Icy Tuesday Morning Commute

If you’re excited about seeing snow I’ve got some disappointing news for you. If you’re excited about some ice (odd, but I’m sure some people are) I’ve got some good news for you!

The storm approaching Connecticut is moving into an environment that features a dry, cold lowest few thousand feet of the atmosphere and a relatively mild pocket in mid levels of the atmosphere. While a period of snow is possible at the onset I don’t expect many areas to exceed 1″ of snowfall. Most of what falls should be sleet, freezing rain, and rain. The morning commute looks tricky.

12zFDS

Here’s the GFS valid at 7 a.m. on Tuesday for Windsor Locks. You can see a sliver of air above 0c and a deep area in the lowest few thousand feet of the atmosphere below 0c. Quickly this sleet sounding will go over to a freezing rain sounding. You can see a pocket of just under 32 degree air a few hundred feet up even into midday n this morning’s NAM.

 

bufkitprofile

So where does that leave us? A touch of snow followed by some sleet across the state. Quickly, that sleet will transition to rain along the shoreline and freezing rain across the interior. Eventually, temperatures will warm above 32 degrees in most areas though in the hill towns – especially above 500 feet – a period of prolonged icing is possible.

Below, on the 4km NAM valid at 10 a.m. Tuesday, you can see the area of <0c surface temperatures banked up on the east slopes of the Berkshires and Litchfield Hills.

hires_t2m_boston_28

Up to 1/3 inch of ice accretion is possible which could cause spotty tree damage and power outages. Typically, 1/2″ of ice is needed to begin causing damage so we should remain under this threshold.

One additional note – I’ve seen many people post about ground temperatures remaining warm due to the mild December and this mitigating icing issues. To be honest, such an argument is total BS. Skin temperatures on surfaces will be cold enough to support icing by the time the precipitation begins. The only time when this is an issue is when the sun angle is high (think March or April) and snowfall intensity is light. This will not be a factor with this storm.

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