SPC AC 251958

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0258 PM CDT Thu Apr 25 2024

   Valid 252000Z - 261200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CENTRAL AND SOUTHERN PLAINS...

   ...SUMMARY...
   Very large hail up to 3 inches in diameter and a strong tornado or
   two will be possible this evening across western Kansas and
   vicinity. Large hail, damaging winds to 70 mph, and a few tornadoes
   will be possible this evening and tonight from northwest Texas into
   central Oklahoma.

   ...20Z Update...
   The Enhanced Risk across western KS has been expanded to include
   more of northwest KS, far northeast CO, and far southwest NE. Based
   on recent visible satellite trends, convective initiation appears
   imminent across east-central CO along/near a surface dryline.
   Additional robust thunderstorm development will likely occur this
   afternoon across northeast CO into northwest KS and vicinity as an
   upper trough continues ejecting eastward over the central High
   Plains. Given moderate buoyancy and strong deep-layer shear, very
   large hail (possibly up to around 3 inches) should be the main
   threat with initial supercells. By early this evening, strengthening
   low-level shear should encourage a greater tornado threat with any
   supercells that can persist, especially as this activity interacts
   with a warm front across northwest KS. A strong tornado or two
   remains a possibility across this area. See Mesoscale Discussion 513
   and recently issued Tornado Watch 133 for more details on the severe
   threat for this region.

   No changes have been made to the separate Enhanced Risk across parts
   of northwest TX into southern/central OK. It still appears likely
   that convection will develop by 06Z across this region, and quickly
   spread east-northeastward through early Friday morning. All severe
   hazards still appear possible with this activity, including the
   potential for a few nocturnal tornadoes given the forecast strength
   of the low-level shear.

   In between the two Enhanced Risks (OK/TX Panhandles), there is still
   a fair amount of uncertainty regarding how many supercells may
   develop along/east of the dryline. Some cu has recently formed over
   the northwest TX Panhandle. But, a 19Z special sounding from DDC
   still shows substantial capping in place. Regardless, a conditional
   threat for supercells posing an isolated threat for very large hail
   and perhaps a couple of tornadoes will exist through this evening
   across this area.

   ..Gleason.. 04/25/2024

   .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Apr 25 2024/

   ...Synopsis...
   Morning water vapor imagery shows a negatively-tilted shortwave
   trough rotating across UT/AZ, with an associated 70kt mid-level jet
   max moving into NM.  This system will eject into the
   central/southern Plains this evening/tonight, resulting in multiple
   clusters of severe thunderstorm activity.

   ...Western KS...
   A quasi-stationary surface boundary extends from northwest CO into
   northwest KS.  Visible imagery shows broken cloud cover across
   western KS this morning, with dewpoints in the low 60s to the south
   of the front.  Strong heating will likely ensue through the
   afternoon, resulting in deepening mixing to the east of the dryline
   and eventual isolated thunderstorm development.  CAM solutions
   differ significantly on coverage of convection, but it appears
   likely that at least isolated supercells will form along the
   dryline, capable of very large hail, damaging winds, and a few
   tornadoes (possibly strong).  

   The confidence of initiation is much higher along the warm front
   from northeast CO into northwest KS, and forecast soundings along
   this corridor show strong low-level vertical shear supporting
   supercell structures.  It is uncertain how far north these storms
   can remain surface-based, but there is an apparent tornado risk
   (possibly strong) along the immediate boundary and a large hail risk
   for some distance northward.  This activity will likely spread into
   south-central NE after dark.

   ...TX Panhandle/Western OK...
   As the primary upper trough ejects this evening, large-scale height
   falls and forcing will overspread the dryline across the OK/TX
   Panhandles.  Forecast soundings show a persistent capping inversion
   along the dryline, and CAM guidance generally shows very isolated
   convective initiation.  Any storm that forms will pose a risk of all
   severe hazards, including very large hail.

   Overnight, a strengthening low-level jet over west TX will likely
   lead to a large cluster of thunderstorm.  These storms will track
   northeastward across northwest TX and into western/central OK in the
   pre-dawn hours.  Large hail will be likely with these storms, but
   damaging winds and isolated tornadoes will also be a risk if a more
   organized linear MCS can evolve.

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