8/25/2004 FCST: Plains

[Amos Magliocco]

This morning's ETA raises the possibility of severe weather on Wednesday the 25th anywhere from Oklahoma to Nebraska. Increasing winds aloft and strong instabilities arrive as height falls begin during the middle of next week. What a weird weird year.

 

[Mike Hollingshead]

Wow at tonights eta for Wednesday. I'm officially pumped for the eastern Dakotas region. Somewhere between Aberdeen, Watertown just to pick a spot. Massive divergence in the upper levels will want to help lift the atmosphere. Cape at 18z before convection seems plentiful....goes downhill by 0z as the area fills in with covection(or at least the model thinks so). 500mb winds in the 30knt area should maybe be enough with the backed sfc flow. Decent low level jet in the region out of the south. And it's showing one hell of a dryline under the upper level divergence...

http://www.rap.ucar.edu/weather/model/eta4...hr_sfc_dewp.gif

850 and 700mb temps look warm enough but not too warm. This just looks like one fine setup to me right now, but I'm certainly no met.

 

[Mike Hollingshead]

New pick for Wednesday....O'Neill Nebraska.

 

[Jeff Snyder]

I think southeastern KS could be game tomorrow... This is further supported by the 0z ETA, which depicts quite a situation possible... 4000-4500 SBCAPE with 350-450 m2/s2 0-3km SR-helicity. Deep-layer shear is not too impressive, but with such intense instability and low-level shear, a brief, strong tornado seems like a possibility, though not too likely. Capping may be an issue, though it looks to be quite breakable from a line from EMP to PNC. If convection does get going, supercells with isolated tornadoes appear likely.

 

[Mike Peregrine]

The 0600 Day 1 is going with a widespread area outlined under a 5% probablistic for tornadoes, ranging all the way from SE KS/SW MO up into Nebraska and Iowa. The cap ... which factored in to the timing of iniation yesterday/last night ... will no doubt play a part again today - along with the fact that there is now widespread convection that has developed in the last couple of hours (as of 5:45 a.m.) across large areas of the target region, again allowing for multiple boundaries.

Today seems like it will be as much of a tough call as yesterday. I'm not sure why such a large area is outlined as 5% yet, since it seems that not a lot has really changed over the last 24 hours as far as the large-scale factors go. Instability will again be high ... maybe this shortwave will exert a little more influence than yesterday and be capable of exploiting cap weaknesses along outflow boundaries. Hopefully we'll have a better idea what to expect by mid-afternoon.

 

[Mike Peregrine]

Wow - the latest outlook certainly seems favorable for a rather widespread possibility for severe weather, all the way down into eastern Oklahoma! ... Will be interested in seeing if this system is capable of helping this verify. Will REALLY be watching the soundings later this morning, and hopefully we can be chasing later this afternoon.

Is this May? I'm confused - - -

 

[Amos Magliocco]

LOL, Mike. It does remind me of early May this season when the surface pattern was weak and disorganized for a while. Hopefully the results will be better. I'm favoring the area beneath the intersection of the mid and low level jets in northeastern Kansas or extreme southeastern Nebraska. Current indications are for CAPE to exceed 3500 j/kg and 0-3k SRH to reach 200 m2/s2 in an area of strong convergence north and northeast of the dry punch, approximately from Kansas City to Manhattan to Emporia.

Some of these features have been forecast by the ETA for several runs and look to be veriifying nicely already this morning. In addition, last night's convection and the scattered showers underway currently are laying outflow boundaries, one of which is very noticable on the TWX loop east of Salina. I wouldn't be surprised to see storms fire on these boundaries and move east into the instability axis with the passage of the day's second disturbance later this afternoon.

I'm in eastern Kansas today and intend to keep my road options open so no definitive target as yet, but that general area in the extreme northeast corner of Kansas seems most interesting to me now.

 

[Glen Romine]

I think we are still in forecast mode - so I'll post here instead of the now.

As mentioned by Jeremy, SPC planning upgrade in the next outlook for portions of KS, MO and IL. I was just looking at the setup for today when I stumbled across the MCD - totally agree with the upgrade. TOP and SGF soundings showing very impressive midlevel lapse rates, deep shear is in place and low-level shear is pretty good. Subtropical jet streak LE region spreading divergent upper level flow over n KS to MO sliding into w IL, diffluent 500 mb flow with vort max over central KS, low-level jet should back as nocturnal effects die down, and the only real neagtive at this point is weak near surface flow. RUC forecast maintains 150-200 0-3km helicity, along with CAPE > 5000 J/Kg, so severe storms look to be a good bet. Sfc winds along the boundary are forecast spotty 15 knots - so maybe a few mesoscale pockets of favorable low-level flow to squeak a tornado or two out. I may have to clear out my afternoon plans.....

Glen

 

[Amos Magliocco]

Surface pressure fields in Kansas are flopping around some and creating veered winds at the surface, a trend the RUC projects to continnue. In fact the RUC eliminates all backed winds from Kansas through 0Z. I won't put too much faith in this, but it's worth noting that this is already depriving eastern Kansas of helicity. Hopefully we can see enough insolation to jack up our CAPE and overcome any low level shear defeciencies. I still think tornadoes are possible from eastern KS into northwestern and north central Missouri, but I wonder now if with a more unidirectional profile that the greatest severe thread becomes damaging wind via MSC and clusters.

 

[Amos Magliocco]

I see there's a NOW thread going. I guess that's for the morning convection? I'm going to ignore it because I'm on a restricted internet connection out here on the road, which is the reason we try to keep things relatively well-organized in the Target Area forum. Since there's no ongoing convection as part of the this afternoon's setup, a NOW thread is premature.

New Day 1 pushes the show east and I see why. Winds in northern MO are backed along the boundary and RUC goes insane with as Glen mentioned CAPE in excess of 5000 j/k. Best helicity values are already shunted in that direction as well. I guess the trick now is how to deal with KC metro ( a test I failed on a famous day last year) or whether to go up to St Jo and not mess with KC at all.

 

[Mike Peregrine]

Amos - check your messages/email ...

You are correct - winds have much better profiles to the east ... the unidirectional elements you mentioned in the messy setup in Kansas become better organized across the river. But can they be expected to stay that way? There has been ongoing convection up there throughout the morning ... things could still easily get monkey-wrenched, I think. I guess I'm still having a hard time justifying a hatched area in my mind, but I won't look a gift horse in the mouth and will continue to hope for something interesting to happen. I'm taking the afternoon off from the regular job ...

I totally love days like this -

 

[rdale]

"Since there's no ongoing convection as part of the this afternoon's setup, a NOW thread is premature. "

I suppose you'd need to ask the thread starter -- SPC seems to think that the IA MCS will play an important role in the afternoon activity.

"BOUNDARIES FROM CURRENT MCS MOVING ACROSS IA INTO IL ...
WILL PROVIDE FOCUS FOR TORNADIC SUPERCELL POTENTIAL BY MID AFTERNOON."

 

[Glen Romine]

I suppose you'd need to ask the thread starter -- SPC seems to think that the IA MCS will play an important role in the afternoon activity.

Exactly - so that puts this mornings convection into the realm of having a role in the afternoon forecast. Also, the text suggested it was isued because a svr box was issued - but that was for elevated hailers - most of us are interested in sfc based convection.

Back to the forecast - I'm concerned by the coverage of back-building storms in to eastern MO - temps still in the mid 60's around Quincy IL - so the boundary could be pretty tight for sfc based storms. Extensive low cloud cover will also make visual chasing tough - and n MO is rough country to chase. I'd target midway between Columbia and Kirksville area at this point - despite being too cold there now - expect a fast recovery. I'll be hoping for things to hold together as storms get further east and ideally cross the Miss. R. before sunset.

Glen

 

[Glen Romine]

New MCD from SPC mentioning tornado watch expected to be issued in next 1-2 hours, with tornado potential increasing into the afternoon.

http://kamala.cod.edu/spc/0408251701.acus11.html

Latest vis sat loop suggest low-level clouds starting to break up some in NW MO - so things are continuing to look up.

Glen

 

[Mike Peregrine]

Glen - for those reasons, it may be a more sound decision to target slightly further south and west ... St. Joseph to Kansas City may also present good options - less cloud cover, more than sufficient heating ... it has become oppressive as moisture is piling up everywhere.

You are right about the terrain - it makes it difficult. It does make it nice to know every back road from here to Iowa in a situation like this. GPS is crucial today.

Here are the skew-t diagrams for St. Joseph at 0z:

http://www.wxcaster.com/modelskewts.php3?f...STATIONID=72449