Significant severe weather (derecho) 6/30

[TropicalAnalystwx13]

Since I failed on making a thread for one of the most amazing days in meteorological history, I thought I'd get this one underway early...just in case.

While some timing differences exist, both the GFS and ECMWF continue to indicate the eastward progression of an abnormally strong trough (by June standards) across the northern United States and southern Canada that would support organized severe weather...including the possibility of tornadoes...across The Dakotas over the weekend.

[EF-5bigj]

We will see what happens I guess this year has not been kind to the Dakota's. Moderate Risk for Sunday.

[EF-5bigj]

Tornado watch up now for Nebaska and Iowa.

[TropicalAnalystwx13]

Forgot I made this, so I decided to change the title so we can use it for tonight/tomorrow.

And wow, tomorrow. What a change the models have went through over the past 24 hours. What looked like a fairly minor threat has become something that everyone in eastern Iowa and northern Illinois need to be aware of. The parameters on the 18z GFS and NAM would suggest a risk for significant to violent tornadoes with any sustained supercells tomorrow as a secondary area of low pressure develops and increases the shear across the risk area. SPC is Slight for now, but a Moderate risk at the 06z outlook is almost guaranteed, and I honestly wouldn't be surprised to see this eventually go High if model trends continue.

A lot of people may be caught off guard by this. I haven't given it my undivided attention and was surprised myself by what the models have shown today. Potentially dangerous situation.

[EF-5bigj]

High risk for for tornadoes??

[supercane4867]

Very nice hook right now for the Iowa cell, still needs to tight up on velocity though

[EF-5bigj]

Wow that thing is really hooking but yeah it does need to intensify a little more.

[Cyclenall]

A lot of people may be caught off guard by this. I haven't given it my undivided attention and was surprised myself by what the models have shown today. Potentially dangerous situation.

Same here, I have been busy and was amazed to learn of the off the charts values being advertised by the models. The SPC tried to debunk that with their Day 1 MDT risk they just released (no shock there), but I still think something is up. June could go out with a historic bang, and cap off what has been an amazing June severe wise and reaffirming why June is my favorite month of the year. The MDT risk area is very large for this time of year too! . Could have violent tornadoes or some extreme severe events like immense straight line wind damage or a derecho cooking...SPC didn't hatch any TOR for some reason and went with 10%. I can't watch it though later today which really, really sucks .

Good luck down there, lets see if history can be made again.

[TropicalAnalystwx13]

Large and extremely dangerous tornado in NE Nebraska...one of what should be several this afternoon (farther east).



SPC just upped tornado probabilities up to 15%.

[TropicalAnalystwx13]

A lot of people may be caught off guard by this. I haven't given it my undivided attention and was surprised myself by what the models have shown today. Potentially dangerous situation.

Same here, I have been busy and was amazed to learn of the off the charts values being advertised by the models. The SPC tried to debunk that with their Day 1 MDT risk they just released (no shock there), but I still think something is up. June could go out with a historic bang, and cap off what has been an amazing June severe wise and reaffirming why June is my favorite month of the year. The MDT risk area is very large for this time of year too! . Could have violent tornadoes or some extreme severe events like immense straight line wind damage or a derecho cooking...SPC didn't hatch any TOR for some reason and went with 10%. I can't watch it though later today which really, really sucks .

Good luck down there, lets see if history can be made again.

SPC stated that the GFS/NAM were struggling with convective feedback and were overstating parameters. That said, as I just said above, the threat for significant and long-lived tornadoes exists across southern Iowa this afternoon.

June doesn't produce historic outbreaks often, but it's the best time for it. Spring-like troughs still dip down occasionally, meeting summer-like instability and moisture.

[Cyclenall]

Large and extremely dangerous tornado in NE Nebraska...one of what should be several this afternoon (farther east).

SPC just upped tornado probabilities up to 15%.

Crazy about the morning "large" tornado, and glad to see the 15% probs...I can't remember what the other days this year featured a 15% tor? I know this day stands out from the rest based on that alone .

[EF-5bigj]

Looks like it could be nasty today.

[EF-5bigj]

Confirmed tornado on the ground. There have been tornadoes and it's not even prime time yet.

[TropicalAnalystwx13]

Looks like activity is congealing into the derecho early instead of remaining isolated supercells. That's good news as far as the tornado potential is concerned (SPC down to 10% unhatched) but wind reports should be significant and widespread.

[EF-5bigj]

We have had a few wind events this year.

[Kalrany]

Looks like twilight outside the window, and it is not even 4:30... We are about to get very wet here in Madison, WI.