SPC AC 170551

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1251 AM CDT Thu Apr 17 2025

   Valid 181200Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM LOWER
   MICHIGAN TO THE SOUTHERN PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms are possible from the parts of the
   Great Lakes to the southern Great Plains, mainly during the late
   afternoon Friday into Friday night. Large hail and isolated severe
   gusts will be the main hazards with this activity.

   ...Synopsis...

   A positive-tilt large-scale upper trough will pivot south and east
   across portions of the north-central to western U.S. on Friday. A
   swath of 60-80 kt 500 mb flow will stretch from the southern Rockies
   to the Great Lakes ahead of the upper trough. At the surface, low
   pressure will develop northeast from the KS/MO/IA vicinity Friday
   morning, to southern Ontario/Quebec by early Saturday. As this
   occurs, a cold front will develop southeast across portions of the
   Mid-MS Valley/Great Lakes and southern Plains. A weak secondary
   surface low likely will develop across west TX, where a dryline will
   extend southward from the eastern Panhandle to the Big Bend region. 


   Southerly low-level flow will transport modest boundary-layer
   moisture northward ahead of these surface features and beneath fast
   mid/upper southwesterly flow. This will support scattered severe
   storms late Friday afternoon into the overnight hours from portions
   of the southern Plains to the Great Lakes.

   ...Lower-MO/Mid-MS Valley to Great Lakes...

   Elevated thunderstorms north of a warm front will likely be ongoing
   during the morning into the afternoon across WI/northern MI. This
   activity may pose a risk for marginally severe hail.

   Meanwhile, a shortwave upper trough embedded within the northern
   branch of the larger-scale western U.S. upper trough will shift east
   across the northern Plains and Upper Midwest during the
   evening/overnight. This will facilitate the eastward progression of
   the surface front through the period, creating a focus for
   thunderstorm development. However, strong capping will limit
   development along the front, likely until closer to 00z, when
   stronger large-scale ascent overspreads the surface boundary and
   cooling aloft ensues. Thunderstorms will likely remain elevated atop
   the strong EML in the 850-700 mb layer, and will likely become
   undercut by the surface cold front given boundary-parallel flow
   through the cloud-bearing layer. Nevertheless, steep midlevel lapse
   rates and sufficient MUCAPE will support organized convection
   capable of producing large hail. With time, cells may become
   training clusters, posing some isolated risk for damaging gusts.

   ...Southern Plains Vicinity...

   As a surface low develops across west TX, a triple point will emerge
   near the eastern TX Panhandle/South Plains vicinity. A stout EML
   will preclude convective development for much of the day. Near the
   triple point and northeast along the advancing cold front, isolated
   to scattered thunderstorms should form in the 22-00z time frame.
   Supercell wind profiles with large MUCAPE, very steep lapse rates,
   and elongated hodographs suggests initial supercells will pose a
   risk for large to very large hail through early evening. Thereafter,
   boundary-parallel flow will result in clustering/training as
   convection also becomes undercut by the front. Damaging gusts also
   may occur with initial supercells given a well-mixed boundary
   layer/steep low-level lapse rates beneath the EML. Additionally,
   some strong gust potential could occur into the Ozarks vicinity as
   clustering ensues, but hail is expected to be the main concern.

   ..Leitman.. 04/17/2025

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