8/24/04 FCST: Midwest/Plains

[mikegeukes]

Since there is a interest in the 24th, I have started a forecast thread for :
Tuesday: August 24, 2004

Latest Day 1 mentions a slight risk of severe weather
for the Central Plains, Lower and Middle Missouri Valley
and the Upper Mississippi Valley

Feel free to post your discussions below.

Mike

 

[Chris C Sanner]

This is for Western Oklahoma, as it looks like we might have an interesting setup taking shape. I'm using the most current ETA run as of this writing to forcast this, so I'm 100% sure this will change completely by Tuesday, but here goes:

It looks like at 200mb we have a strong jet lifting over the southern plains at the 84 hour mark. Looks like over 60 knots and maybe up to 80+. The upper level winds are out of the west still at 300 mb and are still over 50 kts. There's a slight disturbance at 500mb too, which might be stronger come Tuesday. Depending on the timing and strength, we could have some rather impressive, springlike shear dryline setup. Storm Relative Helicity is over 300 in Central Oklahoma and the dryline is bulging in Western Oklahoma, particularly NW Oklahoma.

If things should verify, but we get lucky and get a strong punch by the dryline and a bit stronger mid-level winds, we could get a few very awesome supercells for August. Time to be on standby, but I wouldn't make plans just yet.

 

[Glen Romine]

Looks like it is time to revive this thread, as what could be a favorable environment for tornadoes looks to set up later today across portions of nc to ne KS. Extensive overnight convection has led to flooding, and development of a considerable cold pool, across portions of MO and ne KS. A mesoscale complex continues this morning. advancing slowly into MO. A distinct boundary is evident in the surface winds, with a mesoscale low near DDC and a trough extending eastward, and a mesohigh near Columbia, MO to its north. This boundary will move south early today, then slowly back north as a warm front later ahead of the slow moving mesolow and will serve as a focus for severe storms. Strongly backed winds at the surface north of the boundary combined with modest mid-level flow and extreme instability should provide a favorable environment for slow eastward moving cells. Forecast low-level shear is adequate for tornadoes given the large instability. Picking a target is pretty easy with this scenario - so I'll leave that to the masses.

Glen

 

[Mike Peregrine]

I am also really interested in this afternoon's possibilities, given the results we saw last night from storms riding the outflow boundaries left from storms during the day. The Lawrence storm rode a very nice O.B. - and the slow storm motions were terrific ... loved watching those things back-build on radar over near Manhattan. If we can get that again this afternoon with some of the enhanced wind profiles that look to be in place then there should hopefully be some fireworks. My target would likely be the same area we saw last night. Hopefully I'll get the time to go after one or two - - this time of year it seems like we lose more of the good lighting every day.

 

[Jeremy Lemanski]

Its interesting to note what DTX says about the warm front around the great lakes today:

THE QUESTION
IS...WILL THE GOOD LOW LEVEL HELICITY AND LOW LCL HEIGHTS BE GOOD
ENOUGH TO SPIN UP A RAIN WRAPPED TORNADO AS THE WARM FRONT MOVES
INTO THE SOUTHWEST PART OF THE CWA...DESPITE NO JET DYNAMICS. DON'T
THINK IT WILL HAPPEN

Now, i wonder what will happen and if we, lower mich, northern ohio/ind. can get some spinups along the front later. Something else to watch on what appers to be a pretty active late aug. day.

 

[Mike Peregrine]

It's just a trip to be looking at models in late August - but took a peek at a few parameters, etc. for this afternoon.

CAPE is progged to be explosive at over 5000 for most of eastern Kansas with TDs in the 75 degree range by 2100. Mixing panels also indicate deep penetration of moisture at mid-levels.

Lifted Indices in the -6 range in a corridor from Kansas City westard through Lawrence, Topeka and Manhattan along a projected outflow boundary left from morning convection.

RUC indicates precip breaking out by 0z along the MO/KS line. Satellite shows sufficient clearing in the target area currently with lots of warm, super-saturated air in place. Southern edge of outflow boundary is easily seen across SE Kansas.

Target as of now is wherever the boundary ultimately winds up, which currently appears to be in the Lawrence to Topeka corridor. Surface winds are much more pronounced today than yesterday, making me more hopeful that these boundaries will be reinforced and will ultimately produce something interesting tonight. Any thoughts on cap strength?

 

[Mike Peregrine]

Well the 2000 outlook language is a bit discouraging in terms of timing for initiation - seems to favor a later solution, possibly indicating the earliest initiation in the 03Z timeframe (ouch) ... it will probably be another bumpy, sleepless night for most folks living along the state lines ... just wondering if I can make it far enough west and north to catch the earliest possible stuff.

 

[Glen Romine]

Well, you can see in the cumulus field over eastern KS that the cap is still pretty strong as evidenced by the shear pll roll clouds, but the cumulus looks more cellular along the western extent - so I'm not convinced it will be as late as suggested for CI. I like just east of the Salina area for CI around 2300Z, maybe only to Manhattan for a conservative drive. I'd say it's worth it - but that suggestion comes cheap as I'm not the one making the trip!

Glen