The good ole’ days

I love forecasting weather. After a winter of unclear systems, finally we're getting a system that looks like the those we used to get back in the good ole' days.

Even though it's no fun to endure rain or snow for most of us, weather forecasters tend to love forecasting storms. Big, wet, sloppy storms. The bigger the better.

Bigger "synoptic scale" storms have a large area of geographical coverage. In this part of the world we call them mid-latitude cyclones. The effects of these storms may reach from Canada all the way to the Gulf of Mexico.

Our suite of numerical computer forecast models tends to like big storms. They handle them better than little systems because there are more data points to grab hold of. The system headed in late this week is a classic.

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After a beautiful spring day Wednesday with plenty of sun, light winds and temps in the 50's, we turn our attention south.

The next big low pressure system will wind up with the surface low near Kansas City Thursday. The GFS model takes it just east of La Crosse Friday to near Green Bay Saturday. This is an ideal track for heavy rain or snow for Minnesota.

Another factor working in favor for significant precip is a good fetch of moisture from the Gulf of Mexico. As we say in the weather biz, "the Gulf is wide open" with this one.

The real forecast question with this system appears to be the thermal profile within the storm. Specifically, where will the rain snow line set up? Early indications are that it may set up just north and west of the metro, then move south and east as the storm pulls colder air in from the north Friday. That would mean places like Willmar and St. Cloud and Duluth will see the best chance for all snow Thursday, and the Twin Cities could begin as all rain. As the colder air slides in, we may see a changeover to heavy wet snow in the metro later on Friday.

All systems are different. If this was January and this system was all snow, we'd be forecasting over a foot for much of southern and central Minnesota. As it is, those areas that stay all snow may get that much anyway.

This storm will have to be watched very closely. It has the potential to dump a foot of heavy wet spring snow somewhere close to home from Thursday into early Saturday.

NCEP "GFS" model forecast for 1pm Friday. The lower left panel shows the surface position of the low centered near La Crosse

Want some good news? A pattern shift next week looks to bring sunnier, drier and warmer weather into Minnesota. Hang in there!

PH