06/21/2006 FCST: CO, KS

[Tony Laubach]

One of the better days in Colorado may be shaping up for tomorrow as good low-level upslope flow combined with good moisture will aid to severe thunderstorm development mid-to-late afternoon along the Front Range. Storms will again move into the Eastern Plains and rapidly become severe.

The cap which held storms at bay Monday will be much weaker as temps at 700mb are progged to cool from the north, adding to steep lapse rates. CAPE values are progged to be near 2000J/kg with lower to mid 50s dews all over the plains. Some mixing is possible closer to the front range, but dews should hold on the Plains for storms. Richer dews exist further east into Kansas where 60s are possible, maintaining the severe threat over the area. Temps oughta hold in the 80s, which would give LCLs a chance at becoming low enough for tornado development, particularly along any boundries left over from Tuesday night's convection. Temps in the 90s would result in LCLs that may be out of reach for tornadoes, so hoping the lower to mid 80s verifiy. Wind fields show good shear, however, 500mb flow still looks a bit on the weak side.

I think tomorrow holds potential for some great Front Range action and am looking forward to checking things out again later tonight and early on Wednesday. Will keep very close tabs on this and see what the local mets are thinking about tomorrow's prospects. Hail should be a sure-bet in severe storms tomorrow, but I'm holding on to some tornatic potential if we can get some improvement in winds.

 

[Jason Persoff]

At this point the ETA seems to be calling for fairly warm 700mb temps in the CO/NE/KS area by initiation tomorrow (somewhere in the 5-7deg range) which will be a near ideal cap that can be broken both orographically and from any residual boundaries. The 300mb upper air suggests the tristate area would be in the right rear entry region of a jet streak which is laying zonally over NE by 00z tomorrow. H5 speeds along and N of I-76 look best (50+ kts). Unfortunately, precip seems forecast to remain backed up on the mountains until later in the evening, but my experience in that region is that ETA undercalls isolated covective cells that form--particularly along the DCVZ. Dewpoint depressions are (again) a bit of a concern...forecast looks closer to the 90/55 scenario along I-76. Dynamics would easily favor landspouts, but wonder if the LCLs will (again) be too high to allow sfc-based storms to roll in. Preliminarily I guess my target would be Last Chance to Ft Morgan, CO. I like the areas north of I-70 largely d/t upper level winds there.

Latest SPC hints at upgrading that vicinity to a moderate and currently they're calling 30% hatched for NE CO. Wish I were still out there...

 

[Jeff Snyder]

I was a little surprised that the Day 2 outlook was so bullish (enough to mention MDT risk), and I'd be very surprised if the 6z Day 1 kept that tone. 00z NAM forecast only indicates 10-20kts 500mb flow across most of eastern CO and western KS, increasing another 10kts as one heads north of I70 and east of Hwy183. Granted, there will be easterly/upslope 850mb flow in that area, but the wind profiles still indicate ~30kts 0-6km shear, marginal by supercell standards. The deeplayer shear will be a little stronger north of I70, where midlevel flow is progged to be stronger. Instability won't be a big problem (CAPE >3000 j/kg, mainly across western KS), but the relatively weak flow at all levels leaves a lot to be desired. In particular, the 700mb forecast is pitiful -- essentially light and variable (<5kts) across the entire target area, except for areas northeast of Salina and in far southeastern CO (though 700mb is not too far off the surface there).

The lowest LCLs should remain north of I70, where mid-upper 80 temps and mid-60 dewpoints may keep LCLs in the 1400-1600m range. South of there, temps should warm into the 90s, resulting in high LCLs (again for this year). Previous NAM runs (yesterday) had shown a nice, compact vort max moving into northcentral KS tomorrow afternoon, but that feature is now gone, replaced by a weak, diffuse area of positive vorticity (less curvature to the 500mb flow and only 20-25kts 500mb flow across northcentral and northeastern KS). Of course, some depends upon what happens with convection tonight, but even the due easterly sfc flow yields only marginal deep-layer shear (30kts, maybe 35kts in some places). With all that said, I'd be extremely surprised if the SPC goes MDT on day1.

 

[Brian Press]

Well my brother and I are coming out for a two day chase on a few buddy passes.

I have a forecast question concerning the 0Z ETA run. There looks like there is some sort of low pressure that forms over East-Central CO. 0Z Thurs. (Wednesday evening, right?)in the afternoon. What is that? It looks like there is a notch of 35 to 40knt SE-E winds going into it. Is this the Denver Cyclone that I have read about. Why is there an "H" and not a "L" for low?

It also appears that the better winds will be up in NE CO. So what does this mean for tomorrow. Has this changed since Jeff's comments.

Thanks and I hope I am not to far off topic. Mods can remove this if it's not along the guidelines.

Good night and hope to see a few of ya out there tomorrow.

B.p.[attachmentid=397]

 

[Dan Dawson]

I agree that a moderate on the new Day 1 looks unlikely, considering the new NAM solution (since the Eta is now dead, I guess I have to grudgingly start calling it the NAM now ). However, the 0Z GFS solution gives a little more hope if something like it were to verify. It basically has more robust cyclogenesis in the OK panhandle area than the NAM, with a possible slight enhancement of the 500 mb winds (maybe 25-30 kts) at the base of a weak shortwave (I'm looking at the NCEP model graphics site). This, coupled with backed sfc winds from the E at 10 kts yields marginal shear for supercells in that area. If the warm front/outflow boundary from tonight's convection can set up in that region and enough moisture can pool along the front, as earlier runs of the NAM and GFS were showing further north in central KS, we might have something interesting. Obviously there are a lot of caveats with this. If something more like the NAM were to verify, forget it. This is like so many central Plains setups this year, enough to be somewhat intriguing if all the ingredients fall in place, but so often we are missing that one crucial ingredient. Let's hope tomorrow we are able to pull off a mesoscale accident in this region. At any rate, I'm not ready to give up on this setup yet. I will obviously make a final decision in the morning.

 

[Jeff Snyder]

I have a forecast question concerning the 0Z ETA run. There looks like there is some sort of low pressure that forms over East-Central CO. 0Z Thurs. (Wednesday evening, right?)in the afternoon. What is that? It looks like there is a notch of 35 to 40knt SE-E winds going into it. Is this the Denver Cyclone that I have read about. Why is there an "H" and not a "L" for low?

It also appears that the better winds will be up in NE CO. So what does this mean for tomorrow. Has this changed since Jeff's comments.
[/b]

Brian,

That appears to be an effect of intense convection in east-central Colorado progged to develop before 0z. If you look at the QPF graphics, you'll see a big convective bullseye in that area. In addition, you see a response to this at 500mb and 250mb as a small-scale perturbation/anomaly. The GFS picks this up as well... As a note, the NAM-WRF will likely show these small anomalies more than the old NAM-Eta since there is less smoothing in the NAM-WRF... One good example of this is seen in mountain waves.

 

[Stan Rose]

Brian,

That appears to be an effect of intense convection in east-central Colorado progged to develop before 0z. If you look at the QPF graphics, you'll see a big convective bullseye in that area. In addition, you see a response to this at 500mb and 250mb as a small-scale perturbation/anomaly. The GFS picks this up as well... As a note, the NAM-WRF will likely show these small anomalies more than the old NAM-Eta since there is less smoothing in the NAM-WRF... One good example of this is seen in mountain waves.
[/b]

Interestingly, the 00Z blows up the convection in the same general location as the 18Z. really goes nuts with the qpf--8"/3h rates in spots. And 45Kt in the BL flow from the outflow. Well, ill be very surprised if the spc keeps its harsh wording for CO at 6z (any second now...) especially with the light winds aloft. but still holding out some hope, given the boundaries out there. Buffkit sounding for KLAA not too shabby at around 00Z. Since im working, i know exactly what will happens--tornadoes in w KS, of course

 

[Mark Farnik]

When I saw the wording in yesterday's SPC Day 2 Outlook, for a time I actually believed that my dreams of a High Plains tornado outbreak might finally come to fruition. Then reality smacked me in the face. Alas, those damned weak mid level winds have spoiled what could have been a magnificent (by local standards) tornado outbreak. I don't know WHAT kind of a setup it will take for northeastern CO to ever get a significant tornado day again. :angry: This one has everything going for it; exceptional surface dewpoints (55-60 + dews are rare this far west) with forecasted high temps for today recently revised down into the lower to mid 80's, therefore lowering LCL's to more favorable levels, a solid amount of juicy CAPE available, plenty of rotation enhancing outflow boundaries to be found... it's like Mother Nature wants to cook us up a mean cake, with delicious tornadic substance; she has the eggs, the flour, the spices, and the frosting, but the water is nowhere to be found. What would have been a hell of a good cake comes out half baked because one of the crucial ingredients was missing. This go around, the water is the supportive winds, which are currently forecast to be somewhat anemic at all levels, particularly the mid levels (700 mb is downright pathetic). Basically, the dreidel is there; it just needs the supporting mid level winds to get it a turnin'.
Dan Dawson said:

This is like so many central Plains setups this year, enough to be somewhat intriguing if all the ingredients fall in place, but so often we are missing that one crucial ingredient. Let's hope tomorrow we are able to pull off a mesoscale accident in this region. At any rate, I'm not ready to give up on this setup yet. [/b]

I'm not ready by any state of the imagination to give up either. Several good outflow boundaries have migrated west from that MCS which developed near Yuma and then tore into northern KS and are lingering across northeast CO. If they would collide with that stationary front, any storms that form on or interact with the intersections of the boundaries and the front, or even just the boundaries themselves would be the best bets for any tornadic activity.
We need more than a mesoscale accident; we need a mesoscale miracle (preferably in the form of a shortwave trough with 40-50 kt mid level winds accompanying it) but ANY sort of upper air feature that would increase the strength of the mid level winds would be given the red carpet treatment.
For all who wish to chase today, pray to the storm gods to have mercy upon us and let us have one really terrific High Plains chase day with highly visible tornadoes, even if there are only a few of them.
Today will be interesting, regardless of whether we get two tornadoes or twenty.
Stay tuned. B)

 

[Jay McCoy]

Kanani and I are heading up to Garden City and will grab more data there. The progged temps in the 90's will lead to higher than liked LCL's but I still think given the past few days history that there is a shot a tornado or 2 if you find a storm early enough. Surface low setting up in SE colorado and backed winds in western Kansas and a dryline bulge in the oklahoma panhandle has me leaning on playing west kansas compared to closer to the foothills where most of the storms may fire. I am hoping to catch something isolated ahead of the cluster that is sure to form as they move off the mountians.

 

[Tony Laubach]

The front passing through this morning/afternoon will stabilize the atmosphere initially, so storms that do form off the mountains won't get too far east too early on. This could act as a good thing for chasers leaving DEN later in the day as it should hold off severe chances for a bit later than we're use to here in Colorado.

Post-frontal upslope should set up fairly quickly today and SFC temps should cool a bit behind the front, which may help get LCLs down a bit. Upper level winds as I said yesterday are concerning and still don't look terribly impressive. I don't think LCLs will be as big a problem as usual, but its something that could definately grow concern, so I'm definately not counting them out yet.

In fact, glancing at temps across the region, most areas in Northeast Colorado are progged to be in the mid 80s at the most and even cooler than that in places. Of course, too cool and we may have a problem as well, but temps in the low 80s and dews in the mid to upper 50s.. yeah, good stuff for Colorado.

Tornado chances still aren't great, though... weak winds aloft are still hampering things a bit and as I said, is still my biggest concern. Temps being too cool is the second with that stablizing the atmosphere all day (recovery maybe later on out east).

Still undecided on whether I'll be out today or not; awaiting final word from work before pulling the trigger... I either get today or tomorrow afternoon/evening to play. Probably won't know til the last minute...