Flood 2011 Recap; Late-week snow chance fades?

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The floods of 2011 are still in progress and have caused problems in some areas. There have been two flood related deaths, numerous roads, parks and fields remain under water, especially near the Red River.

But it could have been so much worse.

Here’s a recap of how the floods of 2011 came to pass, and why it appears we have dodged what could have been a disastrous record flood year…so far.

Loading the dice:

The dice were loaded as early as late last summer and fall for spring flooding in 2011.

Record September rains swelled many area rivers to record fall flood crests. September 2010 was the wettest on record for Minnesota, according to the Minnesota Climatology Working Group.

The statewide average rainfall was 6.47″ in September.

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Many southern Minnesota locations south of the Minnesota River were deluged with as much as 10″ to 12″ of rainfall last September.

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As a result, many rivers including the Minnesota reached unprecedented record fall flood levels. In spite of an October dry spell, rivers were high, and soils largely saturated going into the winter freeze up in November.

Snow Blitz 2010-’11:

The winter of 2010-’11 began precisely on November 13th, 2010. That’s the day the season’s first big snow storm covered the Minnesota landscape with as much as a foot of snow…snow that would not disappear until early April in some areas.

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The snow blitz continued at regular intervals with three massive storms to close out 2010, including the infamous “Domebuster 2010.”

Story link: MyFoxTWINCITIES.com

The December “snopacolypse” the snowiest December on record at Twin Cities Airport.

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2011: New year, same weather

The snow blitz continued into 2011. Storms continued to pile up snow on the landscape. By the time March rolled around it was the 5th snowiest winter on record for the Twin Cities.

All that snow contained a lot of water. Much of southern Minnesota had “snow water equivalent” of anywhere from 6″ to 8″+ available for melting, and runoff into area rivers.

In late February, NWS hydrologists issued some alarming forecasts about the potential for record flood levels on many area rivers.

Southern Minnesota: How we dodged the bullet on record floods.

The warm up came in mid-March.

A string of mild days peaking in the 50s, and several nights above freezing started the snow melt.

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As water gushed into area rivers, the rains came. Over an inch of rain fell on March 22nd. This “washed” additional snow cover and rain runoff rapidly into rivers. As a result, rovers were “shocked” into rapid rises, and the first flood crest was on, peaking in southern Minnesota rivers on March 28th & 29th.

It appears at the time that the rivers may have been headed for a record flood, but then came the cold.

Arctic air mass saves the day:

Behind the March 22-23 storm, a big sprawling arctic high pressure system settled in over Minnesota. For 6 days, overnight lows plunged into the teens, and daytime highs struggled to reach the freezing point.

The instant freeze locked up all water in snow cover and on the landscape in place, and almost instantly shut off any additional runoff into rivers. As a result, rivers peaked on March 28-29 and began to slowly fall, instead of rising to the record levels that would have likely occurred with milder temperatures and/or more rainfall.

That’s how we dodged the record floods of 2011.

2nd Crest: A blessing in disguise?

Though southern rivers were falling, the flood gun was still partially loaded. Snow still on the ground packed plenty of water, and the potential for more snow, rain and a sudden warm up loomed.

Thankfully the weather cooperated, and a slow warm up created the perfect “time release” scenario for a “manageable” 2nd crest on southern Minnesota Rivers.

The fortunate fact that we able to “spread the water out” over two different high but manageable flood crests in 2011 may have saved us from what would have been a damaging all time flood of record on river in the south.

Red River: Not so lucky

In the north, the Red River watershed never really got in on the first big warm up in March. Temperatures remained cold enough, that most of the snow stayed intact in mid March.

As a result we are now seeing the effects of the higher “single crest” that was feared on southern Minnesota rivers this spring.

The Red River @ Fargo appears to have peaked at 38.75 feet on Saturday, below earlier forecasts of 39.5 to 40+ feet.

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Still, the 39.75′ crest at Fargo is the 4th highest flood of record for Fargo.

Historical Crests for Red River of the North at Fargo

(1) 40.84 ft on 03/28/2009

(2) 39.72 ft on 04/18/1997

(3) 39.10 ft on 04/07/1897

(4) 37.34 ft on 04/15/1969

(5) 37.13 ft on 04/05/2006

(6) 36.99 ft on 03/21/2010

(7) 36.69 ft on 04/14/2001

(8) 35.39 ft on 04/09/1989

(9) 34.93 ft on 04/19/1979

(10) 34.41 ft on 04/02/1978

(11) 33.26 ft on 07/04/1975

(12) 30.88 ft on 06/09/2007

(13) 30.50 ft on 04/15/1965

(14) 30.16 ft on 03/22/1966

(15) 29.80 ft on 03/31/1907

It is interesting to note that 6 of the top 10 highest floods of record on the Red at Fargo have occurred since 1997.

All in all, it appears in many ways we dodged a bullet for the 2011 flood season.

Snow chances fade for Friday & Saturday?

A weak front may trigger a few rain showers Wednesday afternoon.

You may have heard talk of another major snowmageddon scenario for Friday & Saturday. The GFS model has been in “weather terrorist” mode again this week, portraying the possibility of heavy snow in southern Minnesota Friday & Saturday.

I’ve been watching the models with a skeptical eye, and I think my suspicions are coming to light.

The latest NAM (much more reliable model lately) run is doing about what I expected…tracking a weaker, warmer system further south.

At this point, it looks like mostly (light?) rain for southwest Minnesota Thursday. The rain showers may spread north into the metro Friday, and could possibly mix with some wet snow flakes late Friday night into early Saturday.

At this point I don’t see any accumulations worth writing home about, but the system will still have to be watched.

Look for a return to cool sunshine with highs in the 40s Sunday.

Eau Calire County tornado damage Sunday:

Here’s the damage survey from Sunday’s storms in Eau Claire County.

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PH

  • http://daviddrufke.com David, Minneapolis

    “The GFS model has been in “weather terrorist” mode again this week…”

    LOL