3/7/09 FCST: OK, KS, AR, MO

[Skip Talbot]

I also believe there is still some potential here. The surface winds do back slightly near the low, and there is decent veering with height. That said though, most of the parameters are just a little too marginal. With the capping issues we'll be playing near the cold front where a linear mode is a concern. Dewpoints will be lower here and were marginal to begin with. Forecast instability is fairly weak, although a decent sized area of 1000+ J/Kg forms before 0z. With strong speed and directional shear we could get a few supercells up near the triple point. My main issue is the window of opprotunity. The WRF still shows a nice hole in the cap by later afternoon, but after 0z it fills back in. After dark we quickly lose all of our low level Cape as well. Something has to happen within a couple hours of time and with marginal conditions. I think I'll spare myself the trip from Chicago, but for those in the area... the triple point might yield a chaseable storm.

 

[Rich Thompson]

This looks like one of those frustrating return flow cases where you see days of S/SE winds across TX/OK, but no appreciable moisture increase. Surface trajectories are still originating within the ridge across the western Atlantic (note the upper 40s to mid 50s Tds across FL and Cuba), and that will be slow to change. The depth of the marine layer is relatively shallow and not resistant to vertical mixing over land. I keep seeing afternoon Tds in the 50s across the Yucatan with temperatures in the 85-90 F range. This sets up a situation where the ocean is not warmer than the overlying air mass, so no upward heat flux and convective mixing to deepen the moist layer over water. All you get is moistening of the shallow "skin layer" which mixes out quickly over land.

I'd still lean toward the triple point near Pratt, KS for Saturday evening as the more probable location for surface-based storm development during daylight. The cap will be a little stronger to the south in OK, where low-mid level ascent will be weaker. Maybe you can sneak in a supercell before dark.

 

[Bob Hartig]

Latest surface obs certainly offer hope for moisture return. Okmulgee shows a 57 dewpoint. Ditto by Chickasha, and at Gene Autry there's a read of 63. Farther north, things look pretty dismal, but with a day left, I'm still keeping my fingers crossed. Storms or no storms, I'll be in Norman on Sunday, so mileage isn't an issue; it's just a matter of which direction I'll be coming from.

 

[Chad Cowan]

FULL FORECAST @ http://www.chasethestorms.com/

 

[Greg McLaughlin]

I am not excited about tomorrow from what I am seeing. Low-level moisture is still lacking...plain and simple. Yes, dewpoints will look nice in the morning like they did this morning, however once mixing gets started the T/Dp spreads become quite large. I expect the same thing tomorrow. The model soundings show pretty high LFCs and this with the high T/Dp spreads will likely lead to cold pool generation with any storms (including brief supercell structures) shortly after initiation. I will keep an eye on it tomorrow, but have no chase plans attm. This is a setup everyone would snicker at in May, but I understand many of you are just itching to get out there.

 

[Mark Farnik]

Maybe I'm crazy, but I'm going to sit this one out. The low level moisture just isn't there. Fact of the matter. As Greg mentioned, the significant T/Td spreads, high LFC's and linear storm mode aren't going to be very conducive to chaseable storms, if at all.

I have a pretty bad case of SDS, but it's not nearly bad enough to blow my preciously limited chase fund on such a marginal setup, especially one that's a 1000 mile round trip.

I'm content to bide my time until something better comes along, which given the highly progressive weather pattern we will be in for the net few weeks, shouldn't be more than a week or two down the road.

Good luck to all who are going out tomorrow... I hope you see something worthwhile.

 

[BrandonWhittington]

Im still planning on chasing north-central Oklahoma Tommarrow. Im not really worried about the lack of low level moisture due to the amount of shear that will be in place. Its kinda a 50\50 shot, but since its less than a few hundred miles away, what the heck!! : )

Also, the dryline is taking shape a little further west that models have it. Its taking shape in the far eastern Texas Panhandle...Take a look at the school-net sights and we can see the dryline..

School Net Sights: http://209.40.150.253/

Tommarrow morning will be pretty intresting to say the least.

 

[Bill Schintler]

Chase Target for Saturday, March 7

Chase target:
Lebo, KS (14 miles east of Emporia)

Timing and storm mode:
Storms will initiate in the area through 6 PM CST, with supercells and a tornado or two possible before 9 PM. By mid-evening, storms will evolve into a large linear cluster as severe threat diminishes.

Synopsis:
An ULVL trough will track from UT into WRN KS on Saturday, with an attendant SFC low tracking along US-54 in WRN/CNTRL KS through 00Z, and then NE along the KS turnpike through 06Z-03/08/09. A WF will extend ENE of the SFC low along I-70 while a DL sharpens between 00Z and 04Z along I-35. After 06Z the CF will surge SE while overtaking the DL.

Discussion:
Upstream 00Z soundings (AMA, DNR, and DDC) indicate steep mid-level lapse rates AOA 8.5C/km. LLVL moisture remains limited, with mid-50’s dewpoints currently confined well to the S over OK where the OUN sounding indicates moisture below the 800mb layer. Storms will fire over NERN KS and NWRN MO by late evening as a 45kt LLJ focuses into the area. Overnight, moisture will increase just above the SFC with NWD transport.

On Saturday, convection will be ongoing during the morning hours N of I-70 in KS. Insolation will be inhibited throughout much of the day by a thin veil of CI that will blanket the area through 21Z, before moving E of the Turnpike by late afternoon. Large scale assent will increase with the approach of the H5 trough. Moisture will be adequate for early March in KS, with SFC dewpoints of around 55F FCST. Capping will remain strong throughout much of the day courtesy of the EML, with cap erosion by late afternoon with approach of H5 height falls. The favored location for supercells should be NE of the SFC low in a region of backed LLVL flow beneath a veering 50-60kt LLJ. A window of opportunity for tornadic storms may exist between 00Z and 03Z as directional shear increases over a coupled BL. Later in the evening, storms will evolve into one or more MCS’s with hail the primary threat as the BL decouples.

Modest instability with MLCAPEs AOB 800J/kg will couple with impressive shear parameters. SFC-6km deep-layer shear will increase dramatically after dark with the approach of a 70kt H5 streak. An SPC SREF tornado parameter of between 1 and 1.5, along with a supercell composite parameter of 3, are indicated by 03Z as LLVL directional shear increases beneath a strengthening LLJ of nearly 60 kts.

- Bill

PS: I'll be available for nowcast support - PM me.
10:32 PM CST, 03/06/09

 

[Mike Umscheid]

Yech.. another dud tomorrow. Low level winds will veer substantially tonight as the first surface wave ejects into central KS tonight...taking the lower 50s dewpoints with it. By midday Saturday, surface cyclone will redevelop near Elkhart, KS, but problem: moisture is way east of the best forcing with the main upper cyclone across Colorado. Can't have problems like this in early March and get away with it for surface-based chaseable storms. The other problem is that cold front across central KS. If a storm does form in the ICT-EWK-EMP area during daylight hours, you'll be dealing with a nasty little cold front oriented northeast to southwest across central KS not too far away, and I don't even think surface based storms will form until sunset or so when the real good lift comes out. Could be a nice little nocturnal severe event for KC metro area with maybe some surface-based storms of interest in the warm sector, but I think a majority of storms will be elevated north of surface front tomorrow night. Am a little biased, I guess, since I have to work tomorrow, but I would likely not chase this setup even if I was off.

 

[Gabe Garfield]

As all have expected, today appears to be a fairly marginal day. Nevertheless, I still believe that there is a significant probability of surface based storms in southern Kansas. The 14Z RUC paints a much prettier picture of the moisture/thermodynamic parameters than previous WRF/GFS forecasts: dewpoints are forecast to be >55 F in a narrow E-W corridor along the KS/OK border region, supporting CAPE ~ 1000 j/kg. This does not seem unreasonable since observations already show Tds >55 F close to the target area now. However, the 12Z Norman sounding shows that the Tds of this magnitude do not extend through a great depth in the boundary layer. Moisture pooling near the E-W boundary could offset some of the mixing, though. That said, if the RUC forecast verifies, I would expect some pretty vigorous storms would develop, including the attendant possibility of a few tornadoes.

My biggest concern is the high-level cloud cover. If it should persist with limited breaks, I will probably not venture out. However, if any appreciable insolation can manifest in the target area, I will most certainly head out. After all, it's a relatively short hop for this Norman-based chaser.