Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 232118 CCA AFDOKX Area Forecast Discussion...CORRECTED National Weather Service New York NY 418 PM EST Fri Feb 23 2018 .SYNOPSIS... A warm front moves across this evening, followed by a cold front early Saturday. Another low pressure system approaches for Saturday, with its warm front moving towards the region Saturday night. A low develops along it and this moves across Sunday. High pressure builds from the Midwest Sunday night and remains in control through the middle of next week. A frontal system then approaches for the end of the week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Going into this evening, the temperatures are expected to eventually rise after the warm front moves across. Expecting rain to continue into this evening. Temperatures are pretty much all above freezing with valley soil temperatures in the mid to upper 30s. Through tonight, the main upper level jet stream stays in Southeast Canada near the US border, but will become relatively more zonal. Likewise, in the mid levels, the flow will become more zonal as the ridge off the Southeast US becomes more suppressed with local height falls across the local region. At the surface, a warm front will be moving across this evening as winds switch from a more easterly flow to a more southwest to west flow. Expecting min temperatures to be set early this evening with rising temperatures late this evening and then remaining nearly steady overnight. Rain continues into this evening with the strongest isentropic lift. This lift diminishes by mid to late this evening and with that, rain will be exiting east of the region. Expecting also some patchy fog across the region for the first half of tonight before that more westerly flow develops and for the interior expecting the patchy fog to persist a few extra hours as winds will be lighter. Drier conditions on that more westerly flow can be expected for the remainder of the night. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/... This weekend features a strengthening upper level jet from Baja California extending northeast through the Great Lakes and Northern New England. The jet itself approaches closer to the region on Sunday, with the local region getting close to the right front quad of the upper level jet. The mid levels convey a ridge moving in with its axis oriented southeast to northwest with a nearly steady height tendency Saturday into Saturday evening. A shortwave from the Southwest US will travel and pivot into the Great Lakes Saturday night into Sunday morning. Then for Sunday, this shortwave further pivots into Ontario. At the surface, another low pressure system developing in the South Central US will have its associated warm front approaching. The day starts out dry but there will be increasing chances of rain in the afternoon from southwest to northeast as this warm front approaches and with some forecast increase in isentropic lift aloft. Used a blend of MAV and ECS MOS for high temperatures, getting well into the 50s as a light northwest flow acts as a downslope for adiabatic warming from higher temperatures aloft. Saturday night into Sunday will be the bulk of the rainfall. The warm front will be approaching and with the parent low heading into the Western Great Lakes and deepening, an increasing easterly flow will take place. This will load the atmosphere with more moisture as layer precipitable waters are forecast to increase to 1.1 to 1.4 inches. This will facilitate at times moderate to perhaps heavy rain. For temperatures, Saturday used the relatively warmer blend of MAV and ECS MOS as well as NAM12 2 meter temperatures, mid 30s to near 40. For Sunday, with rain much of the day used GMOS with 2 meter temperatures of GFS and ECMWF, showing a range from the low 40s to near 50. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... The general North American pattern of troughing in the west and ridging east of the Rockies looks to continue into next week. The upper pattern starts to diverge mid to late week next week as a closed low pres system moves onshore in California and continues into the Plains. The EC is much slower than the GFS, but has support from the CMC, therefore this idea was preferred, but there is low confidence in the details late next week since there is also large spread in the GEFS and ECENS. In terms of sensible weather, dry weather returns Sun night as low pres departs and high pres builds from the Midwest. The high will remain in control through the middle of next week, resulting in a continuation of above normal temperatures. Rain chances will begin to increase Wed night as a WAA pattern ensues, although due to the aforementioned uncertainty in the upper pattern, rain could very well hold off until Thu night. Have scaled back on the previous forecasts PoPs a bit in light of the 12z data and the large amount of uncertainty. At this time, atmospheric profiles suggest pcpn starts as rain, with colder air aloft working in late Thu night/Fri. This may be enough for a brief period of a wintry mix across locations N of NYC. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... High pressure over the Canadian maritime and extending along the northeast coast moves east as a wave of low pressure passes to the south of Long Island through 05Z Saturday. High pressure then builds to the north through Saturday. Conditions have lowered to IFR with light rain and fog. IFR to LIFR conditions will prevail into this evening. The rain ends late tonight with conditions improving to MVFR, then back up to VFR after 10Z Saturday, and remaining VFR through Saturday. E winds become SE this afternoon 10 kt or less. Winds diminish this evening, possibly becoming light and variable before becoming NW Saturday morning. A brief period of LLWS is possible 02Z to 07Z. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Varying ceilings from IFR to LIFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. KLGA TAF Comments: Varying ceilings from IFR to LIFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. KEWR TAF Comments: Varying ceilings from IFR to LIFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. KTEB TAF Comments: Varying ceilings from IFR to LIFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. KHPN TAF Comments: Varying ceilings from LIFR to IFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. KISP TAF Comments: Varying ceilings from IFR to LIFR this evening. Low confidence in IFR ceiling heights. Marginal confidence in LLWS. .OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY... .Saturday afternoon...VFR. Becoming MVFR late in the afternoon with a chance of rain. .Saturday Night-Sunday...MVFR/IFR in rain. E wind 10-15kt, G20-25kt. .Sunday night-Wednesday...VFR. && .MARINE...
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With a decreasing pressure gradient, winds will further decrease and likewise the seas are expected to continue to decrease as well into this evening. The more westerly flow late tonight will briefly increase winds but wind gusts are just marginal with meeting SCA criteria. With further offshore flow, expect sub SCA conditions to continue. Sub-SCA conditions are expected and this continues through Saturday evening. SCA conditions look quite probable late Saturday night into Sunday with the possibility of gales as well on the ocean for Sunday morning. Hazardous ocean seas are expected to continue into Mon, with sub- advsy conds thereafter with high pressure building from the west.
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&& .HYDROLOGY... Less than a quarter inch of rain is expected through tonight. The next event Saturday into Sunday is expected to produce around 0.75 to 1.25 inches of rain. There could be some locally higher amounts especially in any areas of orographic lift with the higher terrain. Ponding of water and minor nuisance could be localized for Sunday. && .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 4 PM EST this afternoon for ANZ350- 353-355. && $$ SYNOPSIS...24/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...24 AVIATION...19 MARINE...24/JM HYDROLOGY...24/JM EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.