4/10/08 FCST: OK/TX/MO/AR/KS/TN/IL/KY

[beaudodson]

The NWS in Nashville, TN has just posted this information

UPDATE...REGARDING POTENTIAL FOR AFTERNOON SEVERE THUNDERSTORMS,
THE LATEST RUC 21Z FORECAST SOUNDING FOR A POINT JUST WEST OF THE
TENNESSEE RIVER (NEAR CAMDEN) SHOWS:


0-3 KM STORM RELATIVE HELICITY: 554 M2/S2

POSITIVE CAPE: 1345 J/KG

TRIGGER TEMP FOR CONVECTION: 77 DEGS, TO BREAK MID-LEVEL CAP: 79 DEGS.

WET BULB ZERO: 11,000 FT.

 

[Derek Weston]

Good grief, has this one become questionable. From looking big time to me possibly not even bothering.

Not even sure Northern Missouri into Central Illinois will clear out well enough....

The mess of precip we've got going on now has me really questioning things -- I want to see what the SPC's handle on this is.

 

[Dallas Smith]

Im with you Michael, im going to stay close to home and hope for storm somewhere in northeast Kansas. Latest RUC is only giving, at most, 500 CAPE by 21z. There will be decent shear in place so a low-topped supercell is possible. My biggest concern is the when the mid-level dryslot comes in. The 09z RUC has in moved in by 17-18z so we should get atleast a couple hours of destabilization before the fronts move through. Its pretty sad that its April 10th and I am getting excited about the possibility of a low-topped supercell! I'm ready for a Kansas outbreak!

 

[Darrin Rasberry]

Will be curious to see if SPC will upgrade to a high risk later this morning. I wonder about the greater potential across northern Missouri into Illinois late this afternoon and evening. WRF certainly shows the potential for discrete storms in that region.
[/B]

Dial seems to be a bit conservative in his forecasts lately, and I wonder whether the decision to remove the MDT from northern Missouri is warranted, especially north central Missouri, which is projected to have some nice lifting and decent CAPE if the crud can clear the area in time to allow the sun to help the instability along.

But I do not think a high risk is warranted, given his mentioned EML. Nevertheless, I agree with the ten/hatched tornado area, and would rather replace the notice of the possibility of strong, long-track tornadoes given the 3km Helicity, sufficient instability and dews to break this cap, and good winds. An EML, if present in strength as he stated, will by definition inhibit "pacecar supercell" development in front of the projected squall line, and if the southern Arkansas - Tennessee clearing holds, this could either mean a situation with isolated supercells with incredibly damaging tornadoes, or a few aborted storms signaling nothing more than the arrival of the squall.

Both areas - especially the southern area, which has less potential than the northern area for an evening event - are now hinging on the arriving squall and associated cloud cover. I know that such a factor isn't everything, but it will play an important role in realizing what was previously just a modest forecast of CAPE.

It will be interesting to see the SPC's update in a half hour, and all of the subsequent local area updates in the target range.

 

[Kevin Crawmer]

Well the crapvection is certainly concerning us too. Currently the area around NE AR/W TN looks the best. Once this first round goes through it sounds like there will be a strong cap in place allowing the atmosphere to charge up a bit. The problem is this. Forecast high in this area is 78.....sounding that was previously posted:

TRIGGER TEMP FOR CONVECTION: 77 DEGS, TO BREAK MID-LEVEL CAP: 79 DEGS.

Things are going to be tight. Not sure if it is worth the 5 hr drive or not. That is looking like the best bet of anything though, so I may bite. If discrete cells do pop, the could be monsters. I am anxious to see what the SPC does with this. I wouldn't be suprised to see the 10% probs raised given their heightened interest in this area. I would guess this morning convection could leave boundaries to play off of later too.

Given the terrain down there is much better than SC MO and the likely bullseye of probabilities to be centered there, I am guessing we will set up in the West Memphis area....possibly a little further north, but it appears we can get several directions quickly from West Memphis. We will see if we get confirmation in the next half hour.

 

[Ryan Pfannkuch]

Preliminary 4-county target area in Northwest MO: Atchison, Nodaway, Worth and Gentry

Including the cities of: Tarkio, Maryville, Grant City and Albany

Well, after taking a long hard look at the 9z operational RUC and the various 4-5km WRF runs from 0z, I think I'm just going to play this thing as I typically do for "cold core" style setups. As always, this play hinges entirely on the advancing dry slot providing for some insolation ahead of the sfc low, and I will continue to assume that eventually this will transpire.

In this case, I typically find that targeting a zone roughly 70-140 miles due E or ESE of the sfc low ends up being a decent spot to maximize the overlap between instability and the strong LL shear along the advancing surface boundaries. Depending on when storms actually form and the fact that motions should be 50-60 mph, my main axis of interest in this case would extend along a line from just NW of Kansas City at 18z...to as far north as south central IA by late afternoon. Thus, my target area above reflects a basic middle ground with the focus on the mid afternoon time frame.

If areas farther east across MO start looking better as the day goes on I might re-evaluate, but for now I just don't see myself straying too far out ahead of the advancing sfc low. Good luck to all today with this complicated fcst scenario.

 

[Rob Lightbown]

12Z Little Rock sounding is absolutely insane....especially the storm relative helicity numbers, 1 km of 692 and 3 km of 948.

 

[Brent A. Clair]

OK, I am still new to posting here, so if this goes against guidelines, by all means, yank this and help me to write better the next time.
Here it goes. I am not convinced that the moderate risk should be contained so far south and not be lifted into central IL. Maybe it is my bias to the area, but after looking at last night's and this morning's model runs (mainly NAM), I still believe that the IA/IL/MO intersect still sees a great chance for convective activity, not to mention tornadic behavior. Dry slot that everyone seems to be mentioning can be seen by most soundings. But, UIN does not experience this. Instead, it stays marginally saturated until later this evening. All other indices are in good condition. One question is whether a storm could initiate ahead of this area of support. COU gets the dry bulge around 6pm; enough time to trigger?
As most can tell, I am still feeling my way through Svr Wx forecasting, but learning each day.
"Like a blind man at an orgy, I was going to have to feel my way through this" Leslie Nielson, Naked Gun

Feel free to tear this forecast apart, but tell what I left out.
Later

 

[Jim Cross]

I am heading for northeast Arkansas. I am in Poplar Bluff,Missouri now and will be heading south down 67 to the Newport,Arkansas area. I like how the storms are starting to break up and hopefully get some isolated cells later this afternoon. I will set up in Newport and chase east towards the mississipi river as the day progresses. Good luck to all that makes it out today.

 

[Brandon Sullivan]

I totally agree Brett.

Some clearing taking place in Western MO.. New 12z NAM Shows 1500+ CAPE Developing in NE/NC MO by this afternoon.. Models are hanging onto the dry air wrapping in… Which is evident on the Vis Sat and Radar with the sharp precip edge.. Something tells me not to follow the base my target solely off the SPC (no offense guys, its a ways out) and go to Quincy, or Kirksville…. I just think it will have adequate time to clear out there..… Latest RUC shows the Warm Front around I-80 by 00z with southerly winds in the area.... Warm front now is only at an EAX/LSX line…. 9z SREF looks impressive in bringing the show back this way, with Sig Tors and Sup Composites Jumping around 2100z. Im CERTAINLY not ruling the Quincy area out yet, or Northeast MO either.. Well have to see what comes of the clearing

Brandon

 

[Jesse Risley]

OK, I am still new to posting here, so if this goes against guidelines, by all means, yank this and help me to write better the next time.
Here it goes. I am not convinced that the moderate risk should be contained so far south and not be lifted into central IL. Maybe it is my bias to the area, but after looking at last night's and this morning's model runs (mainly NAM), I still believe that the IA/IL/MO intersect still sees a great chance for convective activity, not to mention tornadic behavior. Dry slot that everyone seems to be mentioning can be seen by most soundings. But, UIN does not experience this. Instead, it stays marginally saturated until later this evening. All other indices are in good condition. One question is whether a storm could initiate ahead of this area of support. COU gets the dry bulge around 6pm; enough time to trigger?
As most can tell, I am still feeling my way through Svr Wx forecasting, but learning each day.
"Like a blind man at an orgy, I was going to have to feel my way through this" Leslie Nielson, Naked Gun

Feel free to tear this forecast apart, but tell what I left out.
Later

I don't necessarily disagree, but I do think that things are up in the air (no pun intended) at this point from a forecast perspective. There appears to be considerable uncertainty as to how far northeast the dry slot will progress before maximum daytime heating has ended.

I do agree that the other aformentioned parameters appear favorable for severe weather, although CAPE will be crucial if it actually ends up staying below 500 J/KG. If we can't get some drying at this end of the system, then I think the threat for tornadic supercells will be much more conditional and far more limited than not. However, I would still expect at least a few discrete supercell thunderstorms, as well as the potential for a major squall line to move through this region tonight.

 

[Kelley Austin]

Jim,
I am here in Newport, looking out my office window we are seeing a little break in the clouds, not much, but some, the Tor warned cell just S. of little rock is tracking straight at Jackson Co. Should be getting here in hour or so. If it holds together we might see a little action close by.