5/31/09 FCST: MN/SD/NE/IA/MO/IL

[John Wetter]

Of the two-day weekend event, I think Sunday looks better right now. Good solid 500mb support will be overhead with a nice boundary in play. Should Saturday actually happen, we could also have some nice outflow boundaries as well. best area right now looks to be SW MN to SW IA.

 

[Dan Rupnow]

I wouldn't rule out SE MN according to this mornings 12Z GFS. 15-20kt S/SE surface winds aided by weak surface cyclogenesis over the MPX area. 40kt W/NW 500mb winds and 60-70kt W/NW diverging 250mb flow should yield decent upper air support. Warm front is progged to be draped across this area with surface temps in the mid 70's along with forecast dews in the low 60's would give sufficiently low LCLs. Instability could be better, but CAPE is still progged to be at least 1,000 J/KG. CINH could be an issue, but a lot of things can change in the 96 hours or so between now and then.

 

[Jeremy Den Hartog]

I too am looking forward to this day. The latest GFS looks promising for Southern Minnesota. This was the 'forecast reasoning' discussing the potential for severe weather out of the Twin Cities NWS office...

"GFS WOULD SUGGEST THERE BEING ONE WITH A 1000 MB LOW TRACKING ACROSS SRN MN AND DECENT INSTABILITY POKING UP INTO SRN MN IN WARM SECTOR"

However, they do go on to mention the ECMWF forecasting the low to go further north in which case the associated cold front should initiate the development of storms so in either case severe weather looks pretty likely at this point...

 

[Derek Weston]

Really like what the NAM is spitting out for Iowa on the 12z... except for the CIN... seems capped off through out the day with no precip breaking out in Iowa through 0z. NAM is showing more backed 850 flow... 500s a bit weak, but ought to get it done... nice curved hodographs. Very nice CAPE as well.

GFS also has Iowa rather capped off... though, does put good instability into Wisconsin (where as NAM has nothing) where upper level shear ought to be stronger. Not as much of a cap, either. (I don't want a chase in the woods, however)

At any rate, I'm sure things will bounce around a bit more before the setup transpires... at the very least... ought to be a pretty good round of severe weather on the last day of May in the midwest.

 

[jshields]

i'm really liking eastern/northeastern kansas too. again the cap could be a problem but the 18Z NAM hodographs look amazing! not much speed shear with basically 25-30 kts of wind at all levels, but the directional shear is really good. however there appears to be a low level jet through northeastern kansas with winds of 35+ kts which would really help the low level shear. hopefully something can bust through the cap as there looks to be a subtle wave that moves through northern kansas on sunday evening

http://twisterdata.com/index.php?sounding.x=497&sounding.y=335&prog=forecast&model=NAM&grid=221&model_yyyy=2009&model_mm=05&model_dd=28&model_init_hh=18&fhour=78&parameter=CAPE&level=90_0&unit=MB_ABOVE_GROUND&maximize=n&mode=singlemap&sounding=n&output=image&archive=false&sounding=y&sndclick=y

 

[Chip Redmond]

Taking a quick gander at the models it seems as if they are doing the same thing with Sunday as they did with Saturday. They want to push good CAPE and some directional and a wee bit speed shear to the north but in the later runs it pushes it south again and weakens it drastically. They are most likely trying to break the pattern to a more seasonable one but can't hold it. I sure hope the current pattern breaks down but each run pushing it back gives me less hope.

Chip

 

[Phil Kurimski]

Taking a quick gander at the models it seems as if they are doing the same thing with Sunday as they did with Saturday. They want to push good CAPE and some directional and a wee bit speed shear to the north but in the later runs it pushes it south again and weakens it drastically. They are most likely trying to break the pattern to a more seasonable one but can't hold it. I sure hope the current pattern breaks down but each run pushing it back gives me less hope.

Chip

Wow...the 00Z NAM does exactly this. It pushes the highest CAPE and shear southern MN to EC KS/Cntrl MO.

 

[Derek Weston]

Wow...the 00Z NAM does exactly this. It pushes the highest CAPE and shear southern MN to EC KS/Cntrl MO.

The good lower level shear stayed in place to the east -- surface low didn't move -- however, it moved the good CAPE west of the good low level shear... which we do not want. (big departure from 12z... unfortunately, 18z trended same way with regards to dewpoints and as a result, CAPE... I'll have to try and figure out why the big change occured)

 

[Phil Kurimski]

I'll have to try and figure out why the big change occured)

When you figure it out change it back...lol. It will be interesting to see what the GFS spits out. However these seems to be a trend with the models...producing a good setup...then back tracking. This kind of trend does not lend itself to a break in this pattern we are in.

 

[Craig McPeck]

Latest NAM Computer model actually quite surprised me with a bullseye of cape of 3500 over NW Missouri 81 hr.

 

[Derrick Herndon]

When you figure it out change it back...lol. It will be interesting to see what the GFS spits out. However these seems to be a trend with the models...producing a good setup...then back tracking. This kind of trend does not lend itself to a break in this pattern we are in.

It seems the NAM is continuing to have issues with forecasting moisture in the boundary layer. This almost certainly is feeding back into the forecast to some degree, affecting the remaining layers and kinematic fields. I have gotten to where I almost do not trust it more than 48 hours out.

 

[Andrew Butler]

It seems the NAM is continuing to have issues with forecasting moisture in the boundary layer. This almost certainly is feeding back into the forecast to some degree, affecting the remaining layers and kinematic fields. I have gotten to where I almost do not trust it more than 48 hours out.

Perhaps it is picking up on the fact the we'll only have something like half a day for good moisture return. And it is saying: "Hmmmm, this warm front is like the others up here this year, moisture starved and capped to all get out."

Sorry, but I'm getting more pessimistic with every run. I wonder if it isn't on to something...

 

[Michael O'Keeffe]

This day looks pretty good down in NW MO IF the cap can break or we can just get a boundary so we can get enough convergence to initiate storms because the atmosphere looks pretty ripe for some nice supercells and tornadoes even.

The reason there is no cape showing up into Minnesota and Iowa is because the moisture won't make it there in time, not because the models are failing but they are becoming more realistic is all.

Anyway here is a sounding for Chilicothee, MO for 0z Sunday.
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=NAM&STATIONID=CDJ
(May be time sensitive)

 

[Derek Weston]

This day looks pretty good down in NW MO IF the cap can break or we can just get a boundary so we can get enough convergence to initiate storms because the atmosphere looks pretty ripe for some nice supercells and tornadoes even.

The reason there is no cape showing up into Minnesota and Iowa is because the moisture won't make it there in time, not because the models are failing but they are becoming more realistic is all.

Anyway here is a sounding for Chilicothee, MO for 0z Sunday.
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=NAM&STATIONID=CDJ
(May be time sensitive)

06z GFS agreeing with NAM now, unfortunately. Agree, Omaha area looked decent... Interesting that the SPC went with the upper mississippi valley region as the main threat region. Apparently siding with the 0z GFS... it'll be interesting to see if the 06z GFS was a fluke... (though, considering the lack of moisture returning to this area Sat/Sun on the NAM, not too optimistic this is the case)

 

[Brian Stertz]

I am kind of monitoring the SE South Dakota area atm for my chase target area on Sunday. Given the 700mb wave...good moisture flux/pooling...a boundary and sfc low nearby....and moderate shear (westerly 30-40 bulk shear ETA forecast at 00z), this day may be worth the gamble. Right now, the chase flight plan looks to be up north of Yankton (and likely pts. east).