Tough Storm Leaves – Finally

This storm was a real pain to forecast. Last week, most of our models had converged on a solution that indicated a major snowstorm was on the way. The GFS model, to its credit, did not.

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The solutions on our computer models from Wednesday and Thursday were followed by much weaker and out-to-sea solutions with varying impacts for the state. Some models showed nothing and many showed a couple inches. By Friday we were confident that we wouldn’t see a blockbuster storm (>12″) but the final amounts were still up in the air.

As it turns out our forecast from Friday afternoon wasn’t a bad one.

Forecast from Friday at 5 p.m.
Forecast from Friday at 5 p.m.

On Saturday we pulled back the numbers a bit and then by Sunday morning basically brought them back to where we were on Friday. There’s nothing worse than a “windshield wiper” forecast but sometime it’s inevitable.

By the time all was said and done the storm didn’t actually produce a whole lot of precipitation in Connecticut – generally under 0.3″. In general that’s a pretty minor event. This storm was able to produce somewhat more impressive snow totals due to how fluffy the snow was. This was a very low density snow. In West Hartford the 3.4″ of snow I measured only contained 0.21″ of water (a 16:1 snow the liquid ratio). In Bakerville coop observer Denis Miller had a 23:1 ratio with 2.3″ of snow containing 0.10″ of liquid.

Snow and liquid totals from CoCoRaHS observers. Reports after 7:00 a.m. are close to final totals.
Snow and liquid totals from CoCoRaHS observers. Reports after 7:00 a.m. are close to final totals.

Why was this?

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This is a forecast sounding this morning off the NAM for Hartford. Notice the white line that juts to the left? That farther left the faster the air is rising. It’s also happening at 12,000 feet above the ground where the temperature is -15C. This is where snow flakes form most efficiently and dendrites (those beautifully ornate crystals) are the favored crystal type. The combination of efficient snow growth and the presence of dendrites allows the snow to pile up quickly. Dendrites accumulate with a lot of air in between them which leads the snow to be low density. Temperatures near the ground were close to 32F which causes the snow to be tacky or sticky which is why it clung so readily to trees.

There’s a lot that goes into forecasting snow totals – figuring out the density of the snowfall is one of the most important things. Ironically, the snow that fell on the first full day of spring was the most fluffy snow I had all season in West Hartford. Strange indeed.

2 thoughts on “Tough Storm Leaves – Finally”

  1. “By Friday we were confident that we wouldn’t see a blockbuster storm (>12″)”…..

    Gee, what are the odds of a >12 ” inch snow in the Tri-State area the last week of March – lol.

    You guys are always trying to shoot for that 99 yard pass with winter storms…esp when we have a mild winter like this past one.

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