Area Forecast Discussion

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

1) Strong to severe thunderstorms are possible late today into this evening.

2) High rip current risk at the ocean beaches today.

3) Heat and humidity build again mid to late week, with a return of unsettled weather.

DISCUSSION

KEY MESSAGE 1

After a hot afternoon, a passing shortwave trough will help drag a cold front through late today into this evening. MLCAPE was nil as of 19Z per SPC mesoanalysis, but should increase through the late afternoon to over 1000 J/kg while unidirectional effective 0-6 km bulk shear increases to 30-40 kt. Storms over western PA in this environment are consolidating, and expectation is that they could arrive a little ahead of HRRR forecast, reaching the lower Hudson Valley and NE NJ between 6-8 PM, then continuing E across NYC, Long Island and S CT through the evening. SPC forecasts a slight risk of severe tstms for most of the area, with a 30% damaging wind threat from about NYC north/west.

Downpours with any thunderstorms could also lead to minor urban and poor drainage flooding, with fast storm motion mitigating anything more significant. The overall flash flood risk is low.

Storms should weaken this evening as they encounter a more stable marine environment E of NYC, but with a brief downpour and gusty winds still possible. Convection should clear ern CT/Long Island by midnight, with drier conditions overnight into Sunday morning.

Another shortwave trough passing through on Sunday could still produce isolated to scattered showers and possibly a tstm, with the better chances across SE CT.

KEY MESSAGE 2

There is a high rip current risk today at the ocean beaches. Increasing SW flow 15 to 20 kt and 3-to-4 ft swells at 8 sec drive this threat. Additional detail in Marine section.

KEY MESSAGE 3

The pattern could become a bit more unsettled mid to late week as high pressure shifts offshore, and a warm, moist flow develops around the ridge. With this, expect increasing humidity with hot afternoons, and heat indices approaching 100F in some areas by Friday. Additionally, with multiple disturbances rounding the base of the upper level ridge, there will be several periods with chances of showers and thunderstorms. Details will become clearer on how strong these thunderstorms can get as we head into the week, but it is worth noting that the CSU-MLP Day 6-8 outlooks show a marginal risk of severe weather.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

A pre-frontal trough moves across the area this evening followed by a cold front passage on Sunday.

Mainly VFR through the TAF period. Showers and thunderstorms remain possible this evening. Arrival time appears to be 22z-00z for NYC terminals on N and W, 00z-02z, western Long Island and southwest Connecticut terminals, and 02-04z for eastern Long Island and southeast Connecticut. Strong, gusty winds may accompany the showers/storms with a wind shift to the W-NW and potential for brief gusts up to 50 kt. The showers/storms should weaken as they move east of the NYC metro, but gusty winds 35-45 kt possible.

Outside of showers/storms, SW winds 10-15 kt with gusts 20-25 kt this afternoon and early afternoon. Winds will veer to the WSW-W tonight as wind speeds weaken to under 10 kt. W-NW flow increases Sunday morning, becoming 10-15 kt with gusts 20-25 kt late morning into the afternoon.

NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty

End times of frequent wind gusts may be off by 1-2 hours this evening.

Amendments for timing of showers/thunderstorms this evening likely. PROB30 could become TEMPO.

Gusts to 50 kt possible if any storms become severe.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY

Sunday Afternoon-Night: VFR. Isolated shower/storm possible eastern CT in the afternoon and evening. WNW-NW wind gusts 20-25 kt in the afternoon/early evening.

Monday-Tuesday: VFR.

Wednesday-Thursday: Mainly VFR. Chance of afternoon/evening showers and isolated thunderstorms. SW wind gusts 20 kt possible Wednesday.

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

MARINE

SCA issued for the Long Island south shore bays as SW winds increase late this afternoon and gust up to 25 kt til close to sunset. SCA also continues on the ocean waters into tonight, with gusts up to 25 kt and seas build to 5 ft, peaking this evening. That said, the bigger threat will be tstms this evening, which could produce wind gusts over 35 kt.

Flow becomes W-NW on Sunday behind a departing cold front. Winds and seas should both remain below SCA levels, with ocean seas 3-4 ft.

Rip Currents: There is a high rip current risk through this evening for the ocean beaches. Increasing SW flow 15-20 kt and 3-4 ft swells at 8 sec drive this threat.

The threat lowers to moderate on Sunday given little wind component and a 4-ft 7-sec S swell.

By Monday, the rip current risk will be low with the lingering S swell falling to 2 ft at 6s.

OKX WATCHES / WARNINGS / ADVISORIES

CT...Air Quality Alert until 11 PM EDT this evening for CTZ005>012. NY...Air Quality Alert until 11 PM EDT this evening for NYZ069>075- 078>081-176>179. High Risk for Rip Currents until 9 PM EDT this evening for NYZ075- 080-081-178-179. NJ...Air Quality Alert until 11 PM EDT this evening for NJZ004-006- 103>108. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ345. Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355.