ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 260842
   SPC AC 260842

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0342 AM CDT Wed Aug 26 2026

   Valid 291200Z - 031200Z

   ...DISCUSSION...
   ...D4/Saturday - Northern Plains to Upper Midwest...
   A mid-level ridge will move slowly east across the Plains with
   slight suppression through the day. A lee trough will consolidate
   into a surface low across the northern Plains through the day
   Saturday. Ahead of this surface low, strong instability is forecast
   across South Dakota and vicinity. Despite the favorable environment
   across this region, primary forcing will be focused on the nose of
   the low-level jet across Iowa and into Wisconsin, well east of the
   greatest instability and near the Canadian border. Therefore,
   limited storm coverage precludes severe weather probabilities at
   this time, but given the favorable environment, it will need to be
   monitored closely. 

   ...D5/Sunday - North Dakota and Vicinity...
   A mid-level shortwave trough will move from the Pacific Northwest to
   the northern Plains Saturday/D4 and Sunday/D5. 00Z guidance has come
   into fairly consistent agreement with the location and amplitude of
   this trough across eastern Montana at 00Z Sunday evening. However,
   there is considerable disagreement with the degree of
   destabilization across North Dakota, where forcing will be greatest.
   The GFS dry bias across most of the Plains has severely lessened the
   instability. However, despite this challenge, it is apparent that
   most of the instability significantly southeast of the upper-level
   forcing. The GFS-Para seems to have a more realistic handle on
   low-level moisture/instability magnitude but it also shows a
   significant disconnect between where this instability is located and
   the deeper forcing. 

   The deterministic ECMWF forecast shows a potentially significant
   severe weather event across North Dakota with strong instability and
   shear ahead of a robust convective QPF signal. This is supported by
   the AI-ECMWF which shows a similar evolution. However, the
   EC-ensemble mean of instability shows at least some trend toward the
   GEFS with primary instability southeast of the best forcing. 

   It is also worth noting that the wave is forecast to eject across
   North Dakota relatively late (~06Z) which may be a somewhat limiting
   factor to a greater threat. This potential timing disconnect,
   combined with some hint of limited overlap between the greatest
   instability and the primary upper forcing, cast enough uncertainty
   to preclude severe weather probabilities at this time. However, it
   is worth noting that if a solution similar to the ECMWF
   materializes, a significant severe weather event is possible. 

   ...D6 and Beyond...
   By early next week, the primary mid-level ridge appears to center
   around the southern Appalachians with broad southwesterly flow from
   the Southwest to the Great Lakes. Within this area of southwesterly
   flow, multiple embedded mid-level shortwave troughs are forecast.
   Predictability of these smaller scale features is relatively low at
   this range, but some continued severe weather threat will likely
   persist around the periphery of the ridge from the Plains to the
   Great Lakes and potentially into the Northeast.

   ..Bentley.. 08/26/2026

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