Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 250912 AFDOKX Area Forecast Discussion National Weather Service New York NY 412 AM EST Sat Feb 25 2017 .SYNOPSIS...
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A cold frontal passage occurs this evening. High pressure then builds south of the area through Monday. A warming trend on Tuesday gives way to another cold frontal passage during the middle of next week.
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&& .NEAR TERM /THROUGH SUNDAY/...
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Fog will continue to be the main story this morning, primarily east of the Hudson River. High clouds appear to be limiting the westward extent of the dense fog development. A Dense Fog Advisory remains in effect for the Connecticut coast and Long Island, with the Bronx and coastal Westchester included. The cold front over eastern Ohio doesn`t reach the forecast area until after 21Z per the model consensus. With the the jet streak tracking into Canada and the best instability axis south of the region, there is a good chance the most significant convection will remain both north and south of the area. There will be some elevated instability as the differential positive vorticity advection comes through, and there could be some residual storms reaching areas west of the Hudson, so thunderstorms have been maintained in the forecast regardless. Outside of the thunderstorm chances, a band of rain should accompany the front with around a half inch of rain per the model consensus. The rain ends quickly overnight and northwest winds usher in a more seasonal airmass. Gusts up to 40 mph appear reasonable with around 35 kt at 850 millibars combined with the rising pressure. Mixing temperatures down on Sunday from 850 millibars yields upper 30s to around 40. Add a few degrees for the super near the surface and this yields highs right in the guidance ballpark, which was subsequently used for the forecast.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
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Initially, clear skies should allow for decent radiational cooling Sunday night. The challenge will be whether high clouds overspread the area early enough to keep temperatures from completely bottoming out, and how quickly the winds subside. For now, the forecast leans milder due to these two potential limiting factors, however the end result could play out 5 degrees or more colder. The system currently off the Pacific Northwest brings some dynamics through Monday and Tuesday. The airmass is modeled to be very dry limiting chances for precipitation at least through Monday. Thereafter, warm air advection aloft will increase chances for some rain as a warm front develops and lifts north of the Tri-State Region.
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&& .LONG TERM /WEDNESDAY THROUGH FRIDAY/...
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The GFS and ECMWF both bring a cold front through on Thursday, so chances for rain remain until the frontal passage. The model consensus breaks down on Friday. The GFS brings a clipper through, with the ECMWF holding off until the weekend. No changes have been made during this period, although the GFS suggests colder and snowier.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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A cold front approaches from the west into this afternoon, then crosses the area from late this afternoon into this evening. High pressure then builds in behind the front. Confidence is decreasing in IFR conditions making it east of the Hudson River, noting it is struggling to set hold at LGA. For now have delayed onset at KEWR/KTEB/KSWF until 11z, but it might occur later than that, if at all. Some doubts about LGA, but with LIFR literally on the doorstep, would think it should build in by 10z. East of the Hudson, LIFR/IFR conditions should continue through the morning, then maybe improve somewhat in the afternoon. West of the Hudson could remain VFR all day, however am not confident enough in this to place it in the TAFs at this time. Still appears that should see some thunder from city terminals on west late this afternoon/early this evening ahead of a cold front. Winds increase out of the SE-S this morning, become S at 10-15kt throughout by mid-late afternoon. Winds become gusty out of the WNW behind the front this evening, with gusts of 20-25kt expected. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late tonight...VFR. WNW winds G25 KT. .Sunday...VFR. NW winds G20-25KT likely. .Sunday night-Monday evening...VFR. W-SW winds G15-20KT possible. .Late Monday night-Wednesday...Chance of MVFR or lower.
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&& .MARINE...
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A combination of swells and winds increasing from west to east will bring seas to SCA levels over the two western zones this morning, and then on the eastern most coastal ocean zone this afternoon. Winds then increase on all waters tonight to small craft levels and continue on Saturday in response to low level cold advection. Looking at low level winds and they appear to generally stay below 35 kt, so do not have confidence in anything other than maybe some isolated 35 kt gusts on the coastal ocean waters. As a result, have converted the gale watch to a small craft advisory on the coastal ocean waters for tonight. I then extended the small craft advisory through the day on Sunday for all marine zones. SCA conditions could linger into Sunday night on the coastal ocean waters, eastern Long Island Sound and the bays of Long Island, and maybe into Monday for the coastal ocean waters east of Moriches inlet. The pressure gradient relaxes over the waters Monday night and remains fairly light into Wednesday, so sub-small craft conditions are expected from Monday night through at least Wednesday morning. There are some indications that small craft conditions could return to at least the coastal ocean waters by late Wednesday if the pressure gradient tightens over the waters as currently predicted.
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&& .HYDROLOGY...
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Around a half inch of rain with locally higher amounts can be expected through tonight. There will be chances for rain throughout next week, however widespread heavy precipitation is not expected at this time.
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&& .CLIMATE... The following are record high minimum temperatures for Saturday February 25, 2017 along with the forecast minimum temperature. Record High Min Temperature Forecast Min ------------------------------ ------------ Central Park........51 (1930) 56 LaGuardia...........49 (1996) 53 Kennedy.............46 (1996) 50 Islip...............47 (1996) 50 Newark..............47 (1996) 53 Bridgeport..........44 (1996) 50 && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Dense Fog Advisory until 11 AM EST this morning for CTZ009>012. NY...Dense Fog Advisory until 11 AM EST this morning for NYZ071-073- 075-078>081-176>179. NJ...None. MARINE...Dense Fog Advisory until noon EST today for ANZ330-335-338-340- 345-350-353-355. Small Craft Advisory from 6 PM this evening to 6 PM EST Sunday for ANZ330-335-338-340-345. Small Craft Advisory until 6 PM EST Sunday for ANZ353-355. Small Craft Advisory from noon today to 6 PM EST Sunday for ANZ350.
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&& $$ SYNOPSIS...12 NEAR TERM...12 SHORT TERM...12 LONG TERM...12 AVIATION...Maloit MARINE...Maloit HYDROLOGY...12 CLIMATE...

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