3-25-07 FCST: TX/OK/NE/IA/MO/IL

[Brandon Sullivan]

GFS and ECMWF somewhat coming together on the evolution of a cutoff low to eject Northeastward this weekend on 3/24 and continue on 3/25. Modified gulf moisture is progged to advect northward ahead of the system.. Modest destabilization should be able to occur on both days. However low level clouds may somewhat inhibit insolation.. But good parameters coming together for a nice event, CAPE AOA 750, 60 + DP, LI's around -6... And CINH is not that impressive.. This could be more of a cellular event, maybe more than linear. Which we ALL love..

Actually, im thinking this be bigger than this Wednesday..... Ill know ill swallow them words..

 

[Brandon Sullivan]

Ok.. Since no one wants to help.. I better update the info..

Discussion.. 12z ETA continues to advertise a fairly good setup for sunday.. The 12z GFS/AVN also shows a system, but is slower and somewhat less impressive than the other models.. Regardless, both models show a nice CAPE increase, with amounts topping off around 1500 J/KG from a line around a EAX to ILX line.. Helicity values are forecast to be somewhat marginal, but 1 KM shear hovers around 35 KTS and 3 KM is around 45 KTS.. Timing of the day will be important, as any insolation and cloud breaks could send things in rising.. With lifting mechanisms in place, and not too much of a CAP, severe storms should develop. and may be discrete for a matter of time...

 

[Dustin Wilcox]

Some serious differences in the 12Z GFS and WRF solutions. The GFS points towards Saturday being the day with a slightly negativly tilted trough slamming into W KS by Saturday afternoon. 60kt flow at 500mb with a moderatly strong 30-40kt LLJ. The GFS also indcates a surface low developing over W KS allowing winds to back along the WF. It also has moisture pooled along the NE/KS boarder at this time if going with the GFS SCNRTL NE and NCNTRL KS look pretty decent for Saturday afternoon. Meanwhile the 12Z WRF has the trough placement significantly different holding back to the west as well as farther south, indicating greater chase potential for Sunday.

 

[Jeff Miller]

Here's hoping for a Sunday chase....Day off of work and already planning on it, but somewhat skeptical of an organized severe weather outbreak at this point, still a ways off from what I can see, will have more to say on this tonight. Biggest concern is available cape and historical grunge factor for this time of year, shear looks reasonable. Worried also that saturday could be the day and I will again be stuck at work.

 

[Mike Hollingshead]

Wow that is a big difference. For what it is worth, the 0z ecmwf is similar to the timing of the 12z gfs. I hope those two are right cause they look pretty good for Saturady.

 

[matt patterson]

Ya Mike they do look really nice for saturday..
I just finished reading the model discussion by the NCEP and they are not taking the WRF/NAM solution into consideration.. They mention that the GFS and ECMWF are in agreement through sun morning... Here is the link to the discussion that was posted at about 2pm CDT...

http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

Maybe saturday will finally be the day that something happens

 

[Ross Lazear]

I've been keeping an eye on this system for awhile, since I'm pretty stormchase-hungry! Recent NAM runs have been stubborn in ejecting the cut-off upper low over the southwest to the central/northern Plains. The GFS hasn't been too consistent, but has generally shown a much faster movement of the system, with the 12Z GFS bringing the upper vort max to approx. Brookings, SD by 18Z on Sunday.

However, the 18Z NAM is EXTREMELY different from its predecessors, in relatively close agreement to the quicker trend in the GFS. This appears to bode well for the potential for severe convection from eastern NE to W/Central IA. Speed shear looks pretty good with a relatively strong southwesterly jet over central IA along the eastern flank of the upper wave. The winds begin to have a more easterly component when you get north of the warm front, but you lose surface-based potential in this area.

I'll continue to try and be optimistic, but it's a tough scenario, because we're dealing with a tough to forecast cut off upper low...the timing of an event like this at 3-4 days is really tough for models to handle. If not Sat-Sun, a very strong cyclone development has been hinted at in the GFS over the northern Plains... At least we're into a good severe weather pattern!

 

[matt patterson]

Just took a quick look at the 18z GFS which is very similar to this morning's runs.... the only difference is the placement of the core 500 winds... the winds at all levels look pretty sweet and as we seen all week moisture will not be a problem...




The latest WRF/NAM comes back into sync with the GFS and ECMWF in terms of timing and placement of the upper support and DL....

 

[afischer]

I'm getting excited about a possible cold core chase on Saturday. Like Matt said, the latest NAM is in pretty close agreement with GFS and Euro. Though not quite as prominent, it likewise hints at a mid-level dry intrusion wrapping in ahead of the northeastward-lifting 500mb vort max. Imperial NE area looking good right now.

Oops, can a moderator move this to 3/24; got my dates mixed up!

 

[Skip Talbot]

The 0z WRF went nuts with Sunday, and its probably too good to be true. There is a sharp dryline forecasted in central IA, strong LLJ, more than adequate shear in the upper levels, somewhat backed yet strong surface winds feeding into a 998mb low in MN. More than ample CAPE/SRH combo for supercells.

NCAR's GFS has the low marked in a significantly different location than its WRF plot. You'll notice though that the isobars are relatively similar and that both models have a fairly comparable solution. The dryline isn't as tight on the GFS, but both models point to the possibility of a nice chase setup over IA or southern MN on Sunday. With temps in the low 70's and dewpoints in the upper 50's, the eastern chasers could have a shot at some nice dryline supercells, maybe more.

 

[Brandon Sullivan]

Ya, I was about to say! I love the WRF too.. But GFS inst soo hot.. O well.. Honestly, I dont agree with SPC SWODY 3, and think MO and IL should definitely be in a slight, with the amount of CAPE.. O well.. They know what they are doing.. But I will be watching, no doubt..

 

[Skip Talbot]

The 12z WRF still looks fantastic. The instability has actually increased and expanded to areas of 2000 JKg spanning across Iowa into southern Minnesota as 60+ Tds are now more widespread. The dryline has actually pushed further east as well (moves the target area a little closer to me). Directional and speed shear still excellent. I did notice a large amount of precip being plotted over Iowa at 12z Sunday. Hopefully this will clear the area in time to hit those forecasted cape values.

It looks like the cape was backed off quite a bit to the east over portions of Wisconsin and Illinois. SPC may extend the slight risk area out that way, but if the model trend continues I expect Iowa and Minnesota to climb up through the risk percentages.

 

[Brandon Sullivan]

Right on Skip!!! I look for a slight risk sunday as well. I see even the SREF is shifting the area this way too!! Im excited..!! hopefully i wont have to drive far.. WRF shows 1407 cape over macomb... !! which is way up from last night!

 

[Fabian Guerra]

I just glanced at the latest WRF run for Sunday and it looks pretty good to me for N IA/S MN. I like the wind fields, the obvious CAPE/Shear combo, and the moisture might even be decent enough too. It looks to me that the basic ingredients for severe and tornadic weather look entirely possible, dare i say "probable" for Sunday (as of now according to the WRF model).

I'm rootin' for this one to happen as Sunday chases in IA are always welcomed opportunities for working stiffs like me who live in Chicago...

 

[Scott Weberpal]

The 00z WRF paints a pretty picture in a terrible area to chase. It appears attm that the highest likelihood of tornadic supercells is approx 100 mi N and S of the IA/MN border starting near Lyle and extending well into WI. It's a great area to fish and hunt, but not a great area for hunting tornadoes. My biggest concern is the veered H85 flow pushing the deeper moisture too far east while storm struggle further west. Something to keep an eye on.