Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290826 AFDOKX Area Forecast Discussion National Weather Service New York NY 426 AM EDT Mon May 29 2017 .SYNOPSIS...
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A low pressure system approaches passes through into this evening. A weak cold front approaches from the west Tuesday, then crosses the area Tuesday night...followed by another on Wednesday. High pressure then builds to the south through Thursday night. Another cold front approaches on Friday then slowly crosses the area Friday night.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Light rain showers continue to move north and east this morning in association with frontal system approaching the area from the west. Two areas of low pressure will be the focus of precipitation over the region. One weak, broad low to our northwest, near the Eastern Great Lakes region, and another stronger low developing well east of the Delmarva peninsula that is forecast to pass well south and east of the area. Much of the tri-state will be caught in between these two lows, leading to relatively heavier rainfall for portions of the Lower Hudson Valley (closer to the low near the Great Lakes) southern and eastern portions of the area, such as Northeast New Jersey, New York City and Long Island (closer to the low offshore). Connecticut should see lower amounts as they will be farther away from both lows. In general, rainfall amounts have been lowered to between a 0.25"-0.50". However, amounts could end up even lower than this, but not confident on lowering them that drastically given uncertainty in placement of lows. Unseasonably cool temperatures today as clouds and rain keep temperatures in the upper 50s to around 60 for highs, some 10 to 15 degrees below normal.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Frontal system pushes east of the area tonight, along with the coastal storm. After some lingering showers early this evening, conditions should remain dry. However, drizzle and fog may develop overnight, with low level moisture trapped under an inversion. Another front approaches slowly from the west. Chances for rain increase from west to east during the day Tuesday. Enough instability for some thunder, but nothing severe expected. Temperatures continue to be below normal. .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The models continue to have differences in how they handle the very broad closed low that will be over SE Canada Tuesday Night through Thursday night. As a result they also differ in the strength and timing of shortwaves rotating around the base of the low, and hence on the precise timing of precipitation during this time frame. However, do have likely pops in for Tuesday night, as the models do agree there should be some measurable rainfall across the region then, but do have differences in timing during the night. Lows Tuesday night should be a few degrees above normal. For Wednesday and Wednesday night have mainly chance pops across northern zones and slight chance pops across southern zones. With Showalter Indices progged to 0 to -2, also have a slight chance of thunder in for Wednesday afternoon and evening. Highs Wednesday and lows Wednesday night should be a few degrees above normal as well. Zonal flow sets up Thursday and Thursday night, and it appears the region and with significant shortwaves progged to the NE and NW during this time frame, have gone with a dry forecast then. The model differences become even more noticeable Friday-Saturday. For Friday, do have chance pops throughout by afternoon and continue through Friday evening (along with a slight chance of thunder). Then limit pops to slight chance from late Friday night-Saturday morning. Then go with a dry forecast Late Saturday/Saturday night as both the GFS and ECMWF show the core of the closed low to the NE then. The new ECMWF has joined the 00z GFS in keeping Sunday dry, but noting it previously had a coastal low approaching (now just suppressed farther S), do have slight chance pops for Sunday. Temperatures Thursday through Saturday night will feature near normal highs and lows a few degrees above normal. Highs Sunday are currently forecast to be a few degrees below normal.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/... A frontal system will approach late tonight into Monday, while weak surface high pressure remains in place and weak low pressure passes to the south this morning. With the surface high remaining in place and dry air still to be overcome especially NE of the NYC metro terminals, this will make for a very difficult forecast in terms of flight category. Rain over NJ and eastern PA has brought widespread IFR cigs to those areas, but do not think this will be the case in the NYC metro, with MVFR cigs developing after daybreak and remaining in that category at least through the morning. There is a chance that IFR cigs could develop late this afternoon or this evening as winds diminish and back a little more NE following passage of the weak low to the south. Removed earlier mention of thunder, as instability fueling storms over central PA should weaken and come to a halt just west of the area this morning. Worst case attm would be mention of VCTS at KEWR/KTEB/KSWF if any storms manage to make it a little farther east than expected. High confidence in winds through this morning, with G20KT at some coastal terminals, then lower confidence on direction this afternoon into this evening, which could range anywhere from NE to SE. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Late Monday night...IFR in low clouds. KGON could remain MVFR. .Tuesday...IFR to start, improving to VFR by afternoon. Chance of afternoon/evening showers and possibly a tstm. IFR conditions possible at night. .Wednesday...Mainly VFR. Chance of afternoon/evening showers/tstms mainly NW of the NYC metro terminals. .Thursday...VFR. .Friday...Mainly VFR. Afternoon/evening showers/tstms possible. && .MARINE...
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SCA in effect today with seas 4 to 6 ft. Extended the advisory through 11 pm tonight as seas remain elevated through this time. Thereafter, waves diminish through the rest of the short term. A relaxed pressure gradient over the region from Tuesday night into Friday should keep sustained winds over the waters around Long Island to around 10 kt or less during this time frame. The pressure gradient is currently forecast to tighten a tad later on Friday, with sustained winds of around 15 kt or less possible over the waters then. Given the relatively light winds, and no significant swell, sub Small Craft Advisory conditions are forecast Tuesday night- Friday.
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&& .HYDROLOGY...
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0.25"-0.50" expected through today. This should have no hydrologic impact. No significant widespread hydrologic impacts are then expected at this time from Monday night through at least Thursday night.
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&& .TIDES/COASTAL FLOODING...
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Additional minor coastal flooding may occur with the high tide cycle tonight...mainly for the southern bays of Nassau/NYC.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ350- 353-355.
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&& $$ SYNOPSIS...Maloit/JP NEAR TERM...JP SHORT TERM...JP LONG TERM...Maloit AVIATION...Goodman MARINE...Maloit/JP HYDROLOGY...Maloit/JP TIDES/COASTAL FLOODING...

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