeper low, further north per nam/wrf when compared to GFS, ECMWF and Canadian NH. Thus QPF is more robust. Assuming this is an outlier, which would result in lower qpf amounts, then attention turns to Ptype. Agree wholeheartedly with previous shift`s analysis, much of it below. Trend has been north, and warmer with various guidance. So a hedge toward lower amounts right along the coast. The weaker GFS solution is likely due to its poor handling of cold air damming east of the Appalachians as high pressure quickly races to the east on Saturday. The location of the high is clearly not ideal for damming, nor for a moderate to heavy snow event. However, the fast development of the low along the Mid Atlantic coast late Saturday afternoon, which quickly passes to the southeast, may only result in a short period of weak onshore flow as the high moves off the New England coast. A SE flow along the coast is typically a snow to rain event, but in this case a rain/snow mix at the onset may go to all snow somewhat quickly as winds shift quickly to the NE. In addition, a deep- layered W-SW flow does not look to erode the cold air aloft, with the main question thus being the boundary layer temperature, through about 1-2 kft. With about quarter to half inch of liquid across the area (possibly up to 3/4 of an inch??), there is the potential for advisory level snows (2 to 4 inches) for much of the region. 3 to 6 north and west of I95, with less near the coast. Cannot rule out a low end warning event (around 6 inches). This depends on exact track, as a further south track places highest QPF along the coast. The best chance for this to occur would be along or just inland from the coast due to the higher QPF forecast, provided the event can be mainly in the form of snow. Temperatures are forecast to be in the 20s inland and in the lower 30s along the coast. So in summation, 1 to 3 inches near the coast, 2 to 4 inches as you head NW, with 3 to 6 across the interior. Highest amounts likely across interior srn CT, New England. Collab with WPC, and surrounding offices. Thereafter, a significant warmup ensues through the middle of next week with a deep-layered SW flow to develop as high pressure strengthens off the eastern seaboard. Highs Tuesday and Wednesday may get to around 60 across parts of NYC and the interior, but it will be considerably cooler along the coast due an onshore flow. A backdoor cold front passes late Wednesday or Wednesday night, with some cooling expected by Thursday, albeit still above normal. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/...
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A warm front moves across the terminals tonight followed by a cold front on Friday. Mainly VFR to start the TAF period. There may be some pockets of MVFR visibility at times ahead of developing rain. The rain moves in 02-04z with conditions gradually lowering to IFR. Have delayed the timing of IFR conditions until after 06z at most locations except for KBDR and KGON. LIFR is also possible at times. The rain ends Friday morning with conditions gradually returning to VFR after 12z. Light S-SW winds tonight will increase and veer to the NW friday morning. NW winds become gusty 20-25 kt Friday afternoon. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday Night...VFR. NW winds G25KT diminishing. .Saturday...VFR. .Saturday Night...IFR with snow inland/rain-snow mix coast. .Sunday...Becoming VFR in the morning. .Monday...Chance of rain with MVFR or IFR possible. .Tuesday...MVFR or IFR early, otherwise VFR with SW wind G20KT possible.
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&& .MARINE... Minor adjustments to the seas on the ocean waters through this evening, keeping seas below 5 feet until toward 05Z. Also changed areas of fog to patchy as fog is not as widespread as seen on satellite imagery. Expect seas to remain just below 5 ft this evening, then increase in response to a persistent SE-S swell. Initially sub- Small Craft Advisory (SCA) conditions are expected on all coastal waters, followed by climbing seas and SCA criteria being met on ocean waters with a tightening pressure gradient. Winds increase to up to 15 kt, to occasionally 20 kt late and help to build seas on the coastal ocean waters to SCA levels. SCA level seas should persist into at least Friday evening, with SCA wind gust over the coastal ocean waters most likely Friday afternoon/evening. On the non-ocean waters, there is a chance for gusts to SCA levels from Friday afternoon into Friday night, but confidence in this is not as high as for SCA conditions for the coastal non-ocean waters at this time. Therefore the Small Craft Advisory remains up only for the coastal ocean waters from midnight tonight through midnight Friday night. If confidence increases, there is a potential for an SCA to be issued for parts of the non- ocean zones for Friday afternoon/ Friday night as well. NW gusts 25 to 30kt are likely to continue through the first half of Friday night behind the cold front, then subside late Friday night. Tranquil winds shift around to the east/SE Saturday as high pressure passes to the north. The winds back around to the NE/N as low pressure passes to the south Saturday night. Low prob for SCA gusts over the ocean this time frame depending on strength of the low and track. High pressure builds quickly Sunday, then passes to the south Sunday night. Winds back around to the south as a warm front passes and the high moves east. The strengthening southerly winds Tuesday should allow seas to build to 3 to 5 ft on the ocean waters. && .HYDROLOGY... Around a 1/2 inch of rain is expected from tonight into Friday morning. No hydrologic impact is expected. It should be mainly dry Friday night and Saturday. Liquid equivalent precipitation Saturday night into early Sunday is expected to range from 1/4 northwest to around 1/2 inch through coastal Connecticut and across Long Island. However, no hydrologic impacts are anticipated this weekend into early next week. && .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 midnight tonight to midnight EST Friday night for ANZ350-353-355. && $$ SYNOPSIS...JE/PW NEAR TERM...JE/19 SHORT TERM...JE LONG TERM...PW AVIATION...DS MARINE...JE/PW HYDROLOGY...JE/PW EQUIPMENT...

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