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Severe Weather 4-15 and 4-16-24


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About as strong of wording as you will see say 6

   The actual severe weather setup appears substantial. Air mass
   modification will ensue northward from the western Gulf on D3, with
   multiple days to improve the low-level moisture profile amid well
   above-normal surface temperatures and a pronounced elevated mixed
   layer. With the likely flow field amplification through the
   troposphere, all ingredients appear present for a significant severe
   weather day on D6/Monday. The areal uncertainty of the synoptic
   features is the primary limiting factor. For now, have added a
   confined 30 percent highlight to indicate the higher-end potential
   and the most probable corridor, while broadening the previous 15
   percent area. 
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2 hours ago, olafminesaw said:

About as strong of wording as you will see say 6

   The actual severe weather setup appears substantial. Air mass
   modification will ensue northward from the western Gulf on D3, with
   multiple days to improve the low-level moisture profile amid well
   above-normal surface temperatures and a pronounced elevated mixed
   layer. With the likely flow field amplification through the
   troposphere, all ingredients appear present for a significant severe
   weather day on D6/Monday. The areal uncertainty of the synoptic
   features is the primary limiting factor. For now, have added a
   confined 30 percent highlight to indicate the higher-end potential
   and the most probable corridor, while broadening the previous 15
   percent area. 

100% chance of chaser traffic jams.

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Interesting, yes, but I’m not on board with a high-end event yet. Still early in the season, so smaller scale variables could still throw a wrench in it. Models are waffling on timing and while it doesn’t look perfect, I don’t see any harm in starting a discussion this far out. Analog guidance suggests a Day 6 30% contour is warranted. 

In fact, just looking at the medium range models, this could be a multi day threat that also includes Tuesday and/or Wednesday. 

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30% contour expanded for D5 with an addition of a 15% contour on D6. Pretty strong wording in the latest discussion text:

 

ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 110856
   SPC AC 110856

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0356 AM CDT Thu Apr 11 2024

   Valid 141200Z - 191200Z

   ...DISCUSSION...
   ...Significant severe weather episode possible late afternoon and
   evening on Monday...
   A mid/upper low over the central CA vicinity at 12Z Sunday should
   evolve into an open wave as it ejects across the Southwest and into
   the central Great Plains by around Tuesday morning. As it crosses
   the Rockies onto the High Plains, the tropospheric flow field will
   amplify with substantial lee cyclogenesis in the central High Plains
   on Monday afternoon. While a moderate amount of spread persists
   across respective ensemble systems, 00Z deterministic runs have
   converged towards greater agreement with the aforementioned scenario
   through D5, with progressively lower predictability in D6-8. 

   With about 3 days of persistent low-level moisture modification from
   the western Gulf beneath an extensive elevated mixed layer, the
   northern extent of mid 60s surface dew points should reach into most
   of OK east of the dryline by Monday afternoon. Late afternoon
   thunderstorm initiation along the dryline appears probable in the
   eastern TX Panhandle/western north TX to western OK vicinity, within
   a kinematic and thermodynamic profile favorable for strong
   supercells. Convective development will blossom both south and
   especially north extent during the evening across the central and
   southern Great Plains. For this outlook, have expanded the 30
   percent area to highlight the greater spatial confidence in a
   substantial severe weather episode.

   Despite increasing predictability concerns and the impact of prior
   day convection, very strong flow fields should persist into at least
   the first half of D6/Tuesday as a deep surface cyclone pivots
   northeast towards the Upper MS Valley vicinity. While instability
   will be weaker compared to Monday, organized severe potential is
   evident within an arc from a portion of the Upper MS Valley to the
   Mid-South.

   In the wake of this lead system, the shortwave trough digging into
   the Pacific Northwest may carve out a broad, positive-tilt trough in
   the West by mid-week. Consensus of guidance suggests that rich
   low-level moisture over the southern Great Plains will not be
   scoured by the lead wave. This may yield daily bouts of severe
   thunderstorms across parts of the central and southern Great Plains
   late in the period and beyond. Predictability for individual day
   highlights is too low to warrant 15 percent probabilities yet.

   ..Grams.. 04/11/2024

Screenshot_20240411_053148.jpg

Screenshot_20240411_053209.jpg

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  • cheese007 changed the title to Severe Weather 4-15 and 4-16-24

Monday has a really impressive synoptic presentation.  There are always ways we can nit pick and say things aren't going to happen but at this point it appears that there will be tornadoes between the red river north to I-70 in KS.  I also have some concerns about how late in the evening/overnight this could go.  Right now this looks like a potent system through the overnight hours and possibility of multiple rounds of severe weather still exists.  OKC, Tulsa, NW Ark, SW Mo could see issues overnight.

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1 hour ago, Wmsptwx said:

Euro trending down, blocking hurting this

Meh, I don't really see that and global models trending down a little at this point? To be expected I'd say.  This is still looking very dangerous.  

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Tuesday also looks like a potentially significant severe event over AR and MO primarily depending on what occurs overnight Monday into Tuesday morning. Very strong flow with the ejecting wave and a substantial dryslot aloft to aid in renewed destabilization. Additionally there appears to be a diffuse Pacific front/dryline pushing east.

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2 hours ago, Crazieman said:

Is there a discord or something everyone wandered away to?  First nice looking severe event in my area in years and I come in to find it virtually dead?

It looked a lot better a couple of days ago on the models.  It had looked like storms would initiate early evening at maximum instability.  It is starting later, and low level instability is low.    GFS showing elevated storms, NAM doesn't show anything.  SPS forecast sounding below.  It might work if a special 18Z sounding but it isn't.  30% at 5 days, that usually means a big outbreak.  Still 3 day ENH, and SPC looks at stuff amateurs like me can't see or don't have time to see.

CapOfForgedSteel.png

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2 hours ago, Crazieman said:

Is there a discord or something everyone wandered away to?  First nice looking severe event in my area in years and I come in to find it virtually dead?

This feels like a snow oriented place and an occasional tropical event gets people going, us severe bros just used Twitter now it seems.

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28 minutes ago, Ed, snow and hurricane fan said:

It looked a lot better a couple of days ago on the models.  It had looked like storms would initiate early evening at maximum instability.  It is starting later, and low level instability is low.    GFS showing elevated storms, NAM doesn't show anything.  SPS forecast sounding below.  It might work if a special 18Z sounding but it isn't.  30% at 5 days, that usually means a big outbreak.  Still 3 day ENH, and SPC looks at stuff amateurs like me can't see or don't have time to see.

CapOfForgedSteel.png

NAM was blehhhh

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by the way: day-2 non-Midwest

Quote
  Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1232 PM CDT Sat Apr 13 2024

   THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTERED OVER
   PARTS OF PENNSYLVANIA

I didn't post much about the last few days because it was a messy system in Texas. Also note: nobody seems to care. Guess what. I'm not going to believe in a tornado outbreak until I see one. The SPC is overcooking everything. It looks like the GFS and ECMWF have a storm near Wichita Falls, Texas on Monday.

 

 

day1otlk_v_20240409_1300a.gif

 

60 kt+ winds aloft where things could get going in Oklahoma on Monday night (03z)

292285865_60ktwinds.thumb.jpg.25097e62ebd5b3d50d89286f406249ad.jpg

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I’ve mostly stayed quiet on Monday because the models keep shifting. Just looking at the last few runs of the 3km NAM, now that it’s in range… the warm sector ahead of the dryline keeps narrowing, to a point now that the 48hr prog for 00z Tuesday looks bleak for pre-sunset convective initiation prospects. 

At this point, daytime initiation in Nebraska seems more plausible than OK/TX, closer to the surface low. 

Tuesday is also getting more intriguing, particularly around the lower Missouri Valley vicinity, but maybe around Arkansas too. The slower progression of the system seems to suggest Tuesday *might* be the main show. 

If trends have taught us anything, it’s that nothing is set in stone, especially several days out. Things may continue to change. 

By the way, last check for Monday is that 4/26/14 showed up as a top analog. 

That event featured isolated severe storms going up around 01-02z in far northwest Texas. The next day… that featured isolated intense (tornadic) supercells in Arkansas, as well as severe storms north into Missouri and Iowa. 

Take analogs with a grain of salt, because 4/14/12 was showing up for a while with Monday. 

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Updated SWODY 2 has two enhanced area, one in N Kansas and Nebraska, a second in W. Texas and Oklahoma, the TX/OK one being conditional on storms developing.  12Z HRRR thinks the dryline in Texas will go, to a lesser extent the GFS as well.  3 km NAM still shows a stout cap.

 

SWODY 3 mentions a possible increase from SLIGHT for the ArkLaTex area.  Not seeing much on 12Z 12km NAM or GFS to support an upgrade, but it is at the limit of the NAMs.

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18 hours ago, Quincy said:

I’ve mostly stayed quiet on Monday because the models keep shifting. Just looking at the last few runs of the 3km NAM, now that it’s in range… the warm sector ahead of the dryline keeps narrowing, to a point now that the 48hr prog for 00z Tuesday looks bleak for pre-sunset convective initiation prospects. 

At this point, daytime initiation in Nebraska seems more plausible than OK/TX, closer to the surface low. 

Tuesday is also getting more intriguing, particularly around the lower Missouri Valley vicinity, but maybe around Arkansas too. The slower progression of the system seems to suggest Tuesday *might* be the main show. 

If trends have taught us anything, it’s that nothing is set in stone, especially several days out. Things may continue to change. 

By the way, last check for Monday is that 4/26/14 showed up as a top analog. 

That event featured isolated severe storms going up around 01-02z in far northwest Texas. The next day… that featured isolated intense (tornadic) supercells in Arkansas, as well as severe storms north into Missouri and Iowa. 

Take analogs with a grain of salt, because 4/14/12 was showing up for a while with Monday. 

4/14/12 was 12 years ago. I'd say that was one of the biggest outbreaks since 2011.

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12z 3km NAM has very good verification with Oklahoma dew points, as moisture is over performing many progs. On the other hand, most models (NAM included) show cloud cover, midday/afternoon precip and limited instability across central Oklahoma on Monday. 

One area to watch may be western Kansas, as some CAMs try to initiate isolated storms around 23-00z. 

I think it was two or three years ago where an early season event looked like a CAP bust, except an isolated storm blew up and went nuts over western Kansas.

The timing of everything seems to be slightly late for widespread CI, but if moisture is over performing and more CAMs are coming onboard with isolated convection, watch out. 

Monday is quite a complex setup with many different areas to watch. I’m not really concerned about Oklahoma (prior to 01-02z), but aside from isolated dryline storm potential in western Kansas… storms also appear likely near the warm front in Nebraska, while some guidance suggests CIN may erode enough for storms farther SE into northeastern Kansas. West/NW Texas could see afternoon storms, although the parameter space seems disjointed enough to suggest mixed/messy storm modes there. Hell, you could even see a storm near the triple point in the Nebraska panhandle or just downwind of the Black Hills. More widespread convection appears plausible after dark across Kansas and surrounding areas. 

It feels like an event that will probably see wide gaps in storm coverage. To a point where swaths of the ENH risk may see nothing at all, while an isolated storm or two could be prolific. It’s still a wait and see type of setup, so I won’t try to nail down any specifics. Confidence is lower than usual given the synoptic pattern. I remain pessimistic, but not as much as say 24 hours ago. 

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This one definitely kind of fell apart for TX and possibly OK.

Adding insult to injury, with yet another late-season PV split and greenland block developing, we're looking at yet another "cold" snap (not cold enough for a frost/freeze, but definitely well-below normal temps with highs in the 50a/60s) for many locations this upcoming weekend.

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First tor watch out for the day with 40/20 probs

SEL0

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 110
   NWS Storm Prediction Center Norman OK
   230 PM CDT Mon Apr 15 2024

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Southwest Oklahoma
     Northwest Texas

   * Effective this Monday afternoon and evening from 230 PM until
     900 PM CDT.

   * Primary threats include...
     A couple tornadoes possible
     Scattered large hail and isolated very large hail events to 3
       inches in diameter likely
     Scattered damaging winds and isolated significant gusts to 75
       mph possible

   SUMMARY...Severe thunderstorms are expected to develop in the next 1
   to 2 hours across northwest Texas and shift east through early
   evening. Large hail and damaging gusts are possible initially, with
   an increasing tornado risk expected during the evening.

   The tornado watch area is approximately along and 70 statute miles
   east and west of a line from 40 miles west southwest of San Angelo
   TX to 50 miles northwest of Wichita Falls TX. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU0).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 109...

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 3 inches. Extreme turbulence and surface wind
   gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean
   storm motion vector 24035.

   ...Leitman
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