SPC AC 221956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Tue Aug 22 2023

   Valid 222000Z - 231200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
   SOUTH TX...THE EASTERN GREAT BASIN TO NORTHERN ROCKIES...AND MI...

   ...SUMMARY...
   A brief tornado or two will remain possible through the rest of the
   afternoon across a portion of South Texas. Isolated severe wind
   gusts will be the primary threat later this afternoon across parts
   of the eastern Great Basin to the northern Rockies. Isolated severe
   hail will be possible across parts of Michigan early Wednesday.

   ...20Z Update...
   The 2% tornado probabilities in south TX have been trimmed to more
   closely align with an arc of convection to the east/northeast of TC
   Harold's center. While low-level shear/SRH will tend to gradually
   decrease with time as Harold weakens, transient low-topped
   supercells capable of a brief tornado or two will remain possible
   through the remainder of the afternoon to the north/northeast of
   Harold's track, as it continues to move west-northwestward. 

   Elsewhere, no changes have been made to the Marginal Risk areas. See
   the previous discussion below for more information, and also see MCD
   2025 for more information regarding the short-term threat from parts
   of UT into southwest WY.

   ..Dean.. 08/22/2023

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Aug 22 2023/

   ...South TX...
   TC Harold near the Lower Texas Coastal Plain will move
   west-northwest and weaken across South TX into this evening.
   Potential for a brief tornado or two should linger to the
   west-northwest through north relative to the center circulation.
   Low-topped convection along the western extent of surface dew points
   at or above 76 F should remain coupled with adequate low-level SRH
   for a few more hours inland before the environment conducive to
   tornadoes diminishes spatially and in magnitude late this afternoon.

   ...Eastern Great Basin to the northern Rockies...
   Similar to yesterday, a moisture plume coincident with a belt of
   enhanced mid-level southerlies will support sporadic strong storms,
   focused on central to eastern UT and western WY. A few multicells
   and transitory/weak supercell structures should evolve this
   afternoon, mainly within a corridor where differential
   boundary-layer heating is most pronounced. While deep-layer shear
   will be sufficient for storm organization, moist profiles will
   render weak mid-level lapse rates, limiting the overall
   magnitude of destabilization and the severe wind threat.

   ...Upper Great Lakes...
   A repeat scenario of elevated thunderstorm development is expected
   during the early morning Wednesday shifted a bit farther east
   relative to this morning across parts of MI. With a stronger
   low-level jet overnight and deeper updrafts regenerating within the
   zone of isentropic ascent along the fringe of an EML expanding east
   from northern MN to western Upper MI, a cluster convective mode
   should largely dominate. This will probably marginalize the severe
   hail risk, while severe wind gusts appear unlikely given the stable
   boundary layer where storms are expected to occur.

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