4/10/05 FCST: Southern/Central Plains

[Tom Dulong]

GFS has been consistent past couple runs of digging an upper low across the central/southern Rockies and cutting it off over Southern Plains by Sunday. Ensemble mean products support this scenario, with relatively small spread in the spagetti plots.

See http://www.cdc.noaa.gov/map/images/ens/ens.html#us

This could be the change in the pattern we have been looking for to finally open up the Gulf of Mexico big-time. Confidence that this will pan out is low-meduim at this point, but will definitely rise if successive model runs remain consistent over the next 48 hours.

Although the focus of this forecast is for Sunday, the potential severe weather event could extend to Monday or even Tuesday if the low system
stalls.

 

[Jeff Snyder]

The only problem is that, AGAIN this time, we'll likely be dealing with MODIFIED continental air, not true Gulf / tropical air, so we'll yet again be dealing with trying to make the best of low-mid 60s. The overall synoptic pattern looks sufficient, but I'm concerned with Gulf moisture (upper 60s / low 70s Tds) again...

 

[nickgrillo]

Yes ... thanks for that! I've been noticing this system for the past few days in the GFS runs, and it's looking pretty darn good ... although I do strongly agree what Jeff said.

Next week could be good for severe weather ... with the threat shifting into the Midwest by Tuesday or Wednesday-ish even.

Here's my latest outlook graphic for April 10th and 11th:
http://midwestchase.com/wxforecasts/04_10-11_05-1.gif

..Nick..

 

[Tom Dulong]

Next week could be good for severe weather ... with the threat shifting into the Midwest by Tuesday or Wednesday-ish even.

Here's my latest outlook graphic for April 10th and 11th:
http://midwestchase.com/wxforecasts/04_10-11_05-1.gif

..Nick..

I understand the concerns about getting good gulf moisture. However, if the low parks up against the southern rockies for 24-48 hours, this should not be an issue.

I concur with Nick's outlook map for 10th-11th. I would even suggest placing a small slight risk area for eastern CO late on the 9th. You only need surface dewpoints in the mid 40s here for severe, given the dynamics are present.

 

[Adam Atkins]

4/10

In my opinion, I'm just fine with low-mid 60's dewpoints any time during the spring. If a storm gets its act together it can modify its thermodynamic environment substantially, espcially via the rear flank downdraft. When cooler, moist air is entrained into the updraft, LCLs can be lowered enough for tornadoes. My concern for this weekend's system is yet another cutoff low will be the mechanism for lift across the plains. I won't chase on days were the shear is dominated by unidirectional winds. A good example of why is yesterday's squall line. Even with a huge cap, the forcing was strong enough to overcome it and blew up a severe line of storms that killed any chance of discrete, tornadic, supercells. The winds seem backed at the low levels more this weekend than yesterday, but 500 mb flow north of the red river is weak, difluent and due south. The best chance for veered mid-level flow will be south into central TX, near the base of the upper level cyclone. I'm still waiting for a longwave trough to park itself across the Pacific northwest and send shortwaves flying over the Rockies day after day...can you believe May is less than a month away?

 

[Jeff Snyder]

Based on tonight's runs... It appears that my two concerns for this possible event are addressed above. First off, there will moderately-strong northwesterly winds throughout much of the Gulf at 850mb though Friday evening, which will scour out the true Gulf moist (YET AGAIN!)...Looking at surface winds, it appears that the front makes it to about the Yucatan before moving back northward on Saturday, though I fear (and models seem to indicate) that we'll be dealing with modified continental air again, so we'll probably be hard-pressed to get those mid-60 Tds.

Secondly, as Adam mentioned, the position of the closed-off 500mb low means that much of OK will be experiencing backed mid-level flow, which acts to minimize deep-layer shear and makes the deep-layer shear vector orientation more parallel (less normal) to the dryline. Therefore, it looks more like a Texas chase for those who favor discrete activity. All in all, it looks quite a bit like the low that touched off the squall line and few supercells Tuesday...

Even if this one is a dud (it's waaaaay to early to tell imo), it certainly appears that it will NOT, unlike it's past comrades from the past few weeks, completely wipe out (scour) the Gulf. Yay! With a high over the Gulf, the low-level flow should remain more westerly through the northern Gulf, and not really allow for the penetration of continental air into the heart of the Gulf. I suppose I need to stop this discussion here, since I'm digressing from the main topic...

Heck, the way things have been going this year, maybe I'll try my hand at cold-core tornadoes... Gosh knows that we'll see more tornado activity with upper 40 Tds than the warm-sector will... :?

 

[Bob Schafer]

Talk about a closed low....

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...fs_200_096m.gif

GFS has it just about closed at 200mb, and 11760 meters? That's what, ~37,000 feet?

Is it just me, or is that bizarre for April 10?

Bob

(Setting new record for latest "first chase of the year" every day now)

 

[Brett Adair]

Talk about a closed low....

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...fs_200_096m.gif

GFS has it just about closed at 200mb, and 11760 meters? That's what, ~37,000 feet?

Is it just me, or is that bizarre for April 10?

Bob

(Setting new record for latest "first chase of the year" every day now)

Very bizarre, Bob. I have to agree that sections of the SRN Plains will crash and burn yet again due to the weakness of the low level flow. Looks like this could be setting up for portions of MS/AL again though...

 

[Karen Politte]

IMO there really is nothing spectacularly unusual about the current setup we're in. Early April cold fronts come through, giving slight chances of severe, and then scour us out for a week or so. So what?

Considering it's only April 7th, I'm not exactly quaking in my boots about the last system or the next system. I'm not getting desperate and I certainly won't be pressing myself into kilo-mile drives unless the situation looks favorable. I am quite content to wait for May - I really don't mind. Really.

By 0Z Mon 11th the Eta hints at 60oF dewpoints once again sneaking up the I-35 corridor. I don't put much faith in models, but I do use them for pattern recognition. This next systems looks like the same song, second verse of two days ago - and to depress some of you even more I don't see the GFS hinting at 60-degree dewpoints ANYWHERE north of DFW in the next 180hrs. It will be interesting to see how underdone that is......if at all. :?

Through a week today (Thurs April 7th) the dewpoints are still looking too mixed and dry in the northern Gulf....and so now my "honesty" clause: Honestly - I'd start fixing my sights on the last week in April and the whole of May. With 2.20 gas in OUN, I wouldn't waste my time with many of these closed, weakening lows as they slide lethargically into northwestern Oklahoma - they just-don't-work (*!most of the time!*). It's great to get that first chase of the year out of the way - which we did on March 21st along with everybody else - but right now I'd really like to see some "real" storms out west. I'll bide my time, and my gas money......

FWIW, if this pattern keeps up - I'd love to see some discussion about what may come of the Texas and Oklahoma Panhandles come mid-May (!!!). Mr. Drummond and Mr. McCoy might be living in 2005's tornado alley. :wink:

KR

P.S. - If I went a whole spring through July with nothing higher than low-60 dewpoints...I think I'd go insane. :wink:

 

[Robert Dewey]

SE Nebraska looks pretty good, as of right now, on the 12Z NAM. That area has the highest combination of CAPE + helicity, but it looks more like a mini-supercell setup. That area is just along the 850mb thermal axis at 0Z MON, and just west of the 700mb thermal axis, so if there is a CAP in place, it will be weakening rapidly as the shortwave slides east. Not too excited though, I would really like to see the 500mb jet max push a little further north into that area. The stuff in KS and OK may be nice and isolated, as forcing doesn't look overly impressive, and there appears to be a CAP in place, as evident on the 700mb temp chart and lack of QPF as of 0Z MON.

This looks very similar to the last event, just a bit further west, and less forcing. I would play the SFC low...

 

[Tony Laubach]

I've been spending most of today looking over the snow potential in Denver, but I have taken some time to check out the potential for chasing elsewhere..

I'm forced to agree with Karen on this one... it has the ring of the past systems that have passed over the Plains; squallish, little storm isolation, etc. The one thing that keeps me very interesting in chase possibilities is the time I have to chase this. A slow moving system moving across the area Sunday into Monday makes for a good couple days in terms of synoptic setup.

The low again seems to be the place to aim as shown by the previous systems we've encountered. I nailed my forecast in the last system by calling best tornado potential near the low, but bit on the eastern setups and abandoned my target area to the west. While there are some differences that make this system a bit more appealing (not much, mind you), I would go out on a limb right now to say that your best chances for tornadoes will be within the vicinity of the low where vorticity will be at a max.

Meager moisture again plays a part as the Gulf still isn't fully opened to bringing rich TDs northward. I think the southern areas of this system may see some isolation, I think storms in North Texas, Oklahoma (including Panhandles), and Kansas will have a harder time finding isolation.

Again, it's still a bit early to rush to judgement on this system, but the climatology of the last 45 days indicates to me that we should expect much of the same with this system. As it stands right now, if I were to go out, I would STAY WITH THE LOW this time! :lol:

Early long-reach targets...

Sunday: Eastern Panhandles
Monday: North-Central/NE Oklahoma, Southeast Kansas

EDIT: HWO in Tulsa using VERY strong words to describe Sunday's potential...

ALTHOUGH THERE ARE UNCERTAINTIES CONCERNING THE EXACT TIMING AND SEVERITY...LATEST DATA INDICATES THAT SUPERCELL STORMS WILL BE POSSIBLE WITH THE THREAT FOR VERY LARGE HAIL...DAMAGING DOWNBURST WINDS AND TORNADOES. THE SEVERE WEATHER THREATS AND EXACT TIMING WILL CONTINUE TO BE REFINED ON LATER FORECASTS.

 

[Robert Dewey]

I'm forced to agree with Karen on this one... it has the ring of the past systems that have passed over the Plains; squallish, little storm isolation, etc.

If that even...

There is no QPF output even by 0z MON... And the 700mb thermal ridge is right overhead. My guess is that the lack of strong forcing precludes the development of significant QPF across that area... Things may be isolated at the beginning, but since this the 84hr time stamp on the NAM, can't say for sure what happens after 0z MON (i.e. massive squall line breaks out as forcing dramatically increases)... Not to mention that the model may not be correct...

Anyway, I'm with ya... I would stick near the SFC low, or just east/northeast of it... This looks like a mirror image of the past system, with perhaps a stronger CAP and weaker forcing over eastern OK/KS...

 

[Tom Dulong]

Here's my latest outlook graphic for Sunday:
http://midwestchase.com/wxforecasts/04_10_05-1.gif

I see a slight risk for severe thunderstorms, including a few tornadoes ... stretching from northcentral Texas into Iowa. NAM has CAPE of 2500 J/KG stretching from C OK ... into C KS and into SE NE/C IA. -12 LI in NE Kansas at 0z Monday ... with 60F dew points and a 70F temperature ... with the low situated in western Kansas at 0z.

eastern Kansas looks the best to me as of now.

..Nick..

After pondering the latest from the models, I generally agree with Nick's forecast area and his reasoning behind it. The only changes I might suggest would be taking the northwest portion toward northwest Kansas and the northeast quadrant of the low. Also, noting similarities with the March 17, 2003 event in this area, central KS to southwest OK look almost as good as eastern Kansas. Surface dews were only in the 50s to lower 60s that day, too. Link to March 17 2003 case is

http://www.spc.noaa.gov/exper/archive/even...0317/index.html

 

[Bob Schafer]

I don't like OK/TX for a target because of unidirectional wind fields (squall probabilities).

The way this thing looks to be stacked up, the only place I want to be is invof theta-e ridge and helicity, i.e. N KS. Whether hugging the sfc low or not is my quandary, but when all else seems equal, I stay closer to home.

I'll predict that the storm reports pattern won't look anything like 030317, though. I expect a WSW/ENE orientation along that wf come Monday.

Bob

 

[Ben Prusia]

I agree with everybody this time with the attitude of staying with the low. So far, the GFS and the NAM are still a little away from setting the path of the low, but so far, I think that the area of Kansas to the east of US Highway 81 and south of US Highway 36 stand the best possibility of severe weather. With LI's of -10, CAPES of 2500, Td's of 55-60, and Surface Temps of 75-80, this area might hold more potential than other areas.

But thinking of the unsuccessful chase I had last Tuesday, I might want to stay away from the dryline and want to stay closer to the Low. I'll update with a more precise forecast tomorrow.