PM Zone 7/8 Mesoscale Update: Winter weather tonight

As discussed in updates for the past few days, a winter weather event is expected to unfold tonight across parts of Southern New England. This will be particularly true in parts of Eastern New York and Northern Connecticut, where we are anticipating the potential for freezing rain and sleet tonight into Wednesday morning. Short term forecast models continue to indicate low level cold air remaining stout in these areas, resulting in concern for slick roads and hazardous travel.

Multiple rounds of precipitation are expected through tonight. Regional analysis showed a low pressure system and associated mid level lows (in the middle layers of the atmosphere) over the Eastern Great Lakes. This is pumping south/southwesterly winds into the area and warming up these atmospheric layers. Therefore, most areas are experiencing plain rain. The surface and low level atmosphere temperature in the high elevations of Eastern NY and CT, however, is colder, allowing for sleet and freezing rain.

Overview of the synoptic setup in the low levels of the atmosphere as of 4:30pm.

Overview of the synoptic setup in the low levels of the atmosphere as of 4:30pm.

This will continue through tonight with multiple rounds of precipitation anticipated. Forecast models suggest steady precipitation during one burst this afternoon through early evening, and then another during the middle evening hours. Low pressure will be gradually transferring from the Eastern Great Lakes to a position off the Southern New England Coast on Wednesday morning. This track could allow moisture to linger in the area through Wednesday morning, resulting in drizzle and slick conditions continuing.

Untreated roads are likely to be icy and wintry across the mentioned areas through tonight and into Wednesday morning. While accumulating snow is not expected to be notable, freezing rain and sleet accumulations can cause very hazardous conditions. Crews should prepare to treat roads in elevated areas of Northern CT and Eastern NY from this middle of this afternoon through the morning hours on Wednesday.

Analysis of the atmosphere’s low levels shows 850 and 925mb (a few thousand feet above our heads) are warming with southwest winds. This will melt any snow flake on its way down, and allow it initially to refreeze as sleet. However, as this warm layer deepens — but cold remains right at the surface — precipitation will reach the ground as rain, and then refreeze…hence the transition to freezing rain overnight tonight.

Additional mesoscale updates will be issued through the mid evening hours.