4/06/06 FCST: KS/NE/IA/MO/OK/AR/TX

[Andrew Stoller]

There's already a large area of precipitation in eastern Oklahoma and Kansas. Does that have the possibility of contaminating todays setup, at least for the southern end of the spectrum? To the north, it looks like the dry air has bulged ahead more.

 

[Mike Hollingshead]

12z RUC SFC

Wow does the ruc bomb that low out between 18-0z. 8 mb in 6 hours. The 850 is very veered right now, but is prog'd to rapidly back by 18z. I'm leaving shortly for either a Hebron NE area or perhaps even west of there. Actually Aurora NE might make more sense for now. Yeah I think I'll stay along I-80 for a while as I still have concerns for something north of I-80. I guess it is pointless to worry too much about all that yet.

 

[Kevin Bowman]

Chasers chasing near Omaha, please take note

PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
825 AM CST THU APR 6 2006

THE KOAX RADAR WILL BE DOWN UNTIL 1530Z FOR EMERGENCY REPAIRS. ADJACENT RADARS INCLUDE KLNX...KUEX...KTWX...KEAX...KDMX AND KFSD.

Edit, if this is out of place, please delete

 

[Mike Peregrine]

Obs out of Topeka look like they are shaping up great right now ... but I'm a little confused by RUC forecast soundings on Earl's page. Looks like nice shear and instability at 15z, but by 0z things shift into becoming more unidirectional and supercell potential falls. I'm guessing this translates into eastward movement of the dryline. But now I'm wondering if this could potentially start by around 15z or so this afternoon. My target stays the same as last night ... St. Joseph and northeast Kansas. Just trying to get an idea of how this is going to actually work.

Vis sat shows crud to the south, over eastern Kansas ... but great clearing in store for NE Kansas target, under the proviso that things do not start firing there. I wouldn't be surprised by an early round or two of elevated convection starting up soon, but am anxious to see the affects any rain cooled air will have on the environment this afternoon. Any effects should be minimized by the ability this system will have to clear the road ahead of the deep convection. For now, the prelim target stands though - -

In addition, nocturnal beasts may indeed rule the night tonight in areas south of KC, through Butler and into SW Missouri.

 

[Gabe Garfield]

There's already a large area of precipitation in eastern Oklahoma and Kansas. Does that have the possibility of contaminating todays setup, at least for the southern end of the spectrum? To the north, it looks like the dry air has bulged ahead more.
[/b]

I just addressed this issue (as a matter of fact) in my blog. Here's an excerpt:

Today, I am focused on a few things (forecast wise). First of all, I’m monitoring the dewpoint temperatures to see if they will rise to the values progged by the RUC model. RUC has forecasted a plume of mid-60s Tds all the way up into NE OK. Should this occur, CAPE would become quite large and the tornado potential would increase markedly. However, models have overestimated the surface dewpoints for the last few systems, so I’m very skeptical of such a forecast. Nevertheless, lower 60s dewpoints should be sufficient for some nasty storms.

The next item on the forecast list is the potential for an outflow boundary. As I write this, elevated showers and thunderstorms are rapidly sweeping across Oklahoma from border to border. The showers are favorably timed (i.e. they shouldn’t negatively impact daytime heating), so the outflow boundary should have plenty of time to cook under the early April sun. Of course, the impact is three-fold (as usual). First, it will enhance vorticity (because of its inherent baroclinicity) via density differences across the boundary (i.e. warm air rises, cold air sinks). This will create a horizontal circulation that can then be tilted and stretched into the vertical (where you need spin when you want a tornado). Second, it will lower LCL heights (on the north side of the boundary), which has been shown to be very favorable for the development of tornadoes. Third, it will create a focus for convergence and storm development (parameters are great, but you still need a storm!). So, all in all, this is a very positive development in our quest for the ever-elusive tornado.

Gabe

 

[John Sickels]

I'm also wondering about the showers in southern Kansas and how this might effect things.

For what it is worth, Wichita NWS writes in their 9 am HWO:

THERE IS A SIGNIFICANT RISK OF SEVERE WEATHER FOR AREAS
MAINLY EAST OF A SALINA TO WICHITA TO WELLINGTON LINE THIS
AFTERNOON...WITH VERY LARGE HAIL UP TO BASEBALL SIZE...DAMAGING
WINDS OF 70 TO 80 MPH...AND STRONG TORNADOES. "

I live in Lawrence so I'm staying right here. If I was a mobile chaser, I would consider Emporia as a setup spot, assuming initiation along the Salina/Wichita line and rapid storm movement.

 

[Mike Hollingshead]

Obs out of Topeka look like they are shaping up great right now ... but I'm a little confused by RUC forecast soundings on Earl's page. Looks like nice shear and instability at 15z, but by 0z things shift into becoming more unidirectional and supercell potential falls. I'm guessing this translates into eastward movement of the dryline.[/b]

The mid-upper flow backs alot by evening. Look at say Beatrice at 18z, 21z, and 0z. sw, s, se while the dryline doesn't seem to want to move as quickly east.

500mb flow

It backs as the low comes out and it's trying to hold the dryline west quite a ways.

7pm Dryline

RUC holds it way west through 7. I still sort of think there will be two good areas with the area in the middle being not quite as good...but who knows.

 

[Gabe Garfield]

The mid-upper flow backs alot by evening. Look at say Beatrice at 18z, 21z, and 0z. sw, s, se while the dryline doesn't seem to want to move as quickly east.

500mb flow

It backs as the low comes out and it's trying to hold the dryline west quite a ways.

7pm Dryline

RUC holds it way west through 7. I still sort of think there will be two good areas with the area in the middle being not quite as good...but who knows.
[/b]

The newest RUC looks *awesome*. If this were to verify, I'd expect an outbreak of tornadoes. However, the RUC still seems to be a bit bullish on Tds (compared to the observations). I love how storm fire in SC KS by 21Z! Further west is much, MUCH better. In addition, it seems that all the vort is compacted into one lobe, which is progged to be perfectly timed with daytime heating. Also, sfc winds are still sig. backed, which is maximizing 0-1 km helicity and keeping storm motions down a tad. I love it! Now, if it'll just verify...

Gabe

 

[Gabe Garfield]

Mesonet showing mid 60s Tds in SC OK right now with SE winds!!! I'd believe this anyday over the ASOS obs. It looks like the moisture is arriving...could this be a just east of 35 show?

Gabe

 

[J.B. Dixon]

http://www.rap.ucar.edu/weather/model/disp...sfc_cape&loop=1

Looking at this RUC loop of CAPE (Yes, I know CAPE isn't everything!), I found this intriguing. I see this "blob" of higher instability that breaks off and rides that Warm front right through the heart of the High Risk area. Granted, storm motion will be fairly brisk, but if you've got a tower that can tap that instability axis, I think you've got a beast on your hands rolling through NE KS, a piece of NW MO, then into SW IA.
I'm guessing EHI's will be through the roof by that time, as well.

Yikes..... Lunch in Beatrice, and some adjustments from there.

 

[Kiel Ortega]

The newest RUC looks *awesome*. If this were to verify, I'd expect an outbreak of tornadoes. However, the RUC still seems to be a bit bullish on Tds (compared to the observations). I love how storm fire in SC KS by 21Z! Further west is much, MUCH better. In addition, it seems that all the vort is compacted into one lobe, which is progged to be perfectly timed with daytime heating. Also, sfc winds are still sig. backed, which is maximizing 0-1 km helicity and keeping storm motions down a tad. I love it! Now, if it'll just verify...

Gabe
[/b]

Gabe not sure what RUC you're looking at. Dryline mixes very fast in the b/w 21-00Z around NE OK/SE KS/SW MO. Forecast soundings aren't the greatest either. Another concern in the isentropic maps from 12Z....305K surface had 5 km of descent from the low to NC OK....THAT'S 5 KM of DESCENT! :blink: Some isentropic lift was back around the north side of the low. Forecast hodographs all over the place are pretty ugly and have been consistently ugly in the models for the past day. This morning soundings are pretty fun, with CTs above 90F and dewpoints still in the upper 50s maybe low 60s. I'd worry about any 60 dewpoints staying around as the dryline mixes through (moisture depths didn't look that impressive unless you were near the Gulf).

 

[Gabe Garfield]

Gabe not sure what RUC you're looking at. Dryline mixes very fast in the b/w 21-00Z around NE OK/SE KS/SW MO. Forecast soundings aren't the greatest either. Another concern in the isentropic maps from 12Z....305K surface had 5 km of descent from the low to NC OK....THAT'S 5 KM of DESCENT! :blink: Some isentropic lift was back around the north side of the low. Forecast hodographs all over the place are pretty ugly and have been consistently ugly in the models for the past day. This morning soundings are pretty fun, with CTs above 90F and dewpoints still in the upper 50s maybe low 60s. I'd worry about any 60 dewpoints staying around as the dryline mixes through (moisture depths didn't look that impressive unless you were near the Gulf).
[/b]

The dline is much further west than earlier runs, though. The trend has def been toward the west, which I like.

As far as forecast soundings are concerned, I don't take those too literally...I just know that the magnitude of the instability/shear should be more than sufficient for widespread tornadic supercells. I'm a little concerned about moisture, but I think there should still be tornadoes regardless of whether or not we get >65 Tds.

And, as far as isentropic descent, who cares (can't imagine why there would be isentropic descent when we're gettin warm air advection)? The DPVA will be more than sufficient to initiate convection.

Gabe

 

[Jim Bishop]

Kinda late getting in a forecast on here, but better late than never. I think some of the best tornadoes of the year will occur today. SPC's doing a great job with the high risk, there i think backed surface and 850mb winds with southelry 500mb flow will be superior for tornadic supercells. A lot of times it seems amazing tornadoes occur with backed 850mb flow. It probably has something to do with the incredible moisture the storm is able to injest, and the cap usually isn't a problem. The hodographs look AMAZING for tornadoes in the Northeast Kansas/Southeast Nebraska region.

I think supercells will initiate north of the dryline bulge across North Central Kansas/South Central Nebraska. I also think there will be somewhat of a double dryline structure and quite a few storms will be firing quickly around 3pm. The good thing about this whole region is the storms will only be moving north to north-northeast around 30mph, much better than 50mph across East Kansas/Western Missouri! Those storms will probably drop long track tornadoes across Missouri/Arkansas. I expect this to end up being a historic tornado outbreak.

 

[Todd Rasmuson]

what does everyone think about oklahoma now? this dl is much further
west then i thought it would be... oun short term seems to think things
could get goin way i read it, i'm gonna keep a close eye on i-35
area

 

[Brian McKibben]

Morning precip will not be a problem. In fact it may even help increase the moisture. If you look at SPC Mesoanalysis, you will see that there is sufficient clearing behind the morning garbage along with around 1000-2000 cape already.

Another interesting note is the ruc is erupting some supercells just west of OKC and moving them through the I-35 corridor. Due to work restrictions I will have a 2-3 hour window to view this. Any other takers on the southern portion of the dryline?