SPC AC 240550

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1250 AM CDT Sun May 24 2020

   Valid 251200Z - 261200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHWEST
   TX INTO DEEP SOUTH TX...ACROSS THE OZARKS...OVER SOUTH FL...AND OVER
   PORTIONS OF THE UPPER MIDWEST...

   ...SUMMARY...
   A few strong to severe thunderstorms are possible from southwest
   Texas into deep South Texas, over the Ozark Plateau, over south
   Florida, and across portions of the upper Mississippi Valley Monday.

   ...Synopsis...
   An upper trough will likely extend from eastern MT southward into
   western NM early Monday morning. Eastward progression of this trough
   will be impeded by strong subtropical ridging over the eastern
   CONUS, but some gradual eastward motion is anticipated. As this
   occurs, an upper low is forecast to develop over the southern
   Plains. The development of this low combined with the eastern CONUS
   ridging will contribute to an eventual split of the upper pattern
   into northern and southern streams by early Tuesday.

   Surface pattern is forecast to feature a cold front extending from
   southern MN southwestward through the TX South Plains. Forcing along
   this front combined with ascent attendant to the developing upper
   low are expected to contribute to thunderstorm development across
   much of the southern and central Plains northward into the Upper
   Midwest.

   Additionally, a tropical wave moving into the eastern Gulf of Mexico
   will foster strengthening low-level winds across southern FL and an
   increased risk for damaging wind gusts and/or brief tornadoes.

   ...TX South Plains/Southwest TX to the Lower TX Coast...
   Portion of the cold front over the southern High Plains will
   gradually push southeastward throughout the day. Convergence along
   the front and ascent attendant to a shortwave trough moving through
   the southern High Plains is forecast to result in convective
   initiation. Steep lapse rates will support robust updrafts capable
   of large hail and strong downdrafts with the initially more cellular
   storms.

   The progressing shortwave trough/northwesterly flow aloft is
   favorable for upscale growth into a convective line that then tracks
   southeastward into the favorable air mass downstream (from southwest
   TX along the Rio Grand Valley/western TX Hill Country).  Strong
   instability will be in place within this air mass, supporting a
   continue severe risk through south TX and the lower TX coast. This
   scenario is supported by all of the medium-range guidance, but given
   the potential for a similar scenario on Sunday, uncertainty
   regarding air mass recovery merits introducing only low severe
   probabilities with this forecast. Increased probabilities may be
   needed in later outlooks. 

   Isolated strong/severe storms preceding the convective line,
   initiated off the higher terrain of northwest Mexico, are also
   possible from the Big Bend into the Edwards Plateau.

   ...Ozark Plateau...
   Widespread thunderstorm development is anticipated from eastern
   OK/southeast KS across the Ozarks on Monday. Much of this activity
   will likely be non-severe multicells. However, mid-level winds are
   forecast to strengthen around the upper low Monday late
   afternoon/evening. Consequently, a few stronger storms capable of
   damaging wind gusts and perhaps even a brief tornado are possible.

   ...South Florida...
   Showers and thunderstorms are forecast to be ongoing at the
   beginning of the period, continuing throughout much of the day, as
   the tropical wave moves northeastward through the eastern Gulf of
   Mexico. Strong southeasterly surface winds beneath enhanced
   low-level (i.e. 1 to 2 km) flow will support large, looping
   low-level hodographs, primarily between 12Z and 18Z. Instability
   will be limited, but any more persistent/deeper updrafts could
   support damaging wind gusts and/or brief tornadoes.

   ...Upper Midwest...
   Warm-air advection (attendant to enhanced low-level flow) is
   forecast to support isolated strong/severe thunderstorms near the
   warm front extending across central WI, both early in the period and
   again Monday evening. This area will be on the edge of the stronger
   vertical shear, contributing to the potential for a few more
   robust/organized updrafts capable of hail.

   ..Mosier.. 05/24/2020

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