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Welcome to the unofficial start of summer in Minnesota. 

Memorial Day weekend is the first of the big three summer holidays. Climatologically it is also the wettest and coolest of the three. The old weather wisdom says forecast rain and hope for better.

It’s interesting to note that forecast models are having a hard time locking onto the relatively small disturbances that may bring rain and thunderstorms this weekend. That’s not unusual in summer. There’s a good reason for this.

Large-scale weather patterns are driven by large atmospheric waves called Rossby waves. 

We could talk all day about this, but here’s the important idea from NOAA.

Short waves are, as the name implies, shorter than long waves. They ride embedded withing the overall long-wave flow pattern. They often trigger areas of precipitation out ahead of the wave.

So, how do long and short waves figure in our Memorial Day weekend forecast? Simply put, short waves are harder for forecast models to pinpoint several days in advance. The American and Canadian models suggest a short wave in southern Minnesota Saturday morning. 

If this timing works out it would trigger a batch of rain Saturday. The Canadian model also picks up a second rain wave into Sunday below.

The European model is trending drier this weekend. It prints out less than half an inch of rain for most of Minnesota, with heavier rains across Iowa.

Stay tuned as the forecast models track the short waves across Minnesota this weekend. Their posting and timing will determine when it rains at your location. 

Weather and Climate News

Updraft® - Minnesota Weather News

Paul Huttner

Author

Forecast models have a much tougher job timing summer rains.

NOAA

Canadian model upper air forecast Saturday morning

Environment Canada via tropical tidbits

NOAA via tropical tidbits

European model (ECMWF) precipitation output

Memorial Day weekend forecast: Models trending drier overall?

Go Deeper.

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