textproduct: New York

WHAT HAS CHANGED

Both the severe and flash flood risk have increased. There is now a slight risk of excessive rainfall through the entire area and and enhanced risk of severe thunderstorms through portions of northeast NJ and NYC.

A Flood Watch is now in effect for northeast NJ and NYC.

There is a high risk of rip currents on Tuesday and Wednesday, with potential for high surf on Wednesday.

The Small Craft Advisory has been expanded to include the South Shore Bays, Peconic and Gardiners Bays and the eastern LI Sound.

KEY MESSAGES

1) Scattered severe thunderstorms and flash flooding possible Tuesday morning through Tuesday evening. A Flood Watch is now in effect for northeast NJ and NYC. Isolated strong to severe thunderstorms and heavy downpours are then possible on Wednesday.

2) There is a high risk of rip currents for all ocean beaches Tuesday and Wednesday. A High Surf Advisory may also be needed for Wednesday. (See Marine section for discussion)

KEY MESSAGE 1

Heights start lowering over the area tonight as an upper level trough moves into the northeast US. At the surface, the center of associated low pressure will track well to the north through southern Canada. Once the high over our area shifts offshore today, a return flow will set up leading the way for a warm front Tuesday morning. A pre-frontal trough will quickly follow Tuesday late afternoon into the evening, with the trailing cold front slowing down and lingering over the area through Wednesday. This set up will bring multiple rounds of showers and thunderstorms Tuesday into Tuesday night, with scattered shower/thunderstorm activity also possible on Wednesday. Both the severe and flash flood risk has increased with the latest forecast.

While no two events are the same, the set up tomorrow is similar to what we saw last Saturday. The first round of convection will move through from the morning into the early afternoon associated with the warm advection. There could then be a brief lull before another round moves in during the late afternoon through the evening ahead of a pre-frontal trough. While an isolated flash flood or severe thunderstorm can not be ruled out with the earlier round, the higher risk looks to be with the later round.

In coordination with neighboring offices and WPC, the slight risk of excessive rainfall has been expanded north through the area and a Flood Watch has been issued for northeast NJ and NYC. CAMs continue to show potential high hourly rainfall rates in and around this area with global guidance showing pwats peaking between 2 and 2.25 inches. Have only included northeast NJ and NYC for now given higher confidence here due to low FFG and urban areas. Portions of northeast NJ have 1 hour FFG as low as 0.65 inches. There is potential for the Flood Watch to be expanded by subsequent shifts, specifically up into the Lower Hudson Valley. Totals across the area are expected to be between 1 and 2 inches with isolated totals around 3 to 4 inches possible. Peak rainfall rates in the strongest storms could be near 2.5 inches per hour.

In terms of severe weather, the enhanced risk now reaches into portions of northeast NJ and NYC. This was due to increased confidence in the damaging wind risk coverage. There has been no increase to expected intensity. The main focus for severe weather will be during the later round in the late afternoon into the evening. This will be somewhat conditional on a break/clearing between rounds, but all guidance has a tongue of 2000-3000 J/kg of MLCAPE stretching north into the area by the evening. The main risk will be damaging wind gusts, but given decent modeled low level hodograph curvature, an isolated tornado can not be ruled out. Additionally there is low potential for large hail.

The trailing cold front looks to slow down and not pass through the area until later on Wednesday. With the upper level trough still overhead, it is looking more likely that we will have additional isolated to scattered convection again on Wednesday. At this time, there does not look to be a flood threat with this, but an isolated severe thunderstorms does look possible. Potential flood threat will depend heavily on how much rainfall we receive tomorrow.

OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY

Tuesday Night and Wednesday: MVFR or lower with showers/tstms.

Thursday - Saturday: VFR.

Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90

MARINE

A southerly flow starts to strengthen overnight into Tuesday morning and peaks Tuesday night. Given the duration of the flow, ocean seas build to 7 to 10 feet by early Wednesday morning. A Small Craft Advisory is in effect for all waters except the NY Harbor and western and central Sound. This is for 25 to 30 kt gusts. There is potential for brief gale force gusts, mainly for Fire Island Inlet to Montauk Point from 20nm to 60nm. SCA conditions may linger on the ocean due to elevated seas into Thursday. Sub-SCA conditions then expected from Friday through early next week.

Rip Currents: The rip current risk was increased to moderate today given surf observations.

A high rip current risk is then expected Tuesday through Wednesday. A strengthening southerly flow will build a wind wave on Tuesday to 5 ft 5s perpendicular to the coast. The flow reaches 20 kt by the afternoon.

By Wednesday, the lingering swell will peak about 7-8ft at 8-9s. This combined with a SW 15-20kt flow will allow the high risk to continue.

OKX WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Flood Watch from 8 AM EDT Tuesday through late Tuesday night for NYZ072>075-176-178. High Risk for Rip Currents from 6 AM EDT Tuesday through Wednesday evening for NYZ075-080-081-178-179. NJ...Flood Watch from 8 AM EDT Tuesday through late Tuesday night for NJZ002-004-006-103>108. MARINE...Small Craft Advisory from 2 PM Tuesday to 6 PM EDT Wednesday for ANZ332-340. Small Craft Advisory from 8 AM Tuesday to 6 PM EDT Wednesday for ANZ345-350-353-355.