Update on squall line with potentially damaging wind gusts tonight:
The squall line will be racing eastward across Long Island tonight between around 9 PM and 11 PM from west to east with heavy rain, possible thunder, and the potential for wind gusts to briefly approach 60 mph from the south. The 1st image is for 9:00 tonight from the HRRR model, and the 2nd image shows the maximum projected wind gusts from the same model.
Here is a great forecast discussion from the National Weather Service covering the Tri-state area:
Model guidance is in excellent agreement on the timing of the strong cold front and associated convective line. Any showers ahead of the line should hold off until late in the afternoon or early evening.
Models can be 1-3 hours too slow with convective lines, so will continue to show it crossing the NYC metro 01-03z (8 PM to 10 PM), and Long Island and Connecticut 02-05z (9 PM to midnight). The strong front and convective line likely will push offshore around or just after midnight.
The risk for higher winds associated with a convective narrow cold frontal rainband (NCFR) exists across the entire region. As noted above, the line will likely just be reaching western zones just before 00z (7 PM), then racing eastward through the rest of the evening. Isolated damaging wind gusts are possible with this line. Instability is weak, but strong forcing is enough to include mention of thunder in the forecast. Many times, the highest winds occur on the leading edge of the convection, with winds diminishing once the heavy rain settles over a given location. Will mention the damaging wind gust potential in the HWO. We will handle the winds with the line with short-fused convective products (SPS or SVR).
Otherwise, a deep trough moves into the Great Lakes, and become negatively tilted this morning. The upper trough then moves over the northeast tonight. Strong low level winds, with a low level jet of 55 to 70 knots, develop ahead of the cold front late this afternoon and evening. Some question as to how much wind mixes down to the surface in the Wind Advisory area (Nassau, Suffolk, southern CT excluding Fairfield County). Strongest synoptic winds may hold off till late this afternoon and early evening ahead of the main convective line in the Advisory area. Sustained winds may be near 30 mph and gusts could push 45-50 mph in the Advisory area. These higher winds seem more likely over central and eastern Long Island. Elsewhere, southerly winds will increase today gusting 25-35 mph in the afternoon and evening.