SPC AC 261732

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1232 PM CDT Mon Apr 26 2021

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
   THE SOUTHERN PLAINS...

   ...SUMMARY...
   Severe thunderstorms are possible Tuesday afternoon through Tuesday
   night, primarily across a portion of the Southern Plains.

   ...Southern plains region...

   A broad fetch of southwesterly winds aloft will become established
   over the Southern Plains Tuesday downstream from an upper trough
   that will amplify over the Southwest States. A warm elevated mixed
   later (EML) will advect through much of the warm sector resulting in
   a strong cap to surface based storms during the day over much of
   this region. Low-level dewpoints in the low to mid 60s will advect
   as far as northwest TX into western OK during the afternoon beneath
   the EML resulting in a corridor of moderate surface-based
   instability with 1500-2000 J/kg MLCAPE possible east of the dryline.
   An early round of scattered showers and thunderstorms still appears
   likely from late morning into the afternoon across parts of central
   and northern Texas into OK in association with ascent attending a
   leading shortwave trough. However, this activity will likely be
   elevated above the CAP, but could pose a risk for marginally severe
   hail.

   Upstream of the early activity, a corridor of surface heating will
   likely occur from western TX into far western OK, and surface based
   storms will likely initiate in vicinity of the eastward-mixing
   dryline by late afternoon. Effective bulk shear from 45-55 kt will
   support supercells as the initial storm mode and this activity will
   pose a risk for large to very large hail. A relatively small window
   will exist for isolated tornadoes as the low-level jet increases
   during the early evening and before the boundary layer decouples.
   Some upscale growth may occur, and activity may continue east
   through parts of northwest and north central TX into OK during the
   overnight with a continued threat for large hail and damaging wind.
   An upgrade to ENG risk for large hail may be introduced from a
   portion of western TX into southwest OK on the day 1 updates.

   A couple of supercells might also develop over the higher terrain of
   northern Mexico and spread into south central TX with very large
   hail and a tornado or two the main threats during the evening.

   ...Central High Plains...

   Upslope flow and low-level convergence near a deepening surface low
   will likely result in thunderstorm development over far northeast CO
   and vicinity Tuesday afternoon. Strong vertical shear may result in
   organized updrafts and the potential for a few supercells.
   Additionally, a cold front stalled across the region could augment
   ascent while also provided a corridor for storm progression.

   ...Upper Midwest...

   Elevated storms early in the period, driven by warm-air advection
   over the front, could occasionally become strong enough to produce
   isolated hail in the vicinity of SD/IA/MN border intersection.
   Additional thunderstorm development is possible later Tuesday
   evening and overnight across southern MI and central WI as the
   low-level jet increases again.

   ..Dial.. 04/26/2021

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