Our old friend - La Nina

I realize that we have heard a lot about la nina in the past year - it was about a year ago that a signal began showing up in the Pacific equatorial waters of a developing la nina - but I think you'd agree that it has played a significant role in our weather over the past few months.  So we are now about to emerge from our cold and somewhat snowy winter cocoon, and the question becomes:  will spring arrive on schedule?

The one thing that I hate to be is the bearer of bad news, but I have to be in this case.  According to the climate records of past la nina years, it may be a chilly start to the spring season.  I'm not saying the entire season will be a chilly one of course, but the initial weeks of calendar spring could average out to be below normal.  First, you have to ask yourself:  what is normal?  The average high temperature for April 1 is 50 degrees, with 64 degrees being the average high by May 1.  That being said, can we expect 60 degree days in April?  I'm quite sure that we will accomplish that threshold several times over.  The statistics for la nina springs, however, point at a below average trend through the first half of April.  According to the numbers for La Crosse from the National Weather Service, 10 out of 15 la nina years have featured below normal temperatures for the February-April period (see graphic below). 

I kind of groaned when I first read this, but there are definite advantages to a slower warmup.  The biggest would be a gradual runoff of the snowmelt that is going to occur in the next few weeks.  If we are so fortunate to get hit with another winter storm (as appears might be the case early next week), that will only add to the amount of water that will eventually run into the rivers.  A lot of people still remember the disastrous flooding that occurred in 1993 when melting snow combined with heavy spring rainfall to create destructive flooding along the Mississippi River.  A fast meltoff due to a quick warmup could very well lead to more massive flooding.  On the flip side, a quick melting of the snow and thawing of the ground will only expose it sooner to the stronger rays of the April sun.  The past few spring seasons have featured fairly dry conditions, which in turn has led to a higher fire danger when you factor in warmer temperatures, low humidities, and brisk winds.  So far this year, I'd say that conditions have been ideal for the ground around western Wisconsin!  Snow cover has protected the ground from the several rounds of Arctic cold, while maintaining a consistent snow cover for winter outdoor enthusiasts.  Now, as we push forward into spring, a slower warmup will reduce the chances of river flooding and/or spring drought and grassfires.  Still, a taste of 50 degree weather in the near future would be nice!

Chief Meteorologist Doug Michaels