Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 300946 AFDOKX Area Forecast Discussion National Weather Service New York NY 546 AM EDT MON MAY 30 2016 .SYNOPSIS... A cold front approaches from the eastern Great Lakes today, then crosses the Tri-State tonight. High pressure then builds down from southeastern Canada from Tuesday through Thursday, then retreats to the northeast Thursday night. A cold front approaches from the west on Friday, then moves across the region this weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Models in general are having issues dealing with current rainfall. The NAM is by far most underdone and the GFS most overdone. A blend of the CMC-Reg/ECMWF/HRRR seems fairly reasonable overall, but loses some details in terms of placement of heaviest rain. Main change in forecast is idea that most precipitation should come to an end by mid-late morning across the Lower Hudson Valley/ne NJ/NYC...and by around midday/early afternoon over Long Island/s CT. Locally heavy rainfall remains a threat until the initial batch of showers with embedded elevated thunderstorms comes to an end. Please see the hydrology section for details. There are some indications could get a second round of showers/thunderstorms by late afternoon over far W zones ahead of the cold front. Noting expected gap in precipitation and some breaks in the clouds, could see CAPES of 1000-1500 J/kg across interior portions of the Lower Hudson Valley/SW CT/NE NJ. If these CAPES are achieved, then isolated strong storms would be possible with 30-35 kt of Bulk Shear. However the main issue likely would be locally heavy rainfall. For highs today, a blend of MAV/MET/ECS guidance, NAM 2-meter temperatures and a mix down from 975-900 hPa, per BUFKIT soundings, was used. Highs should be a around 2-5 degrees above normal. Patchy dense fog early this morning over e Suffolk County/coastal s central/se CT should dissipate by around 5 am as steadier rain moves in. Have addressed with an SPS. There is a moderate risk for the meteorological enhancement of rip current formation at Atlantic beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... A 700-500 hPa shortwave crosses the area tonight...bring with it mainly scattered showers mainly this evening...except over far se CT/Twin Forks of Long Island where they should be more numerous and linger into the overnight hours. Might see showers linger over the Twin Forks into Tuesday morning, otherwise the day should be dry as the low levels dry out with a NW boundary layer flow. This should be enough to overcome forcing from the passing of a flattening 700-500 hPa trough axis. For lows tonight, a blend of MAV/ECS/MET guidance and NAM 2-meter temperatures was used, with values around 10 degrees above normal. On Tuesday, a blend of ECS/MET/MAV guidance, NAM 2-meter temperatures and a mix down from 850-825 hPa, per BUFKIT soundings, was used for highs. reading should be around 10 degrees above normal. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Upper level ridging will build over the region Wednesday and then shift eastward towards eastern New England and then the Canadian Maritimes on Thursday. At the surface, high pressure will traverse across New England on Wednesday and then situate itself over the Canadian Maritimes on Thursday. While the core of the high moves east, it will ridge down across the area. The 00z models and ensembles are in good agreement on this pattern. A northern stream shortwave trough is progged to moved across SE Canada on Thursday which will help push the upper ridge to the east. NHC`s 11pm advisory show the remnant circulation of Bonnie moving off the Carolina coast Wednesday night and then passing around 100 miles south and east of the 40/70 Benchmark. Most of the tropical moisture with the remnants are expected to remain well offshore. This is because of the approaching shortwave and increasing westerlies aloft associated with it. Will continue to advertise a slight chance of a shower for the far SE portion of the area, but think subsidence from the high to the NE will keep conditions mostly dry. Models diverge on the timing and amplitude of the passing shortwave trough Friday into Saturday. Differences continue to grow with the h5 pattern into the weekend. The cold front will slowly approach from the west Thursday night into Friday and then should move through on Saturday. Have kept pops in the low chance category this time frame. It will not be raining the whole time, but cannot rule out a few showers with the front in the vicinity. Instability is lacking, but have left mention of thunder Friday into Saturday with the front. Another shortwave establishes itself late Saturday into Sunday across the Great Lakes region and this is likely to approach late in the weekend. However, there is a lot of spread on how amplified the shortwave gets and how strong the downstream ridge ends up which will ultimately determine the timing of any precipitation. Since this a day 7 forecast, do not want to go to far from a model consensus at this time. Temperatures on Wednesday will be near to slightly above normal. Onshore flow Thursday and Friday should keep temperatures a few degrees below normal. Seasonable temperatures forecast this weekend. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... A weak low pressure trough over the area will weaken today. A cold front will move across tonight. Mainly IFR/LIFR conditions continue, with low clouds/fog along the coast and with moderate/heavy showers and isolated tstms. Last area of heavy showers/tstms moving across central NJ between 09Z-10Z should clear NYC metro before 12Z. Prevailing conditions should gradually improve to MVFR by late morning or midday as low level dry out, with the exception of KGON, which should remain IFR this afternoon. As the cold front approaches, KSWF could experience at least vicinity impact from any accompanying tstms. Expect widespread IFR/LIFR to return tonight especially along the coast. Fairly good confidence in winds, except for timing of wind shift at KBDR/KGON where easterly flow persists attm and may be stubborn to give way to southerly flow. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: KJFK TAF Comments: Timing and degree of improvement today uncertain and may require frequent updates. Higher confidence in winds. KLGA TAF Comments: Timing and degree of improvement today somewhat uncertain and may require frequent updates. Higher confidence in winds. KEWR TAF Comments: Timing and degree of improvement today somewhat uncertain and may require frequent updates. Higher confidence in winds. The afternoon KEWR haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Timing and degree of improvement today somewhat uncertain and may require frequent updates. Higher confidence in winds. KHPN TAF Comments: Timing and degree of improvement today somewhat uncertain and may require frequent updates. Higher confidence in winds. KISP TAF Comments: Timing and degree of improvement today somewhat uncertain and may require frequent updates. Higher confidence in winds. .OUTLOOK FOR 06Z Tuesday through Friday... .Late Tonight...Cold fropa with a chance of showers and MVFR/IFR conds. .Tuesday-Wednesday night...VFR. .Thursday...Mainly VFR. E winds G15-20kt. .Thursday night...Chance of showers with brief MVFR conditions. .Friday...Chance of showers with brief MVFR conditions, and possibly an afternoon tstm. && .MARINE... A dense fog advisory remains in effect through 6am. Conditions should improve as steadier rain develops. Will check webcams around sunrise to verify progress. Given high dewpoints though, cannot completely rule out the need to extend the advisory for a few hours, especially over areas around eastern Long Island/CT. A light to moderate pressure gradient over the region will limit sustained winds to 15 kt or less through Tuesday. For now, it appears that there will not be a significant enough swell to bring seas to SCA levels through Tuesday. It should be noted though, that there is still some uncertainty with how much significant swell, if any, the coastal ocean waters will experience early this week from Tropical Depression Bonnie. Sub-sca conditions are expected Tuesday Night and Wednesday with winds less than 20 kt and ocean seas 3 to 4 ft. Uncertainty remains on how much residual swell will exist Thursday into Friday as remnants of Bonnie pass south and east of the waters. It is possible seas approach 5 ft during this time on the ocean. Winds could also approach sca levels on the ocean on Friday. && .HYDROLOGY... An additional 3/4 to 1 1/2 inches of rain is forecast through this evening, with locally higher amounts likely. The heaviest rain totals are most likely over far se CT and eastern Long Island. This rain will cause areas of minor urban and small stream flooding...and might cause localized flash flooding as well. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Dense Fog Advisory until 6 AM EDT early this morning for ANZ330-335-338-340-345-350-353-355. && $$ SYNOPSIS...Maloit/DS NEAR TERM...Maloit SHORT TERM...Maloit LONG TERM...DS AVIATION...Goodman MARINE...Maloit/DS HYDROLOGY...Maloit/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.