Severe weather risk 4/30 - 5/3

[jojo762]

Latest renditions of the HRRR point to a fairly active day with relatively impressive UH tracks along much of the dryline in S KS and especially near the triple-point. Basing off of the HRRR I'd prefer further south along the dryline as things look like they *could* get fairly messy and HP up north. 

[Upper Level LOL]

Day 1 Moderate over C Kansas

 

Forecast Discussion

SPC AC 011630 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Tue May 01 2018 Valid 011630Z - 021200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS CENTRAL KS... ...SUMMARY... Numerous severe storms are expected over the central Great Plains to the Mid-Missouri Valley. The most likely corridor is across parts of central Kansas between 5 to 9 PM CDT. Tornadoes, a couple of which could be strong, very large hail, and damaging winds will be possible. ...Central Great Plains to the Upper MS Valley... 12Z soundings across central OK and north-central TX sampled mean mixing ratios near 12 g/kg within a plume of 63-64 F surface dew points. Richer moisture with upper 60s and lower 70s dew points remains confined to south TX this morning. This suggests boundary-layer moisture return is probably one day too early from being optimal for a regional severe weather/tornado outbreak. Even so, confidence is relatively large in storm initiation and probable evolution in the late afternoon and evening, rendering increased large hail probabilities. The dryline is expected to mix across the eastern TX Panhandle and western KS as surface temperatures warm into the 80s, creating a T-intersection with a quasi-stationary front arcing across west-central KS into eastern NE. A broad plume of MLCAPE from 2000-2500 J/kg is anticipated ahead in the warm/moist sector. Guidance is consistent in ejecting a mid-level speed max ejects from the southern High Plains into KS by 00Z. This should aid in ascent for probable storm development in the 20-22Z time frame along the KS portion of the dryline. Decreasing certainty exists farther south along the dryline where weak mid-level height rises are anticipated to occur this evening as the broader trough over southern CA digs a bit farther south. 50-kt effective shear, nearly perpendicular deep-layer winds to the dryline, and rather steep mid-level lapse rates will favor discrete supercells producing very large hail. A few of these supercells may become long-tracked across central KS and the threat for tornadoes will increase between 22-02Z as storms encounter richer boundary-layer moisture (toward the I-135 corridor) and as low-level shear increases rapidly in response to a strengthening low-level jet. The synoptic pattern is largely consistent with past Great Plains cases of the evening low-level jet strengthening and aiding in mid/late evening significant tornadoes. However, low-level moisture may remain on the lower margins of what is typical of the high-end events (with similar temperature profiles and hodograph structures). The slightly drier boundary layer will encourage a little quicker increase in convective inhibition, coincident with the strengthening low-level shear. Thus, it is not clear whether or not this scenario will evolve into a long-lived significant tornado threat near sunset, or if the inhibition increase will tend to limit the window of opportunity. Otherwise, clusters of storms (with embedded supercells) should persist well into the overnight hours with an attendant threat for large hail/damaging gusts and a couple tornadoes, from the triple point northeastward along the quasi-stationary front into the Upper MS Valley. ...Northeast CO... An upslope flow regime will help maintain boundary-layer dewpoints in the 40s across northeast CO through the afternoon, north of a stalled front. Surface heating in cloud breaks will yield weak surface-based buoyancy, while deep-layer vertical shear will be favorable for supercells. A couple supercells may form this afternoon in conjunction with the northern periphery of the mid-level speed max ejecting into KS. These storms should move east before weakening by mid-evening. Isolated large hail and strong wind gusts will be possible.

[jojo762]

GREAT and really on-point discussion from SPC. Oddly I believe this outlook stole a (outstanding) paragraph from Thompson's 13Z outlook about how this event compares to other similar cases, and why it might not necessarily live up to that.

[hlcater]

SPC hits the nail on the head for today. The dews in the 67-69 degree range would be optimal, but thinking they max out 65-66, displaced slightly east of the dryline. This isn’t a huge issue as 65-66 will work as storms move off the dryline and into better moisture. I think today is gonna be a nice chase day.

[nrgjeff]

Tuesday: I would start near the triple point TP, with the option to drop south 1-2 cells along the dry line DL. Low levels more backed near TP, and with less risk of moisture mix-out. However it could be messy so keep DL in mind. If in the field, lunch in Great Bend or Hutch, nowcast, avoid gorilla hail, document tubes.

Wednesday: Like DL better. Overnight convection could mess up the warm front. However outflow OFB should drop south toward the KS/OK border. Target DL/OFB intersection. Also could be a DL bulge which backs wind north side of bulge. If together, that'd be great. If not, tough choices but less chaser traffic, and hope both work.

Thursday: Jungle.

[the ghost of leroy]

 

 

 

[OUGrad05]

Just now, the ghost of leroy said:

 

 

 

That's baller AF

We'll see how HRRR handles today, might give us an idea of how it will handle tomorrow.  ANyone know how it did yesterday?  

I'm losing hope in tomorrow, starting to look like very limited mess without proper upper air support. 

[andyhb]

2 minutes ago, OUGrad05 said:

That's baller AF

We'll see how HRRR handles today, might give us an idea of how it will handle tomorrow.  ANyone know how it did yesterday?  

I'm losing hope in tomorrow, starting to look like very limited mess without proper upper air support. 

I have few doubts that tomorrow will initiate if today does with even less forcing/moisture available.

The issue is whether wind profiles will support tornadic supercells when they do initiate or not.

[jojo762]

SPC upgraded to MDT risk for tomorrow. But I guarantee it is not where you think it would be. 

[Upper Level LOL]

Tiiiiiiny little moderate area in the D2 

 

[OUGrad05]

1 minute ago, andyhb said:

I have few doubts that tomorrow will initiate if today does with even less forcing/moisture available.

The issue is whether wind profiles will support tornadic supercells when they do initiate or not.

We'll see.  I keep hoping the models are missing something and we'll wake up tomorrow and it'll all make sense.  

[OUGrad05]

Just now, jojo762 said:

SPC upgraded to MDT risk for tomorrow. But I guarantee it is not where you think it would be. 

It should be in KS or IA from what i"d think.  WHere'd they put it?  I don't have an update yet.

[Chicago Storm]

holla at me if you see a greyish corolla out there.  we can take pics for alek.

I’ll see ya at the wedge.


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[Chicago Storm]

I have few doubts that tomorrow will initiate if today does with even less forcing/moisture available.
The issue is whether wind profiles will support tornadic supercells when they do initiate or not.

Fully agree.


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[MUWX]

11 minutes ago, jojo762 said:

SPC upgraded to MDT risk for tomorrow. But I guarantee it is not where you think it would be. 

Spc also dropped the mention of significant tornadoes tomorrow 

[andyhb]

Man the downtrend into any bigger looking event just never fails these days.

4/26/16, 5/8/16, late April last year, 5/18/17, etc.

[jojo762]

2 minutes ago, andyhb said:

Man the downtrend into any bigger looking event just never fails these days.

4/26/16, 5/8/16, late April last year, 5/18/17, etc.

Ya called it the other day when's I made an apparently premature comment about Wednesday looking like a big day. Likewise, I still think west-central OK looks solid in the evening.

[yoda]

Tornado Watch(es) coming soon for KS into SE Nebraska

[the ghost of leroy]

1 minute ago, yoda said:

Tornado Watch(es) coming soon for KS into SE Nebraska

thanks yoda

[yoda]

 

Mesoscale Discussion 0304
   NWS Storm Prediction Center Norman OK
   0110 PM CDT Tue May 01 2018

   Areas affected...Central KS into southeast NE

   Concerning...Severe potential...Tornado Watch likely 

   Valid 011810Z - 012045Z

   Probability of Watch Issuance...95 percent

   SUMMARY...One or two tornado watches will be needed by mid-afternoon
   (20-21Z) across central Kansas into southeast Nebraska.

   DISCUSSION...Surface mesoanalyses this afternoon showed an area of
   low pressure located in northwest KS, while the equatorward-trailing
   dryline was continuing to shift east through southwest KS.  DDC
   radar imagery showed this boundary located between KGCK and KDDC at
   1740Z and into central portions of the OK and TX Panhandles. 
   Clearing skies per visible satellite imagery have allowed for
   stronger surface heating across the warm sector where the
   environment continues to moisten per southerly low-level winds. 
   These changes in boundary-layer thermodynamics (reduction in
   inhibition) have allowed cumulus clouds to develop along the KS
   portion of the dryline into adjacent part of the OK Panhandle, as
   the environment further destabilizes (mixed-layer CAPE is already up
   to 2500 J/kg).  

   Deeper moist convection is expected by 20-21Z along the KS dryline
   as stronger ascent within the exit region of southwesterly mid- and
   upper-level jets shift into the central Plains this afternoon and
   evening. Trends in the operational HRRR continue to suggest storm
   development along the KS portion of the dryline by 21Z, with some
   potential for initiation by around 20Z. Further low-level moistening
   and increasing vertically veering winds will support supercell
   development with an attendant threat for all severe hazards. 
   Initial storms will be capable of producing very large hail, while a
   tornado threat (some strong) will increase, given a strengthening
   southerly low-level jet resulting in increased hodograph curvature
   this evening.

   ..Peters/Grams.. 05/01/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...OAX...TOP...ICT...GID...DDC...GLD...

[Chicago Storm]

We’re in McPherson now. Going to race west from here.


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[OUGrad05]

40 minutes ago, andyhb said:

I have few doubts that tomorrow will initiate if today does with even less forcing/moisture available.

The issue is whether wind profiles will support tornadic supercells when they do initiate or not.

If it goes early before support is there I'd be worried about cell structure.  If it can hold off till 4pm and cells remain discreet in OK maybe upper support gives a brief window from 7 to 8:30?  I dunno...

[hlcater]

HREF tornado probs for whatever they are worth. Moisture also seems to be slightly ahead of the HRRR with dews(65-66) pooling along the boundary. Given that moisture is what I thought was the biggest hiccup today, will be interesting to see how this evolves.

 

 

[CheeselandSkies]

28 minutes ago, andyhb said:

Man the downtrend into any bigger looking event just never fails these days.

4/26/16, 5/8/16, late April last year, 5/18/17, etc.

What we really need is today's synoptics with tomorrow's moisture. Is that really so much to ask?

Still, looking forward to armchair chasing and seeing how the next 48-60 hours play out. Nice to see spring finally acting like spring, even if it's not the perfect setup.

[yoda]

4 minutes ago, NWLinnCountyIA said:

HREF tornado probs for whatever they are worth. Moisture also seems to be slightly ahead of the HRRR with dews(65-66) pooling along the boundary. Given that moisture is what I thought was the biggest hiccup today, will be interesting to see how this evolves.

 

 

What is the scale for the rest of the colors?  I see 2 is green... I guess 5 is brown, 10 yellow, 15 orange and 30 is the purple dot?

[andyhb]

1 minute ago, CheeselandSkies said:

What we really need is today's synoptics with tomorrow's moisture. Is that really so much to ask?

Still, looking forward to armchair chasing and seeing how the next 48-60 hours play out. Nice to see spring finally acting like spring, even if it's not the perfect setup.

Moisture today looks fine so far, fairly solid mid 60s dews down in OK with an axis extending to Central KS, some lingering cloud cover should help prevent too much mixing not to mention the fact that the moisture is fairly deep (H85 Tds of 14˚C+).

[hlcater]

3 minutes ago, yoda said:

What is the scale for the rest of the colors?  I see 2 is green... I guess 5 is brown, 10 yellow, 15 orange and 30 is the purple dot?

Right. It follows the SPC scale.

[Chinook]

38 minutes ago, andyhb said:

Man the downtrend into any bigger looking event just never fails these days.

4/26/16, 5/8/16, late April last year, 5/18/17, etc.

I am really kind of mystified by the lack of convection shown by the 3km NAM here (36 hours... prime time for tornadoes... no storms in Oklahoma). There's a pretty big signal for having relatively few storms in Oklahoma tomorrow. Seemed like a good setup for several hail/tornado events in SW Oklahoma.

[WhiteoutWX]

6 minutes ago, Chinook said:

I am really kind of mystified by the lack of convection shown by the 3km NAM here (36 hours... prime time for tornadoes... no storms in Oklahoma). There's a pretty big signal for having relatively few storms in Oklahoma tomorrow. Seemed like a good setup for several hail/tornado events in SW Oklahoma.

I have noticed the height falls being depicted for tomorrow across Oklahoma  are not quite as robust as were being shown even a day or two ago. Looks neutral to only slightly negative. May make initiation a little harder.   

[Crazieman]

30 minutes ago, Chicago Storm said:

We’re in McPherson now. Going to race west from here.


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I'll be jumping northwest towards St John after work.

Hopefully the timing works and I get my pick of southern storms.