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SPRING BREAK IS OVER...

Wednesday was another warm spring like day around the Midwest. After some morning showers skies broke out and most areas squeezed out enough sunshine to get temperatures into the range of 65 to 71 degrees. In my western counties, instability was sufficient enough for the Storm Prediction Center to issue the first tornado watch of the year, well ahead of schedule.

No tornadoes were reported but a number of tornado warnings were issued in southern Minnesota. That's really early for that part of the Midwest! Overall, there were 10 reports of severe weather with most of it clustered around Minneapolis.

This was the severe weather risk outlook issued by SPC. That's the first we've seen of this since last fall.

The storms developed ahead of a cold front which was punching east across central Iowa during the evening. This satellite is pretty cool showing the shadows being cast by some of the thunderheads which reached as high as 35-40,000 feet. I'm estimating some of the shadows were cast at least 50 miles east of the advancing storms.

This radar image taken around 7:45 Wednesday evening shows a broken line of storms moving into eastern Iowa. Some gusty winds and small hail were found in spots but it appears everything remained below severe limits. This was a good warm-up for the season that's ahead of us.

Here you can clearly see the clouds and storms along the cold front as it marches towards Illinois.

With winds turning to the northwest behind the front Friday temperatures will be noticeably colder. 2PM readings on the EURO look like this. Spring break is over.

That's down a good 15 degrees from 24 hours earlier.

That brings us to the weekend which is fine Friday and Saturday with dry and seasonally cool conditions. The problems begin Sunday as a strong cut-off low brings precipitation that in many areas starts as rain and in others ends as snow. While the details are far from certain regarding snow, models have been quite consistent showing a wet system with precipitation amounts of an inch or more in the south. The GFS shows these totals Sunday through Monday. The EURO is similar.

The big challenge is determining how much of this comes down in the form of wet snow. Rain which initially is intermittent Sunday increases Sunday night as the upper level energy approaches. Dynamic cooling commences Sunday night when the potential exists for the rain to change to snow. However, the process is only sufficient to make the transition in the northern half or so of my area. The south stays mainly a cold rain. Things had been pretty close between models in terms of where the snow band would set up until about 10 minutes ago when the EURO cleared. It made a significant shift north on the snow band and that brings lots of doubt into what ultimately happens in my area.


This is the point when I put up the snow projections on the models. To be clear, these are not forecasts, just model guidance, (interpretations) of where and how much snow might fall. I use these to establish trends. As confidence grows and we get closer to the event, that's when a hard forecast is issued. After seeing the EURO my confidence level took a big hit and now I'm back on the fence, an uncomfortable place to sit. Now, the outcome is on hold as we wait to see which of the models has the right idea going forward. This is where we take a deep breath and wait for the dealer to pass out new cards. For now, this is the range of what's on the table. Notice the difference in hands.


The GFS

The GEM

The EURO, whoops...big difference here!

The big thing now is not to over-react to any solution as systems with precipitation type issues and transitions are fraught with pitfalls. Not the least of which is calling the rain snow line and how soon the switch from rain to snow occurs. A degree or two aloft can make a major difference. Time is still on our side but the word is out, there are now major issues to iron out between now and Sunday night as to whether we shovel or not. Roll weather...TS

ONLY 26 COPIES LEFT:

I will take this opportunity to mention that I only have 26 copies left of my book on the most expensive thunderstorm in United States history (11 billion dollars in estimated damage). This will be the final printing. If you are interested in having the most authoritative account of this extreme event I would suggest you act now. Don't miss this opportunity to own the weather story of a generation. You can order yours at derechobook.com

BOOK ENDORSEMENT.

*This book has been quite the talk with the Iowa State Library promoting it. I have never seen the State Library promote any books like this unless it was an award winner of particular interest to libraries. Hopefully your sales are through the roof!

Jolene Kronschnabel-Director of Hawkins Memorial Library, La Porte City, Iowa

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