Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 190845 AFDOKX Area Forecast Discussion National Weather Service New York NY 445 AM EDT Sat May 19 2018 .SYNOPSIS... A warm front will slowly approach from the south today, lifting north of the area tonight. A cold front will then pass Sunday into Sunday night. High pressure will briefly build into the region Monday, before unsettled weather returns for midweek. Another high builds in for the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Broad trough moving into the Ohio Valley this morning will shear NE into the Eastern Great Lakes by late today, ahead of an amplifying northern stream shortwave. At the surface, this will have broad low pressure over the Ohio Valley lifting into the Great Lakes today, with its associated warm front slowly lifting north towards the region today. The warm front will likely stay south of the region until late today/this evening, thanks to Canadian Maritime high pressure continuing to nose down into the region. A soaking stratiform rain will develop from south to north across the region this morning ahead of the warm front. Rain could be moderate to heavy at times with modest frontogenetic forcing and a sub-tropical moisture feed up the coast today. Location/orientation of warm conveyor belt, as well as orographic enhancement of easterly low-level flow, favors heaviest rain across NE NJ and the Lower Hudson Valley, with 1 to 1 1/2 inches of rain into this evening. This heavier rain axis could extend into the NYC metro and SW CT. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... Models in good agreement with a weak trough over the Ohio Valley shearing NE, ahead of a couple of northern stream shortwaves digging towards the Ontario/Quebec border tonight. The axis of southern and northern stream energy slides through the NE on Sunday, with mean troughing lingering into Monday. At the surface, good agreement with low pressure lifting northeast from the Eastern Great Lakes late today, and up the St Lawrence River Valley tonight. Its associated warm front should be able to move north through much of the region tonight as a 35-45 kt LLJ moves across coastal areas, and cold front slowly approaches from the west. With vort axis around periphery of Bermuda high sliding across the region this evening, and a marginally unstable sub-tropical airmass advecting up the coast, potential exists for a few thunderstorms with heavy downpours late today through this evening along the warm front as it moves north tonight. Best chance may be across eastern portions of region, coincident with better LLJ forcing. Models in good agreement with weak shortwave axis (remnants of shearing Ohio Valley trough) crossing the region Sunday morning into early afternoon, as stronger northern stream shortwave passes through Quebec. At the surface, a weak cold front passes through the region Sunday aft/eve. Sct shower/iso tstms are possible along the front, across NYC metro and points NW in sub- tropical airmass Sun morning into early afternoon. Heavy downpours would be main threat with any thunderstorms. Convective activity will likely diminish in coverage and intensity with the front as it presses eastward in the aft/eve as instability wanes and perhaps subsidence in wake of shortwave. Thereafter models in good agreement with drying conditions Sunday night into Monday as Canadian high pressure builds down into the NE, and cold front sags well south towards the Mid Atlantic. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... The frontal boundary will head back north Monday night, with a weak area of low pressure or disturbance riding along it over the southeast US/Mid-Atlantic region. At the same time, an area of low pressure will approach the region from the southern Great Lakes region. This will bring unsettled weather back into the area for late Monday night through at least Tuesday night. There are obviously timing, track, and strength differences that will likely be resolved with later model runs. The low currently is forecast to pass north and west of the area Tuesday night, swinging a cold front through. Previous zonal flow aloft will be replaced by upper level trough and high pressure building in at the surface from Wednesday night through the end of the work week. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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A warm front approaches today and moves through late this afternoon. Cigs will lower to ifr as rain overspreads the region. Ifr or lower will continue thru the rest of the taf period. Winds will increase out of the e, then decrease invof the front. Direction will veer to the s behind the front. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late tngt...Ifr or lower. .Sun...Becoming vfr in the aftn. Sct shwrs and tstms possible. Flow becoming nw behind a cold front. .Mon...Vfr with light s winds. .Tue...Vfr with increasing s winds. .Wed...Mvfr possible.
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&& .MARINE... A moderate easterly flow through this morning will produce SCA conditions on the ocean waters. Marginal SCA gusts are possible on LI Sound and Eastern bays this morning into early afternoon. Marginal SCA gusts are possible on the ocean tonight into Sunday morning in a strengthening southerly flow in the wake of warm front. Ocean seas should remain elevated through Sunday night, possibly into Mon morning E of Moriches Inlet. A weak gradient is expected Monday into Tuesday as high pressure moves across the area, with tranquil winds and subsiding s swell. && .HYDROLOGY... Generally 1/2 to 1 1/2 inches of rain are expected through this evening, highest amounts across NE NJ and Lower Hudson valley. NYC/NJ metro and SW CT will be on the border of the heavier rain axis, while eastern areas of the region likely fall closer to the low end of the range. Localized minor urban and poor drainage flood issues are possible in heavy rain axis. Localized heavy downpours are possible tonight into Sunday afternoon, which could cause localized urban and poor drainage flooding. Otherwise, no widespread hydrologic issues are anticipated through early next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 8 PM EDT Sunday for ANZ350-353-355. && $$ SYNOPSIS...JP/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...JP AVIATION...12 MARINE...JP/NV HYDROLOGY...JP/NV is the U.S. government's official web portal to all federal, state and local government web resources and services.