Forecast: Chilly start, becoming pleasant

The coldest night of the season to date occurred from Sunday Night into Monday morning throughout most of the area suburbs. The pine barrens of Long Island, many interior areas of New Jersey, and the suburbs of New York and Connecticut fell into the 30’s with clear skies, light winds and a cool airmass settled into the area. The city and urban locations, however, struggled to fall — with Central Park already observing a temperature in the lower 50s as early as 730am on Monday.

NAM showing 850mb temperatures falling between -4 and -6 C through the Northeast later this week.

Temperatures will gradually warm throughout the day on Monday, making for a mid-autumn gem of a day. High temperatures in the middle 60s, with a light breeze and plenty of sun, can be expected throughout the area — with little chance of precipitation or even cloud cover. The one positive to take out of the next several days is that we can expect much of the same each afternoon.

By the middle to latter part of this week, temperatures will continue a step-down — owing to the large scale Northern Hemisphere pattern change we discussed as early as a week ago. Overnight lows will continue to get cooler, both across the interior and in the city. By later this week, high temperatures may struggle to get out of the 50s. The main story — as far as precipitation and unsettled weather go — will be a potential coastal system which scoots off the coast from Tuesday Night into Wednesday.

NAM model forecasting a weak coastal storm passing off the Mid-Atlantic coast Wednesday morning at multiple levels. 500mb (left), MSLP (center), and 6 hour precipitation (right).

Forecast models have been split on the development of the system, but it seems that any system which forms will do so in a progressive mid and upper level flow, so a high precipitation event is not expected. With the chilly temperatures moving in behind the system, however, some potential may exist for the first frozen precipitation of the year in the interior and higher elevations as the system moves to our northeast. Elsewhere, a cold rain would be the only effects felt from the storm, which will be out of the picture by Wednesday afternoon.

The tail end of the week, behind the storm system, will feature the coldest air of the season both at the surface and in the mid levels. Temperatures could fall below the freezing mark on Thursday morning in much of the area suburbs. The chilly pattern will continue through this weekend, but luckily the afternoons look to be pleasant and autumn-like.