3/8/11 FCST: OK,KS, N TX

[Scott MacArthur]

It's a little far out but I'm excited to see the possible setup for Tuesday after being a little bummed out from Friday's model change. From what I can tell, we have all the ingredients for a nice event, especially across C OK. A nice low moving into the area with dew points in the 60's maybe 70, 1500 j/kg of instability around OKC and a great looking hodograph...
FYI - I am about 9 months into learning this stuff but want to jump out here and start contributing where I can. If I'm completely off base let me know but this is a great way to learn. I learn more from these forecasts posts than anywhere else!

 

[bradjones]

Moisture unlike previous two systems may be severely lacking for this setup here in Oklahoma for Tuesday. you can thank the cold front that will sweep through here tomorrow for that.

 

[Jonathan Whitehead]

Scott--not seeing the extreme dews your talking about (see Brads post above) but def 50 to 60 dews will be sucked Northward overnight Monday into Tuesday. This system is pretty powerful compared to Friday's. Big honking jet crashing down West Coast Monday will punch thru the desert SW and explode out into the Plains Tuesday. Looking at GFS and ECMWF it appears best best area will be somewhere across North TX depending on how far N moisture is able to get. I definately like the prospects for this setup as shear and helicty should pretty well maxed out. Again still way early though but this one def bears watching. Given that Ill be working till 4, the prospects for a sig supercell/tornado will be enhanced.

 

[Scott MacArthur]

Ok, I see the lack of moisture return there, low 60's in N Tx, S OK is what I'm seeing as best case on the latest GFS for 00Z Wed. Hard to read the color change sometimes, thought it was well into the 60's but no cigar there. I'm remaining hopeful, especially since Chris has to work

 

[Jesse Risley]

It's a bit far out to know whether or not the model graphics are accurate at this juncture, but the 12z ECMWF is certainly less magnanimous regarding both moisture and CAPE profiles for this setup. Today's 12z run progs the 55 dewpoint line to only reach the Red River valley by 18z TUE, moving northward to near the KS state line by 00z WED. The nose of the 60 degree dewpoints barely make it across the TX line before 00z; CAPE values >750 J/KG are confined to East Central Texas and points southward for the duration of evening. Things can change between then and now, but that's the current prognostication per the European model.

 

[Verne Carlson]

This day is looking better on the 0z GFS run with a nice 900mb surface low moving across northern KS during the day pulling mid 50Tds up into KS with mid 60s into OK. Nice well placed neutral trough with good timing for peak heating. I can see a couple areas of play. One up east of the surface low along I-70 in KS and then down along the dryline from Wichita to Dallas. Really hope this one holds together and doesn't go the way of tomorrow's setup.

 

[Michael Riedl]

The latest GFS has made me hopeful as it is is bringing moisture, and as a result instability, further north into the central CONUS. With winds backing across the entire warm sector, and 700mb temps more than manageable, a tornado threat could exist somewhere across OK/KS/TX.

 

[Jesse Risley]

There are still some differences between the 00z ECMWF and the 00z GFS that would affect how the event might unfold, but those model differences should be resolved in future runs. At noon on Tuesday (18z), the GFS has a deeper 992 mb low progged to reside over the KS/CO border area, with surface dewpoints in the mid - upper 50s already surging as far north as S Kansas, while the ECMWF has a slightly weaker, albeit more progressive 996 mb lower over C KS, becoming more elongated as it moves ENE, with mid-50s dewpoints only reaching far SC OK. That results in the GFS progging a much broader area of 1000 J/KG+ CAPE values across a larger portion of SC OK, with the ECMWF being slightly less generous on CAPE values, yet still indicating a broad area of moderate instability (750 - 1000 J/KG) across EC OK and far S KS. If future runs continue to indicate that these parameters could materialize, it could be another good localized opportunity early next week.

 

[Jeff Duda]

This day is looking better on the 0z GFS run with a nice 900mb surface low moving across northern KS during the day....

900 mb surface low?!? Are you sure? That would result in 100 kt sustained surface winds!

According to the 12Z GFS, looks like moisture, and thus instability, is still going to be quite a problem. Even with better moisture south of the Red River, being farther from the upper level dynamics and cooler temperatures still don't improve the amount of CAPE there.

 

[Brett Roberts]

According to the 12Z GFS, looks like moisture, and thus instability, is still going to be quite a problem. Even with better moisture south of the Red River, being farther from the upper level dynamics and cooler temperatures still don't improve the amount of CAPE there.

I agree that low-level moisture looks borderline on the 12z GFS, as well as most other recent operational runs. However, I think it's important to note that the GFS is likely underestimating surface temperatures -- and, therefore, CAPE -- by a substantial margin. This is exactly what happened this past Sunday, when the GFS was insistent on keeping afternoon temperatures in the 60-65 F range ahead of the dryline. The verification was more like 70-78 F right up to the warm front.

Of course, there's always a possibility that low stratus really does hang around all day and inhibit instability. But it seems like more often than not, the medium-range models are far too cool at the surface with these early-season setups. I'd wager that if Td's of 60 F can make it to the Red River Valley by late Tuesday afternoon, SBCAPE >1500 J/kg will be realized in that area. At that point, if you believe the shear profiles on this particular GFS run (a big "if"), tornado potential would likely be limited only by marginal LCL heights.

 

[Mikey Gribble]

I agree with Brett on the questions regarding the stratus clearing out and surface temps. Also keep in mind the GFS was more bullish with CAPE until this mornings run. I try and avoid giving much credit to any change in a model run until that trend continues. You can't get too wrapped up in run to run variations.
I just copied and pasted from my blog. I'm too lazy to type something up again. This is probably the most interested I've been in a setup so far this year though. Below is the post from my blog...

I finally had a chance to look over the 12Z GFS. There are a few notable changes. Probably the biggest change is that the 12Z GFS has backed off on the amount of CAPE being forecast ahead of the dryline. I only glanced over the models so far (plan on doing more extensive forecasting tomorrow morning when the NAM picks this up), but it looks like the lowered instability might be a result of the stratus deck not clearing out as much as it did with the previous GFS run. I really need to look at it closer, but for now the details don’t really matter so I’m not going to waste my time on it.
With the lowered instability in the latest GFS run the cap is stronger and it doesn’t break out any diurnal precipitation along the dryline over southern Oklahoma and north Texas. That is definitely nothing to worry about 108 hours out. With the last two setups the GFS has bombed on forecasting cap strength and precip. I doubt it would be wise to trust it this time, especially with the large run to run variation it is showing.
Aside from that everything else looks basically the same with the GFS. It shows moisture advection slowly starting up Monday morning and then really ramping up Tuesday as the low level jet strengthens. BTW I looked at the 84 hour forecast from the NAM just to compare what it was showing for Monday night on moisture advection (since that’s as far out as the NAM goes right now) and it actually shows better moisture advection than the GFS. That is adding a little confidence to my belief that we will get adequate moisture in place over northern Texas and southern Oklahoma by Tuesday afternoon. The NAM is also showing a slightly stronger trough. I am anxious to see what it is showing when it picks up on Tuesday with tomorrow mornings 12Z run. After that happens the forecast should start to become a little more clear.
Anyway, that’s enough rambling for now. The bottom line is that Tuesday’s setup is looking pretty potent right now. There are a few things lacking and we need to catch a couple breaks, but there is definitely the potential for some good quality tornadic supercells along the dryline. Moisture return is still a little bit questionable, but I think we’ll be okay along the southern portion of the dryline on that. Probably my biggest concern is a stratus deck sacking in the warm sector and not allowing us to get enough surface heating for respectable instability. It’s a long ways out though and the models haven’t been consistently showing that as being a problem. There is reason to be concerned about it though.
I will probably update later tonight after I see the 00Z. If not I’ll update tomorrow morning. I plan on posting a more extensive forecast then.

 

[Jesse Risley]

Today's 12z runs continue to show some rather substantial differences between the long-range GFS and the ECMWF, but it looks like there is a hint at cold core potential in SW (GFS) or C (ECMWF) KS as well.

The GFS shows a 996 mb low centered over far SE CO at 18z TUE, pulling moisture NNW, with dewpoints AOA 50 degrees reaching far S KS, but only yielding surface dewpoints AOA 55 degrees from WC OK back into TX by 00z. The GFS is also progging the low clouds to hang around parts of the warm sector (mostly east of the 100 degree meridian) until between 21z and 00z, when a narrow tongue of marginal instability AOB 750 K/JG appears across parts of WC OK into C/SC OK between 00z and 06z, with corresponding LI values of -3 to -4 C. However, a pool of H5 temps AOB -22C overspreads parts of SW KS by 00z WED, producing some very steep lapse rates on the order of 8-9 deg C/km as that narrow tongue of moisture (50+ dews) advects towards the surface low.

The ECMWF remains more progressive with the mid-level disturbance, showing the associated sub-1000 mb surface low already near ICT by 18z TUE, moving into the KS/MO border region by 00z WED. It has some slightly more generous instability values AOB 750 J/KG (with pockets of 1000 J/KG) across SE OK and E TX, thereafter extending into SW AR between 00z and 06z WED. In a similar fashion as the GFS, the ECMWF, though placing everything further east due to its more progressive bias, shows those low clouds hanging around the warm sector through 18z, but between 21z and 00z WED those clouds gyrate eastward, allowing the aforementioned CAPE values to spike as surface dewpoints AOB 60 degrees promulgate northeastward into SE OK and SW AR during that same time frame. An area of higher (convective) QPF values appears over SW MO, far E OK, W AR and NE TX between 00z and 06z WED. ECMWF Skew-T profiles for the synoptically favored cold core region indicates surface temps in the low 60s juxtaposed with surface dewpoints in the low 50s should be overspread by H5 temps of app. -21C near the triple point.

There's room for plenty of change between now and then, and the system assuredly will change over the next several runs. However, the cold core parameters are also worth at least keeping an eye on in the foreseeable medium-range.

 

[RMacDonald]

Here is my latest severe weather threat according to my data. I am picking up some higher instability areas especially in the NC Louisiana and S. Louisiana areas, also a small pocket forming over the Central Oklahoma region. Showing 0-3KM CAPE with -2 to -3 LI and -2 to -3 SSI in that area, which is pinging the higher instability. Any thoughts to the areas in Orange...

 

[TimothyCarroll]

FWIW, I rarely post anything in the forecast discussion forum, but I’m going to give it a go and put in my $0.02 worth. . . I, without any formal training, am only going on what I have taught myself over the years. So please feel free to offer constructive criticism and argue any points that could be incorrect.

As of the latest NAM runs for 00Z 03/08/2011, I am placing my money on or around Bells , Texas as a good starting ground for Initiation around 2000-2200Z, along a fast moving dryline, that at 1800Z was very sharply defined just west of the DFW Metroplex. Forecast CAPE Values at or above 1000 J/Kg were evident on last night and this morning’s 00Z NAM Runs along from appx. Gainesville, TX to Bonham, TX and the US 82 Corridor. Sfc Lifted Index is hovering steady at or around -3 to -4 in areas just along and south of the Red River between the above mentioned areas, Sfc-500mb Bulk Shear is at or over 80kt on both last night and todays NAM And GFS Runs, and 0-6km shear values at or above 350 With Afternoon Sfc Temps of 75f or above and Sfc Td’s nearing 65f near my targeted area of Bells, Texas by 1800Z on Tuesday, I would put at least some of my eggs into the basket for this one.

With decently curved forecast hodographs, showing good low to mid-level rotation, and 20-25kt SSE 10m Inflow winds, I would not be too terribly shocked to see a couple of nice discreet, surface based sups go up somewhere within about 30 miles of my target area, storm motions are NE at 30kts, so they will be racing, but if anything pops out ahead of the dryline along and east of the I-35 corridor, I expect it to rapidly go severe, and possibly tornadic, early in its life cycle, I can see surface based discrete supercells going up from as far as south of the DFW Metroplex, to as far north as Paul’s Valley to Ada, OK and racing east, quickly going linear within 30-45 minutes of initiation. Anything that can form, and stay discrete, and ahead of the QLCS by 00Z Tuesday, has some very good potential. But again, I am half asleep on this one, and just giving it my best, I’ve been a member way too long to not post something of forecasting nature.

** EDIT **
My Forecast area of Bells, TX is also on the far WSW Sector of the SPC 30% Hatch, which in my mind, shows potential to verify for the initiation target, and possibility of a discrete surface based supercell, before it goes QLCS over the arklatex region later.

Further Analysis reveals that, IMHO, if anyone is going to have even a remote fighting chance at seeing anything, its going to be when, and IF, storms fire discreetly out ahead of the Dry Line early in the evolution of this system, everything East of approximately Bonham, Texas, North and South of, becomes rolling hills with sticks, and serves for very unfavorable chasing territory, as well, by the time that SPC is forecasting even embedded supercells with the POSSIBILITY of isolated strong tornadoes, it will be well into the late evening, overnight hours, and well into the west central sector of the arklatex region, therefore really inhibiting any chance at a safe, and visually enabled chase.

Even though, I have seen at least as many, if not more nocturnal tornadoes than daytime, I would not for any reason, jump on a chance to chase a night time Arklatex system. . . That may just be attribute to my lack of desire to kill myself or anyone I chase with . . .

 

[RMacDonald]

Just updating my forecast for tommorrow. Right now I am tracking a the most favored areas for tornado potential across the extreme eastern part of TX, running through Lousisanna area to southern part of Arkansas. Right now I think SW border or LA and AR will see the greatest potential of Tornadic storms. Showing -3 to -4 LI's, CAPES running around 1000, seeing good 0-3KM Shear. Here is the zoomed in threat area. Any thoughts on the potential for these areas.