Heat wave: First 70s arrive slightly ahead of schedule tomorrow

Yes, I just wanted to gratuitously type the word "heat" for the first time in 8 months.

Our spring-like forecast kicks into high gear tomorrow as the warmest day of 2014 rides in on balmy southwest breezes. If Sunday's 62 degrees didn't do it, tomorrow may be enough to restore your faith in the season formerly known as spring in Minnesota.

• 75 degrees flashing on bank thermometers quite possible in the metro tomorrow afternoon

• April 13 -- average date of first 70 degree temp in metro

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Models often under-forecast extremes

There's no doubt about it, weather forecasting is a tricky task. A good dose of science, with a splash of art?

Absolutely.

It's always interesting to watch how many of the forecast models we use under-forecast extreme warmth. Two cases in point jump out in the past few weeks.

• On Monday, March 10 we hit 53 degrees at Minneapolis-St. Paul International Airport. It was the warmest day of 2014 to that point. Most of the models we use vastly under-forecast that temperature spike. Here's what I wrote on March 7 a few days before that sharp warm up.

The European Centre for Medium-Range Weather Forecasts model is even more aggressive on next week’s warm up.  Four days in the 40s next week? We’ll see, but the trend of a more sustained warm up looks solid.

Even the most aggressive model was 6 degrees too low for Monday's eventual high of 53 degrees 3 days out.

• Sunday's high of 62 degrees was also under-forecast. Most of the models leading into Sunday forecast 51 to 55 degrees. I went higher and forecast 58, and then kicked myself Sunday afternoon for not going at least 60 degrees as I had initially intended because that was still too low.

Here's what I penned Friday afternoon for Sunday.

I like the look of the National Oceanic and Atmospheric Administration’s Global Forecast System output for temps overall this weekend, but feel that Sunday’s number may be too conservative. Upper 50s in the metro Sunday afternoon?

Bottom line? Some forecast models we use are tied to climatic norms and have trouble thinking out of the box on extreme temperature days. Tomorrow may be one of those days.

One of the techniques I use here at the Weather lab comes from some tried and true old school forecasting I learned working with some ex Air Force forecasters in my younger days. It's called the 850 millibar mix-down technique.

Basically, it uses the principle that temps about 5,000 feet above ground (850 millibar surface) are a good indicator of how warm it will get on any given day if conditions are right -- plenty of sun and a breeze to "mix-down" the air aloft.

Using that technique for tomorrow yields a potential afternoon temp of 75 to nearly 80 degrees in the metro.

Everything would have to go just right -- southwest breezes, all day sun, no snow cover etc to get that warm, but it's possible. Don't be shocked if we see the first 80 degree temp of the season in southwest Minnesota tomorrow afternoon.

I'll ditch the conservative "Minnesota Forecaster" in me and predict at least 73 to 75 degrees by late for the metro Wednesday afternoon, which should feel great. And of course, I probably just doomed myself to be too warm tomorrow and watch as temperatures hover in the low 70s.

I'll take it.

The most aggressive model tomorrow is the National Oceanic and Atmospheric Administration's Global Forecast System, which cranks out 72 degrees for MSP Airport.

Enjoy!

 Spring hangs tough this week

We cool off a bit late this week, but our Pacific cool fronts now would have been considered welcome warm fronts a week or two ago.

Look for a few showers early Thursday morning. A wetter forecast with more numerous showers and even some thunder looks likely Saturday.

Sunday and next week look cooler than this week but probably 40s and some 50s. No big wintry relapse on the horizon any time soon thank you very much.

In fact there are hints that a milder flow returns around and after the weekend of April 19-20 with many more days in the 60s -- and possibly 70s -- ahead.

A couple of wet systems could bring more April showers. From white to green in the Minnesota landscape in just three weeks?

What a concept.