05/07/05 FCST:Central Plains

[Kurt Silvey]

Well, looking at the latest GFS run (12z 4/30/05) I don’t see much to get excited about for most of the week. The large Canadian low is keeping the northern and central plains locked in with frigid northerly winds at least until midweek. Wed. we should see this system spin itself off into the North Atlantic, and southerly winds begin to return to the plains. The southerly winds should bring warm gulf air and moisture to the upper plains by Fri & Sat, with Dp’s possibly reaching 60. It appears there could be a couple of short waves pass through the central plains Wed. & Thur., but they don’t look too exciting at this time. Later in the week, the models have a neg. tilted system moving into the central / northern plains from the northwest. By Sat. morning this system could be tracking along the CO / WY border and provide an area of upper air divergence over central KS & NE, and a mid level Vort Max in ne CO. The surface low located in the corners of CO, WY, & NE should track ne during the day. At this time I don’t see much change in the wind directions from the upper levels down, except a slight backing from sw to south at the surface. This is all a long way out & could change or not develop at all.

 

[Dan Hawblitzel]

I wouldn't get too excited over this one until the GFS can maintain this forecast within 120 hrs or less. There seems to be this perpetual southwest trough stuck within the 156-228 hour time frame every run for the past week. I think the GFS has been too eager to kick out these Hudson lows this season which has been making its longrange forecasts pretty useless. But, this thing can't spin up there forever so hopefully soon the GFS will be correct in spitting out a nice shortwave into the plains. I of course would like to see the current forecast pan out since it falls on a weekend.

 

[Bob Schafer]

Anyone else believe, as I do, that the southern jet needs to calm down in the spring before the "serious" chase season starts? I've reached that conclusion over the last couple years.
That thing has been howling all spring this year.

You can't see much change at 250mb, but run a 500mb GFS loop.

 

[Ben Prusia]

The 0Z and 6Z GFS from today still show this system, though now it is in extreme northern North Dakota and extreme southern Canada (I don't know what province that is located north of North Dakota). It looks rather potent, and I see some moisture finally coming up to that area, TD getting up to around 55 to 60 along the Canadian/US border. One thing that is not there for severe weather development is upper level winds (less than 30 knots at 500mb). As I see it right now, it is still too far for the GFS model which has been pretty bad at verifying items at the long range and odds are is that it will shift dramatically south, dramatically north, or weaken dramatically to like 1009mb (like last week on Friday). On the other hand, I see some good moisture building into the Southern/Central Plains, but where is the storm system for them?

 

[Adam Atkins]

Next Weekend

This thread may have to be expanded to include the 6th and 8th if things keep speeding up the way they have according to the GFS in the low levels. The LLJ kicks back in midweek and a very nice longwave tough is going to drape itself across the intermountain west. You've got to love May. Anybody else think it's a coincidence things start looking good right before finals week?

 

[Bill Tabor]

I hope this latest run is wrong because I have no desire to drive all the way from south central Tx to North Dakota / Minnesota just to start a chase. I'd maybe go there if already in say Nebraska. What I'm seeing on the GFS doesn't look too organized, and still may be a GFS error / myth. Suffice it to say IMO so far this week doesn't look too good for chasing.

As for someones comment about the need for the southern branch of the jet to settle down....I don't think that is the problem. The southern branch can help do some good stuff such as when you have split jet flow. I think the problem this year has been the timing of the surface and mid level lows compared to when the last strong cold front pushed through and jettisoned all our good moisture far into the Gulf. Too many times we have had the nice sfc and mid low with not much moisture to really crank things up. I guess a better question is why is it out of sync? Right now I'm not sure and would have to evaluate a larger map, but probably has to do with position of blocking lows / highs.

It kind of looks to me that the pattern has now changed and what you're seeing on the 7th is a sign of that; however right now I don't like what I see and I don't necessarily think that the far north ND setup is what the model is changing to. I'm thinking it may be more of a wobble as it restabilizes to a new pattern. Hopefully that new pattern, perhaps coming next week will be something like TX Panhandle, OK, KS and NE. Or, we may have a week or two of 'wobble' before something good sets up again.

 

[Amos Magliocco]

Wow, have to disagree about the prospects on the new GFS. To me it looks very promising, with the potential to run chasers ragged for an extended period.

It seems to me that you can't take the day to day solutions literally past 120 or so, such as whether or not there's a deep surface low in exactly the right spot on the 168 hour panel. I think you have to look at the medium progs sort of like an abstract painting, where large scale synoptic trends are suggested, where low level flow screaming from the GOM on a daily basis suggests from experience what happens when midlevel westerlies carrying shortwave energy overspread a juiced airmass. Add a dash of climo which suggests that South Dakota is never the place to be the first week of May, and I think the picture becomes clearer.

To keep my post on topic, concerning the prospects on May 7th specifically, I think the Texas Panhandle looks like a strong contender for dryline storms given sufficient recovery from a primed, post high-pressure GOM. Directional shear is impressive and surface temps may actually be a little lower than normal considering the current regime, which could help reduce dewpoint depressions and storm bases in a spot already well elevated. A little early to make specific calls, so I post this mainly to comply with forum rules.

 

[Jay McCoy]

I have to agree with Amos on this one. It looks like a possible tx panhandle dryline day with the dryline close to the tx/nm border. The temps will be close to our below normal and the 700mb temps are up so getting through the cap is the only big issue but that will just keep the storms more isolated anyway. I see a true red box day finally for the southern plains. Now if the models will just stay consistent.

 

[Michael P. Morris]

Jared - awesome mammatus! And they are so close to the ground as well.

As for Friday, I almost think we could have a split event with South Dakota and Western Oklahoma as the most active areas. The surface low passes on the NE/SD border at 0Z Sunday (12Z GFS) and good moisture pooling in the warm sector combined with cold air aloft (700 mb freezing isotherm is on the US-Canada border) will provide plenty of CAPE for updrafts that can get going. Speed and directional shear are there with a deep LLJ out of the SW at 30+ knots and decent 500 flow. Weak midlevel flow with big instability means HP supercells though which is no good IMO.

Oklahoma may be a different story because we have basically all the things I mentioned for NE/SD except a strong surface low. The forcing in this case will be convergence along the dryline along with significant midlevel vorticity advection in advance of a shortwave. Stronger flow at 500 mb will also allow storms to be more classic in nature. I really like the shear in this area as well and think that if the event verifies Western Oklahoma/the Texas Panhandle will see a significant outbreak.

Of course, this is all based off of the 132 hour forecast from the 12Z GFS. Things are more than likely to change with the next couple of runs.

 

[Dan Hawblitzel]

I'm optimistic with the relatively decent run-to-run consistency of the GFS after this thread was created on Saturday. 5 runs later and we're still looking at a potentially active day with a progged negatively-tilted midlevel shortwave ejecting into the high plains.

This morning's GFS paints a promising picture for the Texas panhandle with excellent dynamics and such. I'm interested to see how this forecast evolves, especially once it enters the NAM's forecast period.

Of course, ask anyone in the region of interest their opinion of chasing this weekend, and they'll probably ask you to get back to them once it stops snowing.

 

[Dan Cook]

I know this is waay out there and for the Plains, but Davenport's lastest discussion might open up hope here for us around this time:

ITS EARLY OF COURSE...
BUT CURRENTLY PROGGED SIGNALS ARE SUGGESTING A SET UP WITH UPPER
DYNAMICS AND INCREASING LLJ MOISTURE FEED TO PRODUCE SOME STRONG/
SIGNIFICANT STORMS IN THE MIDWEST FOR THE SECOND HALF OF THE WEEKEND
AND INTO EARLY NEXT WEEK

Temps are supposed to be returning to the 70s and possibly 80s, dewpoints so far are nice as well.

 

[Justin Walker]

This system is taking shape nicely now. Good directional shear from sfc to 500mb, although fairly unidirectional from 500mb and up. However that is enough directional low level shear to get things cranking in west tx. And another thing, we might actually get some real gulf moisture to work with this system. Southerly flow seems to get moving late wed. into thurs, so will have decent moisture to work with. This will give us around 2000 J/KG Cape.

NWS forecast discussion in AMA wording seems encourageing for chasers:

AND AT THIS POINT IT
APPEARS THAT THE DRY LINE WILL SET UP IN EASTERN NM. DEEP UPPER LOW
WILL BE SWEEPING TOWARD THE PANHANDLES SATURDAY MORNING SO THE
ENVIRONMENT SHOULD BE PRIMED FOR THUNDERSTORMS.

EDIT: Hmmm....snow and possible tornados in west tx...how fun!!!

 

[Tony Laubach]

A handful of posts have been removed from this thread due to their lack of actually FORECASTING. General comments about this system (including cheers that its happening and boos that its 30 degrees) can be thrown into a TALK thread regarding this particular date. Please remember the TARGET AREA guidlines before making a post.

Thanks,
Tony

 

[Karen Politte]

:?

I'm having a very hard time ascertaining where people are getting information to conclude that this coming weekend's system looks to have good Gulf moisture to work with.

The models maintain surface-HI pressure on the east coast most of this week - and by Saturday May 7th's morning this HI pressure seems settled in to stay over SC - with it's dirty big foot planted right in the gulf. This brings northeasterlies in the GoM until at least 12Z Saturday (look at MSLP on the models).

Accordingly, by the forecast period, dewpoints are struggling to reach 60oF around the Red River. IMO, this does NOT bode well for moisture - especially out west in the TX/OK Panhandles where many are alluding their targets to be.

This system may be worth chasing just because we've hardly had anything out that way to chase recently, and it might be one of the final encores for the Southern Plains' 2005 season. But I wouldn't get my hopes up, nor expect the Gulf to be "open for business" - because it's not. I don't like my fetch coming from Kentucky, personally......

It takes a helluva lot more than just plain southerly winds over the central and southern Plains to give you the true GoM moisture you're looking for......that wind can suck and suck and suck for weeks on end - but if it's origin is the east coast......you're hosed.

KR

 

[Jeff Snyder]

Bill,

I think she's talking about trajectories... Sure, we may be having southerly flow in the plains, but if the central/northern/easter Gulf is seeing northerly-northeasterly-easterly winds, then chances are, it's just continental air being recycled off the US coast, into the Gulf, and back into the plains. It can modify, yes, but it's origins are still from the dry land, so moisture depth is usually an issue. Heck, we've dealt with modified continental air all season, and it where it's gotten us... You've basically been screwed unless you chased the 40 Tds under the mid-level low in KS earlier this spring... I personally don't think we're going to have enough moisture into the plains for this FCST day, and I think the following day will be a close call as well... It looks like we finally get low-mid 60s into the Plains for Sunday, right in time for finals... Even with that, however, I don't think 63-65 Tds in the southern plains with this kind of setup is really going to yield too much, but I'm getting ahead of myself a bit...