3/30/06 FCST: IA/NE southward to central TX/LA

[Jim Bishop]

I feel like the setup, as a whole, doesn't look as good as it did yesterday. Having said that the NAM and GFS are not agreeing as well as yesterday. I like the GFS solution, personally, and feel the best tornado threat will exist just east of the surface low over Eastern Nebraska to Western Iowa, maybe even northern Kansas as well. All the dynamics are going to be there with greatest instability associated with the very cold midlevel temperaures. I just don't think Oklahoma is the best area, but with NAM & GFS disagreeing on the timing and placement of the vort max, things could change quite a bit by this time tomorrow.

Typicall when the GFS & NAM disagree on the timing/placement of a shortwave and the GFS is faster, the GFS verifies. This time the NAM is actually faster, so it will be interesting to see which one verifies.

 

[Daniel Christianson]

I feel like the setup, as a whole, doesn't look as good as it did yesterday. Having said that the NAM and GFS are not agreeing as well as yesterday. I like the GFS solution, personally, and feel the best tornado threat will exist just east of the surface low over Eastern Nebraska to Western Iowa, maybe even northern Kansas as well. All the dynamics are going to be there with greatest instability associated with the very cold midlevel temperaures. I just don't think Oklahoma is the best area, but with NAM & GFS disagreeing on the timing and placement of the vort max, things could change quite a bit by this time tomorrow.

Typicall when the GFS & NAM disagree on the timing/placement of a shortwave and the GFS is faster, the GFS verifies. This time the NAM is actually faster, so it will be interesting to see which one verifies.
[/b]

As of right now i have to work, and you can bet ill be busting my butt of hauling trash as fast as i can to get done... im hoping this is going to be a 5pm show... as of a starting point its going to be home in Omaha, but i feel with thunderstorms likely thursday theres going to be alot of clouds. however that can change if thats the case id be picking Hwy 2 for my route... so i have a way to get north or south... hopefully this will not be a venture into MO... i just dislike chasing in MO.. except one good hwy with no traffic really is 71 i think... or 59 one of the two... anyways ill be chasing for sure even if this turns out to look like bust mode ...

best of luck to everyone ...

take care

 

[Ryan McGinnis]

Just thought I'd pop in and mention that, despite what I said earlier about the unlikelihood of the snowpack melting around here (SE Nebraska) before Thursday, nature today decided to serve me some humble pie. I walked outside this afternoon and found nary a flake of snow on the ground. It's all gone! So the snow no longer has any chance of depressing the temps here on Thursday. Never doubt the power of the March sun, I guess.

 

[Todd Rasmuson]

guys i will admit i have in the past had my fair share of bad judgements but
on this one, i think they are proggin this off to the east way to fast, i expect
a mid afternoon setup on thursday of the dryline basically around the i-44
area basically tul to okc to law to sps,tx and again models could be right on this
one but, i just feel this compared to past setups the dryline has 'hung up' over
wc/sw ok into nw tx, so i stand with my plans for poss convection w of the okc
metro, attm feel best tornado threat could be to the north of the ok/tx area
however this has to be watched extreemly closely for the fact of how much
fires wed night into early thurs, that will be key, also what dp temps are
at by around that time frame as well... so bottom line still up in the air on
my judgement, still feel good chance though across portions of ok into nc &
nwrn tx.. what do the rest of you think on this? i just think logically it could
poss be putting the dryline to far to the east.. well i'll have another post
later tonight or by around midday wednesday

Todd Rasmuson

 

[Ryan Pfannkuch]

Just took a glance at the 0z NAM, and generally it has slowed things down and moved features maybe 50 miles west of where the previous runs showed them.

Focusing on the northern part of the risk area, this trend puts the optimal daytime target area more into eastern NE and northeast KS and less so on western IA or MO. NAM still shows a mid-level dry slot blasting up into the eastern half of NE during the morning over the top of a 995mb surface low near Grand Island by 18z. If everything comes together, a broken line of mini-supercells could form in the narrow instability axis under the dry slot and race northeast. Even if decent instability is realized though, I think the chances of linear vs. cellular (both?) could be almost a coin toss with the 0-6km shear vector largely parallel to the north-south boundary. So many question marks, but you can't win if you don't play. Even on 11-12-05, the general consensus was linear storm mode and there ended up being strong tornadoes SE of the surface low.

For the time being, I am thinking about being in the Lincoln area around noon and adjusting from there.

 

[Kevin Polston]

My forecast here is based mainly off the 00Z ETA (or NAM)......and I haven't seen the GFS yet. It appears to me that the best tornadic potential Thursday afternoon will be over southeast Oklahoma and far northeast TX. If the model is correct there should be a dryline/cold front triple point over south central OK with pretty good convergence. This will also be the "tail end Charlie" area as I believe there will be a line of storms further north across IA/KS/MO extending south to this "tail end Charlie" area. At least low 60's dewpoints should be in the area and it will also be on the southern fringe of the dynamic forcing of the system passing by across the central plains. There should be at least 50 kts of deep layer shear and the vectors will be aligned at a good angle across the boundary so supercells should be the dominant mode in this area. The LCL heights will be marginal to good (not great) but that shouldn't inhibit tornado development. I am not too high on tornado potential further north near the surface low where others had talked about it earlier today. I think there will be too much widespread convection and thebetter source of instability will be down in this area.

 

[Brett Adair]

Storm motion at 18z via ETA

Shear vector at 18z via ETA

Note the storm motions to the right of the shear vector up here towards se NE, while they are more overlapped further south. Not a huge difference between shear vector and motion up here but at least more than points south. Like others have said, it is making me think of November 12 05 as well.
[/b]

Agreed, Mike. I think things may be a little more interesting up in that general area than some may think at this time.

 

[Melanie Metz]

I agree with Kevin that it would be tempting to be south in the higher instability along the dryline. However, while the instability will be limited further north, dynamics do play a larger role this time of year than instability. As long as a narrow axis makes it north as indicated by NAM, I am still hopeful for the target area near the surface Low and better upper air dynamics.

At this time I like the area from Lincoln to Omaha, in the nose of Theta E advection, between 18 and 00Z, adjusting accordingly as new runs come out and the day progresses. Of course, I do have a northern bias since I can't get far enough south to chase the southern target.

Melanie

 

[Alex Lamers]

Day 2 Outlook is out, and there is a moderate risk. Well written outlook by Roger Edwards (I always do enjoy reading his discussions). I agree with the Slight Risk over S Wisconsin for the time being, but I haven't had time to assess anywhere else. Timing is horrible and overnighters in spring tend to lend for a lot of disappointment up here. So those of you out in the Plains, enjoy this one if it pans out!

 

[Bill Tabor]

I pretty much agree with Kevin on this latest run. Tornado and severe potential seems to have decreased quite a bit IMO from last 3 runs. I think the moderate is at risk, but will probably still happen. I'm kind of down on the northern area, but admit I haven't given it a lot of thought since no plans to go that far this early. I think the best area for quality storms / torns is closer to Kevins area - but still I don't count out the 50's dew and very strong dynamics. Will be interesting to see how tonights storms and tomorrow's affect the next runs of the models.

 

[Donald Van Dyke]

Day 2 Outlook is out, and there is a moderate risk. Well written outlook by Roger Edwards (I always do enjoy reading his discussions). I agree with the Slight Risk over S Wisconsin for the time being, but I haven't had time to assess anywhere else. Timing is horrible and overnighters in spring tend to lend for a lot of disappointment up here. So those of you out in the Plains, enjoy this one if it pans out!
[/b]

Edwards is also my favorite forecaster at the SPC. I'm confused about something though. It was my understanding that they could not issue a moderate risk now under their new probability guidelines for day 2 without hatching an area of significant-severe probabilities. The day 2 probabilities currently do not show a hatched area, and Edwards seemed to make it clear in the discussion that his confidence was not high enough to hatch an area when he said,

THEREFORE
SIGNIFICANT-SEVERE PROBABILITIES ARE TOO UNCERTAIN TO CALL ATTM.
NONETHELESS...THERE SHOULD BE ENOUGH AGGREGATE SEVERE POTENTIAL TO
WARRANT AT LEAST MRGL PROBABILITIES FOR MDT RISK.[/b]

Maybe there is some "aggregate severe potential" criteria that is not listed somewhere, but their new probability conversion table seems to make it clear that a day 2 moderate cannot be issued without hatching the 45% area. Anybody have any thoughts on this?

 

[Jason A.C. Brock]

It is an early outlook and perhaps they jsut want to let things evolve more before hatching out an area of higher probabilities. There are always exceptions to many rules criteria etc.
With that being said I will be playing the area from Ardmore to Durant areas of Oklahoma perhaps South into Northern Texas. I would sill not be surprised to see this area shif a bit more West from I-35 corridor to along the I-44 corridor and down into Eastern parts of Western North Texas.
Today I will be keeping an eye on the dryline out West but am not as convinced of initiation as I was previosly due to rain and cloud cover that could taint any daytime heating etc. I may head towards childress as a starting point however if things change by late morning.
Rain and clouds could also create a problem Thursday in areas near I-35 but I like the chances of moisture return the more South one can get. I think this system will actually give some great cold-core type storms further North near the Low but I also think this will be the first tail-end action during afternoon hours along I-35. It will be very necessary to watch what these overnight clusters of storms end up doing or not doing to the atmosphere between now and then both this morning and Thursday morning. Hopefully this weak warm front to the South can be reinforced by some outflow boundaries and or intersect it.

 

[Doug_Kiesling]

Looks like the first tornado chase of the season but I have some major concerns and may yet still call it off and go home.

The one concern for the northern area is still the snow on the ground. After looking at the latest snow depth reports from

http://www.rap.ucar.edu/weather/surface/

it looks like there is still a lot of snow cover in Nebraska.

http://www.rap.ucar.edu/weather/surface/snowNESDISus.gif

Anyone got any first hand reports in the Nebraska area as to how deep the snow pack still is?

Another concern from looking at the ETA is if there is still a great deal of snow pack in the target area and temps in the 50s, what about the fog from the melting snow pack?

It looks like a great system but still need to wait another 18 hours to get a better picture of the target area up north.

 

[Dick McGowan]

Edwards is also my favorite forecaster at the SPC. I'm confused about something though. It was my understanding that they could not issue a moderate risk now under their new probability guidelines for day 2 without hatching an area of significant-severe probabilities. The day 2 probabilities currently do not show a hatched area, and Edwards seemed to make it clear in the discussion that his confidence was not high enough to hatch an area when he said,
Maybe there is some "aggregate severe potential" criteria that is not listed somewhere, but their new probability conversion table seems to make it clear that a day 2 moderate cannot be issued without hatching the 45% area. Anybody have any thoughts on this?

[/b]

They have corrected the moderate risk back to a slight, still with a 45 percent (nonhatched) as of 4:06 am.

 

[Donald Van Dyke]

They have corrected the moderate risk back to a slight, still with a 45 percent (nonhatched) as of 4:06 am.
[/b]

Ah, interesting. I guess it was a mistake then. Personally, I kinda would like the 45% non-hatched to still be a moderate risk for a day 2 outlook, but that's just me anyway. I kinda secretly hoped that outlook wasn't a mistake somehow. No big deal though. At least the apparent discrepancy has been solved.