SPC AC 251252

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0752 AM CDT Sat May 25 2019

   Valid 251300Z - 261200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   TEXAS/OKLAHOMA PANHANDLES...WESTERN OKLAHOMA...AND SOUTHERN
   KANSAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS TO LOWER MISSOURI VALLEY AND THE NORTHEAST STATES...

   ...SUMMARY...
   Severe thunderstorms are likely this afternoon into tonight from the
   Texas and Oklahoma Panhandles into western/northern Oklahoma and
   Kansas. Other severe storms are expected across the upper Ohio River
   Valley and Allegheny Plateau, and possibly other portions of the
   Midwest.

   ...Southern/central Plains into the Lower Missouri Valley...
   Although upstream disturbances/features remain subtle in
   early-morning water vapor imagery, a ribbon of moderately strong
   southwesterly winds aloft will overlie a southern High Plains
   surface low, southward-extending dry line, and
   northeastward-extending front across Kansas to near the
   Iowa/Missouri border, along with warm-sector areas of differential
   heating/decayed outflow. In the presence of moderate to strong
   instability, characterized by MLCAPE of 2000-3000 J/kg, considerable
   thunderstorm development is expected this afternoon, perhaps as soon
   as early afternoon in the Texas/Oklahoma Panhandles as well as the
   Texas South Plains/southwest Kansas. This notion is supported by
   modest capping inversions per 12Z observed soundings from Amarillo
   and Dodge City (18Z special soundings are expected).

   This surface-based deep convection should largely remain
   semi-discrete as supercells in the presence of ample (45-55 kt)
   effective shear. Large hail should be the most common risk, although
   a few tornadoes could occur, particularly across the Texas Panhandle
   vicinity this afternoon, and a somewhat broader area (including
   western Oklahoma into Kansas) by early evening as low-level
   hodograph length/curvature increases via a moderately strong
   low-level jet.

   This evening, convection appears likely to grow upscale into one or
   two larger clusters, spreading northeastward and eastward,
   particularly across southern Kansas and western/northern Oklahoma.
   This would be accompanied by an increasing risk for damaging winds.
   Other storms will likely develop and expand along the front this
   evening as it extends from eastern Kansas into northern Missouri
   accompanied by increasing risks for severe storms.

   Farther north, as mentioned in the prior outlook discussion, if
   convection farther south does not become an inhibiting factor, a
   front/dryline intersection across far southeast Colorado and
   west-central/northwest Kansas may also provide a focus for the
   initiation of at least isolated late afternoon storms, including
   supercells.

   ...Northern Illinois/eastern Iowa/far southern Wisconsin...
   A weakening MCV will continue to cross Illinois and Indiana today
   with decayed-MCS/overturning-related trajectories at least somewhat
   influencing the region early today to the south of a
   slow-southeastward-advancing front. Various model guidance may be a
   bit aggressive in terms of diurnal destabilization, particularly if
   clouds linger through the afternoon, although moistening from the
   southwest can be expected with moderate destabilization and weak
   convective inhibition plausible by late afternoon.

   While upper heights will be tending to rise and near-frontal
   convergence may remain modest, mid-level temperatures will remain
   semi-cool atop the front. In all, given ample buoyancy and
   supercell-conducive deep-layer winds, at least a conditional-type
   severe risk warrants severe probabilities for any possible 
   development later today into this evening, including areas from
   eastern Iowa/far southern Wisconsin toward the southern Lake
   Michigan vicinity.

   ...Lower Great Lakes/Allegheny Plateau/upper Ohio Valley region...
   An upper-level ridge will continue to flatten over the region,
   largely related to a shortwave trough crossing Ontario and Quebec. A
   convectively related disturbance/MCV over the Midwest early today
   may also be a factor in deep convective development this afternoon,
   in addition to lake breeze influences to the south/east of Lake Erie
   and perhaps Lake Ontario. In the presence of 30-50+ kt lower/mid
   tropospheric flow and moderate CAPE, at least a few supercells can
   initially be expected. This could include a severe hail risk and
   possibly some tornado potential, owing to moderate low-level
   hodograph length/curvature, particularly in relative proximity to an
   eastward-shifting warm front. Over time, a couple of upscale-growing
   east/southeastward-moving convective clusters could develop with
   damaging winds a concern.

   ..Guyer/Broyles.. 05/25/2019

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