7/20/04 NOW: NE, SD, MN, IA

Mesoscale Discussion no. 1740 has been issued for parts of Nebraska, South Dakota, Minnesota and Iowa with radar reflectivities beginning to indicate possible convective initiation west of O'Neill, Nebraska in a CU field running visibly in a SW-NE oriented line on satellite.

http://www.spc.noaa.gov/products/md/md1740.html

Discuss nowcasting for today in this thread.
 
Noteworthy watch language includes:

VERY UNSTABLE AIR MASS IN PLACE ACROSS WATCH AREA WITH CAP BECOMING VERY WEAK WRN PORTION. RAPID DEVELOPMENT OF SEVERE THUNDERSTORMS EXPECTED IN AREA OF BEST LOW LVL CONVERGENCE VICINITY NEB/SD BORDER W OF YKN. VEERING SHEAR PROFILES SUPPORT SUPERCELLS WHICH WILL ENHANCE POTENTIAL FOR VERY LARGE HAIL AND ISOLATED TORNADOES.
 
In O'Neill now about to head west. Lots of elevated crappers getting blown off that boundary. Hoping for better organization soon on the more western boundary half way between O'Neill and Ainsworth right where they apparently merge.
 
That cluster is looking very messy presently - - - but some of the storms further south are starting to get better organized ... stick it out a bit and hope nothing fires closer to Yankton (though you should be able to make it up there with no prob if you need to). Hopefully the mess will get its act together and structure-up rather than remain an elevated junk-fest.
 
Look for Action in the SW

I would think the action would be better to the SW of O'Neill, perhaps down by Burwell or Broken Bow. The NWS radar shows two distinctive boundaries. The group of storms west of O'Neill is on the northern boundary, while the group of storms down by Burwell and Broken Bow is on a separate boundary off to the south.

I have a gut feeling the southern boundary will interfere and perhaps cut off the inflow to the northern boundary as the storms grows bigger. Particularly if the southern group of storms gets going eastward. I'm also thinking along the line of a "Tail-End Charlie" situation setting up down by Broken Bow.

GOES-12 VIS SAT is showing the southern line is extending itself all the way back to North Platte. Eventually I think the northern group of storms will struggle until they move forward and get on the southern boundary.

Just putting my thoughts in. Any questions??

8)
 
... stick it out a bit and hope nothing fires closer to Yankton

Why would you not want convection near Yankton? Seems like convection juxtaposed to that are would have a more realistic chance of becoming supercellular. Shear there is much better, both deep layer and near surface, as well as sitting on the tip of the greatest instability axis. Guess I want to defend this region as it is near my target - well my target was a short distance NW of Yankton anyway, and I'd still support that region as having the best chance for supercells this evening.

Thanks in advance,
Glen
 
I should be driving north and get up into SD now..... But, I will give NE it's change...lol. Affraid if this mess organizes it's going to start too far south. I want *some* mid-level flow. Hope was something in SD would drop south. Not so sure about venturing down towards Burwell....ug. Have hopes something around Spencer yet, but if that goes south it will have problems with this crapfest. Then again it is possible anything good wouldn't HAVE to be a south mover.
 
Why would you not want convection near Yankton?
Thanks in advance,
Glen

I WOULD want convection near Yankton if I were there ... but here's what happens in a situation like this ... a big mess starts early down to the south ... a chaser sits there waiting for it to organize itself and get its act together, and meanwhile, something fires an hour and a half to the east in a better wind environment that immediately goes up and starts rotating. Situations like this can end up becoming really frustrating if a person isn't really careful and considers all the options ... that's actually what I was intending when I said that -

So hopefully since Mike is already in position this current stuff will figure out what it wants out of life really quickly ... that, or else if anything does go up further east, he can make it over there in time.
 
Spencer Not Looking Good

Just looked at NWS radar out of North Platte. That cluster of storms near Spencer does not look good. Rather disorganized and the cloud tops are getting blown to the SE.

I do see one good storm getting organized just to the NW of Burwell. Looks like two storms merged together, that would account for its good size. Not seeing any kind of rotation yet.

Still I would put my bet on the storms to the NW and W of Burwell. I would not discount the storms near O'Neill just yet. The separate cells are starting to move together now.

I did some NOW casting earlier back in May for a storm chaser. I saw a storm near Concordia KS that was kicking up a strong rotation. I tried twice to convince my chaser to go south. He didn't and he missed out on a tornado-fest on that day.

Don't miss this one!!

Update: That storm NW of Burwell was severe storm warned:

443 PM CDT TUE JUL 20 2004
THE NATIONAL WEATHER SERVICE IN NORTH PLATTE HAS ISSUED A SEVERE THUNDERSTORM WARNING FOR GARFIELD COUNTY IN NORTH CENTRAL NEBRASKA LOUP COUNTY IN NORTH CENTRAL NEBRASKA UNTIL 545 PM CDT

AT 440 PM CDT, .NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM. THIS STORM WAS LOCATED 13 MILES NORTH NORTHWEST OF BURWELL, AND MOVING EAST AT 20 MPH.
 
Looks to me like things are starting to get better organized. That middle storm is starting to develop some rotation, so maybe it's not all crap...though right now it looks more kidney-bean-ish (HP) than classic.
 
North Platte mentions storms are moving east at 20 mph in their Short Term Forecast, and also a Severe Thunderstorm Warning just been issued for Loup and Garfield County, movement of the storms east at 20 mph. VILS of 79, Echo Tops to 58K, currently on the latest radar at 2140Z.

Holt County now under a Severe Thunderstorm Warning until 6pm CDT.
Storms moving East at 25 mph.

Mike
 
Gotcha Mike P., I guess I should have seen it as sarcastic - a little slow sometimes. Well, maybe another hour of sifting and it will become clearer which cells have a chance do something more 'interesting'.

Glen
 
Action Closer to O'Neill

NWS has issued a SWW for cell SW of O'Neill:

459 PM CDT TUE JUL 20 2004
THE NATIONAL WEATHER SERVICE IN NORTH PLATTE HAS ISSUED A SEVERE THUNDERSTORM WARNING FOR HOLT COUNTY IN NORTH CENTRAL NEBRASKA UNTIL 600 PM CDT

AT 455 PM CDT, NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM. THIS STORM WAS LOCATED NEAR AMELIA, OR ABOUT 22 MILES SOUTHWEST OF O'NEILL AND MOVING EAST AT 25 MPH. THE SEVERE THUNDERSTORM WILL BE NEAR CHAMBERS AROUND 520 PM CDT

Where are you going, Mike??
 
TX, OK, NE Panhandles and KS

Mike P. it looks like you may have to add TX, OK and NE Panhandles and KS to the thread title. Storms are firing up in those areas too!! :shock:

Update: looks like the two boundaries I mentioned in my previous posting has come together SW of O'Neill NE. And that's producing a E-W line of storms. That's not good. There's another boundary just north of Ainsworth NE that looks like its feeding the storms near Spencer, NE. 8)
 
Well, the slight risk does include Northern Illinois and activity is beggining for fire up in that area. A SVR has just been issued for a little, yet potent looking storm in Jo Davies County, IL.

AT 523 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR
GALENA...OR ABOUT OVER GALENA...AND MOVING EAST AT 10 MPH.

..Nick..
 
WOW! That storm is extreme NW Illinois and really picked up. Look at Velocity... it's also showing some decent rotation!

[edit] At 5:49pm: Spotters reported 2" hail from this storm in Galena!

..Nick..
 
As of 6:00 CDT

The SVR TSTM WRNGS for Garfield, Holt, Loup
Counties no longer in effect, only report from the
LBF office has been of 0.88 inch hail. in Boyd County.

Boyd County has a SVR TSRM WRNG till 645 PM CDT.
movement of storms southeast at 5 mph.

WW 659 SEVERE TSTM: IA IL WI has been issued until 10PM CDT.
Reports out of Jo Daviess County so far 2.00 inch hail.

Mike
 
WOW! That storm is extreme NW Illinois and really picked up. Look at Velocity... it's also showing some decent rotation!

[edit] At 5:49pm: Spotters reported 2" hail from this storm in Galena!

..Nick..

Tilt 1 Reflectivies in the mid-50s and mid-30 to low-40 VILs (per the DVN radar) are certainly nothing to write home about... Rotation, what there is of it, remains quite weak as well. While it does look decent on the La Crosse radar, I'd be hesitant to use that radar much for this storm given that it's about 120 miles from it. Meanwihle, the DVN radar is only about 60 miles away, which means it's getting a much "closer" view of the storm, and it's lowest tilt scan is scanning lower in the storm than the La Crosse radar is... The only thing that I "like" about this storm that can show that it is severe is the depth of the higher reflectivities, with even Tilt 4 showing mid-upper 50s reflectivities...

Heading west.... current SPC mesoanalysis via the RUC continues to show a highly unstable environment from southeastern SD south and eastward, with indiciations of MUCAPEs >7500 near OMA currently. However, weak midlevel flow is creating weak 0-6km shear, which is likely the reason that the current storms are struggling to organize. For any storm that can develop sufficient organization, the combination of 3500-5500 SBCAPE and 200-250 0-3km helicity (and ~100 0-1k helicity) would seem to support a tornado risk, especially as storms translate eastward into the higher mean boundary-layer RH (and related lower LCLs) near FSD and points eastward.
 
Well, it went from looking like a devoloping Supercell w/ 2" hail reported and it currently looks like a piece of crap with .5" hail possible. :?

How fast good things come to an end, huh?

A blue box has just been issued for S. WI/N. IL thou.

..Nick..
 
As of 8:53 PM CDT
Latest Mesoscale Discussion for SERN SD through NERN NEB
mentions cap, slow movement of storms, and onset of nocturnal cooling.
http://kamala.cod.edu/spc/0407202315.acus11.html
http://www.spc.noaa.gov/products/md/md1743.html

Sunset Times for cities in and or near the Tornado Watch.
851 PM CDT Omaha NE
857 PM CDT Sioux City IA
900 PM CDT Norfolk NE
902 PM CDT Sioux Falls SD

SVR TSTM WRNGS tonight for SD: Davison, Dewe, Douglas
Hanson, Hutchinson, Lake, Mc Cook, Miner, Potter, Walworth,Counties.

DBZ of 61, VILS of 78, Echo Tops of 61 K as of 2323 Z
1.75 inch so far in Davison and Hanson Counties.

Latest 00Z Soundings from tonight.
http://weather.cod.edu/wx/public/raob/abrskewt.GIF -Aberdeen
http://weather.cod.edu/wx/public/raob/mpxskewt.GIF -Minneapolis
http://weather.cod.edu/wx/public/raob/oaxskewt.GIF -Omaha

Highlights from South Dakota:
3.00 inch hail in MIner County
70 mph winds in Lake County

Mike
 
Nice little cluster also in NW Wisconsin! Check the Duluth radar.

THE NATIONAL WEATHER SERVICE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
BURNETT COUNTY IN NORTHWEST WISCONSIN
WASHBURN COUNTY IN NORTHWEST WISCONSIN

..Nick..
 
A very nice storm has strengthen considerably in the past few scans near Mitchell, SD. This monster supposedly (per the FSD radar) tops >61k feet and VILs near 80. This isn't too much of a surprise, since a loop of the last few hours of Sfc moisture convergence shows that the strong convergence has remain nearly stationary near and immediately west of Mitchell. Indeed, this has likely locally weakened the cap and obviously supplied sufficient convergence for sustained initiation. If the storm can establish itself for a while longer, it will likely organize into a decent supercell, considering the low-level shear and instability nearby... Only wishing it can hurry up east a little bit to get into a better LCL and low-level shear environment, as evidenced by the FSD VAD profile, which shows a nearly ideal veering profile.

EDIT: I didn't update my mesoanalysis... The storm near Mitchell likely has about 5000-6000 SBCAPE to deal with and 250-300 0-3k helicity, making EHIs >9 ... If only mid-levels were a little stronger...
 
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