The Sioux Falls National Weather Service has compiled some more information about the tornadoes that reached EF4 strength near Sibley Iowa Friday night. Here is the path of the most intense tornadic period around Sibley:

There is more information available at the Sioux Falls National Weather Service website:

http://www.crh.noaa.gov/fsd/?n=tor2010jun25

You will read there how brand new cars were completely demolished, and how a car engine was ripped out and thrown around by this violent tornado. The pictures tell the story very well, as a home was completely ripped off of its foundation and another was leveled down to the concrete blocks. This is the reason for the EF4 rating.

I’ve snagged some radar images from the “tail end Charlie” supercell storm. Notice how there is a clear definition of the last cell in the line, and even a little hook or appendage on the west side of the storm. This is where the tornado formed, and why it was continuing to do damage during the storm’s life cycle. The last image is at midnight. Yes, this is late to have tornadoes in our area, as peak time for this is normally 4-9 pm. It was warm and muggy enough though on this night to prolong the tornadic threat.

Dave Winslow

Posted under Weather Blog

The Sioux Falls National Weather Service has done a damage survey of the tornadoes that struck NW Iowa Friday night and will soon be releasing more information. So far, we know that several touchdowns caused damage in areas from Lyon County to Sibley and a little south of there. The most significant was EF4 damage southwest of Sibley, IA. We will continue to follow the latest information and share it with you as it becomes available. Here are a few pictures we have received of the tornado that was most intense after dark, making it a very dangerous situation:

Apparently a dozen or so people were injured while they were traveling on Highway 60 and were caught in the path of the storm. They tried to take shelter in their cars under an overpass. This is not the place to be! But we are very grateful that they escaped with just some injuries. People have been killed in their cars in the past in other situations, so please don’t try to ride out a storm in a vehicle. It’s best to drive away from the storm or to seek shelter in a farmhouse basement.

Dave Winslow

Posted under Weather Blog

A Severe T-Storm Watch has been issued for central and northern Siouxland until 4 am including Woodbury County:

Ironically some storms have formed east of both of the watches that are out there:

The bigger concern though is what’s developing out west.  There’s a chance of a long-lived wind event call a “derecho” moving across Nebraska and into Siouxland.  So we need to be ready for the possibility of damaging winds later tonight along with heavy rainfall.  A Flash Flood Watch is also in effect tonight for all of Siouxland.  Stay tuned.

Ron Demers

Posted under Weather Blog

A Tornado Watch has been issued for western Siouxland until Midnight.  This includes all of our viewing counties in Nebraska EXCEPT for Dakota, Dixon, and Burt:

There will be a slight chance of severe storms early this evening (7 pm to 9 pm) with better chances coming our way later tonight.  We expect storms that have formed in Western Nebraska to race eastward and those along with the additional development of storms out ahead of that region to bring in chances of strong winds and heavy rain from 10 pm on into the rest of the night.  Storms that form earlier will have the better chance of trying to produce a tornado.  The storms that form later will be more likely to produce the severe winds and heavy rain.

Stay tuned to this blog, Twitter, and News Channel 4 for continued updates.

Ron Demers

Posted under Weather Blog

Yet again we are tracking an unending parade of thunderstorms and severe weather possibilities. I would say this chance is a little better than the last few marginal setups.  The warm front that’s been parked over Northern Kansas will finally get shoved north with a southerly breeze.

Future Track at 6 pm:

 So we will be closer to the w arm sector and extremely unstable air. All modes of severe weather are possible from isolated tornadoes in the evening, to very large hail and damaging wind. Several rounds of storms may move through dumping a few inches of rainfall in some spots.

The SPC forecast is for a “moderate risk” of severe storms (you get a handful of these higher risks each severe wx season):

Rain stats:

The rainfall stats are impressive, and this does not even include Monday night’s rain! I wouldn’t be surprised if monthly totals approach 18″ down south.

Dave Winslow

Posted under Gardening, Weather

It’s not every day this kind of risk of severe weather is advertised, but today is one of those once or twice a year days. A moderate risk of severe weather is being forecast by the Storm Prediction Center for all of NW Iowa:

The timing of this episode of severe weather is going to be late afternoon and into the early part of the night. Thunderstorms should begin forming during peek heating between 4-6 pm, and I fully expect a tornado watch for NW Iowa. With the timing of the front, storms should initiate near I29 and become more widespread as they push into NW Iowa. The best time frame for tornadoes will be early evening for a few hours before they merge into a line of storms. Stay tuned for severe weather information throughout the day.

Dave Winslow

Posted under Weather Blog

We’ve had one heck of a rainy and stormy June, but it’s not over with quite yet. Check out this horrific flooding picture from Neligh, NE:

 The Elkhorn river is experiencing flooding that is breaking records. Central Nebraska has seen over 10″ of rain in about two weeks, and the ground can no longer absorb any more moisture. Crops are under water, and roads have been washed away. What’s worse is that a new system is threatening to rain on us again later this week.

The first chance of rain is going to be a small isolated thunderstorm chance for Wednesday afternoon as a warm front pushes into Nebraska. If storms form, it is possible some could be severe with some hail.

8:30 PM futuretrack

SPC outlook Wednesday-Wed. night:

The greater threat for rain will arrive Wednesday night if storms can from in the Western Dakotas and Nebraska, congeal into a giant cluster of storms, and plow through our area with heavy rain and hail being the primary threats:

SPC outlook Thursday-Thur. night:

The final hurrah from this system looks to take place Thursday afternoon as severe storms may try to pop along a cold front that will be in NW Iowa by peak heating (their threat will be better than NE Nebraska or SE South Dakota). If you are wondering if this will be the end of the storminess, I would say probably not. The jetstream will be overhead at our latitude guiding storms systems through the heartland. The flooding threat is not done yet.

Dave Winslow

Posted under Weather Blog

The last three months (April – May) were quite dry, with below normal precipitation each month.  That had created quite a deficit in the year-to-date rain numbers.  Then June came along and we’ve now made up for all three months in just 12 days.  Precipitation data from Sioux Gateway Airport in Sioux City shows that only 3 days of June have been completely dry.  Four days have been what I’d consider wet, with 0.25″ of rain or more.  Here is a look at the rainfall break down through Saturday evening.

The rain has been great for crops, gardens and yards.  But at some point you can get too much of a good thing.  Rivers and streams are filling up fast, and with more rain in the forecast flooding could become a problem.

Mike Zwier

Posted under Weather Blog

It was an impressive rain that we were waking up to Friday morning.  Here’s the way radar looked shortly after 6 am:

The rain lasted most of the morning for many of us leaving us with these kinds of rainfall totals:

Here at KTIV we picked up more than the airport with 1.32″ dumped from our rain gauge.  We have the chance of doing it all again tonight.  And with more heavy rain falling on already saturated soil, a Flash Flood Watch has been posted for most of the area for tonight and tomorrow:

More thundershowers could even linger into Saturday before we calm things down on Sunday.  So much for not enough rain lately, huh?

Ron Demers

Posted under Weather Blog

While some areas reported well over an inch of rainfall Monday night (1.01″ in Akron), we were hoping for more rain but got .48″ at SUX airport. I can already tell things are greening up, so I’m thankful for our decent rain too. More is on the way by Thursday as muggy air is pushed north by an increasing southerly breeze. The exact timing for the couple rounds of storms we may see Thursday is somewhat tricky…but as is usually the case, the early morning and latter portions of the day will feature the best rain chances. Will the storms be severe? It looks like there might be enough instability for a strong storm or two early Thursday especially in the south and west, but better severe weather opportunities may come in Thursday night as more significant instability develops. It looks like we’ll be more concerned with hail and wind than tornadoes at this point as many of the storms will be elevated (rooted above the warm, moist air at the surface).

SPC outlook for Thursday-Thursday night:

Friday-Friday night:

On Friday the cold front from this system will slide through and it too could produce some areas of heavy rain and severe weather. Notice the complex nature of this dual low system:

There will be a few warm fronts that will serve as thunderstorm initiators and that is making the scenario a little tricky to pinpoint. The timing of the cold front I believe is going to be critical on Friday. The later it arrives, the better the potential for some rather hefty storms. If on Friday it ends up near 90° and humid, you know we’ll be in business for an active afternoon.

Dave Winslow

Posted under Weather Blog