The Long Duration Snow Event

The Sun is shining. The birds are chirping. Half my front lawn is snow free. It’s so easy to think spring.

Not so fast, Bucko.

With snow, accumulation = intensity * duration. You can get a significant snow from a brief heavy burst or many hours of light snow. Odds are we’re getting the latter Wednesday morning through Friday morning. 48+ hours of precipitation seems likely!

As has been the case recently, the GFS and Euro disagree on most of the finer points.

The Euro is colder. Often I’ll look at the 850mb 0&#176C line–where the temperature at ~5,000 feet is 32&#176 Fahrenheit. It’s an excellent rain/snow predictor. That line is farther south on the Euro, meaning we’re more likely to see all snow even on the shoreline. The GFS solution leans toward mixed precipitation for the first 12-15 hours.

I’d go whole heartedly with the Euro, except for the addition of the SREF (Short-Range Ensemble Forecast) model. Uh oh, another American model?

The SREF goes out 87 hours and has been optimized to,

address the aspects of winter weather events beyond accumulation – specifically duration, timing, and intensity.

The SREF is actually 21 slightly different models run simultaneously to produce an ensemble. Like its American cousin, the GFS, it’s leaning toward mixed precipitation for the first half day.

Truth is in both the Euro or American models, Wednesday’s precipitation looks light. Even as all snow we’ll get no more than a few inches by nightfall Wednesday.

By Thursday all the models come into agreement on Ptype (precipitation type)–Snow!

By this time the forward progress of this storm has been slowed to a crawl. The GFS shows the central low pinwheeling in place most of the day!

Here’s the bottom line: Mainly light snow inland, with light mixed precipitation on the shoreline beginning Wednesday morning. Accumulations by Wednesday sunset just a few inches inland. Travel Wednesday will be a little slippery, not terribly bad. However, the storm continues.

Light snow overnight Wednesday/Thursday with light to moderate snow continuing through late morning Friday (a little longer toward I-395). Thursday will be a more difficult travel day. Friday morning too!

Final accumulations 6-12″ inland, with highest amounts north of Hartford, in the hillier terrain Northeastern and Northwestern Connecticut and inland near the Rhode Island border. On the shoreline, 4-8″ with lowest amounts in the New London/Groton/Stonington area.

Remember, in this case ‘final’ isn’t until Friday!

More updates to come.

12 thoughts on “The Long Duration Snow Event”

  1. with this storm comming and keeping you busy are you going to be putting anything on for your followers for the comet Panstarrs coming into view beginning of next week

  2. Geoff – thank you for these freebie forecasts which are more in-depth than the ones we “pay” for (via commercials etc.)

    Also, any insights on the comet would be much appreciated! Thank you again!

  3. Really appreciate your forecast, Geoff! You’re the best and we’re so glad you’re still standing by us. Thank you, truly!

  4. Ditto to what the others have said and thank you for a little peak into why the forecasters so often don’t seem to talking about the same state.

  5. Hummm…. well, despite this forecast I still love ya…

    As some one already posted, your forecasts are usually “right on” (a 60’s/Jon Denver moment) Tells me to plan on going up to visit with my Mother Sunday, or early next week instead of the end of this week.

  6. Thanks, Geoff. As nice as Rachel is, she never puts herself on the line and articulates the forecast so that we can figure out what to expect. I know that it is sometimes hard, but you have to com down somewhere sometime and PREDICT the weather. that’s what we all tune in for. You are the only oe who ever did that. Miss ya’. 🙁

    1. Rachel is an excellent forecaster. I stand by every word I said while working with her.

      She and I often discussed her role as your expert. The public understands the forecast will never be 100% right, but Rachel is so dedicated to accuracy that the fear of getting any part wrong sometimes shapes her narrative. It would be difficult to find someone more capable and dedicated than she is.

  7. I enjoy reading your blog daily, yet I never comment. I just wanted to say thanks today. You obviously put a good amount of work into forecasting for us. Thanks even more for all the effort you put into educating us. You are one of a kind!

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