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April 10th - April 13th(?) Severe Weather, Moderate risk in place for Iowa today


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Ongoing severe threat with isolated tornadoes across Arkansas… may continue for a few more hours, toward the greater Memphis area. 

Trying to wrap my head around the local threat in Oklahoma tomorrow. Convection seems obvious near the triple point up near Nebraska/Iowa. Confidence is otherwise growing lower of initiation along the dryline in Kansas, but it’s still possible. 

The only models remaining with substantial CI in Oklahoma are the Euro and RGEM. FV3 seems a bit more subdued, although it has a tendency to over convect anyway. A few ARW members hint at very isolated CI as well. HRRR, NSSL WRF and 3km NAM all show nothing, despite a minimally capped environment near peak heating. 

What caught my eye is that the RAP/NAM both show a shortwave crossing across North Texas toward eastern Oklahoma around 21-00z. Given the orientation of the dryline and local climatology, I’d think that at least one storm tries to go up in southwestern/south-central Oklahoma. Not sold on storm intensity or longevity, but it’s a very difficult forecast from a public awareness standpoint. 

Oh yeah, we’ll probably see some strong/severe convection in North Texas toward the Arklatex well. 

SREF odds of convective precip, in vicinity of favorable instability: 

SREF_prob_combined_0.01_30_1000__f027.gi

Wednesday is complicated. If early day convection doesn’t lead to a mess, it will be a day to remember. Even if there is ongoing convection (East Texas toward the Arklamiss area), there seems to be good model agreement with a broken line of convection with embedded supercells sweeping across Arkansas and southeastern Missouri in the afternoon. Shear vectors tend to line up more parallel with the boundary there, but some hodograph curvature still supports a tornado risk. 

Even if it evolves as a total mess of convection, I’d be surprised if there isn’t at least 1-2 long-track and/or intense supercells, somewhere in the AR/MO/MS/W TN vicinity, given the degree of shear and moist low-levels; low LCLs.

I think we’re in the midst of one of the more profound multi day early spring stretches, that I can recall, in recent memory. 

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15 hours ago, Powerball said:

Models have consistently shown a weak MCV tracking across East Central TX and Western LA during peak heating tomorrow, which (if legit) should help to trigger fairly extensive activity down there.

That said, it might it up leaving somewhat of a "lull" in the coverage of activity to the north of it and to the south of the areas closer to the main trough in KS / IA / NE / MO.

000

FXUS64 KTSA 120856

AFDTSA

 

Area Forecast Discussion

National Weather Service Tulsa OK

356 AM CDT Tue Apr 12 2022

...New SHORT TERM, LONG TERM...

The prospects for severe storms forming to the west along the dryline late this afternoon and migrating into our area this evening appear low due to subsidence behind the subtropical wavementioned above. 

.LONG TERM...

(Tonight through Monday)

Issued at 338 AM CDT Tue Apr 12 2022

Lingering storms with the wave this evening will be moving out early, and most of the night is then likely to be quiet.

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15 hours ago, Powerball said:

Models have consistently shown a weak MCV tracking across East Central TX and Western LA during peak heating tomorrow, which (if legit) should help to trigger fairly extensive activity down there.

That said, it might it up leaving somewhat of a "lull" in the coverage of activity to the north of it and to the south of the areas closer to the main trough in KS / IA / NE / MO.

 

5 minutes ago, Powerball said:

000

FXUS64 KTSA 120856

AFDTSA

 

Area Forecast Discussion

National Weather Service Tulsa OK

356 AM CDT Tue Apr 12 2022

...New SHORT TERM, LONG TERM...

The prospects for severe storms forming to the west along the dryline late this afternoon and migrating into our area this evening appear low due to subsidence behind the subtropical wavementioned above. 

.LONG TERM...

(Tonight through Monday)

Issued at 338 AM CDT Tue Apr 12 2022

Lingering storms with the wave this evening will be moving out early, and most of the night is then likely to be quiet.

000

FXUS64 KOUN 120844

AFDOUN

 

Area Forecast Discussion

National Weather Service Norman OK

344 AM CDT Tue Apr 12 2022

 

...New SHORT TERM, LONG TERM...

 

.SHORT TERM...

(Today and tonight)

Issued at 319 AM CDT Tue Apr 12 2022

 

Severe Weather: A highly conditional risk for severe weather exists to the east of the dryline this afternoon, with uncertainty higher than normal regarding storm initiation. Much of the uncertainty is related to the degree of capping as well as the degree of subsidence that will be over our area in the wake of a southern stream wave clearly evident on water vapor imagery currently ejecting out of northern Mexico. The timing and positioning of the wave will be such that much of our area will be too far north and west to benefit from any lift associated with the wave and will instead be in the subsident region of the wave during peak heating this afternoon. With the parent upper trough still well to our west across the Rockies we do not expect much in the way of broader large scale ascent or mid-level cooling to help initiate storms. It will therefore be mainly up to the dryline circulation as our main forcing mechanism for convective initiation this afternoon. Models have been fairly consistent in their lack of support for convective initiation across much of the area (outside of the ECM model) for days now, which does not add confidence we will see much activity at all this afternoon. However, models are not infallible (see yesterday`s convection across southeast OK) and forecast soundings show little to no CIN remaining along the dryline by 21z this afternoon. It would not take much more than some localized backing/convergence along the dryline to lead to initiation. So while we are currently not expecting widespread coverage of storms, it is entirely possible we see one or two thunderstorms along the dryline by late this afternoon. Perhaps the most likely scenario will be thunderstorms developing and moving into our area out of north Texas on the northern periphery of the southern stream wave, with little to no activity developing across portions of north-central Oklahoma.

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HRRR (t0 be expected) seems like the only high res model with the storms in STX and Mexico.  I think it is nowcast time, off hour balloons, maybe local NWS offices mention AMDAR.  I don't know what is happening today.  Not sure anybody does.

 

Speaking of 18Z or 20Z balloons, SJT or EWX should be a balloon site.  Nothing between Del Rio and FWD balloons (or Houston (no balloon at all)).

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

DFW 12Z sounding looks like a forged steel cap  94F convective temp, still plenty of CAPE, if the cap can erode.

 

https://www.spc.noaa.gov/exper/soundings/22041212_OBS/

TitaniumCap.PNG

FWIW, 94*F is just the convective temperature right now.

As the airmass is modified throughout the day at different levels in the atmosphere, the convective temperature can increase or decrease.

In today's case, the height falls / cooling mid-levels expected, steady advection of low-level moisture keeping dewpoints in the mid/upper 60s and a shortwave that will enhance the forcing of updrafts should all help to lower the convective temps and erode the cap more efficiently than yesterday.

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D1 Mod out for Iowa

SPC AC 121311

   Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0811 AM CDT Tue Apr 12 2022

   Valid 121300Z - 131200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS
   WEST-CENTRAL/NORTH-CENTRAL IOWA...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   CENTRAL PLAINS/UPPER MIDWEST AND NORTH/CENTRAL TEXAS...

   CORRECTED FOR NDFD THUNDER GRAPHIC

   ...SUMMARY...
   Scattered severe thunderstorms capable of producing very large hail,
   damaging winds, and tornadoes are expected late this afternoon and
   tonight across a broad portion of the southern/central Plains into
   the Mississippi Valley. Some of the tornadoes could be strong.

   ...Central Plains/Middle Missouri Valley/Upper Midwest...
   Portions of west-central/north-central Iowa have been upgraded to a
   Categorical Moderate Risk, with a somewhat focused potential for
   tornadoes along with large hail and damaging winds expected late
   this afternoon and evening near the surface low and nearby triple
   point/warm front vicinity.

   Potentially intense thunderstorm development, including
   surface-based convection and elevated storms to the north of the
   northward-shifting warm front, is expected by late afternoon across
   eastern Nebraska/northwest Iowa/southeast Minnesota generally near
   the surface low/triple point. Moisture return across the warm sector
   will be relatively modest (generally upper 50s to low 60s F
   dewpoints), but will be sufficient for the development of moderate
   buoyancy due to the presence of steep mid-level lapse rates and
   relatively cool temperatures aloft. Wind profiles will be quite
   favorable for supercells near the triple point and in the vicinity
   of the warm front, with very strong deep-layer shear and enlarged
   low-level hodographs. Any discrete supercells that develop within
   this regime will be capable of all severe hazards, including the
   potential for strong tornadoes and very large hail.

   Later this evening, more widespread/southward-spatially expanding
   convection is expected along the eastward-surging cold front,
   resulting in an increasing damaging wind threat this evening.
   Damaging winds aside, a tornado threat will also exist with any
   embedded circulations within the line of frontal convection given
   the robust magnitude of low-level winds (upwards of 60-70 kt) in the
   lowest 2-3 km AGL. Overall storm intensity will tend to diminish by
   early in the overnight.

   ...Central/North Texas to the Lower Mississippi Valley...
   A southern-stream/lead shortwave trough nearing the south
   Texas/Mexico border vicinity this morning will continue
   northeastward toward the ArkLaMiss through evening. Storms may
   develop as soon as mid-afternoon near the dryline as it extends
   across north/west-central Texas. Effective shear of 35-45 kt will
   favor a few eastward-moving supercells and/or organized clusters
   into late afternoon/early evening. Moderate-to-strong buoyancy and
   steep mid-level lapse rates will support a threat of very large hail
   and severe wind gusts with the strongest cells/clusters. Any
   supercells that can persist into the richer low-level moisture east
   of the dryline may also pose some tornado threat.

   An additional/somewhat separate corridor of potentially severe
   storms are possible this afternoon and evening farther east across
   far east Texas into Louisiana and southern Arkansas. While the
   details are a bit unclear, strengthening deep-layer shear and
   moderate buoyancy would be supportive of at least some hail/wind
   potential, and low-level shear/helicity, enhanced by a diurnally
   sustained branch of the low-level jet, may be sufficient for a
   couple of tornadoes as well.

   ...Central/eastern Oklahoma and south-central Kansas...
   A conditionally favorable supercell environment will exist late this
   afternoon into evening along and ahead of the dryline that will
   exist from central Kansas southward into west-central Oklahoma.
   However, this region will be between the main mid-level trough and
   surface low to the north, and the ejecting low-amplitude shortwave
   trough to the south. Most convection-allowing models continue to
   show very little signal for deep convective initiation in this
   region. However, some global guidance such as multiple runs of the
   ECMWF depict isolated development across central Oklahoma, and this
   may be plausible given ample post-dryline heating/mixing and
   confluence/modest convergence near the dryline. If/where storms
   develop and sustain, localized intense/significant severe weather
   may occur. Very large hail would be a possibility and a tornado risk
   will likely exist as well, especially if any storms are sustained
   through early/mid-evening as low-level hodographs further enlarge.

   ..Guyer/Smith.. 04/12/2022

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
   CURRENT UTC TIME: 1349Z (8:49AM), RELOAD THIS PAGE TO UPDATE THE TIME
        
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Thunderstorms developing near LRD, where, theoretically, the cap should be stronger than almost anywhere else in Texas.  Might even be hail near Hebbronville  Not seeing it on 12Z/14Z guidance, the disturbance is clear on satellite, but I think Monterrey is the only RAOB site in that part of Mexico and the SW looks mostly N of there..

 

Edit to Add: NWS CRP has a special weather statement for small hail and 40 mph winds.

 

Another edit: 

 

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SEL0

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 110
   NWS Storm Prediction Center Norman OK
   130 PM CDT Tue Apr 12 2022

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Central and northwest Texas

   * Effective this Tuesday afternoon and evening from 130 PM until
     900 PM CDT.

   * Primary threats include...
     Scattered large hail and isolated very large hail events to 2.5
       inches in diameter likely
     Scattered damaging wind gusts to 70 mph likely

   SUMMARY...Thunderstorm development is underway south of Abilene, in
   an environment that favors continued expansion and intensification
   of the storms through the afternoon.  A mix of multicell clusters
   and some supercell structures will be possible, with an attendant
   threat for large hail up to tennis ball size, and damaging outflow
   gusts up to 70 mph.

   The severe thunderstorm watch area is approximately along and 55
   statute miles east and west of a line from 45 miles north northwest
   of Mineral Wells TX to 75 miles south southwest of Brownwood TX. For
   a complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU0).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Severe Thunderstorm Watch means conditions are
   favorable for 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. Severe thunderstorms can and occasionally do produce
   tornadoes.

   &&

   AVIATION...A few severe thunderstorms with hail surface and aloft to
   2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
   few cumulonimbi with maximum tops to 550. Mean storm motion vector
   27020.

   ...Thompson
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60/40 tor and 95/95 hail probs on the midwest watch

SEL1

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 111
   NWS Storm Prediction Center Norman OK
   335 PM CDT Tue Apr 12 2022

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Northwest Iowa
     Northeast Nebraska
     Extreme southeast South Dakota

   * Effective this Tuesday afternoon and evening from 335 PM until
     1000 PM CDT.

   * Primary threats include...
     A few tornadoes likely with a couple intense tornadoes possible
     Scattered large hail and isolated very large hail events to 2.5
       inches in diameter likely
     Scattered damaging winds likely with isolated significant gusts
       to 75 mph possible

   SUMMARY...Supercell development will be possible in the next couple
   of hours, near and east of a surface cyclone along the
   Nebraska/South Dakota border.  The storm environment will continue
   to become more favorable for a few tornadoes (a couple of which
   could be strong) and very large hail, if storms can mature quickly
   enough in the relatively narrow, unstable warm sector near the warm
   front.  Damaging winds will also be possible, especially late this
   evening when storms could grow upscale into a squall line along the
   cold front approaching from the west.

   The tornado watch area is approximately along and 60 statute miles
   east and west of a line from 50 miles northeast of Yankton SD to 45
   miles south of Sioux City IA. For a complete depiction of the watch
   see the associated watch outline update (WOUS64 KWNS WOU1).

   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 110...

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 2.5 inches. Extreme turbulence and surface wind
   gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean
   storm motion vector 22040.

   ...Thompson
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40/20 tor probs but 60/50 hail

SEL2

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 112
   NWS Storm Prediction Center Norman OK
   410 PM CDT Tue Apr 12 2022

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Central and north Texas

   * Effective this Tuesday afternoon and evening from 410 PM until
     1100 PM CDT.

   * Primary threats include...
     A couple tornadoes possible
     Scattered large hail likely with isolated very large hail events
       to 2.5 inches in diameter possible
     Scattered damaging wind gusts to 70 mph likely

   SUMMARY...Clusters of storms will continue to spread eastward across
   central Texas, with some tendency for new development northeastward
   toward Dallas-Fort Worth, and southward to near Austin.  The storm
   environment will gradually become more favorable for embedded
   supercells into this evening, with the potential for a couple of
   tornadoes, isolated very large hail, and damaging gusts.

   The tornado watch area is approximately along and 50 statute miles
   east and west of a line from 50 miles north northwest of Corsicana
   TX to 55 miles south southwest of Temple TX. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU2).

   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 110...WW 111...

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 2.5 inches. Extreme turbulence and surface wind
   gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean
   storm motion vector 26025.

   ...Thompson
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Tornado Warning
TXC027-099-122245-
/O.NEW.KFWD.TO.W.0033.220412T2201Z-220412T2245Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Fort Worth TX
501 PM CDT Tue Apr 12 2022

The National Weather Service in Fort Worth has issued a

* Tornado Warning for...
  Southeastern Coryell County in central Texas...
  North central Bell County in central Texas...

* Until 545 PM CDT.

* At 500 PM CDT, a severe thunderstorm capable of producing a tornado
  was located 8 miles north of Fort Hood, moving east at 30 mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* This dangerous storm will be near...
  Mother Neff State Park around 540 PM CDT.
  McGregor around 545 PM CDT.

Other locations impacted by this tornadic thunderstorm include
Oglesby.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to an interior room on the lowest floor of a
sturdy building. Avoid windows. If you are outdoors, in a mobile
home, or in a vehicle, move to the closest substantial shelter and
protect yourself from flying debris.

&&

LAT...LON 3131 9790 3145 9751 3132 9742 3124 9734
      3119 9786
TIME...MOT...LOC 2200Z 255DEG 27KT 3125 9780

TORNADO...RADAR INDICATED
MAX HAIL SIZE...<.75 IN

$$

Bonnette
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 WOUS64 KWNS 122207
   WOU3

   BULLETIN - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH OUTLINE UPDATE FOR WT 113
New watch up in the midwest. 80/60 tor probs, 80/10 wind, 80/70 hail

NWS STORM PREDICTION CENTER NORMAN OK
   510 PM CDT TUE APR 12 2022

   TORNADO WATCH 113 IS IN EFFECT UNTIL 1000 PM CDT FOR THE
    FOLLOWING LOCATIONS

   IAC025-027-033-047-063-069-073-079-081-091-109-147-151-161-187-
   189-195-197-130300-
   /O.NEW.KWNS.TO.A.0113.220412T2210Z-220413T0300Z/

   IA 
   .    IOWA COUNTIES INCLUDED ARE

   CALHOUN              CARROLL             CERRO GORDO         
   CRAWFORD             EMMET               FRANKLIN            
   GREENE               HAMILTON            HANCOCK             
   HUMBOLDT             KOSSUTH             PALO ALTO           
   POCAHONTAS           SAC                 WEBSTER             
   WINNEBAGO            WORTH               WRIGHT              


   MNC013-043-047-091-147-161-165-130300-
   /O.NEW.KWNS.TO.A.0113.220412T2210Z-220413T0300Z/

   MN 
   .    MINNESOTA COUNTIES INCLUDED ARE

   BLUE EARTH           FARIBAULT           FREEBORN            
   MARTIN               STEELE              WASECA              
   WATONWAN             


   ATTN...WFO...DMX...MPX...
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