2014-05-21 FCST: CO, KS, NE, WY

[Andrew Stoller]

Very active high plains setup looks probable Wendsday; it will be a classic day 2 post frontal passage high plains setup in northeast CO, southeast WY where frontal passage and surface return flow pulls in 50+ degree dewpoints. There will also be decent southwesterly 500mb flow from a closed low over the southwest US providing 40+ knots of deep layer sheer. Hodographs look good with easterly surface winds thanks to the front and southwest winds aloft thanks to the closed upper low. The setup is similar to other events that produced noteworthy tornadoes like the Goshen County WY tornado of 2009 which I believe was also a post cold front scenario where the front and associated easterly surface winds pulled in moisture into the orographic prone area of the Larime range in WY. That, along with the Cheyenne ridge and the Palmer divide can produce additional lift depending on exactly where the front stalls out.

 

[Robert Balogh]

I'm a little curious why there isn't more talk about this setup. 00Z NAM is in and while it doesn't look as good as 12Z did, it still shows mid fifties dewpoints surging into east central Colorado along and just north of the I-70 corridor between 18 and 21Z. (12Z had shown low 60's to at least the Burlington area). The area looks to come uncapped in that time frame. Granted the 500mb flow weakens in that same time frame, and we are talking about the right exit region of the jet. Here's the projected 18Z sounding and 21Z hodograph for around Selber Colorado (along I-70 about halfway between Burlington and Limon). . As of right now, planning to leave OKC metro about 5PM tomorrow and head to Colby, Ks for the night, with Selbert, Co being my tentative target. BTW if I am missing something obvious I would very much appreciate some education from those more experienced than I

 

[Michael Snyder]

I think this afternoons Goodland Disc pretty much says it all as far as potential with the set up.
The NAM, GFS, Euro all have the 55DP line into CO in recent runs.

 

[Jacob Ferden]

The latest NAM has come in line with what the GFS has consistently had, and pretty much killed my interest in this setup. Yes, the dews look good by eastern Colorado standards, but the winds aloft in the target area are pathetic, with a rough average of 20 knots progged at 500 mb at 0z tomorrow night, and less in areas, with the main area of 40-50 knot winds aloft displaced to the east, in Kansas. The high plains have seen beautifully structured, but high-based supercells the past three days thanks to decent winds aloft and good directional shear. If anything, tomorrow should be a step back in that regard, even if the low level winds are slightly better. Barring a last minute change of heart, I'm going to likely pass on this one and focus on the low moving in out of the Southwest later this week.

 

[Jeff House]

Denver Cyclone day

Excellent set-up should unfold today in northeast Colorado, perhaps fairly close to the Denver Metro. Fortunately the classic Denver Cyclone is just east of populated areas. One can grab a decent lunch in the 'burbs and then find a hose or tube not harming anyone just outside of town. I don't have much to add to the SPC 10% tornado, so will get into background just a bit.

Many readers may already know this, but the geography adds confidence to the Denver Cyclone set-up. In addition to the north-south Rockies promoting the lee trough, the east-west Palmer Divide enhances low level shear. Mechanics are the same. Winds cross it and turn cyclonically. Palmer runs south of Denver, approximately from Colorado Springs east. Already backing surface winds will back more north of the Palmer Divide, northeast of the Denver Metro. Today we have adequate upper level winds coming out, in contrast to say mid-June. Therefore the 10% TOR probability is clearly justified.

Good luck. Chase safely and effectively. This is near Twistex home base. Honor their memory today. I know the Stormtrack community will do so.

 

[Adam Adkins]

Only cause for concern now is the cloud deck in Castle Rock. It is still very cool over the palmer divide with thick stratus. Loss of heating will reduce the instability - and latest models are already bringing it down.

However, latest models up slightly on shear so that's a plus! If we can get a few hours of good solar heating today will have lots to see IMO. I'll be looking for cells on the NE side of the palmer divide this afternoon.

 

[Andrew Stoller]

This setup has gone to crap IMO; low clouds/stratus, a lack of surface moisture have killed the instability progged for today; the front has raced south and is at the CO/NM border and has mixed out the moisture to the southeast; by afternoon, south easterly return flow redevelops but there's not enough time to get 55+ degree dews back into northeast CO, which happens tomorrow. But tomorrow there's no shear! Ughh. The RAP has most of the moisture mixed out by 00Z with only 40 + degree dewpoints.

 

[Michael Snyder]

Sterling is DP55 as of 1700z, Kden rising and over 50 now, plenty of lower 50's working up in North Central CO ...what am I missing?

 

[Adam Adkins]

This setup has gone to crap IMO; low clouds/stratus, a lack of surface moisture have killed the instability progged for today; the front has raced south and is at the CO/NM border and has mixed out the moisture to the southeast; by afternoon, south easterly return flow redevelops but there's not enough time to get 55+ degree dews back into northeast CO, which happens tomorrow. But tomorrow there's no shear! Ughh. The RAP has most of the moisture mixed out by 00Z with only 40 + degree dewpoints.

I disagree. I see no indication of this setup going to crap. Moisture is fine, at least north of Colorado Springs. Familiar with DCVZ?

 

[Adam Adkins]

Good towers going up just SW of Denver. Taken from Castle Rock looking west just now.