4/26/09 FCST: KS,OK,TX,MO,NE

[Mike Smith]

Surprised no one has started a thread for Sunday, so I'll kick things off.

Because of convection the previous day, locations are highly uncertain. That said, LCL's, instability and the dynamics may make Sunday a more prolific tornado producer than Saturday.

The soil is moist in most of the southern half of Kansas from heavy rains (and snow) the last thirty days.

The strong short wave coming out of the southern Rockies causes surface winds back in Kansas ahead of the deepening surface low that I believe will be in western Kansas.

If the warm front can re-establish itself across Kansas, significant tornadoes may develop under the excellent flow aloft. Other, less intense/concentrated (assuming my scenario is correct) storms may occur in adjacent states, reaching southeast Nebraska and western Missouri by late evening.

By the way, April 26th is the 18th anniversary of the Wichita-Andover Outbreak.

 

[Connor McCrorey]

TX panhandle just off the dryline FTW.

 

[Andrew Stoller]

I'm liking Sunday better then Saturday for sure - much better upper level flow leading to greater speed shear, and directional shear is even a little better.

Yeeeeeaaaaaaaaaaaaaah. Northern TX panhandle FTW fo sure! - 12z NAM has 1KM EHIs getting to near 4! 3KM EHIs even greater. CAPE maybe not as great as Saturday, but the shear is better IMO. 1KM and 3KM SRH are 300+.

Heck, extreme eastern CO could be good as well with 50+ degree dewpoints creeping in northeast of the surface low, with CAPE into the 2,000 range.

 

[Doug Mitchell]

Based on the 12z NAM, Sunday looks to be the best potential this weekend for tornadic supercells. The dryline in TX/OK/KS becomes better oriented and much more defined than the previous days. Tds in the upper 50s, low 60s yielding modest cape values ~ 2000 j/kg. What I like better about this day is the 40-60 kt h500s being more perpendicular to the dryline. This should ensure good shear but limiting storm speed to a manageable level. Will be interesting to see how the overnight MCC plays out over OK/KS. It may lay down a few add. boundaries or it may push the play further south in the TX panhandle. We'll see.

 

[Brian Stertz]

I am liking the C/E Texas Panhandle for the big show Sunday....60 kts. of sfc/500mb forecasted bulk shear...decent Td's of 58-63...approaching afternoon wave... and of course a solid dryline. Not a blasting DL either making this a more settled down DL and potential trouble for the C/E Texas Panhandle. Not sure how significant the tornadoes will be, but some of the more vicious Texas Panhandle outbreaks in April have been with Td's in Sunday's range. It will be fun to see how potentially active the setup could play out to be. Current target is Panhandle (Carson Co. TX) and yes I will be chasing !!

Update: the triple point low near Holly Colorado looks intriguing. Lots of data to pour over before Sunday.

 

[CZandbergen]

This is starting to be a tough call. I get one chase day this weekend and up till this AM I was sold on Saturday. The last three runs of the GFS and NAM have me wondering at this point. This afternoon I was ready to pass up Saturday and head north of I40 on the OK TX border Sunday afternoon. Now it looks like a wash between the two choices. I for one am hoping the NAM and GFS get their act together tomorrow. NAM seems to be early and GFS seems to be a bit later. Tds look good both days, the position of the dryline isn't that far off on either. The question for me is forcing and what the storms might move into. Playing the triple point on Sunday looks like a line out to me at this point. I still favor the southern solution there. The 0Z run looks like no help at all. Guess I will sleep on it and see what tomorrow brings.

I have high confidence we will see a high chance of tornado favorable storms in western OK/TX panhandle. The question is which day and where. That and dealing with any out flow boundaries from the convection left over from the Saturday setup. My first season of forecasting and just realizing how hard this really is.

Guess that is my problem!

 

[John Hudson]

Looking at the latest run of the GFS for Sunday, I'm really starting to think the best chance for a good tornado showing is likely to be SW KS, into the later evening and perhaps after dark. A decent 850mb LLJ kicks in later in the evening, giving a nice concentration of 2800 j/kg CAPE to SW KS.

I also like the way the low level winds begin to back just a little, making for some nice curvature to the hodographs.

Anyone for a night chase?


John
VE4 JTH

 

[Derek Weston]

This is starting to be a tough call. I get one chase day this weekend and up till this AM I was sold on Saturday. The last three runs of the GFS and NAM have me wondering at this point. This afternoon I was ready to pass up Saturday and head north of I40 on the OK TX border Sunday afternoon. Now it looks like a wash between the two choices. I for one am hoping the NAM and GFS get their act together tomorrow. NAM seems to be early and GFS seems to be a bit later. Tds look good both days, the position of the dryline isn't that far off on either. The question for me is forcing and what the storms might move into. Playing the triple point on Sunday looks like a line out to me at this point. I still favor the southern solution there. The 0Z run looks like no help at all. Guess I will sleep on it and see what tomorrow brings.

I have high confidence we will see a high chance of tornado favorable storms in western OK/TX panhandle. The question is which day and where. That and dealing with any out flow boundaries from the convection left over from the Saturday setup. My first season of forecasting and just realizing how hard this really is.

Guess that is my problem!

As of right now... Definitely like Sunday better. IMO . . . shear setup is bit more of a sure bet... though... instability might not quite be what it was Saturday. SE Colorado to SW KS through the TX panhandle all have a nice shot...

 

[Scott Hammel]

I'm casting my vote for Sunday too. It will be my first chase day of the season as well, so I'm ready to go. Anyway, I think playing the dryline down near the OK panhandle, extreme SE CO and possibly into SW KS will be the best shot at discrete cells. Moisture returns should be adequate and the shear will be there for sure. My main concern is that initiation will occur late and not organize until after dark. So like mentioned before; night chase anyone?

I will throw out my initial target of: GUYMON, OK and will readjust as we get closer to Sunday and get a really good look at the models.

 

[Mike Smith]

If you look at the 12Z NAM 48 hour progs valid 12Z April 26, 2009 you will see some similarities to the actual maps from 18 years earlier, Friday, 12Z April 26, 1991 posted by Tim here: http://stormtrack.org/forum/showthread.php?p=223599#post223599

And, if you look at the 54 hr. surface forecast it looks a great deal like the 18Z surface chart posted by Tim.

The satellite photo tells the tale: The area of thunderstorms in the ICT-PNC area at 12Z 4/26/91 moved to CNU-EMP-MKC-SZL by 18Z and the air mass over central Kansas recovered.

The 12Z NAM is internally inconsistent: It shows showers and thundershowers over the width of Kansas this Sunday but scoots the warm front from the Oklahoma border into southern Nebraska by 18Z. I can't see that happening. One of two things is far more likely:

1) The air mass recovers as it did 4/26/91 and the warm front moves rapidly north as it did that day.

2) The showers and thundershowers predicted by the NAM are correct and the warm front stays in central/southern Kansas and/or washes out.

I lean toward #1. Very preliminarily, I would head to PTT and nowcast from there on Sunday.

 

[Andrew Ryan]

Well once again the NAM has done a complete 180. Sunday looks like the best day. The east TX/OK panhandle looks like the best region for tornadic supercells. The only thing that has me worried is the lack of cape, but models tend to underestimate cape, so I'm not that worried. Waiting on the GFS to see what it has to say.

NOTE: I just finished my meteorology exam and I have a cold/allergies? so my head feels as though somebody just drilled a hole through my head. So, if this all seems off, there's your explanation.

 

[Chris C Sanner]

Sunday looks like it could be a pretty big day for some folks. The shear looks pretty solid and the CAPE is going to be 2000-3000 with adequate heating. I'm still trying to fully digest Saturday and get through it, but I think the gameplan Sunday will be fairly similar to Saturday except a bit further north. Storm speeds will be a bit faster on Sunday, but they should be rather manageable still. The potential is there for a higher end event, but I wouldn't call it a for sure winner just yet.

 

[sebenste]

Sunday looks like it could be a pretty big day for some folks. The shear looks pretty solid and the CAPE is going to be 2000-3000 with adequate heating. I'm still trying to fully digest Saturday and get through it, but I think the gameplan Sunday will be fairly similar to Saturday except a bit further north. Storm speeds will be a bit faster on Sunday, but they should be rather manageable still. The potential is there for a higher end event, but I wouldn't call it a for sure winner just yet.

You'll be south of the strongest upper/mid-level winds, to be sure, so storms may lean on the HP side. But, 40-500 knot 500 mb winds aren't terrible. I say it will be a good day, with more than adequate CAPE, a dryline and shear. What more do you need? Oh, I know...

KFDR (Frederick, OK) and KVNX (Vance, AFB, OK) WSR-88D's just went super-res with their level 2 data. So chasing around Childress and southwestern/northern OK just got better!

 

[Jason McKittrick]

Is anyone else concerned about the lack of a cap across the target area on Sunday? Dewpoints in the low to mid 60's all the way back to the cap rock, all kinds of shortwave 'chunks' and 700mb temps <= 6C. Looks to me like a mess. Having trouble focusing my target. Given the Thermodynamic and Kinematic environment I am certain there will be tornadoes. Might not be as picturesque as we would like though.

 

[Mike Smith]

SPC 1730Z convective outlook: Large moderate risk area and,

CURVED HODOGRAPHS ALONG WITH LOW LCL HEIGHTS SUGGEST SOME STRONG TORNADOES WILL OCCUR LATE SUNDAY AFTERNOON INTO THE EVENING. IF THE CONVECTION ONGOING SUNDAY MORNING DOES INDEED MOVE EWD AWAY FROM THE AXIS OF INSTABILITY...ALLOWING FOR MODERATE TO STRONG DESTABILIZATION...THEN A TORNADO OUTBREAK MAY OCCUR ACROSS THE MODERATE RISK AREA.

Right now, my initial location continues to be PTT.