Heads UP! for a light icy mess on Monday

Air lifted by a weak warm front coming up the east coast will produce an extended period of light mixed precipitation on Monday.

The warmer air will be enough to produce light snow, sleet and rain north of the front as the rain in the warmer air aloft falls into the colder air near the surface and freezes.

How long will the freezing precipitation last?
Perhaps all day, as the warm front does not have a strong storm system strongly forcing it northward. Since warm air is not as dense as cold air, it takes a lot of push to displace that dense cold air near the surface. The warm air takes the easier path, rising over the surface cold air. Rising air wrings out the rain, while the lower layer stays frozen.

A stronger storm goes through the Great Lakes on Wednesday, insuring the warm air finally makes it up the eastern coast of the US. That gives us rain late Wednesday – warm enough so no frozen stuff falls – before a super cold front blasts through on Thursday with a few snow showers.
That puts us back to below freezing temperatures for the weekend.

Here’s the thermal map for midday Monday. Notice the many colors in the area around NYC and Long Island showing the large temperature difference across a small area. A little change, moving more green color into an area, means warmer, with less frozen precipitation.

Temperatures (colors) and wind (white lines) at 1 mile up - 850 mb.

Temperatures (colors) and wind (white lines) at 1 mile up – 850 mb.

Friday, the strong cold front is seen in the tight range of colors being pushed eastward by the winds along the white lines.

850mb map of temperatures and winds for Friday morning

850mb map of temperatures and winds for Friday morning

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