2013-04-08 FCST: TX, OK, KS

[Mike Johnston]

The longer term models are beginning to suggest the possibility of severe setup next Monday. A upper-level trough is indicated with a base right around the four corners area. If anything like the suggested lee surface low of 997mb develops around the OK/TX panhandles, this would usher in a nice environment of warm and moist advection out ahead of a dryline. Looks like perhaps western OK is an initial area of interest. Wind fields look supportive, with surface winds out of the SE, 850mb flow from due S, and 500mb flow from the SW. Some of the forecast maps are even showing dew points reaching 65td across this area. Of course, moisture is always a concern, but, after a long winter, this system really looks like it holds a good chance of advecting some high dewpoints north of the Red River. Timing is still a bit uncertain, as the ECMWF seems to be quite a bit faster than the GFS. This forecast is only a general, synoptic look as it's still 5 days away and obviously alot could change between now and then. However, I would be most interested in other participants' thoughts on this possible setup.

 

[Tony Gilbert]

As mentioned; Cetainly too soon to have any certainty regarding the results for weather patterns this far ahead. Though that aside certainly worth the start of a thread based on the ECWF and to a lesser degree the GFS ATM. Both models do atleast currently maintain a condusive moderate 300mb jet, which this far ahead can be more reliable than the 500mb for indicating reliability for a sustained upper flow. The pattern looks more interesting through Tues and Weds as a more scooped upper flow looks to entrain a stronger surface moisture return northwards. NOAA currently shows around average SST's along the TX Gulf Coast ATM and this is at least a positive condition for now. The current 500mb temp predictions indicate a developing and almost stationary trough over New Mexico through the initial part of the convective period. The predicted upper trough extension currently looks to have the potential for this to breakaway and become short wave. The prescence of a short wave trough can often increase frontal lift under a strong divergent upper vector within the NE sector.'If' a short wave trough develops then we will have further scope for severe weather across SEastern regions later in the convective period possibly as far as a day 9 extension (from todays date). All hyperthetical ATM of course.
Certainly one to keep an eye on!

 

[Marcus Diaz]

Certainly does look like a classic southern Plains tornado-making setup in the works. I've been watching this setup for several days now since it was out in the 300hr mark, and for the most part it has been consistent with the 500mb low rounding down through the southwestern states and ejecting over N TX/OK/S KS. The surface low has been pretty much centered over the TX/OK panhandles area, allowing some good moisture return and backed LLJ of around 60+ Tds. Instability has been pretty much there and looking great for a while, in the order of up to 3,500 j/kg MLCAPE. This coupled with what looks to be about a solid 50 kt bulk shear swath overlapping the dryline, makes Monday look like a classic southern Plains setup.

Tuesday has also had my eye, but its flopping around like a fish out of water. The latest 0z and 6z runs painted a mirror image of Monday's setup, only with more moisture. 12z today now pushing the cold front faster south and pushing it all into northern TX and SE OK. Its pretty much swapping between those 2 scenarios, so let's hope for the prior!

 

[James Gustina]

Other people have noted this, but the only big difference in the Euro and GFS is how progressive moisture return is for Monday. The Euro only undershot the GFS by about 5F so I'm not overly concerned about moisture issues, especially with how soggy the ground will still be from the dousing we've had today and yesterday. The last 00Z and 12Z runs of the GFS kept inching the dryline a bit further east closer to the OKC metro between 18 and 00Z so I've got hope for an easy local chase. Also looks like a pretty strong cap around 18Z so the usual clutter we've been encountering the past couple setups shouldn't be a problem.

Gonna be interesting to see how the NAM and SREF handle this when it gets in range.

 

[Darren Wilson]

The GFS is starting to come into better agreement with the ECMWF keeping a dryline in the KS/OK/TX area Monday and into Tuesday evening. Still a question as to the extent of convective coverage with the 12Z Euro not developing any convection and the GFS producing only isolated convection until around 06Z, likely due in part to both relatively weak upper forcing and capping but there should be plenty of instability given progged CAPE > 3000 J/kg. Wind shear appears favorable with shear vectors oriented across the dryline and surface winds backing with time thanks to a deepening surface cyclone. I agree that moisture should not be an issue, especially here in Central OK thanks to all the rain we've had the past two days but western OK and adjacent areas of SE KS and NW TX received much less keeping the dryline from mixing too far east. Of course things can change being 4 days out but as of right now looks like a classic W OK dryline chase.

 

[Derek Weston]

Starting to wonder if we'll get enough upper energy in time for a big show Monday. Seems it could become one of those days that doesn't get going until a shortwave kicks things off late. Silver lining in that is that you could have a few wonderfully discrete monsters roaming the western plains late in the day. (and with the shear orientation & CAPE predicted, they would be monsters)

 

[James Gustina]

00Z GFS brought the nose of the main jet about 100-200 miles closer on the last run so hopefully that'll help with that cap of forged steel the models keep throwing out. Except for some minor qualms, the ECMWF and GFS both have very strong moisture return with dews ranging anywhere from 60F to 68F. MLCAPE still in the 3000 j/kg+ range with the GFS throwing out deep layer-shear values of 45 kts+. If this run is semi-right, I'd say isolated supercells would almost be a guarantee if that cap gets broken.

 

[mkavulich]

The 12z ECMWF and the last two GFS runs both seem want to bring a lot of upper-level (300 mb) divergence into Kansas and at least the northern half of Oklahoma by Monday evening. It does seem like upper support will be lacking on the southern end of the domain, but as you mention, CAPE and hodographs look fantastic, so anything that did pop would tend to be supercellular and discrete.

Right now I'm hopeful for Kansas, for partially selfish reasons since I can't commit to driving further south than that. But it looks as if the warm front will be near or north of the KS-NE border by 18z, with great hodographs, good CAPE (1-2k) and decent CINH in the south-central part of the state. Combined with the incoming upper jet streak to me it looks quite promising. Of course at 90+ hours out, getting this specific is probably dangerous.

I still consider myself a bit of a forecasting novice so I appreciate any corrections.

 

[Brian McKibben]

Monday 4/8/13... 12Z GFS today (4/5) shows a very impressive wind field for Monday night.

The big problem i see on Monday for central OK and areas south is a stout cap. The moisture should be good with >60F Tds (some >65). The winds are incredible. Here is a forecast sounding. Note the outrageous 627 m2/s2 helicity.

The 12z WRF shows the dryline pretty much stationary during the day in Western OK (perhaps even retrogrades a bit from 18z to 00z). If the systems comes through about 6 hours earlier the setup would be better. Again, like others have said, it is still a little far out for the finer details. Overall, the thermo and dynamics look good. My biggest concern is timing.

 

[James Gustina]

The NAM had better upper-level support entering the region around the 21-00z time frame so its possible that this may be a mid-late evening show. I'm not overly concerned with capping since the NAM/SREF has a downward trend in the lid strength (1-2C last I checked, which would prevent crapvection early). Hopefully there'll be some unresolved mesoscale feature that'll help so we can get isolated storms a bit earlier, because an environment like that going to waste would be a shame.

 

[Mike Johnston]

Time to examine the setup now that it has come into the purview of the NAM model. NAM seems to be just a bit more modest with moisture and instability, but still very supportive of severe. I agree that the cap issue is a legitimate concern with southward extent. Besides the cited timing of upper level support, it looks like the best low level convergence is right along the very southern tier of Kansas. (SPC in its Day 4 outlook references a very small area in NW Kansas where it says the dry line and warm front intersect. To be honest, I'm having a hard time analyzing a warm front in that area - at least based upon the 84 hour NAM run. I'm sure I'm missing something.) Again, I love the wind fields and both directional and speed shear which have been consistently indicated for several days now. Given the issues, as of now at least, perhaps the primary area to watch would be SW Kansas rather than my original target of western OK.

Note to Mods: I believe posts #9 and #10 above are related to 04/09/13, so maybe should move to their own thread as I'm sure Tuesday will demand a forecast thread it its own right.

 

[James Gustina]

00Z runs of the GFS and NAM are in with two different areas. NAM paints the best area as s-central KS/northwest OK with higher MLCAPE values between Medicine Lodge, KS and Fairview, OK. Excellent shear, deep layer at about 45 knots. Also is more aggressive with moisture return out of the gulf, with upper 50F dews reaching all the way to the CO/KS state line. GFS on the other hand still keeps the instability axis further south, south of the I-40 corridor with significant capping. Good news is that it shows a spot more upper-air support with the nose of the jet going through the panhandles around 00Z (around 21Z on the NAM as well). Definitely interesting if the models keep the split decision up to the night of.

 

[Jesse Risley]

Just perusing the full 00z suite of model data, it looks like the models are coming into somewhat better agreement at 500 mb, though I notice that, for Monday, the NAM is a bit further progressive and slightly deeper with the southerly position of the trough and the associated vort max. Also, the ECMWF ejects a perturbation out of NM and into W and NC KS by Monday afternoon, which is not showing up to the same degree on the NAM or the GFS. Between 18z and 00z/9, both the NAM and the GFS have notable energy moving into E CO and W KS, whereas the ECMWF is not quite as aggressive with this, hanging the timing back more than the other two models. This may or may not prove key to convective initiation across the western High Plains given some notable CINH on progged skew-Ts.

The models all do seem to be trying to initiate convection between 21z and 00z across parts of W/NW KS, NE CO, SW NE and SE WY, with a deepening surface cyclone in SE CO (some discrepancies on exact position and depth of the low) and associated dryline/pacific front and warm front draped across points E/NE. Given ample instability and associated dynamics, including wind shear, various modes of severe weather look probable. As of right now, it's hard to pinpoint specifics this far out, but two potential plays appear to be emerging: a dryline play, hoping for initiation owed to forcing, given moisture pooling and favorable dynamics, namely proximal to the Red River valley and points northward in OK, along with a second play E/NE of the surface low in western Kansas (the position of key surface features, e.g., warm front and deeper moisture juxtaposition, are depicted differently on the various models in this region at this time). The more likely scenario, as is what typically happens, is that the upper level energy may hang back until closer to 03z-06z or later, so if the northern target doesn't materialize due to initiation concerns, the southern play along the dryline/pacific front could reward - or both. The 00z/7 and subsequent model runs on Sunday should help narrow down a discernible target for those playing on Monday.

 

[Kelly Sugden]

This image is very foretelling. I think there will be some severe over the next few days. Also think models are overdoing moisture return given observations.

Strong kinematics, high model bias of redistribution of energy per unit mass.

 

[Tony Gilbert]

With the NAM model now into play for Mondays outlook some better comparisons can be made;

Surface (convergence derived) dynamic forcing along the dry line looks to remains fairly consistent specifically for just east of OK Panhandle through to central south KS where NAM is trying to indicate an eastward bulge of dry surface air. Some localised signs of weakened capping now for the said zone. NAM suggests potential for 550 m2 S2 0-3KM helicity values. Though, the upper troughs eastward progress now looks delayed and could certainly have some implication to Mondays outcome regarding upper lapse rates potential. Radar simulation currently seems unable to develop precip for this region by 00Z but then this is fairly common this early on and should not be relied upon. Forecast Hodographs remain conducive to positive directional shear and forecast soundings continue to indicate strong potential instability as a dry air incursion above 700mb overruns the dryline by late afternoon.

Still early to make any solid forecast. Though in general the conditions so far are there for the development of one or two isolated stronger supercell development for the suggested region. ATM looks to be very localised, maybe?