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04/20/05 FCST: South/Central/High Plains

Well, maybe it's time to save the sanity of those amongst us who live in the Southern Plains and try and put out a forecast for the first time in a while. The crystal ball prophecies lead me to post this for the 0Z Wed 20th April timeframe......

GFS has a small wave coming through the KS/OK/TX areas by this time. What is encouraging is that this is forecast to perhaps lean on the open-wave style of system - rather than the closed bowling balls we have seen of late. I'd much prefer to chase a more classical setup with a nice, broad open wave.......and while this one may not be too broad and the flow looks limited, there is still a long time to go before the models really have a handle on it.

A big concern is the rapid generation of a HI that sinks down into SW KS around this timeframe, also. :?

On the upside, the GFS's take on things forecasts dewpoints in much more abundance than we have seen so far this year - with 60's all the way up into Kansas.

As far as upper flow, it's currently looking like the TX/OK Panhandles may be under the gun.

Any takers/speculators?

KR
 
Karen, can see the more classic open low on the model you are looking at. However, looks to me like the strongest & divergent jet is still well south over Mexico. Is this what you are referring to re: upper flow, or am I missing something? BTW - I am a novice forecaster, let alone long-range forecaster, but I do enjoy reading the comments of yours and others who are looking ahead.

Interesting with the higher dewpoints; especially in light of Jeff Snyder's comments over in the other forum re: return flow being more of the recycled continental air rather than the true tropical variety, in light of the position of the high over SE CONUS in the days leading up to the target date. Perhaps we can begin to expect solar heating to compensate for such an effect?
 
Originally posted by Mike Johnston
BTW - I am a novice forecaster, let alone long-range forecaster, but I do enjoy reading the comments of yours and others who are looking ahead.


Mike - you and me both! :lol: I am by no means the most experienced/intelligent forecaster on here.....and sometimes I just open my mouth and let my belly rumble.

Here is the upper-airflow pattern I am referencing at the 500mb level of the atmosphere:

>>Image Removed<<

500mb is where we frequently have a habit of looking when we are searching for upper systems coming into our region for chaseable storms. At this time of year - we look for southwesterlies at 500mb in some sort of jet streak or strong flow pattern to suggest to us that a system is manifesting itself - perhaps. Seeing the constant toughiness in the GoM is concerning also - but I think that the upcoming system next week (whenever it happens) might have a better chance at getting this problem erradicated to a certain degree.

I'm sure there are more knowledgeable folks on here who could chime in about all this.......that moisture next week looks better but probably *NOT* true caribbean juice. But you have to take what you're given, I'm afraid.

KR
 
4/20

The setup for next wednesday will likely change plenty of times. Here's why I think severe weather will be limited to a small area along the gulf of Mexico. Tuesday night might be stormy across the southern plains in the form of a squall line that develops along a surface cold front diving southward. The 850mb 0 degree isotherm makes its way into N OK, not very pleasant for mid-April, after the cold front has passed. The surface features don't seem to be collocated with upper level support this go-around. The OUNAFD mentioned heavy rain to be the primary threat in this neck of the woods, probably due to the surface low along the gulf leading to strong isentropic ascent and latent heat release in conjunction with the surface frontal boundary.

The gulf coast may see one of the 1500 J/Kg CAPE days under complete cloudiness and have a moderate risk issued, solely because of the lack of any sort of cap.

On the plus side, April showers bring May winter wheat so we can get the evapotranspiration started and some higher Td's during the day here in OK. It seems the models have been picking up on this phenomenon in the high plains early next week, which could lead to some neat storms.
 
The waters are a bit muddy for the middle of next week - hence, I guess, why nobody else's taking the plunge with some speculation. So I'll have a go again to at least keep the engine running.....

There seems the potential for severe weather for the timeframe Tuesday April 19th through Thursday April 21st next week. I am thinking that Tuesday may just be too soon for this coming system - but we shall see. The GFS currently has it stuck out over Nevada/Utah on Tuesday, poised to come out the next day.

The ETA doesn't have this period in its sights yet and so the only guidance will be the GFS. I'm not too enthused with the ETA's record of handling these systems so far this year anyways - and so I am quite happy to live in the technicolor land of the GFS for now. One thing that IS evident is that this system will likely be some kind of closed-off low, yet again. It's getting boring, I know - but if it's the first chance in over a week and the last chance in just as long after then - I think we're all going to have to take a stab at it. The closed-low may take on a sort of neutral/negative-tilt characteristic as it comes out on Wednewday/Thursday - so that isn't all bad.

One encouraging thing is the GFS' predictions of mositure availability. Although - as many have discussed - it's highly unlikely to be the true Caribbean juice we are looking for - it WILL be present in greater quantities than previously - albeit modified. 60-degree dewpoints are STILL forecast to be available into Kansas - with the 65oF line teasing us around the Red River. I will have to look more in-depth at current moisture values in the Gulf......

Wednesday April 20th's area to watch may be just east of the surface low in western Kansas - but the positioning of this will almost certainly change with time. If the winds can stay backed sufficiently and the upper support is there - a jaunt into the OK/TX Panhandles for the dryline may also not be out of the question (assuming the mositure makes it that far west - whch it might not).

Just a wishcast - nothing more.

KR
 
Wow.....sheesh I'm the only one sticking my neck out, huh?

Well - the 12z GFS paints an interesting picture. I know you all probably aren't too bothered until like the end of the weekend or so - but the sad fact of the matter is that I have to forecast like this to some degree......as I need advance time to ask off work etc. etc.

Here is what the 12Z GFS shows for 00Z Friday 22nd April (Thursday 21st April 6PM CDT):

75872169891ffcf51143e3a0c33b6ce1.gif

It doesn't take much figuring to imagine that I'm vaguely excited, if this ever came to verify (yeah, right). Nice little jet max streaking across into SWrn KS/OK/tx Panhandles. It almost made me drool.

The moisture for this time period looks a bit grim - with the moisture axis too far east as I had feared. This may be one of those heartbreaking situations whereby it's a case of "what could have been if the moisture had made it".......

MSLP does make me smile somewhat, though - hinting at a nice low in Wrn KS with plenty of backed winds northeast of the low as well as down along the dryline (maybe).

We'll see......in the meantime, I will remain.

KR
 
Looks like we could have pretty steep lapse rates over the western KS and panhandle areas also. Share your concern about moisture, though, especially w/ the high surface temps.
 
MSLP does make me smile somewhat, though - hinting at a nice low in Wrn KS with plenty of backed winds northeast of the low as well as down along the dryline (maybe).

We'll see......in the meantime, I will remain.

KR

I'm in agreement with the few you have stuck their necks out. :D This system is beginning to look better. The winds look good throughout but the limiting factor will be the modified gulf air. But hey...it's April, low to mid 60's will do for me. As of now...I am clearing my schedule for Wednesday and hopefully will dry to play the dryline!! 8)
 
I think there is a decent chance of severe weather in SW Kansas and the panhandles on Wednesday, but the upper level winds are pretty pathetic. We might need to open up a fcst thread for the 21st before too long. Thursday is looking like it might shape up to be the best day in the plains with this system. Time will tell.
 
Still a very long way's out, but the 12z GFS seems to be hinting at a dryline bulge in West Central/Central Kansas... and most of us remember what happened there last time.

In an email exchange with Chris Rozoff (who points out the bulge), he's like me in saying something too soon, but if I were to reach out, I'd be playing Southwest Kansas with room to move south or north.

I think the moisture is gonna finally start being less and less of an issue as it seems the models are indicating good flow from the Gulf into the Plains (looking earlier this morning). But as mentioned above, the winds look kind of crappy...

This, still, is very far out, but worth a look. Hoping the winds inprove and some more GULF moisture can stream up. Looks like half of it will work its way in!
 
Thursday just fell apart with the OOZ run. Wednesday looks pretty much the same with the surface low a little farther South. 30-40 knot flow at 250mb does not get me very excited. The directional shear looks great. Speed shear is a completely different story though. I don't see much of a problem as far as moisture is concerned IMO. I am definitely not pumped about this setup, but I am thinking this is probably going to be our last warm-up chase before the real season starts at the very end of the month so I will probably end up going regardless.
 
A) I wouldn't judge anything by what this morning's models were saying, B) I see a lot of energy and potential with this next system and C) I would tune into the 0Z GFS run currently being issued. I think this morning's run was a burp in what otherwise may be a forecasted interesting event for TX/OK/KS this coming week.

However the above probably isn't too important - as most on here don't seem very enthused about discussing chasing potential if it's any further south than central KS.

KR
 
Okay, I'll bite on this finally. I've been watching things progress over the last couple of days on the models and things look decent at least for Wed. As far as the morning of goes, Nam and GFS are highly different right now as far as the wind fields go, but I'm gonna base this forecast off the GFS since it is the only one showing 0z for Wed.

Looks to be some morning precip around S. Oklahoma/N. Texas which will clear out by the early morning. I wouldn't expect any boundaries laid by this will be west enough to effect the show in the evening. By 0z, precip is broke out in the E. Texas Panhandle along the dryline. Capes are at ~2000 at this time from Abilene to Childress, so things will pop, but as far as tornadic activity, it looks to be limited due to poor speed sheer, but directional sheer will be good. If there is a disturbance that kicks through that is presentely undetected by the GFS, then things could get very interesting on Wed, but I just don't see it just yet. I hope I'm wrong, seeing the flatlands out west would do a soul good at this time of year.

As far as Thu goes, if things stay more isolated (unlike what's indicated right now), shear improves and capes still look like they're in the 1500-2000 range, if overnight convection puts an outflow boundary down, and we get some isolation, there could be a decent storm or two to chase in the area on Thu, but this is all a wishcast right now and its more a wait and see attitude on things right now..
 
I'll bite for Wednesday, as well.

The new 12Z NAM shows this day as having some good potential for severe weather. We have CAPES of 2500-3500 J/Kg in a wide swath from Altus, OK to just SW to Topeka, KS. SRH will be highest in SC/SW Kansas around Pratt, values up to 300. LI's will also be highest in this area, -8 possible in the area around Pratt, SW-ward. Td's in OK and KS are progged to be in the lower to mid 60's, with surface air temperatures around 70-80 degrees, warmer the further south. Still the thing that might kill this storm, like Tuesday's setup over northern and central Kansas is the lack of 500mb winds. Low pressure at 1004mb is centered south of Lubbock, TX. I would target Pratt, southward to Woodward, that general vicinity. I'm on baby watch, so I won't be able to head out.

Personally, for a system in the Southern Plains, I got my eyes on Friday, around OKC, SE-ward.
 
Well, just as nick said, CAPE, Helicity and moisture (although modified gulf air) are all going to be good. But what really concerns me is the mid level winds. 500mb winds are terrible (sw @ 20 kts). Speed shear is not going to be there however, directional shear will be okay: se at surface to sw at 700mb. High CAPE, low shear days mean chasable storms but will be HP's and will rain themselves out.
My target area would be SC KS to extreme NW OK (might as well just say Harper County, thunderstorms seem to like it there. :lol:
 
As far as 500 winds go, I just took a jog around the area forecast office's discussions and they all agree that the models are underplaying the winds and aren't handling the wave strengths very well. This seems to be confirmed with the wave today not being forecasted as strong as it really is..
 
Here is what the 12Z GFS shows for 00Z Friday 22nd April (Thursday 21st April 6PM CDT):

Didn't you mean 7pm CDT? Maybe I'm off but seems standard time 0z 6pm and daylight savings is 7pm. Standard time we are 6 hours from zulu but as we 'spring forward' we move the clock forward and so only 5 hours different then right?

As for the rest of the discussion on Mon, Tue, and Wed of this week. My biggest concern is the placement / strength of the 500mb / 300mb winds. I think that is the deal breaker or maker.
 
Upper level winds (500mb & 300mb) are going to be too weak to support supercells both Tuesday and Wednesday over the central plains (according to the 00Z Monday NAM).

Right now I see only two possibilities for supercells:
1) Moisture and instability become sufficient northwest of the low near the Nebraska/Kansas/Colorado border where the 300mb winds will be near 40 knots.

2) A storm is able to ride a baroclinic zone and ingest vorticity into its updraft.

Otherwise, any storms that form will quickly be undercut by their own outflow.
 
May be worth noting that a chance for severe storms has also developed in Northeast Colorado for Wednesday. A frontal system is expected to pass through NE Colorado on Tuesday, then retreat northward again on Wednesday actin as the focal mechanism. Low level moisture is expected to move into the area. With help from a potential Denver Cyclone, we could have some added convergence, although I think the action will fall along the northward-moving frontal system. CAPE values of 1000-1500J/kg are nosing in behind the system into NE Colorado along with a small tounge of theta-E. Some 50s TDs are also nosing in as well, which is more than sufficient for storms here in NE Colo. Good shear also appears to be forecasted for the area, so severe storms are a possibility with the potential for landspoutish type tornadoes. There's a big ol' bulls-eye of 400 3km SRH right over NE Colorado on Wednesday as well with some 50/100 1km over the same areas...

While I was hosting Kansas as my target on Wednesday, I may elected to play it closer to home Wednesday and see how NE Colorado shapes up in the forecasts over the next 24 hours.

EDIT, BTW folks, all your strong 500mb winds are sitting over Colorado as well! :wink: 35 to 40 all across Eastern and Northeastern, CO... Kansas still sitting near 20... models still won't change their minds out that way.
 
I am liking southcentral/southeastern NE/KS border area. NAM is showing >3500 j/kg sbCAPE just to the north of the surface front, in an area of very strong low-level shear (200-400 m2/s2 0-3km SRH) given east-northeasterly sfc winds, easterly 850mb winds, and southwesterly 700mb winds. The magnitude of low-level shear and instability would suggest a threat for tornadoes, though the relatively weak mid-level flow would argue for short-lived mesos. That said, given the easterly flow in the low-levels, the net 0-6km deep-layer shear is in the 30-35kt range, which would support supercells given the strong instability. I'd be thinking about a significant tornado risk in this area if we had strong mid-level flow. Alas, we don't, so we'll see...
 
Originally posted by Tony Laubach
May be worth noting that a chance for severe storms has also developed in Northeast Colorado for Wednesday.

This has held for the last two operational NAM runs, so improved confidence in this scenario coming together. Agree - this region looks the best - but potential may exist further east as well for slow moving cells tracking along the front. Edge of the stronger cap along the KS/NE border - so either this slipping further south or the boundary setting up farther north would enhance the chances for surface-based convection to develop. Deep layer shear looks good across the zone along/north of front - but better west. Upper level shear much better west, HP mode appearing more likely to the east - but with lower LCL. Shear profiles over CO look great for aesthetic storms - but high bases could preclude significant tornadic activity. Looks like it could be a decent chase day though for folks in the region. Maybe Sterling to Goodland looks best right now.

Glen
 
Glancing at the latest ETA runs, NE Colorado still looks pretty good. The 500mb does show the LOW over Idaho with good difluence over the NE Colorado with nice speeds over the area. The 850 winds are nice as well in terms of direction sheer over NE Colorado with winds from the SE. Flow from the southwest at 500mb over flow from the southeast at 850 not only means great directional and speed shear, but upslope as well.

Temps progged to be in the 60s and 70s across NE Colorado with a nose of 50s TDs moving in over the area as well over the SFC low. LIs in the -4 range, so definately nothing wrong with instability. CAPE values are good for the High Plains with values over 1000J/kg and approaching 1500J/kg in some areas in extreme Northeast Colorado.

3km SRH values are at least 200 all over NE Colorado with values approaching 400 over the Sterling/Julesburg areas, sweeping back along I-80 in southern Nebraska. Low level SRH at 1km is only about 50 over the Northcentral/Northeast part of the state with values climbing into the 200s over the Julesburg area in the far northeast corner of the state. Not much CINH over the area either.

As it stood right now, I'd likely head up I-76 for at least Fort Morgan, maybe even as far as Sterling on Wednesday afternoon. The ETA breaks out precip in a bulls-eye over an area from about Fort Collins eastward towards Fort Morgan. I would think the better storms would be east where the better instability and shear would be, so at 48 hours out, I would say someplace I-76 between Fort Morgan and Sterling.
 
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