Severe Weather May 20-25, 27th, 2020

[Quincy]

The synoptic pattern favors episodes of severe thunderstorms from the High Plains, across the central/northern Plains through mid to late week and potentially continuing through this weekend.

The trough axis over the Rockies early this week should initially favor the High Plains Wednesday/Thursday and gradually shift east across the central states in the 2-3 days following.

I’ll defer further discussion to y’all from here on out, as I’m trying to not get too caught up in the medium range. 

Wednesday features an enhanced (ENH) over the far eastern Wyoming and adjacent areas...

[jojo762]

SPC is interestingly bearish. Hardly even mentioning severe potential across the central/southern plains in the D4-8 time period. Very interesting, as models have consistently showed at least some potential in the Thur-sun time period. 

[Chinook]

Aside from the weird 500mb pattern, we could have some potential for supercells in SW Kansas and the Oklahoma panhandle on Day-3, and near the Red River on Day-4. The SPC has put eastern Wyoming in an enhanced risk for tomorrow. The NAM and Euro have convection at the same place in SW Kansas on Day-3, possibly a squall line.

[Quincy]

I’ve had an opportunity to look more closely at progs for tomorrow. 

Upper level winds are unidirectional and display some VBV characteristics, especially across the northern High Plains. It does not help that deep shear vectors will be nearly parallel to the initiating boundary in most cases. Low-level CAPE looks minimal at best.

With that said, wind profiles show enlarged low-level hodographs with 850mb winds SSE/SE. 

My guess is there could be a few initial supercells before storm mergers and surging outflow turn the storms into a linear mess.

CAMs are varied with where CI will occur, but really a tall swath up and down the High Plains could see activity. 

[nrgjeff]

Kansas Saturday is all-or-nothing. Could be a beautiful cell or two on DL bulge near outflow intersection. Could be blue sky cap bust. I'm not a big fan of the cold front in Nebraska, unless another boundary intersection is present - quite possible even if it's just the synoptic triple point. Oklahoma convects, overcomes warm 850 mb, but upper support is meager.

Saturday is obviously a local chase day. Still in all of 2020 I have yet to go more than 60 minutes away from my front step. Easter night almost came to me - not good! Couple days of East Tennessee low top low probability but good visibility days. Never chased true Dixie. Saved it for May Plains. Ooops!!

[jojo762]

Today was my first official day of my mini-chasecation. Made it to AMA this afternoon after staying the night last night in Edmond OK, and chased dryline convection down to near Hart TX. Storms struggled to get going, and nothing really got well organized — combo of weak shear and weak lift. 
 

Going to sightsee in the panhandle tomorrow morning then head to near Garden City, KS for tomorrow’s round of storms. Expect a decent amount more of organization out of tomorrow’s storms, nonetheless things could and probably will get messy pretty quickly.

Friday and Saturday offer several potential targets (although they aren’t super far apart necessarily), and both days are looking pretty boom-or-bust attm.

EDIT: actually after having looked at 00z guidance... I’m not so sure on garden city as a target. Gonna be a bit of a obs day.

[Quincy]

Started in Wyoming today. Chased a couple of initial supercells forming near the Laramie Mountains. Not much worth sharing.

Next, dropped into the Nebraska panhandle into a more moist low-level environment, but the linear convection kept unzipping southward.

Finally watched a tail end transient supercell put on a lightning show in northeastern Colorado. One of my goals this year is to step up my lightning photography game, which could use some work.

 

[stormdragonwx]

Been debating on making the 8 hour drive out to the panhandle area myself tomorrow even though its on the marginal end of the slight risk spectrum. Gotta take what we can get though. This May has been pretty disappointing overall as others have mentioned.

[David Reimer]

I'm hoping a boundary from Wednesday's convection will stick around and help the eastern TX Panhandle become a magical 'sweet spot' later today. For sure there will be chaser hoards galore up in Southwest Kansas - and I'll probably be among them unless the Panhandle target becomes more tempting. 00Z TTU WRF does have boundary magic on the TX/OK border, but certainly a conditional threat ATM. It would sure be nice to only have a three hour drive versus a five or six hour journey to the target area. 

[yoda]

What a night in Montana, especially in the KGGW CWA (Glasgow, MT)

[Quincy]

Wind profiles are not ideal today, but I’d expect semi-discrete storm modes for at least the first couple of hours before an MCS begins to develop.

Tomorrow’s setup heavily depends on the nature of the MCS overnight/early tomorrow and where the outflow boundary ends up. I could foresee targets ranging from western North Texas to southern Oklahoma or the eastern Oklahoma/Ozarks vicinity. Some CAMs suggest the OFB may linger near or retreat back to I-44 in Oklahoma, but I am skeptical about that. 

Here’s another vantage point of the scene I captured last night:

 

[Chinook]

13 hours ago, yoda said:

What a night in Montana, especially in the KGGW CWA (Glasgow, MT)

There was a bow echo that tracked northward to the Canadian border. At one point, there was an embedded circulation in the middle that had a tornado warning. It's pretty weird to see a bow echo not tracking eastward or southeastward.

[Quincy]

Kansas mesonet obs show dews mainly in the mid to upper 50s around southwestern Kansas, about 2-4F lower than these obs:

 

[Chinook]

Holly, CO is under a tornado warning. There was one confirmed tornado southwest of the town. Holly had a direct tornado hit in 2007, so I hope nothing happens.

[WhirlingWx]

Several reports of landspouts/tornadoes around the CO/KS border

[Chinook]

Confirmed tornado outside of Garden City, KS with much more of a mesocyclone (within a blob of storms) compared to landspouts with a few storms before.

[Quincy]

I opted for the tail end Charlie near Liberal, KS. When I got there, it was struggling and I almost went home, but I’m glad I didn’t. 

This supercell reintensified and an even better organized storm popped up to its immediate west. I watched this slow moving, distinctly structured supercell for about an hour before it got dark. 

Got lucky with the lightning self portrait, even though it’s a little cut off. Camera was set to 1/15 and the first shot wasn’t in focus. The second happened to catch some lightning off to the side. 

[Chinook]

6 hours ago, Quincy said:

Wind profiles are not ideal today, but I’d expect semi-discrete storm modes for at least the first couple of hours before an MCS begins to develop.

Tomorrow’s setup heavily depends on the nature of the MCS overnight/early tomorrow and where the outflow boundary ends up. I could foresee targets ranging from western North Texas to southern Oklahoma or the eastern Oklahoma/Ozarks vicinity. Some CAMs suggest the OFB may linger near or retreat back to I-44 in Oklahoma, but I am skeptical about that. 

Here’s another vantage point of the scene I captured last night:

By the way, you and I got pictures of the same storm from a different perspective last night. (See Mountain West discussion)

[yoda]

SPC goes ENH for today with 10% hatched TOR probs along with 30% hatched hail

[yoda]

Written by Broyles/Lyons fwiw

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1229 AM CDT Fri May 22 2020

   Valid 221200Z - 231200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN TEXAS AND OKLAHOMA...

   ...SUMMARY...
   Severe storms will be likely today across parts of the southern
   Plains northeastward into southeast Kansas and the Ozarks. An
   enhanced threat for tornadoes, very large hail and wind damage is
   expected from north Texas into southern and eastern Oklahoma.

   ...Southern and Central Plains/Ozarks...
   An upper-level low will move east-northeastward across the central
   Plains today as an associated trough moves across the southern
   Plains. At the surface, a cold front will move into central Oklahoma
   with a moist airmass located ahead of the front. A line of
   thunderstorms is forecast to move across northern Oklahoma this
   morning into the Ozarks this afternoon. South of the outflow
   boundary, a moist and unstable airmass will remain in place from
   north Texas into eastern Oklahoma, where moderate to strong
   instability is expected to develop by early afternoon. MLCAPE values
   should peak in the 3500 to 4500 J/kg range from near Wichita Falls,
   Texas northeastward to south of Tulsa, Oklahoma. Convection is
   forecast to initiate along this corridor during the late afternoon
   with several discrete storms moving eastward across eastern and
   southern Oklahoma. During the early evening, storms will also likely
   develop in north and west-central Texas.

   In addition to strong instability, RAP forecast soundings in parts
   of the southern Plains show a favorable wind profile for supercells.
   In southeast Oklahoma and north Texas, winds are forecast to veer
   with height in the lowest 3 km AGL with speed shear in the
   mid-levels. This combined with 700-500 mb lapse rates near 8.0 C/km
   will be favorable for large hail with the stronger updrafts.
   Hailstones of greater than 2 inches in diameter will be possible
   with supercells co-located with the greatest instability. A tornado
   threat is also expected to develop as low-level shear gradually
   increases during the late afternoon and early evening. A couple
   strong tornadoes may occur with the more dominant supercells, with
   the greatest potential from between Wichita Falls and Fort Worth
   northeastward to near McAlester, Oklahoma. An Enhanced Risk has been
   added along this corridor.

   The severe threat is expected to extend eastward into northern
   Arkansas during the evening where large hail and wind damage will be
   possible. Further north into western Missouri and eastern Kansas,
   weaker instability should keep any severe threat more isolated. An
   isolated severe threat is also expected in west-central Texas where
   storms are expected to be very widely spaced.

[WhiteoutWX]

With the MCS already nearing the edge of the enhanced me thinks they’ll be trimming that a bit.

[Sydney Claridge]

2 hours ago, WhiteoutWX said:

With the MCS already nearing the edge of the enhanced me thinks they’ll be trimming that a bit.

Yep, the 10% with SigTor hatching was just removed and the ENH was shifted southwards somewhat.  On the flip side, the hatching for significant hail now covers much of the Metroplex (30% hatched), with a 5% tornado probability on top of that.

[cheese007]

Went to bed to a marginal risk and woke up to an enhanced with sig hail. TX weather is something+

[jojo762]

Don’t know if even the current ENH risk area is far enough south, given how fast the OFB is surging southward.

[Sydney Claridge]

The question will be how much further south the OFB gets before storms initiate (which will be a while).  Though not the most current, satellite imagery clearly shows the OFB location just south of the Red River.  SPC thinks that the boundary will eventually stall; needless to say I'm going to get a bit concerned about severe storms particularly if the OFB stalls out near the Metroplex, since the OFB may very well be the focal point for afternoon severe storms.

[Sydney Claridge]

Enhanced risk is now centered over north Texas, including the Metroplex, and has been trimmed away from southern OK.  OFB is now over the Metroplex, albeit with strong heating on the immediate north side of the boundary based on observations and SPC outlook.

[Quincy]

Not sure what to make of today. The atmosphere is recovering across Oklahoma, but not quite enough. The convection surge has pushed all the way to the Arklatex, outrunning sufficient deep layer shear for supercells. 

The outflow boundary in western North Texas looks the most intriguing. Large CAPE and marginal shear. The intersection with a dryline and/or cold front are interesting, but CAMs have been performing poorly and may not be resolving CI in the right areas  

My gut says we see messy blobs of convection by mid to late afternoon. We’ll see. 

[Quincy]

Put up a thread on Twitter to go into more detail. Just pasting to save typing. If I was going to pick a conditional target area, it would be western North Texas into southwestern Oklahoma. Maybe near Wichita Falls. A storm could thread the needle, but I expect mostly an HP mess. 

[Sydney Claridge]

Looks like some attempts at convective initiation may be occurring near Jacksboro, TX.

[WhirlingWx]

Mesoscale Discussion 0668
   NWS Storm Prediction Center Norman OK
   1255 PM CDT Fri May 22 2020

   Areas affected...Portions of North-Central Texs

   Concerning...Severe potential...Watch likely 

   Valid 221755Z - 221930Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Thunderstorm initiation is expected within the hour
   somewhere near Young County, TX.

   DISCUSSION...Towering cumulus have persisted along the western
   portion of an outflow boundary from the morning MCS. This boundary
   currently extends from near Childress to the northern suburbs of
   Dallas/Fort Worth. Temperatures south of this boundary have warmed
   into the mid to upper 80s with dewpoints in the upper 60s to low 70s
   yielding MLCAPE around 3000 J/kg per SPC mesoanalysis. This boundary
   has slowed its southern motion recently and may start to lift back
   north slightly within the next hour or two as it encounters stronger
   southerly flow ahead of the boundary. 

   The combination of short residence time along the boundary and dry
   air entrainment have stunted storm development along the boundary
   thus far with evidence of a few orphaned anvils. However, SPC
   mesoanalysis indicates MLCIN has eroded near the boundary.
   Therefore, it shouldn't be long before storms start to develop. The
   most likely area for initial storm formation is in Young County, TX
   where convergence is maximized along the outflow boundary. This is
   further supported by the 17Z WoFS which shows a maturing storm in
   this area between 18Z and 19Z. The strong instability, combined with
   effective shear around 35-40 knots per SPC mesoanalysis supports
   some supercellular structures. Mid-level lapse rates around 8-9 C/km
   per 12Z FWD sounding will support the threat for very large hail
   with these storms, especially initially. 

   Stretching of low-level vorticity in the region of the outflow
   boundary may provide a brief tornado threat this afternoon, but
   weakening low-level flow (per FWS and FDR VWP) will be a limiting
   factor to the overall tornado threat this afternoon. However, later
   this evening, the low-level jet is expected to strengthen
   substantially which will enlarge hodographs and lead to an
   increasing tornado threat.