Showers and thunderstorms will be coming our way

Tuesday has been a lovely day for most of Minnesota with afternoon temperatures rising well into the 60s and 70s. As is often the case, temperatures along the shores of Lake Superior were 20-some degrees chillier than those reported just a few miles inland.

What is not usual are the cool temperatures in southern Minnesota where thermometers have been blanketed by thick clouds and showers. Preston in the southeast reported just 51 degrees with light rain at 5 p.m. while Hallock way up in the northwest was a toasty 79.

Unsettled weather will surge a bit farther north tonight. Wednesday and Thursday appear likely to bring showers and thunderstorms to much of Minnesota. While amounts of rain are very difficult to forecast for specific locations, here is one prediction of rainfall for the three-day period ending at 7 a.m. on Friday.

The blob of possible heavy rainfall off the southeastern coast will be the result of a disturbance now southeast of Florida. It is forecast to strengthen as it drifts slowly north and is a reminder that the tropical storm season is not too far away.

Tornado season has arrived

I hope that you have had a chance to read Paul Huttner's excellent personal recollection of the Twin Cities' deadliest tornado outbreak in Updraft yesterday.  The date was May 6, 1965, which was 50 years ago Wednesday. If not, click here to jump to it.

While we are accustomed to the benefit of severe weather outlooks including the possibility of tornadoes so we can protect ourselves and our families, there was a time when such advisories were not permitted. Until 1950, meteorologists at the U. S. Weather Bureau (now the National Weather Service) were prohibited from using the word "tornado" in weather forecasts because it might cause panic. "What happened to cause a change in policy?" you might ask. Read on.

On March 20, 1948, a tornado struck Tinker Air Force Base in Oklahoma. When two Air Force meteorologists working there studied their weather charts for that day and then recognized that a very similar weather pattern was developing five days later, they issued a tornado forecast for that afternoon. The base safety plan was implemented and a very damaging tornado struck in late afternoon. There were injuries, but because of the awareness and preparation there were no deaths and damage was mitigated.

Here is a link to the full story of how that first successful operational tornado forecast came to be.

As a result of that forecasting success, Weather Bureau meteorologists were authorized to issue tornado alerts to the public beginning in 1950.

In 1952, the first public tornado outlooks were issued by the new Severe Local Storms (SELS) forecasting unit in Washington, D.C.

What we now call convective outlooks with risk areas for tornadoes, hail and wind damage are issued by the Storm Prediction Center in Norman, Oklahoma. The Storm Prediction Center also is responsible for issuing tornado and severe thunderstorm watches when severe weather is likely within the next several hours. Once a watch has been issued, the responsibility for issuing any warnings is passed to the National Weather Service Office(s) for that area.

The goal is that something looking like this will not strike without people having sufficient warning to get to a place of as much safety as possible.

Fortunately, the risk of severe weather in Minnesota over the next few days is quite low.