SPC AC 150526

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1226 AM CDT Tue Sep 15 2026

   Valid 151200Z - 161200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
   SOUTH-CENTRAL PLAINS INTO PARTS OF THE MIDWEST...

   ...SUMMARY...
   Strong to locally severe thunderstorms may occur from the
   south-central Plains into parts of the Midwest this afternoon and
   evening, with at least isolated damaging wind gusts possible.

   ...South-central Plains into parts of the Midwest...
   A vigorous mid/upper-level trough will move quickly eastward across
   Ontario and the Upper Great Lakes region today, before reaching
   southern Hudson Bay and Quebec by this evening. A deep surface low
   will accompany this system, as a trailing cold front moves across
   parts of the central Plains and Midwest. To the south of the
   ejecting trough, an upper ridge is forecast to amplify over the
   Southeast. 

   Persistent clouds and precipitation to the cool side of the front
   will help to reinforce the baroclinic zone as it moves southeastward
   through the day. The front will impinge on an increasingly warm and
   unstable environment by late afternoon, and scattered storm
   development is expected from the TX Panhandle into parts of the
   Midwest. The strongest mid/upper-level flow will be displaced north
   of the front, and low-level flow will tend to weaken through the
   day. 

   This weakening flow regime, combined with gradual midlevel height
   rises and an eventual tendency for storms to be undercut by the
   front, results in uncertainty regarding the magnitude of the
   organized severe threat this afternoon and evening. However,
   seasonably strong heating and relatively large PW and buoyancy will
   support potential for localized downbursts and outflow-driven
   clusters, with attendant damaging-wind potential. Hail potential
   appears generally limited by weak midlevel lapse rates and only
   modest deep-layer shear, though small to near-severe hail may occur
   with the strongest cells. 

   A relatively broad Marginal Risk has been maintained from the
   south-central Plains into the Midwest. Corridors of locally greater
   potential could eventually evolve within the broader risk area,
   especially near any pre-frontal outflow boundaries generated by
   early-day convection. 

   ...Parts of UT/western CO...
   Anomalous moisture will remain in place across parts of the Four
   Corners region and Southwest today. The strongest deep-layer
   flow/shear will reside from UT into western CO, in advance of a
   mid/upper-level trough over the Pacific Northwest. While a few
   strong storms will be possible, generally weak heating and
   destabilization are currently expected to limit the magnitude of the
   severe threat. Small hail and gusty winds could accompany the
   strongest storms.

   ..Dean/Supinie.. 09/15/2026

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