Freezing Rain Potential Inland

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By Quincy Vagell on December 14, 2012, 11:20pm Last modified: December 17, 2012, 10:38am

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00z NAM model forecast 2-meter temperatures at 1 p.m. Sunday.

Although Sunday may be more wet than white, it could also get very icy for some.

Warm air is expected to move over colder, more dense air near the surface. The result is rain, but that rain could fall into a cold enough atmosphere to freeze on contact.

After an initial period of wintry precipitation Sunday morning, which could start as snow, I am seeing a strong signal for some freezing rain.
I do want to first say that coastal Connecticut should see almost 100% plain rain and that areas closer to the Massachusetts border have the higher probability of getting some icing. The concern is that the lowest levels of the atmosphere across portions of northwestern and northeastern Connecticut may get stuck near or below freezing for much of Sunday afternoon and evening. The result would be a minor to moderate ice storm as rain would freeze on many surfaces on contact. (areas being northern Litchfield County, northwestern Hartford County and towns in extreme northeast CT, like Stafford, Union and Woodstock)

Southern CT: Precipitation may start as a wintry mix, but then conditions warm and periods of rain fall from late morning Sunday through the rest of the day.
Near the I-84 corridor: Light snow or a wintry mix may coat the ground before freezing rain takes over. Light icing possible (under 0.25") before a change to plain rain.
Northwest & extreme Northeast CT: Light snow changes to a period of freezing rain and some areas may get 0.25"+ of icing. Worse icing possible if temps stay below freezing.
*This does not look like a big snow event, as most areas should get under 1" of snow.

The higher resolution models, the NAM and RGEM, are typically better to look at for situations of cold air damming. In this setup, high pressure north of New England noses down and keeps cold air locked in below about 900mb for much of the day on Sunday. The 2m temperature forecasts on both models only have highs between about 32 and 34F near the MA border on Sunday. The top image in this article shows the approximate high temperatures from the 00z NAM. The RGEM is very similar, as the two models say that portions of extreme NW and NE CT may have trouble rising above 32F.
A closer look at some grid data also shows this. The 00z grids for BDL show a high temperature of 34F with a period of freezing rain. What may be even more important is that 2m dew-points never rise above 32F. If steady precipitation moves in quick enough on Sunday, that will only help lock in the colder air. 

What's this all mean?
Well, forecasting ice storms and cold air damming can be very tricky in Connecticut. I have seen many times over the years where the computer models were 2 to 4 or even 6+ degrees TOO WARM in their forecasts. Although I don't think we see a huge bust like that here, all it's going to take is a degree or two to make the difference between isolated icing and more widespread icing. On the flip side, we do have a warm air-mass moving up and into the Northeast. The real question will be how strong does the cold air remain. 

Stay tuned to WXedge.com for the latest forecasts and discussions.
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Quincy Vagell

Town: Naugatuck, CT  

Reporting for WXedge since January 2012.

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