Area Forecast Discussion
Issued by NWS Upton, NY

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830 FXUS61 KOKX 240245 AFDOKX Area Forecast Discussion National Weather Service New York NY 945 PM EST Fri Feb 23 2018 .SYNOPSIS... A warm front moves across overnight, 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/... The fcst is generally on track, although the warm front is still a good distance from the area and will be slower to arriver than previously fcst. It was 61 degrees at KPIT at 9pm. The front will be moving across overnight as winds switch to a more southwest to west flow. Expecting some fog across the region for at least the first half of tonight before that more westerly flow develops. The 00z OKX sounding indicated a saturated airmass up to about 4500 ft. This deep moist layer is likely limiting the density of the fog. Still, with winds slackening off significantly there could be some pockets of dense fog to develop. 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 /03Z SATURDAY THROUGH WEDNESDAY/... High pressure builds to the north through Saturday as a frontal boundary remains stalled to the south. Conditions are predominantly IFR-LIFR in stratus and fog tonight, but gradual improvement is anticipated overnight as high pressure and drier air moves back in. Although VFR conditions will be possible by the early part of Saturday, rain will once again approach from the west by evening, with MVFR conditions possible. Winds diminish tonight, possibly becoming light and variable before becoming NW Saturday morning. A brief period of LLWS is possible through 07Z. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .Saturday Night-Sunday...MVFR/IFR in rain. E wind 10-15kt, G20-25kt. .Sunday night-Wednesday...VFR. && .MARINE... 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. && .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 flooding 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...None. && $$ SYNOPSIS...24/JM NEAR TERM...JMC/JM SHORT TERM...JM LONG TERM...24 AVIATION...MD/19 MARINE...24/JM HYDROLOGY...24/JM EQUIPMENT...

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