Cannon River rages: Anatomy of a record flash flood; Metro siren update

8"+ rainfall totals near Stanton & Cannon Falls Thursday

12 feet - The "spike" in the level of the Little Cannon River Thursday night

20.4 FEET - New record flood level on the Cannon River at Cannon Falls Friday AM

Flash Flood - "A sudden rise in river or stream levels causing flooding" (Glossary of the AMS)

Saturday: Scattered T-Storms likely at times High near 82. Slight severe risk.

Father's Day: Mostly sunny & nicer for Dad's Day. High 85.

Rock The Garden: A 60% chance of a T-Storm. Temps near 80.

MSP quick look forecast:

Source: Twin Cities NWS

Grandma's Marathon: Probably dry for race time. Mixed sun & clouds. Temps in the 50s to lower 60s. Light winds off the lake. T-Storms likely PM & evening.

Duluth-Two Harbors quick look forecast:

Source: Duluth NWS

Cannon River in "record" flood.

Source: Cannon Falls Police

Cannon River reaches flood of record Friday. Damage reported.

Here's the latest from the Cannon Falls Police Department on damage sustained in Friday's record flood.

Media Release:

As of 6:00am on June 15, 2012 the river level of the Cannon River continues to rise and is currently above the levels experienced during the September 2010 flood.

As of 4:00pm on June 15, 2012 the river level of the Cannon River continues to drop steadily. It has lowered about 37 inches in the crest level. The Little Cannon River has dropped about 55 inches from the crest level. The crest occurred about 6am. The roadways that had been flooded within the city have been reopened. MN DOT reopened highway 20 at approximately 11am.

The amount of damage is significant, but will not be fully determine all damages until the rivers have returned to within the banks. Several large trees were toppled and washed into the foot bridges crossing the Little Cannon River. One of the foot bridges appears to have been washed off the footings.

Flooding occurred to both residential and business properties. In addition to river flooding there were reports of basement flooding from rain water and foundation damage to walls. The Salvation Army has provided the City of Cannon Falls with cleanup kits. The can be obtained from the Police or Fire Departments.

Anatomy of a Flash Flood:

Flash floods occur when excessive rainfall in a short period of time overwhelms drainage.

Land of 10,000 (new) lakes?

MPR's Bob Collins surveyed the flooding by air near Cannon Falls Thursday.

The result is rapid runoff, standing water, rapidly rising creeks, streams and rivers, and it can be catastrophic. Two homes were destroyed and significant tree and riverside damage occurred in and Near Cannon Falls as the Cannon River crested early Friday.

Source: Cannon Falls Police

Thursday night had all the right atmospherics for a flash flood event.

-A strong low pressure system and a stalled frontal boundary

-Strong slow moving storms "training" over the same ground for several hours

-Rainfall rates over 1" per hour for several hours

The result was rainfall totals over 8" near Stanton and Cannon Falls.

Source: Twin Cities NWS

One gauge near Stanton reported over 10" of rain Thursday PM & evening in just a few hours.

Source: WxUnderground

A wider area picked up 3" to 6"+ rainfall during the event.

Source: Twin Cities NWS

The 8"- 10"+ rainfall totals had nowhere to go, so rivers & creeks rose rapidly Thursday night

Check out the NWS Hydrograph on the Little Cannon River near Cannon Falls. That's a 12 FOOT rise in about 7 hours.

Source: Twin Cities NWS

Notice how quickly the flood recedes as the "bubble" of runoff runs downstream. That's why it's called a "flash" flood...it comes & goes in a flash. NWS differentiates flash flood events from river "Flood Warnings" which generally occur over longer period of time from longer term rainfall or snow melt.

Forecast: Weekend "Split"

The next wave of low pressure will bring scattered T-Storms to the area Saturday. Though the overall situation does not look "explosive" we'll have to keep an eye out for a few severe storms.

Source: Twin Cities NWS

Source: NOAA/SPC

Sunday looks good for Dad's...more sun and highs in the mid 80s. I see a boat ride in my future.

Outdoor Sirens: An update

Source: NWS

Here's an update I received from Eric Wagge with Hennepin County Emergency Management on the status (and some changes) in the way outdoor warning sirens are used for severe weather in Hennepin County and most of the metro.

There is a change in the way most of the metro will sound warning sirens now...and that is they will blow them for tornado warnings and for anticipated or observed winds of 70 mph winds or higher.

Remember, sirens are primarily designed as an outdoor warning system and are just one (important) part of your "multiple severe weather safety net" that includes NOAA Weather Radio, TV/Radio, smart phone etc.

Here's the update from Hennepin County Emergency Management:

(I apologoze this is pretty long...but it's important info to get out there!)

Purpose of Outdoor Warning Sirens

Outdoor Warning Sirens exist to alert people who are outdoors that an emergency situation is imminent or in progress.

Outdoor Warning Sirens are one element of a more comprehensive alert and warning system that warns people in many different situations. Indoors, at home or work, people should obtain a NOAA Weather Radio to monitor National Weather Service (NWS) signals and be provided continuous indoor alert services.

The Emergency Alert System is used to warn people engaged in listening or watching broadcast media. A new NWS program called Wireless Emergency Alerts sends warnings to mobile devices. No single element of this system is capable of reaching all people at all times. These elements work together as an overlapping alert and warning system.

Actions to take when Outdoor Warning Sirens are heard:

1. Get inside. Take immediate action to find shelter inside. Small, interior rooms, away from windows on the lowest level are best. Have items available to use for personal protection, such as sturdy furniture, cushions and helmets.

2. Get information. Find a source of official information to know what type of emergency is happening and what to do next. Broadcast media are critical to get quick and accurate information at this time. Have a battery powered radio, television or other mobile device capable of getting news.

And here's the updated siren policy in Hennepin County. (and most of the metro)

Reasons for Outdoor Warning Siren activation:

Natural Hazard - Severe Weather

- Tornado Warning. Tornado Warnings are issued by the

NWS based on trained spotter reports and specific radar indications. A Tornado Warning means that a tornado has been spotted or is imminent. Sirens are sounded immediately when the NWS issues a Tornado Warning.

- Winds at or above 70 miles per hour. Measured or NWS forecast wind speeds at or above 70 MPH will trigger siren activation.

Please understand the following regarding severe weather...

- Winds at or above 70 MPH will cause the NWS to issue a Severe Thunderstorm Warning, however the NWS criteria for a Severe Thunderstorm Warning starts at lower wind speeds of 58 MPH. Forecast hail of 1 inch diameter or larger also results in a Severe Thunderstorm Warning. Hennepin County does not sound sirens for hail or winds below 70 MPH, therefore sirens are not sounded for all Severe Thunderstorm Warnings.

- Why was 70 MPH selected by Hennepin County? Collective experience in the weather and emergency management communities suggests that 70 MPH is the speed where winds start to present a serious threat to life safety. At about this speed, some large healthy trees will start to fall, structures begin to pull apart and flying debris can become deadly missiles.

What you'll hear:

What will sirens sound like?

- An ALERT SIGNAL is used for all Severe Weather and Industrial Accidents. The ALERT SIGNAL is a five minute steady tone. Five minutes will allow you enough time to 1) Get inside, and 2) Get information.

- An ATTACK WARNING is used for situations where an enemy attack is imminent or in progress. The ATTACK WARNING is a five minute wavering (rising and falling) tone.

- Outdoor Warning Sirens DO NOT sound an all clear tone. Sirens will not tell you when the situation is 'clear.' People must use official sources and broadcast media reports to determine when it is safe to come out.

Also here's the policy for more metro counties.

Coordinated Regional Siren Activation Standards:

- Most Twin Cities Metropolitan Area counties (including Hennepin County) have decided to adopt a single severe weather standard for Outdoor Warning Siren activation. A regional standard reduces confusion about sirens as people travel between counties to work, live, shop or for recreation. The regional Outdoor Warning Siren standard activates sirens for 1) an NWS-issued Tornado Warning and 2) activation for actual or forecast 70 MPH winds.

- Metro Counties adopting the regional siren standard include Carver, Chisago, Hennepin, Ramsey, Scott, Sherburne, and Washington.

I'm pleased to see a move toward a more "coordinated" and uniform approach to sirens so the public knows what they mean when they hear them. Now I encourage Dakota and all other Minnesota Counties to join in and create a metro and statewide uniform standard for siren activation!

Back in the day at WGN-TV...

I had to laugh when a friend from my WGN-TV days sent me this video. I worked with Larry Potash and Robin Baumgarten (who you'll see in the video) back in the 90s at WGN-TV. I was hired as the meteorologist for the debut of the WGN Morning News (or as we used to call it the "WGN Morning Zoo") in 1994.

WGN Morning News team back in the 90s.

(What's up with the bad hair day and cheesy moustache?)

Check out the latest promo from my former colleagues courtesy of TVSPY. Larry Potash nailed this one.

It's good to see some people are still having some goofy fun in this business.

After 2 years of sleep deprivation I moved on to working nights in Arizona and was happy to relinquish my gig to weather guy Paul Konrad (also in the video), who's a native Chicagoan and is still a part of the show today. What a great crew to work with, and yes...Tom Skilling really is that cool.

Have a great weekend!

PH