High alert: Significant risk today for severe storms and tornadoes

Every now and then we get one of those days in Minnesota where the severe risk is high enough we don’t pull any weather punches.

Today is one of those days.

A well advertised potent low pressure system and warm front surges north into Minnesota today. The risk for severe storms and tornadoes with this system is significant. Today is the day we talk about when we urge a high level of “situational awareness.”

Here are some critical severe weather headlines for today:

  • There is a moderate risk for severe storms that may spawn tornadoes across southern Minnesota today.
  • Tornado watches and warnings are likely this afternoon and evening
  • The National Oceanic and Atmospheric Administration’s Storm Prediction Center is highlighting the potential for violent EF3 tornadoes in Minnesota today.
  • The highest risk hours appear to be between 2 p.m. and 10 p.m. today.
  • Up to the minute storm reports and warnings on the MPR News Live Weather Blog.

Moderate risk

We don’t get many days each year when NOAA’s Storm Prediction Center issues a moderate risk over Minnesota. Today is one of those days. Here’s the risk map from SPC.

NOAA Storm Prediction Center

Closer look at tornado threat

Here’s the risk factor for tornadoes today. I don’t know about you, but even a 10 percent-plus chance of an EF2 to EF5 tornado within 25 miles of my house gets my attention.

The big concern today? Individual, “discrete” tornadic supercells capable of dropping down a few large violent tornadoes. While I can’t say for sure storms will turn tornadic, there is a good chance that that will happen today.

The highest risk area? In Minnesota, it’s a zone anywhere between Worthington, Redwood Falls and Willmar to the Twin Cities and down to Mankato.

NOAA / SPC

Here’s the attention getting language for Minnesota from NOAA’s SPC in today’s Convective Outlook.

…SUMMARY…
THE GREATEST THREAT TODAY WILL BE THIS AFTERNOON WITH AN ARC OF THUNDERSTORMS FORECAST TO DEVELOP INTO SUPERCELLS OVER PARTS OF MINNESOTA AND IOWA…THEN MOVE NORTHEASTWARD. TORNADOES–SOME POTENTIALLY STRONG–AS WELL AS LARGE…DAMAGING HAIL AND SPORADIC
SEVERE GUSTS ARE EXPECTED.

…MN/IA REGION…IN AND NEAR MDT RISK…

ONCE WARM-SECTOR AIR MASS FAVORABLY DESTABILIZES…SUPERCELLS SHOULD DEVELOP THIS AFTN NEAR SFC LOW AND ALONG ADJOINING COLD-FRONTAL ARC. SOME OF THESE CELLS SHOULD BE DISCRETE AND MAY MATURE LONG ENOUGH FOR CYCLIC TORNADO PRODUCTION AND LARGE/DAMAGING HAIL

Hail threat again

Last night’s storms featured some hail larger than golf balls in Lakeville. Thanks to Amy Juaire for sharing this remarkable photo of some impressive hailstones.

Many of us will see large hail again today into this evening. NOAA’s SPC paints a 45 percent chance for severe hail across a good chunk of Minnesota today.

NOAA / SPC

This is a good day to consider some indoor parking for your vehicle like Tim Hawkinson did last night before damaging hail pounded his location.

Prime time: metro afternoon rush? 

We don’t say this often, but it might be a good idea to consider altering your plans as we approach afternoon rush in the metro today. The hours between 3 p.m. and 8 p.m. appear to be the highest risk for damaging hail and tornadoes in the Twin Cities and southern Minnesota.

Our worst nightmare as meteorologists? A tornado cutting through rush hour traffic. If you have a safe place to shelter this afternoon and evening that is not on the roadways, now is the time to make adjustments.

The Twin Cities National Weather Service agrees. Here’s a snippet from the early morning forecast discussion.

AS FOR WHAT IS EXPECTED…BASED ON HI-RES MODELS…STORMS LOOK TO DEVELOP BETWEEN 18Z AND 20Z OUT IN SW MN…THEN RAPIDLY BUILD NORTH AND EAST…REACHING THE I-35 CORRIDOR BETWEEN 22Z AND 00Z. TIMING WISE…WE COULD HAVE SIGNIFICANT ISSUES AS SCHOOLS OUR LETTING OUT WEST OF THE TWIN CITIES…WITH ACTIVITY REACHING THE METRO DURING THE EVENING RUSH.

EF Scale: What does it mean?

The mention of “strong tornadoes” from NOAA should get our attention. EF2 to EF5 tornadoes produce incredible damage. Once you get into EF3 range you are dealing with 3 second gusts of around 150 mph. That’s enough to tear even well constructed homes apart.

NOAA

Here’s a good guide to what various EF-Scale damage looks like. I hope we don’t see any images like this in Minnesota by tonight.

NOAA

 Mother low

Finally, here’s the weather culprit responsible for our severe threat today. A strong low and warm front spinning into Minnesota from the south. This one is wrapped up enough to spawn some big storms today.

NOAA

Bottom line: There is a moderate risk for severe storms that may produce tornadoes today. Stay situationally aware today for severe storms. Watches and warnings are likely this afternoon and evening. Have a plan for where you will shelter if it becomes necessary. Keep the kids, your family and neighbors aware of the threat today.

Stay safe Minnesota.