3/21/2007 FCST: TX / OK / KS / NE / IA

Weds looks like the ‘pick of the litter’ with a 995Mb surface low in sw KS, Tds in the low 60s up into OK and +60Kt divergent SW flow overhead at 500Mb. The trend on the GFS is to neg tilt the trough on this day into Thurs, further increasing the divergence. GFS breaks out precip in central OK nicely. Weds looks like a 'must chase' day.
A little early, but what the heck. Latest GFS is exploding precip and thunderstorms in the Eastern TX and OK Panhandle. I have noticed that with each run, GFS is deepening the low and is becoming more negitive tilted. If everything stays the same and models are correct, major severe weather might be upon us on Tues and Wed of next week. Moisture levels are also expected to rebound nicely and there will be plenty of time for moisture to make it up this far north. Wed is the Pick of the day. On the other hand, systems like this, storms seem to fire and be more isolated the day before the main storm system arrives. Either Tues or Wed are looking good in the Panhandles.

Do you mean the 21st and the 22nd?

(might as well post all my thoughts in this thread tho)

I think the dryline will remain capped on the 20th, and even if a storm does form, deep layer shear will be marginal at best.

On the 21st, an initial impulse which swings around the digging longwave trough will move across the area. We could use some deeper moisture, but overall the setup looks pretty impressive with possible supercells developing along the dryline and propagating east at pretty chaseable motions.

On the 22nd, the longwave trough will amplify. We'll see how much it does, because if it amplifies too much 500mb winds will turn southerly and we get squall line vs. supercells. One thing seems likely (especially if the longwave amplifies over the Plains rather than over the Mississippi Valley) and that is there will deeper moisture.

Interestingly, the European model cuts the longwave off over the Desert SW, and the GFS Ensembles are divided over this issue. So this threat is not etched in stone yet.
I think the 21st will be the best day out of any of them. Western Oklahoma and far southern kansas have my eye right now. Also the eastern texas panhandle could be in the playing cards if this thing slows down any at all. However I think storms will form in the far eastern texas panhandle and far NW Oklahoma on into Southern Kansas and then move NE at 30 to 35mph, (much better thank 45 to 55mph lol!!!). Supercells seem likely with large hail and tornadoes. The 22nd is kind of a wild card right now. Anywere from SW Oklahoma on east into SE oklahoma will be possible targets along with northern Texas. However like Jim mentioned if 500mb winds do not cooperate then a squal line looks more likely for Thursday.
The gfs's ways remind me a lot of the Feb 23-24 event. That time from waaaay out it showed it around the 23-24 for the central plains, then it started to jump around and be less appealing. Then at about this same distance out the 18z run reverted back to close to what it had shown the whole time. Well check out today's 18z run of the gfs, it just flopped back closer to where it had been, and it's a lot more similar to the ecmwf as far as wanting to bring the big upper low out as a whole a bit later.
I agree with Mike I just checked out the latest GFS and the low is ejected into the Plains on Friday and is quite strong. The low seems to be placed on the KS/OK border.
It should be "go time" Wed.

I think the setup for Wed. looks very good for the chase...I am liking the C/SC Kansas area more and more...quite a few favorable parameters seem to be overlapped there...strong 700mb wave, triple pt. & SE quad of sfc low, more backed winds, strongest sfc/850mb convergence, enhanced upper divergence, etc. I will probably favor a position between Great Bend and Med. Lodge for the main action zone Wed. afternoon & towards the I-135 corridor by Wed. evening. Things should become more elevated the further east the storms get Wed. night.
Last night's run didn't look to good to me last night. There didn't seem to be very much convergence near the dryline. The 12z run looks a lot better, still aways out, but Western Kansas has got my attention. Guess we'll wait and see.
The GFS has trended slightly further north with the location of the surface low (Northeast Colorado/Northwest Kansas), which is in better agreement with the European. Therefore , next Wed looks more certain for a severe weather event, imo, based on that alone.

Regardless the last few runs of the GFS have been pretty concistent, suggesting supercells firing along the dryline from West Texas north to the Texas Panhandle into Western Kansas. The 30-40 knot southerly 850mb flow above 15-20 knot southeast surface winds, coupled with dewpoints in the upper 50s to lower 60s and 1000-1500 CAPE, suggests the potential for tornadic supercells.

Too bad for me this occurs in the middle of a work week...
I am pretty much in agreement with Jim, but I still have a few concerns. Mid level SR winds could be better for this time of year. I am also still concerned about good moisture making it all the way up to KS. If moisture is going to be a problem in KS moving South down the dryline would be my play. I do love the strong inflow level winds though. It is still way too far out to get into any specifics, but I am thinking it is more than likely going to be a chase day.
This "Event" is still a long ways off, but i cant help thinking that with all the precip that is forecasted all week long, that we may have trouble getting instabilities in place for large scale severe weather in KS/OK/TX..... Not to be pessimistic just making an observation...

we shall see...
I feel the moisture return problem would be solved quite easily if the surface low ends up forming more south, which in return will give a much shorter distance for the gulf moisture to advect. I'm thinking this system will have a definite spring like setup. Those to the north will probably want to hug the warm front. The CAP will be a bigger problem farther south with warmer and probably drier 850mb winds. Current OK Mesonet readings show Tds just after peak heating on Saturday in the mid to upper 40s. After looking at the 12Z NAM runs this moisture should hold in place. However, a cold front is progged to stall out somewhere over the state on Monday. Hopefully that front stays farther north. This will allow some 850mb moisture advection through Monday, before the LLJ really kicks in on Tuesday.
I honestly think this will be the pick day to chase this week. The gulf is WIDE OPEN so I don't think Td of high 50's to low 60's will be a problem in the target area. Obviously it's still a long ways out and many things can and will change. If I had to pick a target area right now I would have to go with the eastern part of the OK panhandle near Woodward. I think there will be a fairly significant warm layer aloft to deal with if one targets too far to the S or SW. Any further N and I think the moisture won't be quite as good for surface based convection. Looking for outflow boundaries from previous convection may end up being a key player to get that extra low level helicity for the storm to work with. Anyway, I'm sure things will be interesting and I imagine my target area will change by Wednesday.
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I totally agree with Jason.......Dew points are already in the upper 40s in western, OK and Eastern panhandles. The gulf will be open for a while now and dew points should be in the mid 60s on Wed. Systems like this seem to be a little stronger than models indicate. My gut feeling is to be somewhere in Beaver County. Like Jason, from Beaver to Woodward Looks good. I just feel that being closer to the Warm Front (if present) will be best. I know its early, but need to get ready for Wed.
I wont rehash jasons post except to say the GFS is trending a bit further south today which would move the best dynamics under a pretty strong lid. Finding the right area with enough energy to get through the cap and still have enough moisture might get tricky. The big player will be where the stalled front ends up sitting. Still too early to even think of a target but I do think wednsesday will be the choice day for this area. Thursday might be good a bit further east towards OKC. Hey I am off work.. I am ready for a few days of chasing.
Moisture Levels are spreading north at a pretty good clip. Canadian, TX TD is already sitting at 55 and this is expected to climb. The way things are looking, TDs should easily make it into the 60s before Wed. One thing I like to see, that is that the moisture be in place the day before the event. I have noticed that when the moisture is not present the day before, the Dryline seems to wash back and forth across the panhandles. With this being said, TDs are not going to be a problem at all. The one thing that does concern me with prospects of Wed is the amount of Rainfall we get here in the panhandles on Tuesday. This could limit and cool the surface and not allow a lot of heating to occur. But never the less, Wed looks to be a heck of a day for chasing. Also, I have pretty much thrown the GFS model out of my forcasting. There is just too much flopping between each run. I dont believe that the system will dig that far south...... Wed, as of right now, I feel that sticking around the warm front will be the key. Somewhere in the northern panhandles.....Also, does anyone really have an opinion on CAPE values on Wed??????? Everything I look at keeps flopping around...
Honestly CAPE values IMO will be next to impossible to nail down until the night before or morning of due to the models not interpreting where rain will be falling and how much convective crap gets left behind... I am exited about the prospects but it looks like it will be a day where we have to monitor data constantly to find the best spot....
Kind of stating the obvious here, but I think the "chaseability" of this set-up will hinge almost entirely on the character/timing of any lead impulses ejecting out of the mean trough position. The 12Z NAM and GFS are both forecasting a well-defined lead impulse (good), but they vary considerably on the timing and location of it (NAM appearing to be more favorable, which isn't saying much given the trough is still out in the Pacific). As a result, the forecast location/strength of the dryline and forecast shear profiles are all over the place, as well. Models also want to forecast a large batch of stratus ahead of the dryline, which I guess isn't surprising given the calendar month. With ~10 g/kg mean mixing ratios and -15C or -16C at 500mb, MLCAPE won't be outrageous by any means... maybe 1000-1500 j/kg given strong heating. This is plenty, of course, if everything lines up right.
I really think wednesday has the potential for a pretty significant severe weather event across Oklahoma. The moisture will be deep, wind feilds will be strong, and the cap should be strong enough to keep things isolated. In my opinion Shamrock texas seems to be a good target as of right now. I will not be playing the warm front, mainly because I think there will be widespread precip develop along the warm front. Ya there might be some tornadic storms at first but then things should become widespread. The dryline should be a key player in this event and any outflow boundary that is present. The cap to the north will be broken to easily, allowing for widespread storms. The further to the south the more isolated the storms should be thanks to a stronger cap. Also windfeilds look stronger the further south you go, along with instability.
I find it very interesting that both the GFS & WRF back the surface & 850mb flow over the Texas Panhandle between 18Z & 00z. Both models still indicate the dryline will continue to mix east throughout the day, despite falling pressures west of the dryline. Assuming convection does indeed initiate along the dryline in the Texas Panhandle by the late afternoon/early evening, low level shear profiles would be supportive of tornadic supercells.

Considering good surface heating, increasing low level moisture throughout the day, an approaching upper trough, and many small ripples caught within the upper flow, it seems pretty clear that convection would indeed fire along the dryline.
Interesting scenario

It looks like there could be a two point severe wx focus for Wed. (3/21) based on the 18z MesoEta. It looks to me that target #1 will be across SW/SC/C Nebraska on the for sure triple point...and target# 2 will be on the dryline across SW/C Kansas southwest into the C/E OK & TX Panhandles. Timing of the strong 700/500mb neg. tilted wave looks pretty good for target# 1 to produce. It may be a slightly later show for target# 2, but still very interesting depending on what model you sink your teeth into. Lots of runs to go before deciding on a chase target to lock in.
I like the Texas Panhandle around and east of Amarillo if the Eta varifies. I think this is where the best combo of shear, instability and helicity will be. Upper 50 dewpoints along the dryline will lead to strong convective development that is likely to become supercellular and tornadic. Storms may also be discrete enough for a long period of time. Target as of now is Claude, TX (SE of Amarillo on US287). Many more models to come out before a final target area is made.
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It looks to me that target #1 will be across SW/SC/C Nebraska on the for sure triple point... Timing of the strong 700/500mb neg. tilted wave looks pretty good for target# 1 to produce. Lots of runs to go before deciding on a chase target to lock in.

00Z NAM remains consistent in this regard, with what seems to be a fairly well-timed shortwave trough into the central NE/KS border region. http://www.wxcaster.com/CONUS_ETA_500_GPHTMPVORT_72HR.gif It's also forecasting notably stronger CAPEs up there than previous runs, IIRC.

The 18Z GFS continued with the faster solution just like the 12Z GFS, which certainly wouldn't seem to bode as well for initiation around peak heating along the dryline... namely if the s/w is contributing to junky showers/elevated convection in the warm sector before the cap to surface parcels is able to erode. http://grib2.wxcaster.com/wxcaster4/CONUS_GFS_500_GPHTMPVORT_78HR.gif
oz nam shows a marked increase in temp and a solid increase in dew temp, nice 2000-2500 j/k cape because of it, really like that increase to
-6 LI too. Things are looking better thermodynamically at this point.
I noticed this also samuel. The GFS has picked up on this also, although I think it is a day or so faster than the NAM. Moisture will not be a problem with this system, especially if we get heavy rains one day then the next it clears out allowing for surface heating and evaporation. One day this week or possibly more could easily turn out to be huge severe weather events across Oklahoma and Kansas, along with parts of Texas. All I can say is if surface heating takes place for very long along the dryline or outflow boundary anyday this week I think severe weather will be likely, especially Wednesday and Thursday.