05/07/05: TALK: Southern/Central Plains

Here's a talk thread for the 7th...

It appears that SUN will be holding more widespread action then SAT will, but SAT still appears quite favorable for severe weather across W OK/TX/KS. I see a problem with moisture, but as someone said earlier in the FCST thread, supercells can EASILY form in 60F dew points. I'm currently liking W OK...
 
I dont know if I would call it "quite favorable" at this time. The latest model runs I analyzed today have a nice dry line from central Nebraska into the western panhandle of Texas. Forecast temperatures of at least 80F are located ahead of this boundary. Surface winds from the south, possibly a slight backing of the winds ahead of the dry line.
The main problem isn't so much with moisture or WAA advection on this one, its the shear. I could see some multi-cell clusters or a squall line from this setup, but the chance for tornadoes would not be very high. The upper-air winds at 250mb are forecast to be SW and even SSW along the dryline. The best chance for rotating storms would probably be closer to Texas, according to the latest model data, but this will probably change at least slightly.
Until we get a bit closer to Saturday, I wouldn't say much more than a chance of severe weather at this time.
 
I'm currently thinking W OK for SAT... And may I add that this next week could be an extremely active week. Severe thunderstorms are possible everyday (on the southern/central plains) starting Thursday and continuing into the next week...
 
Amarillo NWS is backing off a little on their POP's for T-storms. They are thinking less moisture. Any thoughts on this? Maybe chances are shifting a little farther north.

I was hoping to at least got onto some convection on Friday, even if it isn't severe. I still like Saturday for some more significant weather, and I'm not dissapointed by the way the weather looks after that.
 
Just from looking at the latest dewpoint forecasts, looks like Friday should still be fairly marginal. After Friday - dewpoints and therefore potential for instability generally increase across the plains - but convergence line may well already be E of Amarillo by then. Note the OKC long term HWO speaks of an increasing potential for severe over the weekend.
 
I am thinking the same as Mike, GFS shows the dryline a little more east, near the OK/TX border, it may be hard for east TX Pan. to get some storms. It looks like west OK's turn!
 
It looks as though things are finally setting up for the 7th and 8th. I was waiting for a good couple of days to begin my chase vacation and here they are. I am heading out later tonight from Northern Virginia (NOVA) and heading to the Central/Southern Plains. I hope to get out to NW KS for Friday and then play it from there for Saturday. As of now I am thinking W. OK or maybe the TX panhandle for the best setup Saturday. I have been planning like crazy and believe I have dotted every "j" and crossed every capital "I".

I can't wait to get out there yet again. If ya see me around on the plains come say hi, I am driving the black "honda" with three antennas on the trunk and the wifi antenna on the roof. Good luck everyone.
 
Boy, I can't wait to get out there and do some chasing myself. Saturday does look like a pretty descent day to be out and about. After the 5 inches of snow we had on May 2nd, I will be happy to see some storms. Looks like the eastern TX panhandle has the best opportunity for severe wx on Saturday.
Good luck to everyone!
 
The strong upper level system up in ND/SD/MN sure looks tempting to me, only if the upper level winds were better, but I am watching both of the setups. Since I'll be out on Friday, I'll have to make a crucial decision, head N to MN/ND/SD or south to OK/TX...

EDIT: Or as the SPC Day 3 looks, stay here in KS...
 
Originally posted by nickgrillo
Here's a talk thread for the 7th...

It appears that SUN will be holding more widespread action then SAT will, but SAT still appears quite favorable for severe weather across W OK/TX/KS. I see a problem with moisture, but as someone said earlier in the FCST thread, supercells can EASILY form in 60F dew points. I'm currently liking W OK...

Cut y'all a deal... Keep the weather in OK and TX for the weekend and send it up to KS next week. I've got a turkey hunt with friends I haven't seen in 3 years and I'm not missing it!


JH
 
From the new SPC 3-Day outlook...

Originally posted by Broyles of SPC


NAM AND GFS SHOW A DISTURBANCE MOVING ACROSS OK AND KS BY EARLY EVENING WITH FORECAST SOUNDINGS SHOWING 0-6 KM SHEAR VALUES OF 35 TO 45 KT. THIS SHOULD BE MORE THAN SUFFICIENT FOR SUPERCELLS. AN UPGRADE TO MODERATE RISK MAY BECOME NECESSARY IN LATER OUTLOOKS

Glad I'm not the only one liking the set-up for Saturday. I believe that this is the only possibility for tornadic supercells during the entire weekend with this first trof. The low-level shear in SD in vicinity of the surface low should be sufficient, but one has to think the the Td's are being overdone in that area. Shear will be in place across the Plains on Saturday before the forcing goes linear on Sunday. Td's won't need to be too incredible to get some High Plains tornadoes out in Western OK and KS. It is reassuring that the NAM and GFS are in sync now as well, the 84-hour NAM isn't even worth looking at with its awful performance.

That being said next weeks system looks to be much more potent and could be the major outbreak of the severe season. Time to get back to work on a 25 page paer so I can get some chasing done in the midst of OU finals week!
 
I'm a little bit baffled with the SPC's decision to include the area with some of the best tornado potential in a 15% risk. I really can't see any justification for this...

I agree that the upper level winds are a bit weak, but are more then sufficant enough to support supercells/tornadoes (especially across NW OK/SW-SC KS). I sure hope they decide to upgrade by the 1730...
 
25% and hatched doesnt always mean tornadoes, it can also spell slop and disorginization. And large HP sups. But farther south in SC KS and N OK things look to be more discrete and isolated. Thats good, I would rather chase an isolated cell than a cell that keeps merging with other storms in its area. And SPC has there reasons for painting it that way but im sure things will definetly change by 1730. I did notice how early that posted Day two last night as well. Came out the same time Day 1 did and day one came out 15 minutes early. Was it rushed?
 
Originally posted by nickgrillo
I'm a little bit baffled with the SPC's decision to include the area with some of the best tornado potential in a 15% risk. I really can't see any justification for this...

I agree that the upper level winds are a bit weak, but are more then sufficant enough to support supercells/tornadoes (especially across NW OK/SW-SC KS). I sure hope they decide to upgrade by the 1730...

Yeah, I was surprised when I did not see a moderate risk, actually. Well, it looks good enough for me to drive up to northwest OK from Houston!
 
What are other's thoughts on the ETA's very aggressive progged moisture recovery for this Saturday's timeframe?

Today's 12Z May 06 ETA run forecasts a "dry hole" (due to overnight precip/MCS?) to move from central TX to around the SPS area by 1200UTC Saturday morning - with this area containing sub-50oF dewpoints. It THEN progs a VERY rapid turnaround in the afternoon bringing 60s across the board all the way through SPS, western OK, and up into South Dakota!!! By 00Z Sunday it plays around with 65oF dewpoints near SPS, too.

How realistic does the list think this is?? I don't quite know where it's getting it's moisture from - especially from taking a look at the current surface pattern and noting that there are NO 60-anything degree Tds onshore ANYWHERE in Texas, and also looking at buoy data and seeing that the highest dewpoint locatable in the Gulf is 63.0oF at Scenic-Route Station 42020 in the north-western Gulf.

I am wondering just *how* we are going to realize these ETA-progged 60-65oF dewpoints on Saturday evening from San Angelo to Fargo.

:?

I'm not being pessimistic - goodness only knows I want this higher-moisture resolution to verify......because I will, barring unforeseen circumstances like grungefest - be out there.

KR
 
It THEN progs a VERY rapid turnaround in the afternoon bringing 60s across the board all the way through SPS, western OK, and up into South Dakota!!!

http://www.rap.ucar.edu/weather/surface/sfc_ict.gif

http://weather.cod.edu/forecast/ETA/previo...0mb_dewp_18.gif

Last nights 0z eta at 18z looks pretty dang close to me(actually almost spot on up here). Temps have now risen and the sfc tds are holding nicely in the upper 50s with some low 60s in most of KS, NE and western IA. It is called pooling. If a convective cluster forms in sc SD or ne NE today and plows se I think one can count on that much more pooling south of it tomorrow.

http://www.rap.ucar.edu/weather/surface/sfc_aus.gif

Even did well down south too. This isn't saying tomorrows progs will be spot on, but at the same time I don't see it as being all that crazy.

Also, the gulf intrusion shunted decent moisture westward and that is likely what has travelled up here...just the long way into Mexico and sw TX. With the flow starting to come more off the gulf it is going to start pulling up that recycled air, but the good stuff isn't far behind. Maybe that is why the tds are falling off like rocks with heating down there right now. I hope that isn't what is in place up here on Saturday...though with added pooling and rapid transport it should all be ok.
 
Regarding Karen's question about the veractiy of quick dewpoint recovery, I believe in the case of this system, it has at least as much to do with the dynamics of convection as the source/quality of the heat and moisture. The height lines at 850mb are oriented very much north/south. Advection does not occur when the height lines are parallel to isolines (eg., isotherms); can't advect warm/moist air where it is already equally equally warm/moist as the "source." When the flow meets a more perpendicular isoline, however, positive advection occurs. That is why we are seeing with this system the phenomenon of dewpoints pooling in various places (eg South Dakota) over the plains. Think of it like a comet soaring overhead with a long, thin tail. In this particular case, it looks like we have a somewhat e/w isotherm kind of dropping south over night, perhaps in the wake of today's convection up north, and then tomorrow - boom - the 850mb flow hits it perpendicular and we see dewpoints rise rapidly during the day on Sat in places like N Central TX.
 
Originally posted by Karen Rhoden
What are other's thoughts on the ETA's very aggressive progged moisture recovery for this Saturday's timeframe?

Today's 12Z May 06 ETA run forecasts a \"dry hole\" (due to overnight precip/MCS?) to move from central TX to around the SPS area by 1200UTC Saturday morning - with this area containing sub-50oF dewpoints. It THEN progs a VERY rapid turnaround in the afternoon bringing 60s across the board all the way through SPS, western OK, and up into South Dakota!!! By 00Z Sunday it plays around with 65oF dewpoints near SPS, too.

How realistic does the list think this is?? I don't quite know where it's getting it's moisture from - especially from taking a look at the current surface pattern and noting that there are NO 60-anything degree Tds onshore ANYWHERE in Texas, and also looking at buoy data and seeing that the highest dewpoint locatable in the Gulf is 63.0oF at Scenic-Route Station 42020 in the north-western Gulf.

I am wondering just *how* we are going to realize these ETA-progged 60-65oF dewpoints on Saturday evening from San Angelo to Fargo.

:?

I'm not being pessimistic - goodness only knows I want this higher-moisture resolution to verify......because I will, barring unforeseen circumstances like grungefest - be out there.

KR

Karen,

I think that, with May now, we're starting to see the NAM pick up on diurnal increases in Tds courtesy of evapotranspiration (thank you plants!). There seems to have been nice daily diurnal fluctuations the past several days, so I think we can attribute the increase in Tds not to advection, but rather to evapotranspiration. Afterall, as you inferred, you can't get >60 tds from TX to the Dakota's in 12 hours. LOL I suppose you could, but would we really want to be chasing with synoptic-scale flow from the south at 80mph? LOL..

EDIT: Moved my discussion over to FCST thread.
 
Jeff Snyder wrote:

There seems to have been nice daily diurnal fluctuations the past several days, so I think we can attribute the increase in Tds not to advection, but rather to evapotranspiration

Oh, I agree - in general - the improvement in daytime Tds has much to do with evapotranspiration at this time of year. However, I think to explain the apparent anomaly of higher dewpoints much further north on the plains than dewpoints further south - followed by a reversal the next day - you have to look at the mechanics of advection, especially with a system such as the one we are forecasting now. That is why I mentioned not to worry too much about the source - the molecule pooling up in SD may not have travelled all the way from the gulf in a few hours - but it likely did advect from somewhere south, be it air over greener pasture or whatever.
 
I've spent this morning and afternoon looking at this.....still don't quite know what I'm thinking LOL, but...

Yes it's May and yes we have to be wary of evapotranspiration. I wonder if the massive amounts of ground saturation in the TX Panhandle over winter will come into play at all.

But aside from that - what I really think will be the driving factor behind attaining true moisture tomorrow may just be the Scenic Route. I would keep an eye south and west for your moisture......don't sit watching Houston's harbor......cause that ain't where it's going to come from this time!

Thanks to all who've discussed the mositure with me this afternoon. I agree with all of your points.

KR
 
Originally posted by Mike Johnston
Jeff Snyder wrote:

There seems to have been nice daily diurnal fluctuations the past several days, so I think we can attribute the increase in Tds not to advection, but rather to evapotranspiration

Oh, I agree - in general - the improvement in daytime Tds has much to do with evapotranspiration at this time of year. However, I think to explain the apparent anomaly of higher dewpoints much further north on the plains than dewpoints further south - followed by a reversal the next day - you have to look at the mechanics of advection, especially with a system such as the one we are forecasting now. That is why I mentioned not to worry too much about the source - the molecule pooling up in SD may not have travelled all the way from the gulf in a few hours - but it likely did advect from somewhere south, be it air over greener pasture or whatever.

Mike,

My comment was in connection to the increase in Tds from the 50s in the morning to the 60s by afternoon across most of the plains. A large-scale increase in Tds in ~12 hours during the day signals evapotranspiration primarily. This higher-Td air can then be advected elsewhere, as you noted in your example of advection from some greener pasture. There will also probably be some moisture pooling owing to decent surface convergence, especially in the northern plains. Minor large-scale moisture advection has been occurring courtesy of the southerly flow bringing up SOME moisture from the Gulf as well. At any rate, I should end this since it's going off-thread.
 
Evapotranspiration !! Look at the amount of rainfall we've had (heck, even snow) over the plains/high plains regions. OK Mesonet already shows 60 degree dewpoints in Altus, and many other places... even as far north as Alva, OK.

That's my answer. I don't think this is TRUE gulf flow of 70 degree dewpoints, I think it's modified continental air that, by this time of year, coupled with evapotransporation, can get DPs well close to 70 degrees.

The moisture, however shallow, is moisture, and I'll take it !!! :wink:

In addition, I don't want HP cells anyway. Too tough to mess with. Give me a few classic dryline cells and keep them out over some picturesque countryside, oh what fun !! :D
 
I note an area of thundershowers/precip located around Midland TX and moving far northeast of there towards the Oklahoma border. Much of this may not be reaching the ground nearer OK, but the Midland stuff is moving NE and definitely raining on somebody.

It will be interesting to see what effects this precip. causes over tonight. Will it moisten things a bit more? Will it lay down boundaries around CDS that get long-forgotten by T-time tomorrow?? Is this a sign of moisture creeping northwards??

Hmmmmm......

KR
 
All of the above, Karen. :wink:

Any moisture will only enhance what we already have in place, and boundaries left over from any overnight convection can only help as well.

As far as an indication of returning moisture, I just don't think it's TRUE gulf moisture returning. As Jeff refers to it quite often, I think we're just seeing modified cont. air returning on the southerly winds. I think now that we've pretty well reached capacity on our vegetation "greenage", it's now going to be very difficult to supress our dewpoints lower than ~45 degrees, even after the dryline passes (speaking for central Oklahoma). Yes, I know, high plains, different story. Later in June, different story... as vegetation is cut and dries with the summer sun.

I think the next 4 weeks are our best time, as everyone will likely agree, for seeing action in our area (central Oklahoma), but I still don't see a major gulf airmass today, more moisture flux coming in by Sunday leaves me VERY optimistic then, and ESPECIALLY NEXT WEEK, but keeping on focus for this particular talk thread for tomorrow, I think the excitement should be building in everyone for some good potential dryline stuff tomorrow afternoon.
 
Dick McGowan and I will be heading out west from KC area by 9:00 this morning. Our plan is to make directly for the crossroads of Salina via I-70, to arrive by noon, and pause to evaluate guidance at that point. Our current thinking is Salina will put us at the SE base of a target box extending to Hayes area to the W, and up through Concordia, KS to York, NE to the N via US 81. Like the chances for greater upper level flow and proximity to approaching dry line to the W of Salina, but SPC's higher tornado probability area currently forecast to the N of Salina. Hopefully, we will at least have a mesoscale discussion out by shortly after noon that we can hang our hat on.

Good luck to all chasing today!
 
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