3/29/05 FCST : Plains

[Ben Prusia]

Looks like the Plains are in for a beating come next Tuesday. I did some looking on the long range on the GFS and it looks like a major storm is coming in. Temps are predicted to be around 65 degrees for most of eastern Kansas with Td's coming into the 60's in the same area. This is my first attempt to make a target area post for a date that is far in advance, I'm still a freshman meteorology student, so correct me if I am wrong!

I also noticed the KC/Pleasant Hill NWS HWO mention this in their outlook for Tuesday:

UPDATED PORTION...BY MID WEEK NEXT WEEK...A PATTERN CHANGE SHOULD BE
TAKING PLACE THAT MAY RESULT IN A MORE WIDESPREAD OUTBREAK OF SEVERE
WEATHER. WITH THE TIMING AND EXACT TRACK OF THIS SYSTEM STILL VERY
UNCERTAIN...

 

[Dan Cook]

Looking at the 180 GFS is showing a potant looking low in that area.

http://www.rap.ucar.edu/weather/model/gfs1...hr_sfc_mslp.gif

Shear wouldn't be a problem either.

http://www.rap.ucar.edu/weather/model/gfs1...0hr_500_wnd.gif

 

[Mikey Gribble]

Tuesday is still a long way off, but it is looking good so far. Here is a quote from Wichita NWS,
IF WE CAN GET DECENT MOISTURE RETURN INTO THE PLAINS TUESDAY
AND THE BIG ASSUMPTION THAT THE ECMWF IS GOING TO PAN OUT, TUESDAY
COULD BE AN INTERESTING DAY.

 

[Dan Cook]

They're still talking about an outbreak for that period.

Also, the Low deepens to 987 on GFS:

http://www.rap.ucar.edu/weather/model/disp...hr156hr168hr180

 

[Jeff Snyder]

The big problem with this low will again be meager surface moisture. With 30-40kt northwesterly flow across the Gulf on the heels of this weekend's low, it's going to be dang tough to get any significant moisture into the Plains, even modified continental air, much less true tropical air. The kinematics look just fine, but the thermodynamics are going to be difficult to get in order (which isn't uncommon for this time of year)...

 

[Karen Politte]

I glanced at the GFS for this posted date just now. I don't like what I see with the models showing no real low-level focus in the form of a low.

The moisture looks hosed for this time period - with a dirty big anticylone over the northern Gulf sure to send the moisture return screwy if it verifies. It has dewpoints in the low 50s progged for the norhtern Gulf by 0Z Wed 30th.

However, this all may be because this system/trough is trying to hold off until Wednesday 30th until pulling out onto the Plains - which would give us perhaps a little better chance at moisture return. I will look at this - and if it seems feasible, will start another FCST thread in here for Wed March 30th.

KR

 

[Ben Prusia]

Yeah I just verified the GFS and it appears that the system is moving slower. 12Z GFS also has the L at 1001, so we will see if this storm will pan out, if possible.

Pleasant Hill still mentions of severe weather, but has the weather further south than Kansas City, rather in the southern Plains, and this storm would happen on Wednesday, rather than on Tuesday as this date was set. I have enclosed part of the Forecast Discussion that the Pleasant Hill NWS put out at 3 this afternoon:

Originally posted by Kansas City Forecast Discussion

THE
MEDIUM RANGE MODELS ADVERTISE STRONG FORCING AND IMPRESSIVE WIND
SHEAR, SO A SEVERE OUTBREAK MAY BE IN THE CARDS, ESPECIALLY FOR
PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY.

 

[Karen Politte]

Originally posted by Ben Prusia
Pleasant Hill still mentions of severe weather, but has the weather further south than Kansas City, rather in the southern Plains, and this storm would happen on Wednesday, rather than on Tuesday as this date was set.

LOL - don't sound so down about the possibility of storms being further south - that's what I (and a lot of people!) are hoping for at this time of year, I think you'll find.

I'm not really bothered about what all the WFOs are thinking right now......I'm trusting my own interpretation of the models to see what's supposed to happen.

I am awaiting some newer models runs before seeing if a date change/new FCST thread needs to happen for this event next week. I'm still not impressed with moisture return signatures so far, but I don't think the GFS has a good handle on any of it, right now.

KR

 

[Mike Hollingshead]

For those that look at this before 0z Sat. The gfs has been trending negatively on the system mentioned(last 3 runs anyway). Even at that it still does manage to bring some >60 TDs up into the central plains by 132hr(with weak sfc reflection too). It is kicking out a positive tilt trough which of course no one wants. I found this interesting difference between the eta and gfs at 84hr. I would think the jet orientation off the nw coast would stand a better chance at kicking out a more neutral to negatively tilted trough than the gfs is showing at the same time. Is there any truth to this? To me the 84hr jet on the eta says neg tilt to follow more-so than the 84hr gfs. It looks to allow something to dig more. Just an ob.

http://www.rap.ucar.edu/weather/model/eta8...4hr_300_wnd.gif

http://www.rap.ucar.edu/weather/model/gfs0...4hr_300_wnd.gif

 

[Jeff Snyder]

It's also interesting to note that the ECMWF provides a considerably different solution than the latest GFS... The European still has a strong (989mb I think) low in the central plains, rather than the washed-out trough solution that the GFS has trended towards. Regardless, I still feel that the 30-40kt northwesterly 850mb winds across the Gulf from late sunday to late Monday will wipe out any significant moisture available, especially if the GFS verifies, as it pushed the front all the way through the Gulf and into the northearn Carribean area! UGH! The ECMWF, however, would provide more optimism for chasing since it shows a strong low-level jet from the western Gulf / eastern TX northward, which would give us the best chance of getting any sort of real moisture up into the plains...

 

[Glen Romine]

This fish still looks too small to keep to me. I'd throw it back in and wait for the next system that should come out a few days later. A much more impressive storm is progged to come out around the 31 st in the latest series of medium range guidance - so +/- a day or so. The system on the 29th has looked progressively worse with time, of course the next system always looks better in long-range forecasts.

Glen

 

[Mike Umscheid]

Interesting setup for western Central KS today. Very impressive shortwv trough will be over the panhandles by afternoon with deep sub 990mb sfc low in western KS. Strong mid level CAA of -20C / 2C at H5/7 respectively means that only marginal moisture return is necessary for positive area on the sounding... about 800 J/kg of SB CAPE in a background environment of very strong upward vertical motion...should be enough to allow high-based supercell hailers. Some of the veterans like to call these types "Vacuum cleaner" supercells. High based, very photogenic most of the time, on the leading edge of the synoptic dry intrusion... target is Great Bend down to Medicine Lodge. Will finalize by noon when I wake up after recovering from this morning's mid shift.

Mike U

 

[Jeff Snyder]

Moisture is the obvious enemy today, though the 50 Tds have crossed the Red River, heading northward. Overall, it would have been nice to not have to be worrying about moisture yet again, since this sytem, along with the past couple, could have been quite good for chasers had we had enough moisture. That said, I guess I shouldnt' complain too much since that's what's often the limiter this time of year:

WERE IT NOT FOR THE LACK OF DEEP LL MOISTURE AND AN OVERABUNDANCE OF CIRRUS...THIS WOULD BE A CLASSIC SETUP FOR A PLAINS SEVERE WX OUTBREAK.

 

[Glen Romine]

Interesting scenario - as it seems the high cirrus shield has prevented deep boundary layer mixing and allowed the shallow but modest moisture to make good progress northward today. Coupled with the further south than expected track of the low - there is some posssibility of mid 50's dewpoints overlaid by nearly dry adiabatic lapse rates. Question then becomes if sufficient moisture pooling can occur ahead of the front to support convective initiation, and if the cloud cover limits heating too much to overcome the cap. So, perhaps a rogue high-based cell or two can get going in KS later today.

Glen

 

[JHadorn]

I don't know so much about today. Latest RUC pretty much nullifies CAPE today, with a pretty good capping inversion in place across much of the heartland. Of course I could be wrong since I'm unfamiliar with what values (as far as CIN goes) sugests a strong cap. I just don't like what I see. ETA also aggrees that CAPE is nil.


The dewpoints are looking good with 50's creeping up even into southeastern Nebraska (yay me). 60's in southeastern Kansas. Near 70's in parts of Oklahoma and Texas. GFS is a little more aggressive in respect to dewpoints for my area, putting it around 60.

LI's in the latest RUC aren't anything to write home about, unfortunately. Things look interesting on the 30th around 0z in northwest Kansas as far as LI values, but that's another discussion.

My limited understanding of all things forecast related tells me to bet conservatively and say nil on severe weather. At best I expect to see a few surprise severe cells, but even that's a wager I wouldn't put money on.