Tuesday's Severe Weather

[NWIASpotter]

There are several models that develop some strong storms. The GFS, NGM, and the MM5 from the Air Force develop strong storms in the midwest.
First the GFS, it has storms ongoing in eastern South Dakota tomorrow morning, these move off to the southeast going throughout areas around Sioux Falls(12z), Worthington(18z), LeMars(18z), Spencer(00z), Storm Lake(00z). This t'storm complex puts down to as much as 2.5 inches of rain.

NGM, this model develops thunderstorm, not quite as strong as the GFS, but NGM is noted to be drier then normal. It is not quite as large and is taken on a little more southern track. Areas include Sioux Falls, Yankton, Sioux City, LeMars, Storm Lake. It is moved through at about the same time period as the GFS which looks to give me a good clue that something is bound to break out.

MM5, the air force model develops these thunderstorms sooner then the other two models. Puting them through the areas around 3 hours sooner. Areas included in this model are Sioux Falls, Worthington, Pipestone, New Ulm, Mankato, and Rochester.

It is going to be very difficult to tell when the storms are going to develop. It will depend on the Cap on the atmosphere, how much cloud cover is over these areas from tonights possible storms, and with outflow boundries possible will make it even harder. My forecast is going to put a large area of precip, some being heavy with 2 inches plus, over SE South Dakota, SW Minn, through NW and Central Iowa overnight. The MM5 is an excellent predictor on hail, and looks to have some decent sized hail possible. Damaging winds are possible, and there is a chance that some tornadoes could develop with the beginning supercells.

[NWIASpotter]

And to ssm, yea...your right, but the way it looks is that there might be some clouds come tomorrow morning. Do you ever head out chasing or do you just stay around your area??

[Guest]

Looks like my area will be on the fringe of the activity for most of Tuesday. There might be bit too much cap over a majority of Nebraska. Wednesday looks a bit more favorable for my environs.

[NWIASpotter]

Yea, I might head out tomorrow if something develops. All I know is that it is cookin outside, last i checked it was still 84 outside with a heat index of 93, and that was at 9 tonight!!!

[ssom04]

And to ssm, yea...your right, but the way it looks is that there might be some clouds come tomorrow morning. Do you ever head out chasing or do you just stay around your area??

Yeah I go chasing all the time probably like 5-7 times a month unless its an active month I'm only 14 so I havent gotten my skywarn spotter certification yet.......I'm getting it this up coming spring...so mostly I go with my dad or my friend that can drive. I've seen 5 tornadoes in a year and a half, so I think we fair good chasing wise

[NWIASpotter]

Did you get down here in northwest iowa on june 11?? 9 tornadoes in 2 hours!! All within one county, you count the surrounding counties you had some where around 25 i believe. It was a dangerous day, tornadoes were droppin left and right. I'm only 17, and I was working for the local radio station in Spencer running the radar that they have there. We could only see one tornado out of the window, around 5 miles to the north.

[ssom04]

Did you get down here in northwest iowa on june 11?? 9 tornadoes in 2 hours!! All within one county, you count the surrounding counties you had some where around 25 i believe. It was a dangerous day, tornadoes were droppin left and right. I'm only 17, and I was working for the local radio station in Spencer running the radar that they have there. We could only see one tornado out of the window, around 5 miles to the north.

Nope didnt get down there..but when that supercell moved north in to Se minnesota we caught up with it but didnt really get any tornadoes just some strong rotation in the wall cloud

[NWIASpotter]

Since I have time this morning I think I'll give an update on the models for this morning (12z).
RUC model from 12z starts developing some
thundershowers in north central nebraska as well as southeast north dakota at 21z(4 pm). By 00z these storms have formed into a line, from Aberdeen southward to Sioux Falls, then back to around an O'neill, NE area. Nothing to great from RUC, rainfall amounts are around .5 inch.

Eta run at 12z starts off storms in southeast north dakota as well as further south into eastern south dakota at 18z. At 00z the storms a more of a cluster formation over a Pipestone to Sioux Falls area, at this time only at .5 inches of rain at most. By 6z, just after midnight, the main focus of storms looks to be from Worthington, Algona, Fort Dodge, Storm Lake, Sibley, back to Worthington. The storms looked to have intesify after diurnal heating stops, which most likely allowed the ongoing storms to completly break the strong cap over Iowa.

The 12z NGM is not available yet, same for the 12z GFS. But, looking at the off hour GFS(6z) it starts development at around 18z from southwest Minnesota and southeast south dakota. By 00z the strongest area of storms is a Waterloo, Mason City, Fairmont line. At most only putting down .5 inches of rain. By 6z it has those storms dissapating and backbuilding occuring from Algona, Storm Lake, Sioux Falls, Pipestone and back to Algona area. These storms are a little stronger then the previous cluster putting down .75 inches. But being the off hour GFS not quite as many things are put into factor. So the 12z GFS will give a much better idea.

Overall it looks like Strong to Severe Thunderstorms will develop over areas of SW Minn. and NW Iowa as well as possibly NE Neb and SE SD. The best chance for severe will be in the MN/IA area. Large hail and damaging winds are main threats, but with a weak warm front in the area of IA/MN it will allow for low level veering of winds so ISOLATED TORNADOES are possible.

[Guest]

It appears the SPC expanded the slight risk a little further west into Nebraska, generally along I-80.

In fact, from Omaha/Council Bluffs northward, they have a 2 to 5% probability for tornadoes, and the same area is hatched for large hail up to baseballs!.

A bit of cap to work through, but with all this heat on the surface, it could potentially explode later on.

[NWIASpotter]

Yea, looking at the new outlook I'm dead center!! That hatched area of hail, otherwise still a 25%, wind is at 25%, and the tornado risk is at 5%. Not to great of chance for tornadoes, but these storms are bound to have some pretty good rotation, especially if there going to hold baseball sized hail. Looks like I might just get a lil busy here later on!

[NWIASpotter]

Since I've now had a chance to look at some of the models once again I'll add some more depth. Looking at the severe parameters from Eta at 12z they look to be quite impressive. The absolute helicity is expected to be around 240, lifted indicies around -8. Sweat Index is to be up around 550, a huge number for northwest iowa. Buoyant CAPE is to be around 4500 J/kg, also a huge number. Totals is also to be around 54, and 40+ is good enough to get severe storms going.

GFS is not thinking anything even close to as strong as ETA is. The 12z run at most put around .5 inches of rain through parts of sw minnesota and northwest iowa. The RUC & RUC20 still have it growing stronger through 3z(10 pm). Will have to wait an hour or so until RUC gives us there full picture. AFMM5 still puts it further north by about 50 miles then the other models do. But still has strong thunderstorms. Overall some severe storms look to be very possible as we go on in the evening and overnight. NEWeatherguy you get some good storms tomorrow so that can be your day for some weather. But hopefully today is mine, haha.

[Guest]

NEWeatherguy you get some good storms tomorrow so that can be your day for some weather. But hopefully today is mine, haha.

Today might be both of ours, . Meso. Discussion

[NWIASpotter]

We should move this discussion to the new post I set up...TORNADO WATCH #657