4/23/07 FCST: TX / OK / KS / NE

[cedwards]

Monday appears to be better than Saturday. Moisture will not be a problem as the entire east half of the Panhandle will have TDs in the 60s. Nice classic dryline setup. 200-300 helicities, CAPE ~1600. CAP erodes by 0Z
Hopefully nothing comes in to mess this one up.

 

[Jay McCoy]

I am glad Matt Hines and I arent the only ones who noticed this. We have been talking about all day. Looks like a much better chance of isolated storms compared to Saturday where it should line out after the first 3-4 hrs.

Moisture returns in earnest so nobody can argue about Td's and dewpoint depressions. Already put in for half day off work.

 

[Glen Romine]

This day is something of a mystery in terms of timing of the arrival of the next wave. Shear might still be ok and perhaps enough convergence for severe storms regardless of timing, but if the next jet streak/shortwave picks up the pace just a little bit things could be quite interesting back in the TX panhandle. The new NAM - which has had really bad forecasts on the far end of the range, suggests much more favorable timing for Monday. 00Z GFS was well behind, so worth watching the trends over the next few model runs to see which way things trend.

 

[Matt Hines]

I do still like what I see for Monday. Moisture should not be a problem. The placement of the dryline will be the main question, but if we have learned anything from this year, the farther west solution seems to be the way to go. 12z NAM looks to have a nice show for most of my area...still far out and we have Saturday first...but I may not be getting a lot of sleep over the next 3 days.

 

[Matthew Crowther]

A little surprised that there is not more buzz about this day- the new NAM is very promising for the Panhandles/SW kansas for Monday- nice 500mb jet just beginning to impinge on the Plains, the moisture should be much deeper by then- no AM convection to gunge things up etc. I was convinced enough to plunk down a good chunk of $$ to fly out for a 2 day excursion....that is probably the thing working against this set-up the most...

 

[AlDanks]

Looks good so far...

It's a ways out, but at this point I'm looking to make the drive to the panhandle for this one. Probabilities of tornadoes look strong enough and two consecutive chase days with the second heading back toward home.

Any chasers with similar ideas in IN or IL who might like a ride - PM me.

 

[Matthew Crowther]

Still looks good for this day with one caveat- the 00Z model suite shows that the main vort max hangs back well to the west, and there is no real strong short wave ahead of the main system- so right now the main possible chase failure mode may be a very late show, with a small chance of no storms before dark. Otherwise everything else looks just fine and dandy regarding the moisture and shear for tornadoes. Kansas or NE Colorado may actually as good or better than the panhandles at this point- time will tell.

 

[Mikey Gribble]

I haven't done much forecasting yet, but after taking my first look at things I like two targets (Woodward and Lawton). Lawton has a nice long curved hodograph by 00Z. Woodward's isn't as impressive, but OK. I think both targets will have the potential for tornadic supercells tomorrow. Moisture and CAPE should be slightly better in Lawton by 00Z, but low-level winds should be backing more by Woodward due to it's proximity to the low. It is a tough call and one that I'm not going to make until I put a lot more time into working on this forecast. It definitely looks like a chase day though.

 

[Kevin Scharfenberg]

I agree completely with the upgrade to MDT risk Monday. Moisture will be in place by early-mid afternoon with low-mid 60s dewpoints back to the dryline, which will probably be along the edge of the caprock in the eastern Panhandle. The system is fairly far west and still an open trough, with a good angle of flow aloft across the dryline, so supercells should be the mode. Shear profiles are progged to improve dramatically between 21Z and 03Z, with really nice low-level hodographs by dark.

My forecast is for scattered supercells developing along a corridor from Garden City KS to Altus OK to Benjamin TX, and maybe farther south. Several of these should be tornadic with potential for significant tornadoes as the low-level shear increases around sunset. Storm motions should be relatively slow so a much easier day to chase than previous events this spring. I think for Oklahoma, this may be the best setup since 5/29/04.

 

[Adam Atkins]

Kevin good, warranted post! I agree there are good shear profiles as time progresses, and the low level shear only gets better with the approaching shortwave and associated height falls. Models are in agreement concerning the thermodynamics and warm frontal progression tomorrow. The boundary might provide a good focal point for initiation (in conjunction with the dryline) and especially for enhanced low level shear.

Concerns involve the timing of the shortwave. The best mid-level flow is well behind the dryline, and approaches near dark. The greatest risk for tornadoes might be late as supercells approach more populated areas (Central OK-SC KS).

I'll be embarking probably w/nw OK and trying to find the boundary and hopefully I will get a tube for my birthday

 

[Kevin Scharfenberg]

After looking at everything carefully, I still like this setup a lot, but there are 3 things to keep an eye on:

1. Obviously weaker winds aloft moving out over the plains too late would be a negative, with less response in the low-level winds resulting in smaller hodographs before nocturnal stability sets in. In this case I think we'll still get nice supercells with adequate deep shear but tornado threat would be a lot less.

2. Cirrus will probably be brought up from Mexico on the subtropical jet. If too thick insolation may be inhibited so that initiation becomes a question.

3. A subtle shortwave trough in the subtropical stream might be badly timed, moving over Oklahoma during the midday. If this feature is strong enough there might be subsidence in the wake of it over the dryline during peak heating, a negative to robust convection.

 

[Chris Wilburn]

New model runs should be out by now, but I will not have time to look before leaving for work in about 30 minutes. So this forecast is based on 12z data this morning. I like an area form extreme sw Oklahoma to nw Texas. Moisture will be no problem with low to mid 60's likely. CAPE should be in the order of around 1,500 -2,000 J/kg and shear looks really good. I do like the forecasted shear of 500mb of roughly 50kts which will make for slower storm speeds. I too have some concerns that the best upper wind dynamics may not overspread the dryline early enough to get good storm before evening approaches, but we will just have to see. I like nw Oklahoma for the better low level shear and back surface winds in response to the surface low in sw Kansas, but I like the instability/moisture/500mb winds better in sw Oklahoma. 500mb winds look rather weak in nw Oklahoma, but that may change. I will have a couple extra seats if anybody wants to head out. I should be in Tulsa by 8:30 and will likely go through Oklahoma City on my way to Altus if things still look good there. I will check my pm's before I go so if anybody is interested let me know.

 

[Mikey Gribble]

I just glanced over the new run of the NAM so I will post a more detailed forecast tomorrow morning, but my initial thoughts are that the environmental conditons look extremely favorable for tornadic supercells in western Oklahoma. I think the bullseye will be along and E-W of an Elk City to Altus line. The one thing that bothered me a little was weak winds at 500mb, but that isn't something that will preclude a tornado outbreak IMO. I have only been forecasting for literally 10 minutes, but from what I've seen so far I am very optimistic about a localized tornado outbreak tomorrow.

 

[Kenny Drake]

New model runs are out, well NAM at least. It is pretty much the same as the 12Z run. I took a look at the Altus NAM forecast sounding valid 18Z, what a beauty...
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=018&STATIONID=_KAXS

Uncapped environment, shear profiles are looking great, moisture is there, CAPE is >2000 J/kg. Things are never perfect in weather, but this is close to one of the best profiles I've seen. As for a chase target zone, well looks like I'll be heading out with Chris Whitehead probably to Lawton, then westwards towards Altus.

EDIT: After looking at the parameters more closely its still a decent profile, but I noticed one major component that could be better. With the jetmax still upstream the upper level winds will be slightly less than favorable, however directional shear is still more than adequate. My concern is reflected nicely in the Altus forecast sounding with 0-1km SRH of 13.5knts and BRN shear of only 9.2kts. I would like to see BRN a bit higher, more or less between 10 and 40'ish. As for 0-1km layer SRH I would like to see around 20'ish to be considered a "great" profile.

EDIT: I know this is more of a "NOW" thing but Td's have jumped 20F in an hour according to a Mesonet meteogram for Pauls Valley. Let thy warm front surge north!

 

[Billy Griffin]

Watching the latest WV imagery, it appears that the system is deepening, and appears to be slowing down as it positions itself near Reno / Carson City, NV. Tomorrow is one of those days that's really tough to call for me. A lot of parameters scream tornadoes, yet something feels almost "too good."

Upper support may be late in arrival, and I think that will be the key! So what I feel at this moment is tomorrow will be a very late / nocturnal event which will leave some great boundaries for Tuesday, when the system finally kicks out onto the Plains. I wouldn't be surprised to see tornadoes tomorrow, but as of now, I think that too could be very close to nightfall.

Just for fun, here's my forecast for tomorrow: HIGH RISK - Primary SVR threat will be nocturnal MCS / significant wind event over central and southern Oklahoma.

Discussion: Initiation will hold off until very late in the day or near dark, when the jet kicks in and cap erodes, whereas storms will quickly go from supercells to cell mergers, and cluster into a complex MCS which will march across much of Oklahoma and western north Texas with a significant wind event overnight. 10% tornado risk during early initiation over far west Oklahoma and northwest Texas. I would hatch out an area over most all of western and central Oklahoma for significant wind and also mention the possibility of a significant derecho, which would coincide with the arrival of the jet.

Target for potential tornadic activity = Mangum/Hobart/Cordell, OK. Secondary target = Watonga/Seiling/Vici, OK.
Significant tornado risk should be limited to SW Oklahoma in a narrow time corridor of 6pm - 9pm.