Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221743 AFDOKX Area Forecast Discussion National Weather Service New York NY 143 PM EDT Sat Sep 22 2018 .SYNOPSIS... A cold front will slowly slide south from Long Island through the weekend, while high pressure gradually builds in from the Great Lakes. A frontal system will then impact the area Tuesday into Wednesday, ending with a cold frontal passage Wednesday night. High pressure returns for the end of the week. && .NEAR TERM /THROUGH TONIGHT/... Region under near zonal upper flow this afternoon in wake of departing Canadian maritimes shortwave. At the surface, Canadian high pressure builds towards the region from the Great Lakes. Gusty N winds will continue to subside this afternoon into evening. Otherwise, partly sunny skies continue as mid- high level clouds continue to pass through in the upper flow. Gradual cold advection will keep temperatures failry steady through the afternoon. Highs generally in the mid-upper 60s interior to lower 70s-75 city/coast. Dewpoints will fall into the upper 40s to lower 50s. A moderate risk of rip current development exists today. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... The high will continue pushing westward, and the region will be under a more easterly flow. The stalled front will linger off the Delmarva with the GFS indicating the front pushing back north with some rain late Saturday night into early Sunday morning. Other models continue to indicate the front remaining well to the south, so have kept a dry forecast through Saturday night. Overnight min temperatures will be near seasonable in the upper 40s for the northern areas and in the 50s around NYC metro and across Long Island as cloud cover will mitigate radiational cooling. High pressure remains in control on Sunday with temperatures a few degrees cooler than Saturday with an easterly wind and a partly sunny sky. There is a moderate risk for the development of rip currents at the ocean beaches Saturday morning, with a low risk in the afternoon and on Sunday as winds diminish and seas subside. && .LONG TERM /MONDAY THROUGH SATURDAY/... A confluent flow across eastern Canada and the Northeast will allow for strong high pressure to pass to the north through Monday. There is some concern with a frontal wave associated with a shearing mid-level shortwave trough, but will maintain a dry forecast on Sunday with some morning clouds mainly near the coast. Any light rain should stay south of Long Island. The GFS which does produce some measurable rain across the NYC metro and Long Island appears to be overdone based on the depth of dry air and the northern placement of the upper jet in comparison to the model consensus. The weather then takes a downhill swing for the midweek as an upper trough out west races eastward with a frontal system impacting the area Tuesday into Wednesday. First of which will be with overrunning rain Monday night into Tuesday night and then with scattered convection on Wednesday. The cold front follows Wednesday night. Additional timing issues have now risen with the GFS trending against the model suite by stalling the front Wednesday night into Friday, with multiple waves of low pressure riding along the front. In this scenario, the kicker will be with a late week cold frontal passage. All the global models support the late week kicker, the differences though arise with the lead shortwave trough lifting out to the NE Wednesday night into Thursday. The magnitude of this feature and its wavelength separation with the next upper trough/surface frontal system, will determine whether the first boundary makes it through. Even the GGEM which sends the first front east of the area Wednesday night, is close enough for a coastal low to impact the area Thursday night into Friday. Thus, there remains quite a bit of uncertainly for the Thursday into Friday timeframe and have maintained a low chance for rain at this time. Seasonable temperatures will start the week, but it then gets warm and humid Wednesday in the warm sector. The end of the week is a bit tricky depending on the placement of the aforementioned frontal boundary. && .AVIATION /18Z SATURDAY THROUGH WEDNESDAY/... A broad area of high pres builds into the region thru Sun. Generally vfr thru the taf period. Some light rain may develop aft 12z Sun and impact the NYC area and LI, producing periods of MVFR. The probability of this however is too low to include in the tafs attm. N winds will decrease and veer to the ne thru 00z. Light ne flow tngt will then veer to the se on Sun, with speeds blw 10kt. .OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... .Rest of Sunday...Mainly vfr, although mvfr is possible at times from the city to Long Island. Light se flow. .Monday...Pockets of mvfr possible, otherwise vfr with e winds up to 20-30kt. .Tuesday...Periods of rain with mvfr or lower. Increasing se winds abv 30kt. .Wednesday...Showers possible with mvfr or lower at times. .Thursday...Showers possible with mvfr or lower at times. && .MARINE... Marginal SCA nearshore gusts and 4 to 6 ft seas on the ocean this morning are expected to weaken through the late morning/early afternoon. Sub-SCA conditions then expected through the weekend. E winds strengthen Mon into Mon night and continue into Tue ahead of an approaching warm front. SCA conditions are likely to develop during this time, with on outside chance of gale force gusts on the ocean waters. High seas are likely to linger into Wed, with a S flow as the warm front passes to the N and a cold front approaches later that day. && .HYDROLOGY... No hydrologic impacts expected through the weekend. A frontal system could bring locally heavy showers/tstms Tue into Wed, first via warm fropa on Tue, then again via trailing cold fropa on Wed. Anticipate only localized nuisance impacts at this early point. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ350- 353-355. && $$ SYNOPSIS...CB NEAR TERM...CB/NV SHORT TERM...CB LONG TERM...DW AVIATION...JMC MARINE...Goodman HYDROLOGY...CB EQUIPMENT...

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