5/24/06 FCST: IA / IL / MO / KS / WI

[Matthew Havin]

Surface low pressure moving across the Dakotas overnight is progged to move into MN during the daytime tomorrow. 00Z NAM has sub-1000mb sfc low over central MN by 00Z Thu. Primary target for severe wx tomorrow will be ahead of the cold front that will extend from S.MN thru E IA and dividing Missouri from NE to SW.

Chase targets can be divided into 2 areas:
1. E IA/NW-WC IL/NE MO
2. SE KS/SW MO

1. Primary area of activity will likely develop ahead of the cold front in E IA-NE MO and into western IL north of Saint Louis (stay out of STL...we never get tornadoes in severe weather season). 00Z NAM has best colocation of 2000+ CAPE (mid 60s Tds) and 0-1km SRH 150-250+ m2/s2 near Quincy IL ....giving a model-based EHI of 3-5 by late afternoon. However, due to linear wind profiles, primary storm mode will likely be a squall line. Another big concern that is a negative is question of how much convective debris will be left over from overnight action in the area during the midday. What may make this area deliver, and a point the SPC brought up, was if any boundaries left over from morning convection are present...then they may trigger isolated pre-frontal storms that will have a fighting chance in this region.

2. Conditional secondary target of activity will be across SE KS/SW MO where more likely daytime surface heating will lead to 2500+ CAPE by afternoon. Wind profiles here will be less unidirectional...with SSW 850mb and WNW 500mb flow. Progged 0-1km SRH is lower (50-150m2/s2), and the cap in the area may supress storm development until early evening. However, with any assistance from mesoscale boundary interactions.....a few isolated supercells may be possible in this region where futher up north along the front in IA/IL it will be rather unlikely.

 

[J West]

Chase targets can be divided into 2 areas:
1. E IA/NW-WC IL/NE MO

What may make this area deliver, and a point the SPC brought up, was if any boundaries left over from morning convection are present...then they may trigger isolated pre-frontal storms that will have a fighting chance in this region.
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It appears there is already one OFB sitting in a N-S line from far southern WI south through Sterling, IL. The possibility exists for another OFB to set up shop behind the convection currently SW of Iowa City, IA.

If the timing is right and the current cloud cover can thin out and let the sun in then your chase area above may light up nicely. The CAPE doesn't look promising too far north into IA/IL, but there is plenty of moisture on tap with Td's near 70 into SW WI by 21z. The Quincy area looks to be a good shot, esp. if another boundary sets up shop in the area.

 

[Jesse Risley]

SPC has just upgraded the region to a moderate risk. If surface winds remain more SE in advance of the front it appears that the tornado potential will be enhanced. My target area will be a Burlington-Macomb-Quincy axis. Could be an interesting event!

 

[Bill Schintler]

Chase target:
Parsons, KS (35 miles northwest of Joplin, MO.). Note: this is a southern target today. A second target obviously exists in IA, although that will be a marginally chaseble squall line event.

Timing:
Storms backbuilding into the area though 4 PM CDT.

Comments:
Linear, mostly non-severe storms. Small hail and winds to 50 mph will be the primary hazards.

Discussion:
The trailing end of a CF will provide the focus for convection this afternoon. Ample instability will couple with marginal shear for the possibility for strong storms. As was the case yesterday in NE, storm inflow will be parallel with linear storm orientation, limiting overall strength.

- bill

 

[Eric Flescher]

Interesting target choice. I may decide to head down that way based on your ideas.
Dr. Eric Flescher ([email protected]), Olathe, KS:913-780-5902: (mobile) 913-486-1274: Storm Satori- http://members.aol.com/kcstormguy/stormsat...tormsatori.htm: E.O.A.S. (Earth, Oceans, Atmosphere and Space Blog) -http://www.xanga.com/dreric1kansas
**

Chase target:
Parsons, KS (35 miles northwest of Joplin, MO.). Note: this is a southern target today. A second target obviously exists in IA, although that will be a marginally chaseble squall line event.

Timing:
Storms backbuilding into the area though 4 PM CDT.

Comments:
Linear, mostly non-severe storms. Small hail and winds to 50 mph will be the primary hazards.

Discussion:
The trailing end of a CF will provide the focus for convection this afternoon. Ample instability will couple with marginal shear for the possibility for strong storms. As was the case yesterday in NE, storm inflow will be parallel with linear storm orientation, limiting overall strength.

- bill
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[John Farley]

I'm also looking at a possible target in the Quincy area due to the combination of instability and lower-level directional shear that others have mentioned. SPC seems interested in the area between COU and STL, but a real drawback of that area is getting chased by the storms into rush-hour congestion in STL. So I would prefer the Quincy target, but will wait for a while before deciding.

Besides the obvious factors mentioned by others - weak upper wind fields and the likelihood of quick evolution to a linear mode - I am also concerned that there just may be too many storms, resulting in a massive, difficult to chase MCS. The RUC model is showing widespread QPF over the entire area of interest from early afternoon on. With the dewpoints as high as they look to be, that could be an issue.

Doesn't look like convective debris from last night will be too much of a problem - it's already bright and sunny here in Edwardsville.

 

[Jesse Risley]

Doesn't look like convective debris from last night will be too much of a problem - it's already bright and sunny here in Edwardsville.
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It's clearing out quite nicely here in Macomb as well with temps AOA 75 degrees and dewpoints in the lower 60s. My only concern is that there are no outflow boundaries in the Quincy-Macomb area, as last night's convective debris remainder more over northern Illinois, or at least north of U.S. 34.

I find the terrain between Quincy and St. Louis more unfavorable for chasing. I would imagine the squall line may begin to organize into a more linear mode after the system crosses the Mississippi, but I could be wrong. Any other thoughts on that one?

 

[Jason Persoff]

I think that I'll target Manhatten/Topeka area which is due south of my current location with reassessment from there. This will be another challenging day as the upper levels parallel the lower level wind fields and the probability for linear cells similar to yesterday. In all likelihood I'll have to watch the satellite for fields and boundaries that may help. Definitely want to avoid moving too far east of the MO/KS border as that terrain is just hilly enough to make it difficult to see storm bases (and can be frustrating).

On a side note...In contrasting '05 with '06, the upper air dynamics couldn't be more dissimilar (ridge vs. trough). Yet, both pose remarkably challenging weather for the chaser. Biggest difference this year has been the sweltering 700mb temps despite a beautiful trough. Additionally, forcing has been parallel to sfc winds this year. Anyway...we'll see how the day goes and then I'll be relaxing for the next few days. Will try to massage the GFS in the "future of the season" thread later today (where I'll wax philosophic ).

See you guys out there!

 

[Andy Wehrle]

Sun's out in south-central Wisconsin, wind from the south, maybe a boundary or two from the earlier convection. I'm sure anyone on the north end of this neighborhood who recognizes the implications of this is a wee bit nervous right now. :blink:

 

[Joe Zemek]

I see more appeal in the northern target given the better potential for some veering with height and backing at the SFC. Going by RUC (grain of salt) the main field of unidirectional winds from 850-500 seems to be setting up across IA into IL, with better HEL (veered 850) located in SW WI and up. This area overlays the tongue of the forecasted local CAPE max, which given upper cooling always = good.

Caveats: convection does transition to a line, and moisture could be limited by southern complex. However, the short window for discrete supercells renders the long term availability of good SFC moisture moot. Who cares if the inflow is gunky if the storms are lining out?

As much as I would like to be chasing, today looks like a potentially frustrating day, with very fine lines for successful tornadic interecepts.

Virtual Target: Platteville in SW Wisconsin

 

[J West]

I will be headed out within the hour to somewhere in SC/SW WI, perhaps at or near Andy's neighborhood. Both MKX and SPC are mentioning a brief tornado threat right away as the storms build, so I'll be playing that risk.

It's a balmy 70/65 just south of Milwaukee right now, and the sun just popped out after a brief storm. There have got to boundaries west of here just waiting for something to fire along it, based on the line of storms that just passed through SE WI.

 

[Mike Johnston]

Interesting to note the severe parameters building over W Central and S Central MO as of the last hour. Surface moisture seems to have held up fairly well so far under the heating of the day...w/ SB cape of ~2,500 to 3,000 j/kg, lifted indices of -8 to -9, and generally low LCL and LFC heights, it's worth keeping an eye on for chasers favorably located. Moderate, but less than ideal, 850/500 mb wind crossover, and also moderate 30-35 kt deep layer shear indicated.

Consistent with the fairly unidirectional flows of this overall system, glaring negatives are 1) weak surface convergence (barely the ghost of a surface trough accompanied by very subtle wind shift line, and...it says "cold front" on the synoptic map, but 82t ahead of the front and 92t behind the front??), and 2) very weak upper level SR winds which do not provide much venting and favor an HP storm mode.

At any rate, expect at least some contribution from LLJ to kick in and some energy release over this area this evening. The prospect for rotating supercells is at the margin, but as moisture and bouyancy are more favorable at this point in the day than the "tail end" environment of yesterday's storms, perhaps there will be some interest and activity.