‘Midnight Chinook’ micro thaw overnight, blustery today, 30s return tomorrow

Upside Down Temperatures

How did we fall asleep in the Yukon and wake up in Des Moines, Iowa?

A very interesting and relatively rare weather occurrence happened overnight in the Twin Cities and southern Minnesota. Temps actually rose 18 degrees overnight in about 8 hours. In fact, we cracked the thawing point in the Twin Cities for the first time since Dec. 3.

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  • 15 degrees at Minneapolis-St. Paul International Airport at 8 p.m. last night

  • 33 degrees at MSP at 4 a.m. today

  • +18 degrees in 8 hours

614 temp graph
Image: Weatherspark

Our overnight micro thaw is courtesy of a westerly breeze that blew in a milder Pacific air mass. Here's a look at surface winds from http://earth.nullschool.net.

614 msp wind map
Image: http://earth.nullschool.net/

Temps will be a little upside down today as cooler breezes blow in behind the next cold front.

614 sfc map
Image: College of Dupage

Cooler tonight, thaw returns tomorrow

Minnesota lies in the battle zone between Pacific and Arctic air masses this week. Cooler winds blow in tonight, but breezes turn southerly again Wednesday, and a noticeable (welcome?) one day thaw is on the way.

Unlike our overnight micro thaw, this one brings the axis of mildest air, the so called "thermal ridge," right over southern Minnesota Wednesday afternoon.

If we get any sunshine, temps will soar. At this point, mid to upper 30s look quite possible for the metro. I'm bucking the (more conservative) models a bit, but I won't be shocked to see 40 degrees in southern Minnesota by Wednesday afternoon. Here's a look at forecast high temps Wednesday afternoon.

Temps in the 60s just west of Kansas City, Mo.,  a week before Christmas?

614 MaxT2_uppermissvly
Image: NWS

Twin Cities: 6th coldest December on record so far

It's not your imagination, its cold outside.

The Twin Cities National Weather Service has a good look at our 6th coldest start to December.

614 dec so far
Image: Twin Cities NWS

Looking ahead I think our temp moderation will probably ease us out of top 10 coldest range for the month in the last half of December.

Buyer beware on model driven forecasts and smart phone apps?

These days it seems like everyone is a meteorologist.

We all have great weather apps, instant doppler, "MeCasts " and temps on our cell phones 24/7. Weather information is literally everywhere these days. The question is: How accurate is all of that (model automated) weather information, and how skilled are you at interpreting it when it's off the mark?

Stand in a group of hockey dads and everyone can tell you their most accurate version of the forecast. "This band of snow is going to miss us to the north." We've all heard it before. Just enough (weather) knowledge to be dangerous? I've seen it happen.

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Radar and smartphone weather apps are great. But user beware, radar is an animation or static snapshot of what's just happened or happening now.

What it it doesn't tell you is how things may develop in the next few hours. An experienced meteorologist usually knows how a front or incoming moisture will interact and change the radar picture hours before you see it on your weather smart-app.

Sometimes things can even sneak by a well trained meteorologist or the best supercomputer driven numerical forecast models.

Case in point. We all know that the warmest temps occur in the late afternoon, right? Not always. Our overnight, stealthy, Chinook induced micro thaw is a perfect example.

Temps struggled to make 17 degrees in the metro yesterday around 4 and 5 p.m. They began to pull back after sunset as usual. Then a funny thing happened. The surge of milder Pacific air working into western Minnesota boosted overnight temps by as much as 18 degrees!

Temps actually rose at MSP Airport from 15 degrees at 8 p.m. last night, to 33 degrees by 4 am.  That's a highly unusual occurrence on a winter night with snow cover on the ground.

614 33 degrees
Image: Twin Cities NWS

The forecast models totally missed this rare occurrence. Here's what the North American Mesoscale Forecast System model (one the the models that may feed your smartphone weather app) said would happen with overnight temps. It held temps at 17 to 18 degrees all night.

614 nam
Image: NOAA via SUNY Albany

Ooooops.

That's a 15 degree temp error, not easy to do in the first 12 hours of a forecast.

The bottom line? Your smart phone weather app is great, and provides valuable information most of the time. But it's not a substitute for interpretation from well trained, experienced meteorologists who can see things changing and who know about the inherent biases of many models.

Thankfully for our job security, the models are still far from perfect, and meteorologists can still usually improve on model driven forecasts.

There is still plenty of art in the science of weather forecasting.

That said, mashable.com has a good list of 13 weather apps you may want to look at. I'm a Weatherbug fan. Simple, with easy to use displays. I also like RadarScope for more advanced radar displays.