8/9/06 FCST MN/SD/NE/IA

[Mike Hollingshead]

Thought I'd start this for anyone wanting to discuss tomorrow's potential. It is looking pretty interesting to me. Low level flow may be a concern, but perhaps it'll be ok for anything turning right/south. A few things seem fairly certain, one is that moisture won't be an issue. Along this front in the area there are some 18+ dewpoints at 850mb right now(saw some 20's last night).

Meso-eta is showing a wave over c MN at 0z with a broad area of 40-45 knots out of the nw at 500mb. Above this at 250mb along the IA/MN border is a more westerly or wsw jet of 60+ knots. It seems to me that this backing going up from 500 to 250 is a good thing as it will help keep the precip away from the storm motion more. Maybe that's not correct, but I would assume it's a good thing to have backing rather than veering in that area. If anything turns more right/sse perhaps this flow can help keep them from becoming outflow mushbombs so quickly.

Here are some afternoon forecast soundings for northern IA area.

Mason City 21z

That looks pretty tasty to me.

Farimont? at 21z

Spencer IA at 21

Take away the low level flow and that is scary. 353 3km cape? All the convective temps over there aren't all that high.

It should be interesting what can happen in this environment with high instabality and good flow aloft but weak low level flow. It certainly looks worthy of a chase. I have no idea of a target at this time thanks to the diffuse nature of the sfc boundaries.

For the cape lovers out there: Norfolk NE at 0z 7100 :blink:

 

[Scott Olson]

Definately looks like a favorable environment. SREF showing 45kts of effective shear, strong instability and importantly strong 0-3km CAPE (even if the NAM is overdoing it by X2, the adjusted levels would still be considered significant). 12z & 18z NAM both show 0-3km SRH values of 200-350 m2/s2. ML LCL's look to be in the 1000-1200m range for the interested area, which in 2006 terms is very good. Moisture looks good with GFS/NAM forecasts of mid-70's and even some upper 70's. 700mb temps are progged to be around 10C by late afternoon. Lift from MN wave should help get things going & both NAM runs showed convection forming around peak heating in NC IA. There is neglibile CINH forecasted by 21z. Moisture convergence along the front should be quite strong in IA and could be releatively weak further west.

Just have to wait and see how things play out tommorow morning. There are indications of an MCS in IA/MN early in the morning, outflow boundaries & lingering cloud cover could have a big impact for good or bad. Assuming late afternoon development & a right-turner moving south. The environment 100km south at 0z looks comparable in most aspects.

Could be an interesting day if storms develop and if things play out as forecasted. I'll be out, barring any major spoilers. Good luck to all!

For starters, I'd say Algona Iowa.

 

[Dustin Wilcox]

For the cape lovers out there: Norfolk NE at 0z 7100 :blink:
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OAX Cape at 0Z 9402.1 convective temps are awfully high however.

http://www.wxcaster.com/etaskewts.php3?mod...&STATIONID=KOAX

Just a quick question does the Heat Index count towards reaching the convective temperature?

 

[Jayson Prentice]

I don't believe the heat index is considered into convective temperature, although higher heat index means the more likely you are looking at very moist air and thus high intstability which may lead to the storms firing anyway.

But, nope, don't believe heat index counts.


As for true forecast discussion, tonights NAM does push things south, but I think it does this in response to the MCS it develops tonight and rides just to the north of it through the morning, limiting its' northward extent. I do see some storms starting to fire along the IA/SD border right now, if that is the nightime MCS potentially getting going we'll have to watch that closely.

Its' all going to depend where this 'lack of surface feature' warm front sets up, just about a county north of that front is where I will probably be. Somewhere in western Iowa.

 

[Sean McMullen]

After looking at the new runs and comparing them to the new 0600Z outlook I'm torn between parking myself east of Council Bluffs in the area with the geatest tornado risk or heading west and catching the monster that seems to be coming out of central Nebraska and holding together for for about 3 hours and heads straight for omaha.

Take a look at the simulated radar on the 4.5 km wrf from hours 21 to 27.

http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/