Area Forecast Discussion
Issued by NWS Upton, NY

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957 FXUS61 KOKX 231743 AFDOKX Area Forecast Discussion National Weather Service New York NY 143 PM EDT Fri Sep 23 2016 .SYNOPSIS... A cold front will approach from the north today, then move across the Tri-state this evening. Strong high pressure then builds in from south-central Canada through Sunday night, then slides offshore Monday. A slow moving frontal system could impact the area from Monday night through Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Upper level features the southward shift of a longwave trough and jet stream across the Northeast. The SW-W flow, while light, will lead to a warm day. Temperatures will climb into the 70s and 80s, with the warmest locations acrossthe NYC metro area. There is a possibility for isolated showers and thunderstorms late this afternoon across interior locations ahead of the cold front. There is a moderate risk of rip current development at Atlantic Beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Aloft, the upper level trough and jet stream move farther south into the region with associated height falls. At the surface, the cold front moves across tonight from north to south during the evening hours. Showers are confined to along the boundary and behind the front, lingering out east perhaps through much of tonight while a more brief period is possible for western sections. In addition, multiple models show some negative Showalter indices moving across just behind the cold front. Therefore, this is suggesting some thunderstorms will be possible. With limited instability however, kept these isolated in coverage. Showers will be isolated to scattered, greater coverage farther east in the region. Without much of moisture sources to draw from, total rainfall is expected to remain quite light. Strong high pressure builds in behind the cold front. A northerly flow takes shape behind the front which will bring cold and dry air advection. This will allow for a cooler and drier airmass to build in for late tonight and Saturday. The lows tonight though will be limited though due to the lingering clouds which will mitigate radiational cooling. ECS guidance was used for lows tonight. For Saturday, the northerly flow continues with dry weather returning that morning through the rest of the day. There could be a few showers remaining out east during the early morning but otherwise expecting a dry day. It will also be remarkably cooler with highs only in the upper 60s to mid 70s, closer to normal than recent days. MET guidance was used for this to depict some southern coastal locations getting downslope flow and relatively higher temperatures. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... The region will be under northwest flow aloft Saturday night-Sunday night as it remains in between a cutoff low slowly lifting through the Canadian Maritimes and a deep layered ridge moving into the Great Lakes and Ohio Valley. It should be dry with minimal cloud cover as a result. Lows Saturday night were based on a blend of MAV/MET/ECS guidance and NAM 2-meter temperatures, weighed towards the coolest guidance outside of urban areas to reflect likelihood of decent radiational cooling conditions (did adjust normal cold spots down a tad more than the blend above would suggest). Lows should be generally around 5-10 degrees below normal. Highs on Sunday were based on a blend of MAV/MET guidance, NAM 2- meter temperatures and a mix down from 875-825 hPa per BUFKIT soundings. Highs should be around 5 degrees below normal. Lows Sunday night were based on a blend of MEX/MEN/ECE/ECM/EKD/WPC guidance and NAM 2-meter temperatures weighed towards the coolest guidance outside of urban areas. Lows should be around 5-10 degrees below normal. The deep layered ridge axis builds over the area on Monday, keeping things dry. Cloud cover should be minimal until maybe late in the day, when some high clouds could begin to build into far western zones. The models continue to differ greatly in their handling of the Omega block over the country early next week and the developing cutoff low that should come down from central Canada towards the middle of next week. The CMC is the strongest with the ridging in the middle of the block and keep things dry until Tuesday night, the ECMWF is weakest with the ridge and brings in precipitation Monday night, with the GFS in between. Noting that multiple cutoff lows are involved with this pattern, there likely will be quite a bit of model spread for several more days. Even though the ECMWF has been fairly consistent over the past 3 runs in how it has handled the system, it is likely too progressive given the relatively high amplitude of the forecast Omega block and the fact that multiple cutoff lows are involved. Both of these factors typically favor a less, not more progressive movement of systems. As a result only bring slight chance pops into the NW 1/3 of the CWA late Monday night. With decent overlap in precipitation coverage between the ECMWF and GFS on precipitation coverage 12-18z on Tuesday over roughly western 1/2 of the CWA - do have chance pops there. Otherwise have slight chance pops CWA wide from Tuesday- Thursday. Though there is at least moderate confidence that there will be some rain over the entire area in this time frame, confidence in exactly when any rainfall will occur is too low at this time to warrant higher pops. Temperatures Monday-Thursday were based on the Superblend and start out below normal Monday, then generally run within a few degrees of either side of normal from Monday night-Thursday. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... A cold front approaches from the north late this afternoon. The front passes through this evening with some SCT -SHRA (with a very low CHC for TS) mainly N and E of the NY Metro in its wake. VFR conditions are anticipated through most of the forecast period. Behind the front, MVFR ceilings are expected after midnight into the early morning Saturday. W to SW winds will lighten as the cold front approaches by evening. Timing of cold frontal passage with distinct wind shift to the NNE may be 1-2 hours sooner than forecast this evening. A few gusts to 20 KT are possible from time to time. NY Metro Enhanced Aviation Weather Support... Detailed information...including hourly TAF wind component fcsts can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: S winds will lighten before the cold front moves through. Timing of wind shift to the N/NE could be off an hour or two. KLGA TAF Comments: Winds shift to the S by 19-20z. Then timing of wind shift to the N/NE could be off an hour or two this evening. KEWR TAF Comments: SW winds will lighten before the cold front moves through. Timing of wind shift to the N/NE could be off an hour or two. KTEB TAF Comments: W winds will lighten before the cold front moves through. Timing of wind shift to the N/NE could be off an hour or two. KHPN TAF Comments: W winds will lighten before the cold front moves through. Timing of wind shift to the N/NE could be off an hour or two. KISP TAF Comments: S winds will lighten before the cold front moves through. Timing of wind shift to the N/NE could be off an hour or two. .Outlook for 18Z Saturday through Wednesday... .Saturday afternoon-Monday...VFR. NW-N winds diminish during this time. .Monday night...VFR with possible showers developing. .Tuesday-Tuesday night...Mainly VFR. Chance of showers at times. .Wednesday...Any showers end. VFR. && .MARINE... Light winds today, with swells producing 3 to 4 ft seas on the coastal ocean waters. The pressure gradient increases tonight, and remains fairly tight into Saturday. This coupled with cold advection behind a passing cold front tonight, should bring gusts to around 25 kt on all waters after midnight, so have an issued an SCA for all waters starting at midnight. Frequent gusts to 25 kt or likely to come to an end around sunrise, so end the SCA on the non-ocean zones at 10z. However, the gusty winds combined with a SE swell should produce seas to around 5 ft across the coastal ocean waters through the day on Saturday - so have the SCA on those waters valid through 22z. A light to moderate pressure gradient over the waters Saturday night- Tuesday will keep sustained winds to 15 kt or less and gusts less than 25kt. It is possible, depending on exact strength of winds and the extent of swells on Saturday night-Sunday that the coastal ocean waters could see seas up to 5 ft. Otherwise, seas and waves are expected to be below Small Craft Advisory thresholds Saturday night through Tuesday as well. && .HYDROLOGY... Generally less than a quarter of an inch of rain tonight/early Saturday. Otherwise, it will be mainly dry through Saturday. It should also be dry from Saturday night through at least Monday evening. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from midnight tonight to 6 AM EDT Saturday for ANZ330-335-338-340-345. Small Craft Advisory from midnight tonight to 6 PM EDT Saturday for ANZ350-353-355. && $$ SYNOPSIS...JM NEAR TERM...JM SHORT TERM...JM LONG TERM...Maloit AVIATION...PW MARINE...Maloit/JM HYDROLOGY...Maloit/JM

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