Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 131220 AFDOKX Area Forecast Discussion National Weather Service New York NY 720 AM EST Sat Jan 13 2018 .SYNOPSIS... Low pressure along a strong cold front move through the region early this morning. As the low moves northeast today high pressure will build to the west. The high builds to the west today into Sunday morning, then moves north Sunday afternoon into Monday night. Weak low pressure will pass across on Tuesday. A stronger offshore low will develop offshore mid to late week as high pressure builds to the west. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low pressure was over the region, along a strong cold front, and was quickly tracking to the northeast with the cold front moving through the region. Much of the precipitation has now moved north of the region with the possibility of some wrap around moisture across the region through early this morning. As the low and cold front move through this too will come to an end. With the colder air moving into the area the precipitation well inland may transition to a period of light snow and maybe some sleet before ending. Some snow melt will continue before temperatures fall back to near and below freezing. In addition runoff from the precipitation continues. However, the treat of flooding and flooding from ice jams has diminished and the flood watch has been cancelled. Tough forecast with the temperatures and dew points this morning. Highs for the calendar day occurred just after midnight, with daytime forecast highs likely to occur at 12Z/700 AM. Temperatures and dew points then fall through the day. Depending on how quickly temperatures fall below freezing and any remaining residual standing water a flash freezing will be possible. Remainder of the day will be dry and colder. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Upper troughing continues to build into the region tonight into Sunday as Arctic high pressure builds to the west. Winds chills late tonight into early Sunday morning will fall to below zero (-5) inland and to the single digits above zero elsewhere. Across the metropolitan area winds chills will be near zero for a time late tonight into Sunday morning. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Active and amplified pattern, with model discrepancies noted in pattern details, thus lower confidence in forecast details, especially beyond Tuesday. Aloft, longwave trough digs across much of the eastern United States, with western trough approaching. Closed low develops and traverses across the Appalachians next week. Trough axis makes slow eastward progress, with differences noted aloft on various medium range model progs by mid week. At the surface, center of sprawling high pressure passes to the north across SE Canada by Monday giving way to clipper low that moves across the Great Lakes region. Timing for this clipper low looks to be passing sometime Tuesday, with little QPF associated with it. Thereafter, coastal low development over the western Atlantic appears to be likely per ensemble consensus, but position remains in question, as does timing. There is the potential for a late Wed/Thursday impact to the area depending on exact track, which of course depends on eventual evolution of upper level trough/closed low. Overall, temperatures through this time frame remain below normal. Cold Sunday into Monday, then temps warm slightly Tuesday closer to seasonal norms. Once the coastal low develops, colder air will work back in with a return to below normal mid to late week. Sensible weather would be predominately snow Tuesday in a light QPF event, and certainly mid to late week if precip does indeed occur. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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Low pressure as lifted north of the terminals this morning. A cold front will push across the region this morning, followed by high pressure. Most of the precipitation has come to an end. There is a low end chance that KSWF sees some light wintry mix. Have covered this with a tempo group. Otherwise, expect gradual improvement today. Visibilities should quickly improve to VFR, however ceilings may may not reach VFR til late morning or early afternoon for NYC, and early to mid afternoon for points east. Winds become NW 15-20G20-30kt behind the front. Gusts may become occasional tonight. .OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY... .Sat night...VFR. NW winds diminishing to 10-15G20kt. .Sunday and Monday...VFR. .Tue and Wed...Chance of snow. IFR conds possible.
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&& .MARINE...
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The Small Craft Advisory will continue on the Eastern Sound and Peconic and Gardiners Bays til 10am and the coastal ocean waters through Sunday (mainly due to persistent swells Sunday). In addition, a Marine Weather Statement remains up til 9am for any leftover patchy dense fog. Otherwise, northerly winds today will turn toward the northeast as high pressure builds north of the waters. These winds shift around to the south by Tuesday, but through this period, winds remain under 15-20 kt. By Wednesday, winds shift back to the north of NW as a coastal low develops well south and east, and will likely increase closer to SCA thresholds by late in the day or at night. Lingering rough ocean seas Sunday should subside some as the winds remain rather light for a two day period, Sunday through Tuesday. Swells however could keep seas running around 4 or 5 ft on the ocean into Monday. Assuming seas subside late Monday and Tuesday, they will likely build yet again by Wednesday as offshore low develops. Non ocean waters remain rather tranquil, under 2 ft Sunday through Wednesday.
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&& .HYDROLOGY... No significant precipitation is expected. && .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 until 6 PM EST Sunday for ANZ350-353-355. Small Craft Advisory until 10 AM EST this morning for ANZ330- 340. && $$

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