Area Forecast Discussion
Issued by NWS Upton, NY

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KOKX 270131 AFDOKX Area Forecast Discussion National Weather Service New York NY 931 PM EDT Wed Oct 26 2016 .SYNOPSIS... High pressure across the region moves east late tonight as a warm front approaches from the southwest. A frontal system moves through the Great Lakes and northeast Thursday and Thursday night. High pressure builds in on Friday and lasts into early Saturday. A cold front moves through late Saturday, followed by a weak low passage to our south on Sunday. High pressure then returns early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Made some adjustments to increase cloud cover based on the latest satellite images. Otherwise, the forecast was on track and no other major changes were made. The center of high pressure will be passing well to the north, across southern Canada, tonight as a warm front approaches from the southwest. Winds are expected to decouple inland late this evening and late tonight while along the coast some gradient is expected to remain with a northerly flow veering to the east. Also, high clouds were already overspreading the CWA, to be followed by a mid deck late tonight. While there will be a period of radiational cooling, conditions will not be ideal. As a result went a little higher with overnight lows especially along the coast. This conditions will preclude the formation of any frost. Also, temperatures mostly above freezing along the coast. Will not have any frost or freeze hazards tonight. With weak warm advection set to begin after 06Z and a warm front approaching, light precipitation will be possible across the western zones around 06z. Temperature profiles support a chance of light snow inland and a mixture of snow and sleet, possibly rain into northeastern New Jersey. The warm air above freezing looks to move in too late for a chance of freezing rain. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... As the warm front approaches Thursday morning a mixture of snow, sleet and rain will be possible farther to the north and east. And as the warm air aloft rises to above freezing surface temperatures are also expected to rise to above freezing, so again will not mention any freezing rain. If the warmer air at the surface is not scoured out there will be a chance of a brief period of freezing rain. This will be possible as the parent low remains well to the west and north, and another low begins to develop along the triple point around 15Z. The warm front itself looks to move through the coastal areas by Thursday afternoon and transition from stratiform to convective precipitation. Along the triple point and developing low lift will be increasing and a moderate rainfall along the coast will be possible late in the afternoon and into the evening. The coastal areas destabilize Thursday evening with lifted indices falling and showalters zero to minus two, so will have a mention of thunder along the coast. The low is moving a little quicker than previous forecasts and will be ending precipitation after 06z Friday. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Trends in the latest model and ensemble data continue to indicate that the strong shortwave and its associated low pressure system will be east of the region Friday morning. The atmosphere dries out quickly around day break, so will continue to go with a dry forecast after 12z. Ridging builds aloft behind the shortwave and high pressure takes hold at the surface. The gradient between the departing low and building high will set up a breezy day with NW winds gusting 25 to 30 mph. High temperatures will be slightly below normal in the middle and upper 50s. The synoptic pattern will be progressive for the upcoming weekend with middle and upper ridging moving east on Saturday and a northern stream shortwave approaching from the northwest during Saturday. The cold front associated with this shortwave looks to swing across Saturday night. There are some differences among the latest guidance with how much the shortwave will dig into New England. The overall trend in the last several runs is for the shortwave and its energy to pass to the north. The system also will have limited moisture to work with, so have continued with slight chance PoPs. SW flow ahead of the front will help increase temperatures into the lower 60s for high temperatures. The front should settle to the south of the region late Saturday night into Sunday. However, the 12z ECMWF stalls the boundary a little closer to the region than the other models. There is a general agreement among the models that another shortwave will also pivot across the region on Sunday. The ECMWF is the furthest north with a weak low developing on the frontal boundary, with the rest of the deterministic models further south across the Carolinas. There is an approaching 80 kt jet at 300 hPa late Sunday and the region will lie near the left exit region. Do not want to remove the slight chance PoP at this time with the shortwave, and approaching upper jet. In any case, moisture is limited so do not expect any significant precipitation. High temperatures on Sunday will be near normal. The shortwave quickly departs to the east Sunday night with ridging rebuilding aloft Monday into Tuesday. High pressure will also return at the surface. Temperatures may fall a bit below normal on Monday before returning to near normal levels on Tuesday. Uncertainty increases late in the period as another cold front may approach Wednesday. However, there is low confidence in the timing of this system as the GFS may be breaking the ridge down too quickly. For now have just followed a model consensus on Wednesday with temperatures above normal and dry conditions. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... High pressure moves across the area tonight and then gives way to a low pressure system approaching from the Ohio valley on Thursday and crossing Thursday night. Light N/NW veer to the NE overnight and then E/SE on Thursday. E/SE winds increase Thursday afternoon with gusts. Mid and high level clouds will work in from the west tonight and then lower toward morning with light rain developing around daybreak. At KSWF...precip could start as a period of wet snow with little to no accumulation expected. There is a low chance of any freezing rain and/or sleet. MVFR conds likely develop from west to east during the late monring into early afternoon with steadier light rain...dropping to ifr in the late aft/eve in moderate rain. Timing of deteriorating conds may be off by 1 to 2 hrs...depending on how quickly the low- levels moisten. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. KLGA TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. KEWR TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. KTEB TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. KHPN TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. KISP TAF Comments: Timing of deteriorating conditions may be off by 1 to 2 hrs. .OUTLOOK FOR 00Z FRIDAY THROUGH SUNDAY... .Thursday Night...IFR or lower conds in rain in the evening...improving to VFR in wake of cold frontal passage after midnight. SE winds 10 to 20 kt with gusts to 25 kt Thu Eve...shifting to W in wake of cold frontal passage. .Friday...VFR with strong northwest flow behind a cold front. Gusts 25-30kt. .Saturday...VFR with gusty southwest flow possible. Low chance of showers Saturday afternoon/evening. .Sunday and Monday...VFR. && .MARINE... High pressure will be across the forecast waters tonight with a frontal system approaching late tonight and moving through the waters Thursday and Thursday night. Thursday afternoon gusts on the ocean will be around small craft levels ahead of an approaching cold front. Seas will be building as well and reach small craft by Thursday evening. Thursday night there will be occasional small craft gusts on the remainder of the waters as low pressure moves through, and small craft conditions continue on the ocean waters. Increasing pressure gradient between low pressure departing to the east on Friday and building high pressure to the south will present SCA conditions on all waters. The SCA will continue on the ocean through Friday evening, and will go into effect on remaining waters 10z Friday. There remains a possibility for gale force gusts on the ocean, but confidence is low on the occurrence being more than occasional. Will continue to highlight in the HWO, but for just the ocean waters. Winds will weaken Friday night as the high settles over the waters. Seas will also subside below SCA levels. High pressure shifts offshore Saturday with an increasing SW flow. Gusts to 25 kt and seas building to around 5 ft will be possible in the afternoon on the ocean waters. These winds will slowly diminish Saturday night as the front moves through, but seas may take longer to subside. For Sunday into Monday, high pressure builds over the waters with sub-SCA conditions forecast. && .HYDROLOGY... Precipitation develops late tonight and continues through Thursday night. Liquid accumulations of 1/2 to 3/4 of an inch of likely, with a trace to 1 1/2 inches of snow and sleet possible across portions of the Lower Hudson Valley into Northeastern New Jersey, and Northern Fairfield county of Connecticut. Widespread significant precipitation is not expected for the rest of the forecast period. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 6 AM to 6 PM EDT Friday for ANZ330- 335-338-340-345. Small Craft Advisory from 2 PM Thursday to 6 PM EDT Friday for ANZ350-353-355. && $$ SYNOPSIS...DS/MET NEAR TERM...JMC/MET SHORT TERM...MET LONG TERM...DS AVIATION...NV/DW MARINE...DS/MET HYDROLOGY...DS/MET is the U.S. government's official web portal to all federal, state and local government web resources and services.