Storm Prediction Center Aug 7, 2021 0600 UTC Day 2 Convective Outlook

   SPC AC 070457

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1157 PM CDT Fri Aug 06 2021

   Valid 081200Z - 091200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   KANSAS INTO WISCONSIN...

   ...SUMMARY...
   Scattered strong to severe storms are possible Sunday over parts of
   the lower Missouri Valley into the upper Mississippi Valley, and
   across central Montana.

   ...Lower MO Valley into the Upper MS Valley...
   A weak shortwave trough is forecast to move east out of the central
   Plains on Sunday, with a moist and unstable air mass extending into
   the MS Valley. A dryline will extend from eastern NE into central
   KS, with a convectively reinforced warm front over WI and Lower MI
   early. Pockets of enhanced midlevel wind in excess of 35 kt will
   exist with the upper wave, but deep-layer shear will generally be
   marginal for organized severe storms. However, instability will be
   strong, with substantial low-level southerly winds aiding storm
   relative inflow. 

   Early day storms may be ongoing near a warm front from southern WI
   into Lower MI, but they are expected to weaken as the warm front
   develops northward. Scattered diurnal storms will develop by mid
   afternoon from eastern KS into MO and IA, moving into WI and IL
   toward 00Z. Lack of capping along with ample moisture and favorable
   time of day may result in numerous storm clusters, with mixed modes.
   The most likely severe threat will be damaging winds as storms will
   easily propagate along outflows in the moist, uncapped air mass.
   Marginal hail is possible with the initial development before storms
   grow upscale. Isolated tornado threat is less certain, and will
   depend on mesoscale features such as modified outflow boundaries
   near the warm front.

   Due to substantial storm coverage/interference and the marginal flow
   aloft, will maintain a broad region of low severe probabilities,
   with a more focused categorical upgrade possible in later outlooks.

   ...MT...
   A strong shortwave trough and cold front will move across MT during
   the day, with significant height falls across western and central MT
   through 00Z. Lift along the front and very steep lapse rates
   developing ahead of it will favor a line of convection despite only
   a few hundred J/kg MUCAPE. Damaging wind gusts will be the primary
   concern, with the threat ending across east-central MT after 03Z as
   the air mass cools diurnally, and with the rapidly progressing cold
   front.

   ..Jewell.. 08/07/2021

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