Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 301942 AFDOKX Area Forecast Discussion National Weather Service New York NY 342 PM EDT THU JUN 30 2016 .SYNOPSIS...
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High pressure will move east tonight. A frontal system will approach on Friday and then move across Friday night. High pressure will build in for the holiday weekend. Low pressure may track close enough on Tuesday to spark a few showers and thunderstorms, then fair weather will return for the rest of the week.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Northern stream shortwave digs into the great lakes tonight...with a weak lead shortwave rotating through this evening. At the surface...a warm front develops over the from the mid atlantic states tonight and begins lifting towards the region. Moisture lacking with first shortwave this evening...but with developing deep sw flow ahead of digging great lakes trough...increasing cloud cover expected overnight...with increasing chance of showers towards daybreak with developing llj and theta-e advection. With weak instability developing towards daybreak...cant rule out an isolated tstm. Mild night on tap with lows generally in the 60s with increasing dewpoints and lowering cloud cover.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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Strong shortwave for this time of year negatively tilts from the Great Lakes towards the NE Friday afternoon. Shortwave axis pivots through Fri evening...while the main trough continues to deepen into the NE Fri night. At the surface...the warm front continues to lift north towards the region on Fri...while a pre-frontal trough develops/approaches from the west Fri aft/eve...before cold front swings through Fri night. Generally scattered shower/isolated tstm threat expected areawide in the morning in waa pattern...but without a clear focusing boundary. With increasing lift...moisture and instability Fri afternoon ahead of the approaching surface trough...expectation is for increasing coverage of showers and tstms from w to e across the NYC/NJ metro and points west. Deep layer shear is expected to be supportive of organized convection...with sct morning shower activity and afternoon cloud cover being key for instability forecast. With an increasingly moist airmass being advected in...a modeled borderline marginal to moderately unstable airmass looks reasonable for this area...which presents potential for a few severe storms...even a supercell if a low-level boundary (sea-breeze, outflow, warm front) can enhance low-level veering. Main convective threat appears to be wet microbursts based on the moderately strong mid- level wind fields...but cant rule out large hail with any rotating storms...or even a weak tornado if coincident with a low- level shear enhancing boundary. Expectation is that this shower/tstm activity will move east into LI/CT in the late afternoon/evening with the shortwave forcing. Wind shear and forcing will remain supportive of organized convection into the evening...and with ample elevated instability if not surface as well...could support a localized strong to severe threat to the coast. Depth of marine layer will be the limiting factor. See hydro section for details on localized heavy rainfall threat. Shortwave axis crosses in the evening...which should bring any organized convection threat to an end. Trailing cold front crosses the area through midnight with lingering shower/tstms activity coming to and end...and cooler drier airmass advecting in by Sat morning.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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Mainly fair and seasonably warm weather can be expected through the long term. For the Fourth of July weekend, any rain is expected to quickly wind down by around sunrise Saturday per the 12Z model consensus. The data suggests this forecast timing may even be too conservative, and the rain could end more quickly. Regardless, a massive sweep of dry air in the mid levels of the atmosphere will bring a sunny day. Perhaps some fair weather cumulus on Sunday, then high clouds may begin to filter in by evening. More extensive high clouds possible on Monday, but limited opacity is expected with the moisture above 30,000 ft. The only apparent threat for rain is in the Tuesday time period as a mid level trough passes through the region. The model trend however is for the bulk of this activity to pass south of the Tri-State Region, so the probability of precipitation has been limited to 20 percent. Dry weather appears likely thereafter as an upper level ridge builds in. The Superblend was used for temperatures, with highs close to or a few degrees above average.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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High pressure moves offshore tonight. A warm front approaches from the south Friday morning. VFR. Sea breezes are a little slower to move across KLGA, KEWR, and KTEB. Have delayed the timing to around 21z when the sea breeze should move across those terminals. Flow becomes light and variable at outlying terminals and out of the S-SE at city terminals around 5 kt overnight. SE winds then increase to around 10 kt Friday morning. Showers are possible Friday morning, but confidence is low in location and timing of any shower. MVFR conditions also cannot be ruled out near the coast. Showers are more likely in the afternoon with thunderstorms possible. Timing and location uncertain at this time, so have left thunder out of the extended TAFs for now. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: S-SSE winds 10-13 kt through early evening. KLGA TAF Comments: Sea breeze boundary just south of terminal. Winds are likely to vary in direction from NW to SW until sea breeze passage around 20-21z. KEWR TAF Comments: Sea breeze boundary a few miles east of terminal. Winds are likely to stay out of the west until sea breeze passage around 21z. KTEB TAF Comments: Sea breeze boundary a few miles east of terminal. Winds are likely to stay out of the west until sea breeze passage around 21z. KHPN TAF Comments: Seabreeze likely to move through terminal between 20 and 21z. KISP TAF Comments: Southerly winds 10-13 kt through early evening. .OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... .Friday afternoon-Friday night...MVFR or IFR conditions possible in showers/thunderstorms. .Saturday...VFR. NW winds G20-25KT. .Sunday and Monday...VFR. .Tuesday...Mainly VFR. Slight chance for Showers/Thunderstorms.
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&& .MARINE...
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Winds and seas should remain below SCA through Fri monring as weak high pressure moves over the waters. Isolated and marginal sca gusts possible on the ocean Fri aft/eve ahead of approaching cold front...with potential for marginal sca ocean seas developing late Fri night into Sat as southerly swells arrive. Confidence too low for sca at this point. High pressure will keep winds and waves below small craft advisory levels Saturday through Tuesday. Seas may build to around 5 ft on the ocean Wednesday, as weak low pressure passes south of the coastal waters.
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&& .HYDROLOGY...
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Numerous showers and tstms should bring a basin average of 1/4 to 1/2 inch of rain Fri Aft/Eve. Locally though...potential for 1 to 3 inches of rain with any training tstm activity...resulting in a localized urban flash flood threat. NCAR ensemble and SBU WRF support this notion with localized 2+ inch probs and explicit output respectively. There is a chance for some rain on or about Tuesday. Otherwise, widespread measurable rainfall is not expected Saturday through Thursday.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JMC/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...JMC AVIATION...DS MARINE...JMC/NV HYDROLOGY...JMC/NV

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