4/10/05 FCST: Southern/Central Plains

[Chris C Sanner]

Congrats on the baby Michael!

0z NAM is out, and I'm going staying firm with my backyard as the chase target. I think, depending on when things go off, I may have to go west some to get the convection, which I do not mind at all . Things are coming together nicely, and I think the Red River will be the spot to play come Sunday if the 0z name is to be believed (so I'm not that confident ). Capes are 1500+, LIs are maxed here at -6, and, with a deviant storm motion, you could get some pretty impressive shear numbers here. The only concern is the cap, and how strong it will be. Right now, at 18z the Cap is anywhere between 2.8 at PVJ to 1.8 at DUC to 2.2 at SPS on forecasted soundings, so things look like they may be able to stay discrete for a little while at least on Sunday, but by 0z, things are eroded pretty well across the entire region. So if a storm or two develops around 2ish in the afternoon along the dryline, I'm fairly confident it will stand a good chance of producing before things probably squall out later on in the afternoon or evening. Gonna be interesting to see how it pans out at the very least..

 

[Adam Atkins]

Late night

I'm starting to believe Sunday might have a tornado threat. If the GFS proves right, CAPE, helicity, and precipitation patterns favor discrete cells initially across central OK. Low level directional shear is quite good, but the downside is once again the backed mid-level flow. The NAM has deepened the system dramatically over the past couple of runs, but the shear vectors, in conjunction with the dryline, are once again favorable for rapid squall line development Things will most likely evolve into a severe line quite fast. The dryline will tighten quickly in synoptically driven events like this and convergence usually overcomes strong capping inversions. What's the first thing you think of during strong forcing, marginal CAPE days? I don't even have to answer... Another concern is the precipitation that may develop early in the period creating a very narrow axis of instability just ahead of the dryline, which seems to happen oh so often during these dynamic setups. Bottom line is, I'll be chasing this weekend for the first time along with the rest of the state of Oklahoma, I fear. I'm thinking of investing in a chasecopter...anybody know of a good make and model?

 

[Ben Prusia]

Looking at the new 12Z NAM data, it is now tracking the Low a little north than the Kansas/Oklahoma border (as have indicated with previous runs), and with that shift, shifts the potential chase target from Pratt, Kansas to Salina, Kansas. Salina, Kansas will have CAPES approaching 2000 J/Kg, along with LI's nearby of near -6. Temperatures have taken a small drop on the NAM model compared to previous runs but the dewpoint has stayed the same, hoping for a lower dewpoint depression. Storm relative helicities will also be highest nearest to Interstate 70 when the storm system passes through the Sunflower State. Overall, I still have very low confidence in this system, but most likely will stay with the Salina area rather than along the dryline as shear parameters are more than adequate to provide for yet another last Tuesday's storm through Oklahoma while Kansas has 9 tornadoes. I will provide another forecast for Sunday when the new 00Z NAM data comes out.

 

[DanHinch]

Well this morning’s 12Z NAM is quite a bit different from last nights 00Z run. I think the 12Z run is in better agreement with the GFS and most other models and it is in better agreement with previous runs which makes me think that last nights more southerly track might have been "out to lunch." The ECMWF is the only model that really takes the low further South. Either way it looks like there will be two areas of interest tomorrow. The area east of the low near the triple point and somewhere in central to southern OK probably near I35 on the dryline. I do like the deeper moisture along the dryline in south central OK, but I fear that this area may go linear quite quickly as we saw earlier this week. I do like the fact that this system is not as stacked as the last couple possibly offering up some better shear. I think no matter where you are in the southern plains tomorrow, Td's will be in the upper 50's and possibly low 60's which is reasonable for the first part of April. With some decent heating, barring any cloud cover tomorrow I think that CAPE's of 2000 J/KG will be possible. At this point with this much uncertainty to what will happen with this system its to early for me to pick a target but chances are I will be out, and I like the continued chances on for storms on Monday closer to home for me, I could make this a two day chase. One thing is certain being a weekend and looking pretty good, chances quite a few people will be out, so everyone play safe

Dan

 

[Tony Laubach]

Glancing at the new ETA (COUGHNAMCOUGH), I'm in agreement with a shift of the target area. Several bulls-eyes develop at the SFC near the Salina area in response to the positioning of the low. While not as tilted as previous runs, it doesn't show as much stacking as I feared.

CAPE values in the area exceed 1500J/kg. SRH values struggle to near 100 both in 30km and 10km. ETA for 0z Monday has posted a 59.8 TD near Salina, which means some pooling for high 50s TDs in the area at 0z. A bulls-eye of -4 LI's is centered above all this as well. Looking further up, shear isn't the greatest, but its still there. Winds from the south at 50kts at 500 with SSE winds at 850 shooting 25kts. The vorticity near back near the low will enhance low level rotation and hopefully aid in tornado development.

With this run, I would adjust myself a bit further to the north, maybe not as far as Salina, but probably keeping along I-70. This way, I can still drop south quickly and be in position in case the low maintains a more southery track along the border.

Still working out some details with chase partners and the potential blizzard here in Colorado, so it'll be a last minute decision for me, I'm afraid.

 

[Aaron Kennedy]

Ok... I'll be going out tomorrow. Can't resist a chase on a weekend. Prelim target will be some where along the red river where a) moisture should be better and B) storms should hopefully start off more isolated.

SPC has gone mdt with 35% hatched across the OK region. I'm still afraid stuff will go up along the dryline way to quickly, but we'll see.


Aaron

 

[Tony Laubach]

The SPC Mod risk is tempting, but am still sticking with Northern Kansas NE of the low. A boundry is expected to set itself up which could aid in supercell development. Backing winds due to the low are also progged to help with low level shear. Most Colorado chasers heading out today for Kansas... my chase partner and myself leaving late tonight. Tentatively talking Salina, KS... may back a bit west on I-70, but will stick with the interstate til tomorrow's runs indicate otherwise (if they even do).

 

[Gabe Garfield]

Alas, when good moisture shows up (Tds up to 65 F in N TX), the kinematics refuse to cooperate! IMO, 500 mb flow is just too backed at this time...I look for a quick transition to squall line unless flow can be more veered at this level. Otherwise, this would be a very significant event.

I think the ETA is a bit too fast with the progression of the dryline, so I'm thinking that the best cells of the day will be just a tad further west than currently progged. Since N TX has the best shot at more veered 500 mb winds, my target is on the southern fringe of the SPC moderate risk.

Current target: Decatur, Texas

Gabe

 

[Kiel Ortega]

I'll probably be going out tomorrow...it's the weekend, might as well for S & G's. Couple things I am looking at which concern me: 1) the Gulf Coast soundings from this morning. Moisture depth very small...not good. Even if we get good surface moisture up to OK, the dryline will be able to mix fast to the east given the small depth of the moisture. 2) This UA pattern is most intriguing. If this ridge builds in and cuts off our low too soon, might have problems. Also, this low kicking out of the northern US should provide some fun as it has carved out an area of lower heights (with some luck, maybe our low will be tempted to move more to the north ~wishful thinking~).

 

[Ryan McGinnis]

I see the SPC speaks of tornado potential in Northern Kansas, and I'm inclined to agree with them since they're much more experienced and talented at this than I, but both the NAM and the GFS are showing no real directional shear between 850 and 500 in this area. Great low level jet, though. I think I'll still aim for northern KS, since it's close and I haven't tasted rain in a year.

 

[Shane Adams]

I agree with the overall perception that KS ENE of the LOW or deep south in central/E Texas are the places to be for maximized tornado potential. It will be interesting to see exactly where the LOW is tomorrow morning and where it is moving, via satellite images. The sure bet for tubes looks to be KS near the LOW, but you've got to be almost perfect in your timing, as storms will be tornadic early and not for long. This focus area shifts ENE throughout the day to NC Kansas, but whether or not favorable conditions will accompany this LOW across the Sunflower State remains a mystery...

I'm still eyeing the RR valley, as I cannot by nature ignore the thetae tongue in that area. Whether or not this juice maxima coincides with the dryline push/forcing/initiation is anyone's guess at this point, but suffice to say, there will be storms in this area. I'm still very tempted to dive south across the border into N Texas and see if maybe this time the shear can get its act together and produce more than linear junk right off the bat (April 5).

I've whined about blowing cold core days by not migrating straight to the LOW, but still, the chaser in me does not want to drive to where the moisture is not. Seems quite a trick to time a cold core ENE quadrant sup for tornadoes. I still can't get N Texas out of my mind.

 

[Amos Magliocco]

I'm looking toward Kansas as well, expecting a chance for both cold-core storms very near the low and then perhaps low-topped or more classic supercells as the dryline bulge pushed into central Kansas.

Like Shane, I'm worried about conditions once the storms move north, though they should have the welcoming environment of a stationary front draped northeast from the low. I don't like midlevel southerlies up there or the moisture questions so far north. However, deeper moisture has been moving through Missouri into eastern OK and eastern KS all day, and I suspect both the dewpoints and depth of moisture will be better than advertised now that our GOM trajectories are more efficient.

It seems counter-intuitive to turn my back on the better instability in Texas, but down there I have concerns about a prematurely veered surface winds and the potential effects on the boundary layer of similarly veered 850s.

There are problems with both spots, I suppose. We'll see what it looks like in the morning.

 

[Karen Politte]

I mentioned this once before and wanted to mention it again since this is something folks will invariably be looking at during the course of this timeframe.

There is a bogus ob in southwestern Arkansas - I think it is Mena, AR. Anyways - it is the station due north of the DeQueen, AR station. It currently seems to be reading Tds around 7 degrees higher than they actually *ARE*. This can be confirmed by investigating obs further south of this sounding - revealing that there is nowhere from which this station could be acquiring its current 64oF dewpoint.

As an aside - I don't feel good about tomorrow, never have and I stand by this. It doesn't mean I am any *less* of a chaser - it just means that this is a pessimistic time of year for me. We will likely intensely monitor from home to make sure we aren't missing anything. On the upside - I still feel that the models are vigorously underdoing moisture return signals.

I'm worried about the precip. signals just south of Childress TX. that the RUC breaks out overnight.

KR

 

[Jeff Snyder]

Well, moisture return doesn't seem to be as big of an issue as before:

Originally posted by OUN AFD PM Update
00Z SOUNDINGS SHOW SIGNIFICANTLY MORE LOW-LEVEL MOISTURE TO OUR SOUTH THAN SATURDAYS 12Z MODELS INDICATED. DRT SOUNDING HAS 9C HIGHER DEWPOINTS ALL THE WAY FROM THE SURFACE ALMOST UP TO 800 MB THAN THE 12Z ETA FORECAST FOR 00Z. AND AT MIDLAND THE DEWPOINTS ARE 3 TO 6 DEGREES C HIGHER THAN THE FORECAST UP TO 600 MB... WITH THE EXTRA MOISTURE... THE FORECAST SOUNDINGS GIVE MORE CAPE AND LESS CIN FOR TOMORROW WHICH WILL LIKELY INCREASE THE SEVERE WEATHER POTENTIAL.

So, deeper moisture = slower dryline mixing. I'm still all for the Red River area. Latest NAM shows improved dryline / shear-vector orientation with nearly 45-70 degree from the parallel from Red River southward ( see http://www.wxcaster2.com/CENTRAL_ETA_250M-...VECTOR_24HR.gif ). Additionally, with the >65 Td isodrosotherm to the River by 0z. CAPEs >2000 look pretty good. Not the most-backed low-level flow, but I'll worry about that later.

I'm heading down to ADM, leaving OUN at about 11am. I'll stop at the Love's or Microtel in ADM for a wifi stop, and I assume that I'll be more towards Gainesville/Bowie/Decatur/Denton area by early-mid afternoon.

 

[Gabe Garfield]

I'm worried about the precip. signals just south of Childress TX. that the RUC breaks out overnight.

Actually, I think that could provide a bonus outflow boundary. It would be really nice to be able to back the flow up north, considering the SSW 500 mb flow. In addition to this, evapotranspiration could help the Tds up closer to the sfc low.

I'm still thinking N TX/S OK...but it could be C. OK should moisture return be greater with and outflow boundary in the mix. I'm very heartened by the 65 F isodrosotherm up to the Red River by 00z (per NAM/ETA forecast). This could make things quite interesting tomorrow.

Gabe