6/11/09 FCST: OK/TX

[Jeff House]

Thursday could be an alright setup in a localized area. I like southwest OK, perhaps northwest TX, depending on where the dry line and warm front intersection sets up. Southwest flow aloft is in place and as I write energy is moving ashore in Calif. It should be ejecting across the target area Thursday.

Right at the warm front surface winds will be backed plenty, but they look a bit light. The 850 flow is also a bit light too. South of the warm front both sfc and 850 could get veered off pretty bad. Good news is that moisture is plentiful. Extreme instability might work in our favor, and hopefully be enough. Not getting too excited but hope springs eternal.

 

[Ken Johnson]

SPC has the slight risk further east. However, I'm not sure I totally agree with that. The 00Z Nam has east winds along the Red River, with 2 to 4,000 Cape values. 850 winds are weak during the day, but do strengthen during the evening. This produces quite an increase in SRH. Mid level wind max should move east by late afternoon. This will increase deep layer shear.
The dryline buldge should be somewhere south of SPS. There does appear to be a cap in place, but convergence along the dryline and WF intersection combined with speed max could break a few isolated supercells. If storms can ride the boundary, then they could produce brief tornadoes. It does look a bit iffy. The GFS breaks no convection out in this area and the NAM isn't too optimistic either and keeps most across east Texas and another batch rolling off the higher terrain of the Rockies.
My target area would be in my backyard of Wichita Falls...

 

[Bill Schintler]

Chase Target for Thursday, June 11

Chase target:
Vernon, TX (just west of Wichita Falls).

Timing and storm mode:
High-based storms should initiate by 6 PM CDT west of Childress. These will move into the target area through 8 PM. Storms should generally remain below severe limits, however a supercell or two is possible early in storm evolution.

Discussion:
A WF extending E from weak low-pressure centered over the WRN TX panhandle will serve as the focus for afternoon convection. Synoptic lift will increase within the exit region of an 80kt H3 speed max with an associated vort max and H7 shortwave. Localized orographic lift will be focused along the WRN extent of the Red River valley, W of CDS, as easterly flow rises up the Caprock Escarpment. It appears as though the orographic forcing features will line up well with the synoptic boundary, favoring initiation near Wayside (25 miles SE of Amarillo). Of course, moisture will be limited over much of the panhandle, and storms will later reach an environment with favorable thermodynamics east of CDS.

The NAM seems to have a good handle on SFC dewpoints, while the GFS is too low with moisture in the panhandle where 60-65F 03Z dewpoints have already verified. The latest GFS brings the location of the SFC low further west, which is now inline with what the NAM has been indicating. This increases confidence in easterly or southeasterly flow and attendant moisture retention in the Red River valley from 18Z to 00Z. Upstream 00Z soundings (AMA, MAF, EPZ, ABQ, and TUS) indicate steep lapse rates from the SFC though 500mb. LLVL directional shear, while initially weak, will increase by early evening as a westerly LLJ increases to 30kts; additionally, deep-layer shear AOB 40 kts should be sufficient to support storm organization.

- Bill
11:10 PM CDT, 06/10/09

 

[Matthew Crowther]

CO needs to be added to the title, that is where we are now and that is where will stay. SPC has their slight risk up here and this time I agree with them. Will monitor both the Palmer Divide and Raton Mesa.

 

[David Wolfson]

The RUC has been pretty firm in setting up a darn good southern caprock dryline scenario later this day. Obs this morning are indeed showing instability and shear building toward the southern caprock. I'll go so far as to say that I'm seeing a significant severe threat developing there. The weakest element has been low-level shear but even that respect seems to be improving with the combination of some boundary focusing and predicted storm motion from 290/25 or so.

Based on yesterday's NAM and with the same basic reasoning that Bill detailed, I was (virtually) in Turkey, TX, last night. This morning I am moving south a bit for a very hopeful virtual lunch in Spur, TX, FWIW.

 

[Warren Faidley]

Target for today (and the next few days):

Today... Eastern Colorado, near a line from Denver, Limon to LHX. Centered in areas currently clear of cloud cover.

Far NE CO and SE areas appear too stable ATM to support sustained threat per visible satellite images and DEN discussion. Raton Mesa area looks interesting if the area can warm up. Target might change if clouds clear in other areas by 17-19z.

W.

 

[Tom Dulong]

CO needs to be added to the title, that is where we are now and that is where will stay. SPC has their slight risk up here and this time I agree with them. Will monitor both the Palmer Divide and Raton Mesa.

I agree. This could be another decent "landspout day" for northeast CO and the Front Range. Having worked this area in the past as a forecaster with the NWS, I see this as one of those "classic" setups that seems rather benign dynamically as compared with the classic lower plains events. However, do not be fooled by the forecast of 500-750 units of CAPE. That is plenty by Colorado standards.

Based on mesonet data, there appears to be a weak cyclonic circulation at the surface along I-70 east of Denver near the WSR-88D site. This meso-low should tighten up a bit as the upper short wave comes in from the southwest. Look for the higher terrain of the Palmer divide to light up first after 2 pm and then the convection should spread northeastward.

If I were to chase today (which I cannot), I would head out somewhere between Denver Int'l Airport and Byers and then wait for the show to begin.

 

[Andrew Stoller]

I wouldn't discount southeast CO as well. A surface low looks to form per the RUC right around Trinidad and upslope flow really pushes some decent moisture in from OK/TX panhandles. The east end of the Raton Mesa might be a good place to play for people that can't make it all the way into northeast CO. There's a nice shortwave that'll be moving through southern CO today which should give good vertical velocity and decent storm coverage, which is kind of hard to chase in eastern CO on these types of days. You want to be on the action early!

 

[Andrew Stoller]

Per SPC mesoanalysis, southeastern CO is still fairly capped. The Denver Cyclone also looks like it's really getting going looking at surface winds. Plus, northeast CO has 1,000 J/KG CAPE at the moment.

 

[David Wolfson]

Matters seem to be coming together with convergence on vis satellite and clear air LBB radar concentrating off the caprock. Virtually hanging tight in Spur, TX. TW just issued for the area.