3/26/09 FCST: TX/OK

[Connor McCrorey]

Well, we finally have a day where instability hopefully won't be a problem! This morning's 12Z run of the GFS is showing a large area of 2000+ CAPE across much of TX and SE OK, with a dryline from central TX up to around Wichita Falls and 60+ dewpoints everywhere (and 65+ dewpoints south and east of DFW. One big problem is that a strong cold front will probably be blasting in from OK. But if a storm can break the cap early, what appears to be excellent directional shear could easily get it rotating. LCLs should be low, with T-Td spreads <10 F. Storm speeds could be nice and slow relative to what we've seen so far this year, and it could be right over my backyard, so I'm thinking I might sit out Monday and save my gas for Thursday at this point!

 

[Chris Lott]

I'm glad you brought this up Conner. I have to work Monday night, so I was hoping for some early action Monday but gave that up. Thursday does look interesting. Wind fields look good, although I would like to see a little stronger, but finally some good instability to work with, if it verifies. I will have to watch this closely over the next few days, but it looks good so far.

 

[Chris C Sanner]

Well, well, well....what do we have here?

I just took at look at tomorrow and am very surprised that so few are talking about it. Flow in the mid and upper levels is pretty decent but flow in the low levels is rather weak. However, the presence of a boundary is going to make things very interesting tomorrow. 0-1 Helicity values are locally much higher along and just N of the warm front, so if you can get storms tomorrow around the triple point, which will likely set up in N. Tx or S. Oklahoma, you could get a nice little surprise.

From a chasing standpoint, I like tomorrows setup a lot more than Monday. For starters, storm motions are going to be very slow, 30mph or even less. With the tougher terrain, that will make chasing manageable. The moisture is there and CAPEs are running 1500-2500 j/kg. If the models underestimate things like they did on Monday, you could be upwards of 3000 j/kg. The key is getting the warm front to retreat north of the metroplex and to be firmly on one side of the Red or the other so there are options for chasing. Either way, it's not going to be a huge risk day or anything...but these are the types of days you love to see pop up on the radar from time to time

 

[Andrew Ryan]

Chris you got me really interested in this after reading your status on facebook!

I've briefly looked into the situation for tomorrow. Looking at the current dewpoints across southern Oklahoma, it's hard to believe that there will be a chance of severe weather tomorrow. Dewpoints are in the low to mid 30s across the "target area." But quality moisture is not too far behind, with dewpoints in the 70s on the Texas Gulf coast. Looking at the 12z soundings at Brownsville and Corpus Christi the boundary layer is completely saturated. Granted it's the morning the boundary layer is probably still decoupled, but I still think the moisture is still pretty deep down there.

As the warm front lifts tomorrow up to the Red River valley, it will bring those 60 and 70 degree dewpoints with it. Though the problem will be that it will be just in time moisture. Another problem I see is the stout cap in place across the Red River valley on all the 12z NAM forecast soundings. Though, any storms that break through the cap will experience some great 0-1km helicity (~200 m^2/s^2). This will make conditions favorable for supercells and low level mesocyclones.

I will be watching this setup and see how all this progresses over the next 24-36 hours.

 

[Jeff House]

Agree that Thursday could be one of those sleeper days that surprises to the up side. Warm front already lifting off the Texas Coast nicely today, which bodes well for a North Texas arrival tomorrow.

Couple challenges need to be overcome. Lead shortwave should exit Texas pre-dawn. Morning rain should leave outflow but the rain needs to depart before Noon. The 850 winds are a concern. Lead shortwave should veer them. We need the evening shortwave to come out soon enough to back 850 winds a bit and of course trigger convection.

I like the warm front lifting north and will target the triple point if I go. Moisture will be no problem in Texas with a warm front that never cleared the coast lifting north. Believe Thursday could yield a few tornadoes.

 

[Connor McCrorey]

Well the big question is, "Will the cap break?" Tonight's NAM shifted the triple point a ways to the SE, but is still indicating nearly 4000 J/Kg of CAPE with awesome shear tomorrow! Again, moisture will not be a problem, especially given the rain this area got today. I will be chasing tomorrow, although I'm not exactly sure yet, depending on where the WF and DL setup. Hopefully that cap breaks and we get a few tornadoes!

 

[Brandon Lawson]

While many people, I'm sure, are already looking ahead to Friday's potential southeast outbreak, tomorrow presents itself with some tasty parameters. Of course, this day will be a highly conditional threat. Once again, the pains of chasing in the southern plains, strikes again. We either don't have the moisture/ instability, or we get the uber cap of doom and not enough forcing. In tomorrow's case, it's the latter. Current models are showing next to no precip. breaking out tomorrow in northeast Texas.

Best chance for storms will be along the warm front, where capping is weakest, but even then it may not be enough. A 993mb low over east New Mexico/west Texas will be advecting warm air at the 850mb layer, into northeast Texas, creating a fairly sizeable capping inversion.

Further south, forecasts soundings around Corsicana, TX display a very high amount of CAPE, plenty of shear, and no cap. EHI's of 4, and lift indexes of -10 make me want to chance the poor terrain. However, if there is no forcing for storms, then there is no point.

It's always frustrating when you can have storms pop up all over the place, and a tornado warning in 30 degree dewpoints, and then the next day a big cap preventing all chances of convection. I'll probably check things tomorrow morning and make a decision on whether to make the trip into Texas. http://www.youtube.com/watch?v=-Qae_TUTeGo

 

[Jim Bishop]

We are going to need upper level forcing to cool the mid levels today over Central Texas if we hope to initiate surface based convection along the dryline this afternoon/evening. Dryline mixing isn't going to cut it.

Models indicate that throughout the day 850mb flow will be out of the southwest. So the warm and extremely dry air from Midland and Del Rio will be advecting into Central Texas this afternoon. The 850mb temperature at both locations this morning was around 16C. Surface temperatures are only going to reach the lower 80s today across Central and North Texas, and mabye only the upper 70s if the fog from this morning takes loner to mix out. So dryline mixing isn't going to break the cap, and models don't bring any significant shortwave into the region this afternoon or this evening.

The WRF does indicate a weak vort max moving through the Red River valley after dark, and initiates convection across Southeastern Oklahoma, for what that's worth.

I see today being a big waste of CAPE, shear and low level moisture, all because the CAP just cannot be broken. What a shame.

 

[Jeff Snyder]

Well, the setup doesn't look that bad for N TX and perhaps a sliver of extreme S OK, IMO. Current sfc obs indicate that the >65F TDs at the sfc remain locked up closer to the coast as a result of weak sfc flow overnight, but the 12z FWD sounding reveals that better moisture has returned northward just off the sfc. As such, assuming the current dense fog in the are can mix out, some of the better juice should mix downward with time (in addition to being advected north/northwest on S/SE sfc flow). The 12z RUC is forecasting strong instability (3000-4000 j/kg CAPE, which seems to be on the upper-end for March around here) with ~65F Tds making it close to the Red River by 0z. Mid-levels are cool (16-18C); lapse rates aloft are steep. Capping appears to be the greatest problem with this event, as veered 850 mb advects in warmer air not too far above the sfc. Fortunately, 850 mb isn't very strong, so advection isn't going to be very significant either. There does appear to be some vort DPVA across far N TX later today downstream of a weak vort max, though there are some timing differences between the 12z RUC (suggesting DPVA late afternoon) and 12z NAM (suggesting DPVA after sunset). That said, the 12z RUC and NAM remove most of the CINH by late afternoon. Deep-layer shear should be around >50 kts across N TX up to the warm front (greater N of the WF where sfc winds are heavily backed, not surprisingly), and low-level shear, while not terribly impressive, could support tornadoes given that winds stay backed to SSE (or given interaction with the warm front and/or any sfc baroclinic boundaries that may develop as a result of differences in when the fog mixes out).

I'm about 50/50 right now, so I'll bring my gear with me to school/work. I'll keep a close eye on vis satellite through the next few hours to make sure that the fog and low clouds do mix out soon enough to allow for temps to hit >75F. In addition, with the triple point perhaps being an option, keeping in touch with sfc obs will be important (then again, when is it NOT?). Prelim init target near GLE, likely better conditions a bit E of there, hoping for init somewhere likely W of I35 N of the DFW area.

 

[Brandon Lawson]

Dallas/Ft.Worth Office is leaning towards a few storms possibly breaking the cap, with a planned launch of a sounding this afternoon. I was encouraged by their 12z sounding, which only showed weak capping. With adequate heating, we may only need to worry about the forcing for initiation.

Dry line is setting up west of I35, but cloud cover is still hampering daytime heating. I think I plan on heading out this afternoon, especially since Friday is not looking as great, at least location-wise(I wonder if anyone will target the superdome?), and Saturday I would have to drive to east TN. Will take the scenic drive across the river and hope for the best. KGLE, KPRX, KTRL, doesn't matter. Just give me a Cu-field.

Not too bad of a sounding out of Paris, TX:
If we can get storms
Gainesville too:
will the cap prevail?

 

[Jonathan Whitehead]

Taking a look at the 20Z sounding from FWD shows a rather stout capping inversion that doesnt appear to be letting up any time soon. In fact on the skewt, the warm nose is oriented 90 degrees to the vertical. Rarely will you see caps like that overcome.
SPC mesoanalysis has a bullseye of 3000 SBCAPE W of the metroplex within 50kt of 0-6km shear, which combined with 60+ dews is more then adequate for rotating supercells.
A look a visible over the last several hours has shown a few attempts at convection...one just SW of SEP around 2:30 and now another east of SPS.
FWD still thinks there is a chance at storms but that window is closing with each passing hour.