06/05/10 FCST: IL/IN/OH

[Chip Redmond]

Surprised noone has anything going on this day yet. Since I plan on going out I will start a thread.

Once again, as with this time of year the outflow from the following days storms will be the main indicator of storm activity. Instability, its June and will not be a problem. With the NAM, 850 winds seem to really shift out of the south during the day tomorrow. Zonal winds 700 on up, and a strong surface wind out of the south, a fairly good amount of shear will exist at the low levels. Precipitable water around the two inch mark has me slightly bothered as storm mode could lean towards the hp side (definitely not what I want) but none the less, a classic type is also possible. A vorticity maximum located in northern IL and moving into northern IN may be the focus for increased shear as well.

Have had pretty good luck with June chases the last few years so we plan on stationing out in the Danville, IL area in the morning and rolling from there.

Chip

 

[Dave Gore]

Yep, surprised as well no one has mentioned anything yet. With the amount of moisture available, I'm expecting HP'ish structures tomorrow. We plan to be in eastern Illinois (Danville area) by 1230 local time.

Good luck and stay safe everyone.

 

[Alan Black]

The 18z NAM run has 0-3k Helicity of well over 500 m2/s2 across N. Central IL at 21z along with better SBCAPE across N. MO. By 0z the 0-3km Helicity is roughly the same over N. Central IL and while the highest SBCAPE hangs back across MO there is an area of ~2500 CAPE is evident across W. Central IL. This area has roughly 250 m2/s2 0-3km Helicity. 18z GFS has a similar setup but a little further south at 0z. Given this, I'm thinking of targeting the Peoria, IL area or perhaps further NW towards Galesburg where there looks to be a good combination of helicity and CAPE. The big question for me right now is how convection sets up tonight across the area and clearing tomorrow.

 

[Matt Hunt]

I'm really beginning to wish I hadn't committed to babysitting my niece! Don't get me wrong, I love her, but wow, this is easily the best local chase of the year so far! I'd really like to be positioned in N central IL by noon tomorrow, but unfortunately it's not going to happen. The only chance I have is at some evening storms in Indiana, just north of Indy. Hope it works out! Shear is no problem at all, CAPE depends on the model you're looking at, but I don't think it will be an issue. The biggest issue will likely be these cells going HP, and then becoming linear quickly. Would also love to see some strong wind and/or hail in the Indy area, as this would definitely help out my roofing business! Good luck to all chasing tomorrow (today)!

 

[Chip Redmond]

Meh, this has really turned into exactly what I didn't want. Discrete storms just don't seem to probable because of the amount of instability. Couple this with such mammoth precipitable water and you get a rainy bonanza. Looks like a boundary, if one gets established from this morning convection will be situated farther south than expected along the eastern 70 corridor and west through central IL. This will be further away from the vort max and greatest helicity values than what we had planned. The overall tornado potential doesn't seem to be very high except for maybe a spin up or two along the northern parts of bow echos. Will most likely truck it a bit farther west to Champaign to see how things evolve if this darn convective mess will just scoot east already.

Can anyone say muggy? Low 70 temps with 70 dewpoints.

Chip

 

[Ryan Wichman]

Made a brief forecast on the site last night after a successful chase in NE Missouri yesterday. Here is most of the text, you can get the graphics and rest at: http://convectiveaddiction.com/2010/06/04/fcst-060510-iailmoin/

Saturday could be another day of potentially active weather across the Central Lowlands. A 1004 mb low is progged to be situated near the IA/NE border region by Saturday morning (per the NAM, GFS and ECMWF), though exact placement varies slightly by model choice.

A nearly stationary frontal boundary should be present from south central Iowa into central Illinois and Indiana. The NAM keeps the frontal boundary confined to roughly the I-80 corridor, whereas the GFS is much more aggressive in driving the frontal boundary well north of the I-80 corridor by 00z Sunday. A robust warm sector will likely develop south of the front, with CAPE values AOA 2,000 J/KG in some areas. While the NAM has a slightly more picayune warm sector confined to southern IA, northern Missouri and west central Illinois, the GFS depicts a much more capacious warm sector engrossing the southern third of Iowa, most of Illinois and the southwest third of Indiana by 00z Sunday.

Of greater significance will be the evolution of an overnight MCS that is currently forecast by models to track somewhere between I-80 and US 136. The actual evolution and track of this system, as well as its timely exit from the region, will determine the amount of instability that is able to evolve prior to convective initiation Saturday afternoon, as well as the ultimate location of any OFBs. A belt of 90-100 kt winds at 250 mb will be juxtaposed with 500 mb longitudinal flow on the order of 60-70 kts, along with modest southwesterly winds of 25-30kts, yielding SFC-500 mb bulk shear value AOA 50 kts (70 kts across far N IL).

Current thinking is that storm initiation will occur by late afternoon INVO remnant OFBs, though with zonal flow aloft, any shortwave has the potential to either spark convection spasmodically or contravene convective chances altogether. As is typically the case, a good morning forecast based on surface features will be on order to ensure successful intercepts on Saturday, should the severe threat materialize. All modes of severe weather are possible on Saturday, including tornadoes, severe hail and damaging winds. Given the potential strength of shear near the frontal boundary, any storm that becomes rooted in the boundary layer and peregrinates parallel to the front could have an enhanced tornado potential. The greatest threat for damaging winds > 70 mph and an enhanced tornado threat appears to lie along an axis roughly parallel to and immediately north of the US 36 corridor from KUIN to KIND.

 

[Derek Weston]

Plan to be on initial storms firing in Iowa.. hoping for a bit of discrete activity.

There will be a small(ish) window for this.

Directional shear isn't great... but probably enough to get it done in I-80 region. Could see a storm really taking off with a bit of deviant motion... will look for any subtle boundries left over from early convection.

 

[Rob Wadsworth]

Looking at the 15z RUC, CAPE values have fallen off sharply S/SE of Des Moines. It looks as if NW MO is getting the lion's share of it now. Looks like the NAM fcst is playing out more than the GFS as far as the CAPE is concerned.

I'm a noob; any tips or comments welcome via PM.
Targeting -if I should go- would be S of Des Moines/Osceola IA I-35 at this time. Or is it going to be Burlington by 21z?

 

[Chip Redmond]

Southern most boundary just doesn't seem as intriguing as before with the RUC taking the best shear to the north. With clearing behind the convective crap, things should start cooking soon. Still don't see much of a problem with the instability. PW's are slightly lower in that region also that may help a wee bit. Waiting on new SPC outlook to see if they can also verify these thoughts that everything has shifted to the NW. Sitting in Champaign currently and will most likely move towards Quad Cities soon.

Chip

 

[Bill Schintler]

Chase Target for Today, June 5

Chase target:
40 miles west of Iowa City, IA.

Timing and storm mode:
Supercell storms should redevelop across the area after 4 PM CDT. All modes of severe weather are likely, including tornadoes. In addition, very heavy rainfall totals are likely, locally to several inches.

Discussion:
Ongoing convection across the southeastern portion of the state will weaken and move out of the area as the low-level jet weakens. Once clearing takes place, rapid destabilization will occur. A surface boundary parallel to and 10-20 miles south of I-80 by mid-afternoon will provide the focus for renewed convection. Winds may be increasingly backed immediately east of a compact area of low-pressure between Pella and Grinnell Iowa between 4 and 6 PM.

Once storms form, all parameters should support rotating storms. Dewpoints will climb into the low-70’s with help from evapotranspiration from recent rainfall. MLCAPEs will increase to nearly 2500J/kg despite modest mid-level lapse rates. A shortwave embedded in zonal flow will approach the area through 00Z while amplifying. SFC-3km SRH should increase to 300m2/s2 as a 30kt low-level jet impinges on the area. Additionally, SFC-6km shear in excess of 70 kts will support storm organization.

- Bill Schintler

11:05 AM CDT, 06/05/10

 

[Mike Hollingshead]

I'd probably target somewhere between Des Moines and Red Oak by 4pm. Winds are backed some along the outflow of the mess in north MO. That area should lift ne, though not overly sure anything will remain backed instead of just washing out. Doesn't matter, cold front should set things off in sw IA. Hard to love much about today and not sure I'm even chasing. I'd go with that area and be leaving Nebraska fairly soon if I were to go. Front should help them deviate just by it pushing se, just not sure they don't turn into a big mess at the same time. Low levels are just whack, but I can see it being possible things could work with big cape and nw flow. If I liked anywhere, it would even be this area given I wasn't close to it as it is. Getting real tired of all the setups this year being so "on the fence" type deals where you just don't love them.

Edit: http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/12/

That is the idea I'm having but more nw/slower. Man I'd take that and just wait at home. At least then I'd know the day would be worth it(I'd know before going much of anywhere lol).

 

[Kevin Crawmer]

Rob, I don't consider myself a great forecaster at all, but I am agreeing with what you are saying. Surface analysis shows the low a bit further north than originally displayed and the warm front accompanies it. Something could fire in NW MO, but I'm thinking as the low moves east that areas along I-80 and possibly a bit further north could get into the action. I think if you get too far south of that there may not be adequate CAPE to realize what we (I?)were hoping for in SE IA/NE MO.

 

[Kevin Crawmer]

...but the SPC doesn't seem to agree with me. They are better than I am though, so I will trust their judgement .

I'm still uneasy about how things are going to turn out. The cloud cover west of SE IA/NE MO worries me. Tough call today.

 

[EricGraham]

Watching clearing between I-88 & I-74 moving e/se. Currently sitting at home here in Lafayette, IN. Temp:79 Dew:73 Humity:82%. If I had to choose to select a target looking at Remington, IN and points west along highway 24. Looking at iniciating around 4:00 and after.