ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 160837
   SPC AC 160837

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0337 AM CDT Tue May 16 2023

   Valid 191200Z - 241200Z

   ...DISCUSSION...
   Medium-range models appear to be in reasonable large-scale agreement
   through Day 6 (Sunday), after which fairly substantial
   synoptic-scale differences begin to emerge over the U.S. --
   initially surrounding timing/amplitude differences related to a
   short-wave trough progged to dig southeastward across the Canadian
   Prairie.  While the GFS keeps this feature entirely confined to
   Canada, turning it in a more easterly direction through Day 7, the
   ECMWF brings this feature much farther southeastward -- across the
   Upper Mississippi Valley and Great Lakes region Days 7-8.

   Prior to this breakdown in agreement however, there is more
   substantial agreement that a cold front crossing the central third
   of the country will continue moving eastward across the Midwest and
   southward across the southern Plains Day 4, and then to the Atlantic
   and Gulf Coasts Day 5.  With this front suppressing higher theta-e
   low-level air to the southern/southeastern U.S., a
   second/reinforcing front Day 6 is forecast to surge southeastward
   across the central and eastern states -- maintaining this southward
   suppression of warm/moist air.

   As a result of the above, the overall pattern is suggestive of
   minimal severe-weather risk.  The greatest risk apparent during the
   time period appears to reside over the southern Plains Day 4
   (Friday), as the initial cold front shifts southward across the
   southern Plains.  While weak short-wave ridging aloft is forecast to
   prevail, glancing influence of an upper trough moving across the
   upper Midwest should be sufficient to support thunderstorm
   development as the airmass destabilizes during the afternoon.  With
   moderate (around 30 kt) mid-level westerlies expected atop the warm
   sector, threat appears sufficient to warrant 15% areal inclusion at
   this time.

   As the front sags farther southward -- to the Gulf Coast vicinity --
   Day 5 (Saturday), some risk could evolve near the boundary across
   the Gulf Coast states and Georgia.  However, some uncertainty
   regarding frontal location/progress precludes any risk area
   inclusion at this time.

   By Day 6, with higher theta-e air likely suppressed to the Gulf,
   appreciable convection would likely remain confined to the Florida
   vicinity, and deep South Texas, where more limited instability and
   shear should generally prevail.

   ..Goss.. 05/16/2023

   CLICK TO GET WUUS48 PTSD48 PRODUCT