El Niño rules: 40s again this week; Christmas Day snow chance?

This is how you draw up an El Niño winter in Minnesota.

They could have played the Vikings game outside Sunday afternoon with few complaints. Minnesota's El Niño-flavored winter has hit full stride. Sunday's high of 46-degrees in the Twin Cities is almost 20 degrees warmer than average. Temperatures pushed the 50-degree mark in northern Minnesota Saturday afternoon!

So far December is running 3.1 degrees warmer than average in the Twin Cities. We add to that positive temperature departure with highs in the 40s again this week. The average high in the Twin Cities this week is 26 degrees.

A white Christmas? It's on life-support for parts of Minnesota. More on our distant snow chances in the blog below.

Models underestimate extreme temperatures

So why did so many models and forecasters predict highs only in the upper 30s across Minnesota last weekend?

MOS.

Say what, Paul?

The numerical forecast models we use spit out forecast temperatures and other weather data called model output statistics, or MOS.

Here's an example of North American Mesoscale Forecast System MOS temperatures forecast numbers for Minneapolis. I've highlighted the predicted maximum and minimum temperatures MOS forecast numbers. (X/N)

Notice how the NAM mos forecast highs only in the 30s the next few days. Like last weekend, I'm predicting highs in the 40s again this week in the Twin Cities and much of Minnesota. Forecast model MOS numbers have a difficult time with extreme temperature events because they're still tied to climate norms.

Here's a good explanation from the National Oceanic and Atmospheric Administration.

That's why so many models and forecasters underestimate extreme temperature events. Also, the psychology of forecasting extreme events leads many forecasters to make a conservatively "safe" forecast.

Forecasting temperatures in the 40s when the seasonal average is 27 degrees? It's risky an people remember if you don't get it right. That's why you see so many forecasts "on the 9's" (like 39-degrees) as I like to say.

40s again this week

Monday's weak cool front is enough to keep many spots in the 30s. But that's still well above average. Highs hit the 40s again Tuesday and Wednesday across much of Minnesota.

I'm forecasting 44-degrees in the Twin Cities on Wednesday. Cooler, but still milder than average, air arrives late this week.

Brown and browner 

There's a lot of bare ground now across central Minnesota. Here's NASA's MODIS 1,000-meter resolution shot from Sunday.

Christmas Day snow chance? 

I still don't see any big snow chances between now and Christmas Eve. Forecast models hint at a chance for snow Christmas Day. NOAA's Global Forecast System model hints at the possibility of rain after that.

Stay tuned.