Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 180229 AFDOKX Area Forecast Discussion National Weather Service New York NY 1029 PM EDT Sun Jun 17 2018 .SYNOPSIS... Offshore high pressure remains through Monday. A cold front will approach from the north Monday and move across early Tuesday. Weak high pressure builds in Tuesday afternoon into midweek. Outside of a reinforcing cold front Wednesday night, high pressure will remain across the region through Saturday. A frontal system then approaches Saturday night into Sunday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... The forecast remains on track. Cirrus will continue to spill over the large ridge centered across the southeast US through the night. High pressure will be offshore in the Atlantic. There will be S-SW flow, allowing for warmer and more humid conditions. Used a combination of MAV and ECS for the lows, ranging from near 70 in NYC to lower 60s in some parts of the interior, SE Connecticut and Eastern Long Island. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/... The mid level and upper levels have nearly zonal flow that remains but there will be some progression eastward as the base of the ridge moves farther east in the Southeast US. There will be a mid and upper level trough making its way into Quebec. The mid and upper level trough moves across Northern New England Monday night into early Tuesday. The trough begins to lift northeast of the region Tuesday afternoon. At the surface, low pressure moves eastward just north of Maine Monday, moving into the Canadian Maritimes Monday night. This will bring a cold front that will approach the region from the north Monday night. The front moves across the region early Tuesday. Weak high pressure builds in from the north behind the front. For Monday, hot and humid conditions with highest combination across the Lower Hudson Valley and Northeast NJ. Just high enough temperatures and dewpoints across Northeast NJ and the Lower Hudson Valley to make for heat indices near 100. Elsewhere, expecting heat indices in the mid to upper 90s for NYC (mostly 95 to 97) and in the 90s for Southern Connecticut and Nassau into Western Suffolk. Lower heat indices are expected farther east. Actual high temperatures are in the mid 90s across parts of Northeast NJ and the Lower Hudson Valley and with moisture advection and pooling of dewpoints near the Hudson River, that is why the heat indices are a few degrees higher for these locations. Actual highs for NYC are in the lower 90s with dewpoints more in the upper 60s. The highs forecast on Monday are a combination of the 00Z ECS and the previous forecast, going a little above the MAV and MET guidance. Rain returns to the forecast in the form of showers and thunderstorms late Monday afternoon through Monday night. These will taper off early Tuesday. These could produce locally heavy rain and gusty winds, but the severe threat looks to be limited to locations farther north of the region, where more wind shear will exist with lower heights and closer to the base of the upper level trough. Went for warmer lows Monday night (mainly in the 70s) as airmass remains very warm and humid with showers and thunderstorms across parts of the region. Some model differences on whether this moves across as a MCS or a weakened one. The lows Monday night were from a combination of MAV/MET/ECS. Expecting another warm but drier day Tuesday behind the front. Went with warmer combination of MAV/ECS for highs, mid 80s to near 90. There is a moderate rip current risk for Monday. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Models have continued to trend toward a drier forecast with mainly seasonable temperatures. There had been concern with the proximity of a frontal system stalling close enough to the area for potential wet weather toward the end of the week. However, a northern branch upper trough drops southeast across eastern Canada and into the northeast for the midweek period, lifting out toward the end of the week into the weekend. A southern branch shortwave trough approaches for the second half of next weekend. At the surface, high pressure prevails across the region through much of the period, until a frontal system approaches Saturday night into Sunday. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... High pressure to the south of Long Island tonight into Monday morning will give way to an approaching cold front late Monday and Monday evening. Mainly VFR through the TAF period. There is a chance for MVFR conditions in TSRA Monday evening. S-SSW winds will continue to diminish through the night. SW flow increases during Monday with sustained winds 10-15 kt and gusts around 20 kt in the late morning and afternoon. .OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY... .Monday Night...Chance of MVFR in showers and thunderstorms. .Tuesday...Mainly VFR. Small chance of a shower or thunderstorms in the morning. .Tuesday Night-Friday...VFR. && .MARINE... Weak high pressure based offshore, will keep a weak pressure gradient and conditions below SCA for tonight into early Monday. Winds and seas increase ahead of a cold front Monday afternoon into Monday night, but forecast has conditions staying mainly below SCA outside of some brief 25kt gusts on the ocean. The sub-SCA conditions remain on Tuesday. High pressure prevails Wednesday through Friday with winds 10 kt or less and seas 2 ft or less. && .HYDROLOGY... Showers and thunderstorms late Monday through early Tuesday could result in locally heavy rain. The precipitable water value of the airmass is forecast to reach near 2 inches. Locally minor flooding is possible. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Heat Advisory from 11 AM to 8 PM EDT Monday for NYZ067>071. NJ...Heat Advisory from 11 AM to 8 PM EDT Monday for NJZ002-004-006- 103>108. MARINE...None. && $$ SYNOPSIS...JM/DW NEAR TERM...JM/DS SHORT TERM...JM LONG TERM...DW AVIATION...DS MARINE...JM/DW HYDROLOGY...JM/DW EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.