Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 010140 AFDOKX Area Forecast Discussion National Weather Service New York NY 940 PM EDT THU JUN 30 2016 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 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 shower toward daybreak with developing low level jet and positive theta-e advection. With weak instability developing toward daybreak...can not rule out an isolated tstm. Mild night on tap. Lows will be generally in the 60s, with increasing dewpoints and lowering cloud cover. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... 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. && .LONG TERM /SATURDAY THROUGH THURSDAY/... 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. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... High pressure moves offshore tonight. A warm front approaches from the south Friday morning and a cold front moves across Friday night. Mainly VFR forecast except for showers and thunderstorms Friday afternoon into the evening which could present temporary MVFR or below conditions. In addition, some temporary gusty winds are possible with thunderstorms. Confidence lowers going into Friday as the timing of any showers and thunderstorms as well as lower conditions could change a few hours with subsequent forecasts. S winds 10-15 kt for city terminals and near 10 kt for other terminals will lower tonight to 5-10 kt and become more SE Friday and increase in the afternoon to 10-15 kt, again highest for city terminals. Winds will briefly become light and variable late Friday night before becoming more NW. 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: High confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. KLGA TAF Comments: High confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. KEWR TAF Comments: High confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. KTEB TAF Comments: High confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. KHPN TAF Comments: Moderate confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. KISP TAF Comments: Moderate confidence forecast for tonight but lowering for Friday as timing of showers and thunderstorms along with their MVFR and lower temporary conditions could vary 1-3 hours compared to when they actually occur. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday Night...MVFR or IFR conditions possible in showers/thunderstorms early with chances dropping by late evening. Before NW flow increases late, there could be some patchy fog with possible MVFR conditions. .Saturday-Sunday Night...VFR. NW-WNW flow Saturday and WSW-W flow Sunday. Gusts up to 20 kt for both days. Winds diminish at night. .Monday...VFR. .Monday Night-Tuesday...Mainly VFR. Slight chance for Showers/Thunderstorms. && .MARINE... Marginal SCA conditions are possible on the ocean Fri afternoon into Saturday with a passing frontal system. Confidence too low for SCA at this point. Thunderstorms Friday afternoon/evening will pose a greater hazard, with locally strong winds, frequent lightning, and heavy rain all possible. Ocean seas may build close to 5 ft on Wednesday, as weak low pressure passes to the south. && .HYDROLOGY... Numerous showers and tstms should bring a basin average of 1/4 to 1/2 inch of rain Fri afternoon/evening. Much higher local amounts of 1-3 inches are possible with any training activity, which could cause localized flash flood threat. NCAR ensemble and SBU WRF support this notion with localized 2+ inch probs and explicit output respectively. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$

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