Area Forecast Discussion
Issued by NWS Upton, NY

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648 FXUS61 KOKX 282359 AFDOKX Area Forecast Discussion National Weather Service New York NY 759 PM EDT TUE JUN 28 2016 .SYNOPSIS... A cold front will approach from the west this evening, then slowly cross the Tri-State through Wednesday. Weak high pressure builds in Wednesday night through Friday. A cold front then approaches and moves across the area late Friday night and Saturday. High pressure builds in behind the front from Saturday night through Tuesday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Added some patchy fog to the southern portions of Long Island and New York City, as cameras have shown a fog bank offshore. Otherwise, 700-500 hPa trough builds into the region tonight, as an 850 hPa cold front moves into, then stalls over the area as it becomes parallel to fairly weak flow at 850 hPa. Should see showers, with maybe some embedded thunderstorms slowly build into far western zones this evening, then spread eastward mainly after midnight per latest high resolution model runs. CAPE of 500-1000 J/kg limited late this afternoon to W of the Hudson River, with CAPE quickly diminishing after 00z. However, do have showalter indices around 0 this evening throughout, hence at least a slight chance of thunder everywhere. It does appear that even the instability aloft diminishes after midnight, so have gone over to just showers overnight. Region remains under slight risk of severe storms tonight over Orange County with a marginal risk just to the east, mainly for areas W of the Hudson River. However, bulk shear remains below 20 kt, outside of Orange County where it is 25-30kt, until the CAPE subsides, so Severe threat likely will be contained in Orange County. However, will continue to highlight both Slight and Marginal risk areas in the HWO, with the main threat strong gusty winds. Also, with precipitable waters forecast over W zones to reach upwards of 1.25 inches, could see some locally heavy rainfall as well. See the hydrology section of the AFD for details. For lows tonight, a blend of MAV/MET/ECS guidance and NAM 2-meter temperatures was used, with values forecast to be a few degrees above normal. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Core of 700-500 hPa trough lifts NE into eastern Quebec Wednesday, taking the best dynamics with it. Best jet forcing will be in the morning with the region in the right rear quadrant of a 75-80 KT 300 hPa jet and having a 50 KT 500 hPa jet pass over western portions. However, the mid levels are forecast to be rather dry, along with a cap centered around 650 hPa, with these likely being the limiting factors in any convective development. For now have slight chance pops across the N tier of the CWA Wednesday (area closest to the best dynamic forcing), mainly E of the Hudson River, with a dry forecast elsewhere. Highs Wednesday were based on a blend of MAV/MET/ECS guidance, NAM 2-meter, and a mix down from 950-800 hPa per BUFKIT soundings. Highs should be around 5 degrees above normal, except near normal in the immediate NYC Metro area. The main 700-500 hPa trough axis exits to the east Wednesday evening, with drier air working in behind it in the low levels, to go with the already dry air aloft. As a result, expect any cloud cover to clear out overnight, with decent radiational cooling setting up. Based on this, lows were weighed towards coolest of MAV/MET/ECS guidance and NAM 2-meter temperatures at any given point outside of urban areas. Lows should be near normal. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Weak high pressure builds across the area on Thursday and Friday. A cold front will move through the area late on Friday night and into early Saturday, brining showers and the potential for some thunderstorms. High pressure builds behind the front Sunday and remains through the holiday weekend. Temperatures during the extended period will be near normal for this time of year, with temperatures during the day in the low to mid 80s and low temperatures in the upper 50s to lower 60s. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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An approaching cold front passes through the region late tonight into Wednesday morning. S/SE winds around 10KT into early tonight will become light and variable later tonight until the frontal passage Wednesday morning. Then winds become more NW and will stay light with therefore sea breeze formation Wednesday afternoon for coastal terminals. Though there is more uncertainty with wind directions Wednesday afternoon with therefore a low confidence forecast that timeframe. Conditions will become mostly IFR/LIFR this evening and continue into early Wednesday morning. Highest chances for showers will be in the 02Z-06Z timeframe for NYC terminals as well as those to the N/W. Chances remain to the east thereafter. Thunderstorms are only forecast to be sparse in coverage early this evening so with much uncertainty in exact timing and placement, these were not included in TAFs. After the frontal passage Wednesday, conditions gradually improve to VFR. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: VLIFR is possible at times tonight. End time of LIFR/IFR could be 1-3 hours off. KLGA TAF Comments: End time of LIFR/IFR could be 1-3 hours off. KEWR TAF Comments: Timing of IFR/LIFR could be 1-3 hours off. KTEB TAF Comments: End time of LIFR/IFR could be 1-3 hours off. KHPN TAF Comments: End time of LIFR/IFR could be 1-3 hours off. KISP TAF Comments: End time of LIFR/IFR could be 1-3 hours off. .OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY... .Wednesday night through Friday morning...VFR. .Friday afternoon and night...MVFR or IFR conditions possible in showers/tstms. .Saturday and Sunday...VFR.
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&& .MARINE... Added patchy fog to the ocean and South Shore Bays tonight. Otherwise, a relaxed pressure gradient over the waters around Long Island will keep winds at 10 kt or less through Wednesday night. With no significant swells forecast, seas/waves should be 3 ft or less as well during this time frame. Winds and seas are forecast to remain below small craft advisory levels Thursday through the holiday weekend. && .HYDROLOGY... From 1/6-1/2 inch of rain is forecast through tonight, with locally higher amounts possible mainly west of the Hudson River. Areas that do experience locally heavy rainfall could experience minor flooding of urban/poor drainage areas with a very small chance of localized flash flooding. However, most areas will receive no hydrologic impact from this rainfall. No significant rainfall is expected from Wednesday through Friday. Scattered showers and thunderstorms are possible late Friday night and into early Saturday. Antecedent conditions are very dry, so widespread hydrology issues are not expected. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...FIG/Maloit NEAR TERM...JMC/Maloit SHORT TERM...Maloit LONG TERM...FIG AVIATION...JM MARINE...JMC/FIG/Maloit HYDROLOGY...FIG/Maloit is the U.S. government's official web portal to all federal, state and local government web resources and services.