8/1/2004 FCST: Northern Plains

Dan Robinson

Heads up for northern US chasers. Moderate Risk is up today for MN/NE/IA/SD/ND. Main threats are hail and wind, with 5% tornado probabilities. Could be an interesting day with surface low, +70F dewpoints and a cooperative cap.
 
Yeah it could get very interesting this afternoon with ML cape of around 4000 J/kg 40-45 kt of deep layer shear :D

Then later tonight looks like a big bow echo event 8)
 
I am in York, NE right now on my way up to Souix Falls, SD. I left Norman last night at 2am and drove through the night. Sure do like the looks of todays setup. We will have monster CAPE in the order of 4000-5000j/kg, great shear both speed and directional, super moisture and realtively low LCL's. The SPC put out a 15% tornado area which is probably were I am heading. Another nice frcst is the -12 LI the eta model was predicting last night!!

Well gonna get back on the road and head towards Souix Falls gonna take a quick nap when I get there to be ready for this afternoon.
 
The area between the WF and CF is definitly a good target today. Looks like the Low Pressure may move eastward heading into mid 60 Td. That mixed with the instability already present at OAX and ABR (no station in target area... Wierd) the Sioux Falls area may see much action today. Looking at the ETA model i see that this area will have huge CAPE. But, the model shows that at its max we see a cap develope. I dont think that will be a problem seeing that all the ingredants are there the storms should fire and get rolling well before the suposed cap forms. Hopefully by that time good shear will develope.
Target: Madison to Wentworth SD

Now if I can only find a ride :)
 
The SPC just popped us up to 15% on the tornado outlooks with 35% in both hail and winds. Hail is hatched, too. Not to suprising with how fast these updrafts will go if the cap breaks. CAPEs are up in the 5000 range for this afternoon, and shear looks stunning. The only negative thing I can find about this situation is that there is a cap, but that is expected to be broken by 21Z.

Going to be an interesting day for a backyard chase! If any of yall are in southeast south dakota and see anything interesting give me a hollar!
 
TORN watch box

Looks like SPC is considering a TORN watch box for the MEDIUM RISK area in the Northern Plains:

TORNADO WATCH LIKELY WILL BE ISSUED FOR PORTIONS OF ERN SD...SWRN MN ...NERN NEB AND NWRN IA WITHIN THE NEXT 1 TO 2 HOURS.

That MSC was issued at 1:48 CDT.
 
I am currently in Yankton, SD and watching the haps. Looks like the cap is erroding some, per SPC MD. It is hot and humid here right now, feeling like a good storm day. The SFC winds are kinda weak though and I am thinking about heading east towards I-29. I am worried about the MO river and limited road crossings. Looks like storm motion will be to the SE and crossing will be necessary. Anyone have any suggestions for good crossings or where to avoid? This is my first time chasing in SD, MO river valley.
 
Two Other Areas Being Watched

SPC is having MSC discussions about two other areas in the Northern Plains:

MONITORING PORTIONS OF SWRN IA/NWRN MO...AND PERHAPS EXTREME SERN NEB AND NERN KS FOR A SEVERE THUNDERSTORM WATCH.

We may have some storm action in the Central Plains before long.
 
Jason, if you have to cross south, there is a good road south out of Yankton and a road south out of Vermillion. Avoid the Sioux City area going across the river if you have to. If you get to Vermillion and think you will need to get further south, that is the place to cross, though it will cause problems with visibility given trees and such.
 
Chasing Yankton to Vermillion

Originally posted by James McCormick
Jason, if you have to cross south, there is a good road south out of Yankton and a road south out of Vermillion. If you get to Vermillion and think you will need to get further south, that is the place to cross, though it will cause problems with visibility given trees and such.

The road south out of Vermillino is new and may not be on older maps. Also highway patrol has a speed check set up at Meckling today (hwy 50), where the hwy speed suddenly changes from 65 to 45, so watch out there.

I'm located 12 miles northeast of Yankton, so I'll be watching you all closely today!
 
I tornado watch has been issued:
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

EXTREME NORTHWEST IOWA
SOUTHWEST MINNESOTA
EASTERN SOUTH DAKOTA

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 315 PM UNTIL 1000
PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

maybe a now thread soon?!

Update: looks as though the cap has broken down through to the Sioux Falls area. Shear looks good, great dew points, and -10 to -12 LI. I really think initiation will take place soon so for those who are out there (wish i was) stay on your toes and good luck.
 
Latest Sounding Data: Strong Cap on the 18Z soundings.

18Z Soundings:
http://weather.cod.edu/wx/public/raob/18Z/...BR.skewt.18.GIF -Aberdeen
http://weather.cod.edu/wx/public/raob/18Z/...PX.skewt.18.GIF -Minneapolis
http://weather.cod.edu/wx/public/raob/18Z/...AX.skewt.18.GIF -Omaha

00Z Soundings:
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

Sunset times: 840 pm to 900 pm CDT in SW Minnesota, Eastern Nebraska and Eastern South Dakota.

Mike
 
Nothing's happening :( The energy's and stuff are just sitting there and building...I'm not to sure if this cap is going to be broken...
 
This is one of the situations where the capping is much stronger than the forcing, or the forcing is weaker than the capping. Examining the RUC plots on the SPC mesoanalysis page, there is only weak-at-best surface moisture convergence in the eastern SD / southwestern MN area. This is obviously too weak for the relatively strong capping, and thus the reason why we aren't seeing any convective development in the tornado watch. Latest MCD from SPC concerning the situation only mentions storms way upstream in nc SD and sd ND, neglecting to mention anything about the current situation in the watch box area. I'm awaiting 0z soundings, which will likely show a decent cap in place. Too bad FSD doesn't do a sounding....

Just to mention, none of the models initiated convection this afternoon in the watch area. Well, at least the 12z and 18z ETA and the 21z RUC. The 12z ETA did show precip into IA by afternoon, but not much in the sw MN and eastern SD area... Experience has shown the capping is often stronger than anticipated/forecasted, and thus on these decent-cap days, there tends to be a strong tendency to bust. Who knows though... something could pop... anytime...

EDIT: Indeed, latest 0z soundings do show >75 CINH in the area. Since the area-of-interest is between the ABR/OAX/MPX sound sites, it's tough to know exactly what's going on in the watch box area. However, it does confirm a stronger-than-forecast cap, which confirms what I've experienced in the past...
 
For the chaser's up that way. good luck
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 682
NWS STORM PREDICTION CENTER NORMAN OK
745 PM CDT SUN AUG 1 2004

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

CENTRAL AND EASTERN SOUTH DAKOTA
EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 745 PM UNTIL
200 AM CDT.
TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 65 STATUTE MILES NORTH AND
SOUTH OF A LINE FROM 55 MILES SOUTHWEST OF MOBRIDGE SOUTH DAKOTA
TO 30 MILES EAST OF WATERTOWN SOUTH DAKOTA.
 
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