Most of you have heard there is a nor’easter on the way for late Monday night and Tuesday.  This storm at about 5 p.m. was located off the mid-Atlantic coastline and will move northward over the coming 24 hours, eventually turning east and weakening over the Atlantic Ocean.

Typically, a storm taking this track would be a good snow maker for much of New England.  However, the lack of cold air is a problem and will not allow for a lot of snow from the coastline into the foothills.

A nor'easter will bring a mixed bag of precipitation to the area tonight and Tuesday

A nor’easter will bring a mixed bag of precipitation to the area Monday night and Tuesday.

The biggest challenge with the forecast is in knowing how much warm air will be present between the ground and the clouds where snow is being manufactured by the dynamics of the storm.

If the temperatures from the cloud to the ground are below freezing, we would be looking at a 12- to 18-inch snowstorm.  If the temperatures at the ground are really warm, we would be looking at an inch, perhaps 2, of rain.

In this upcoming storm, we have a combination of warm and cold air with a layer of warmth just big enough to melt the snow, and a layer of cold just thick enough for it to refreeze.  The image below is a prediction of the atmosphere over Portland on Tuesday morning.  The black line on the right represents temperature and this is forecast to bulge above freezing. This sandwich of warm air will melt the snow falling from the clouds, but the rain will then freeze into pellets of ice known as sleet.   It’s this funky profile that is the reason snow isn’t the primary concern.

Warm air at about 6 to 7 thousand feet will create a sleet and freezing rain situation

Warm air at about 6,000 to 7,000 feet will create a situation of sleet and freezing rain.

The exact depth of each layer determines whether you receive sleet or freezing rain, and I suspect we will get a bit of both.  Along the coastline, warm air off the ocean will change the precipitation to all rain much earlier than over the foothills and mountains.  In these areas, up to 5 inches of sleet and snow could accumulate.

Advertisement

Sleet and snow will make for slow travel late Monday and Tuesday

Sleet and snow will make for slow travel late Monday and Tuesday.

It will be breezy, but not excessively so, and I don’t expect any wind damage from this storm.  Coastal flooding, if any, would be minimal as well.

This is a moderate- to high-impact storm for travel because of the ice. This isn’t a major snowstorm or a major ice storm.  While there will be freezing rain on top of the sleet, I don’t expect it to become heavy enough for widespread power outages.  There can, of course, always be scattered issues in any storm.

You should expect precipitation Monday after 9 p.m and continuing through Tuesday.  The storm will wind down Tuesday evening, mostly in the form of rain.

Expect clearing skies Wednesday along with a mild flow of air.


Only subscribers are eligible to post comments. Please subscribe or login first for digital access. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.