SPC AC 241955

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0255 PM CDT Sun May 24 2020

   Valid 242000Z - 251200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH TEXAS
   AND EASTERN COLORADO INTO THE UPPER MIDWEST...

   ...SUMMARY...
   Severe thunderstorms, with large hail and damaging wind, are
   expected through the evening hours, in a broad swath from south
   Texas to eastern Colorado and into the upper Mississippi Valley.

   ...NE/IA/MO Vicinity...

   The Marginal and Slight risk areas have been expended across
   portions of NE and IA. Mid 60s to low 70s surface dewpoints and
   strong surface heating has resulted in 1500-2500 J/kg MLCAPE. An MCV
   across eastern Kansas is providing increased forcing and enhancement
   of vertical shear across the region (effective shear around 30-40
   kt). As a result, storms are developing further west than previously
   expected. Damaging gusts and hail will be the main threat with these
   storms as they move across WW 217. The SIG hail area was also
   expanded further east and west across parts of this area in
   NE/IA/MO, with baseball size hail recently reported in Clinton
   County MO. 

   ...Southwestern/South-Central TX...

   The only other change to the ongoing forecast was to add 2% tornado
   probs across portions of the Edwards Plateau/mid-Rio Grande Valley
   vicinity in south-central TX. Rich boundary layer moisture is in
   place across the region and forecast soundings show somewhat
   enlarged, curved low level hodographs this evening, and a tornado
   can not be ruled out. Higher tornado probabilities are precluded by
   relatively weak midlevel flow, resulting in potentially less
   favorable cluster/linear storm mode. An increase in wind
   probabilities was considered across this same region, but hi-res
   guidance varies on location and areal coverage of any more intense
   bowing structures developing this evening. Furthermore,
   aforementioned weak midlevel flow could hinder a more robust/damage
   MCS from developing. As such, will maintain 15%/Slight risk.

   Elsewhere, the outlook remains unchanged and the forecast on track.

   ..Leitman.. 05/24/2020

   .PREV DISCUSSION... /ISSUED 1112 AM CDT Sun May 24 2020/

   ...Central/South TX...
   A very moist and moderately unstable air mass is present today over
   most of central and south TX, with dewpoints in the 70s and strong
   daytime heating expected.  Forecast soundings show relatively steep
   midlevel lapse rates and a weak cap.  This should lead to scattered
   robust thunderstorm activity this afternoon and evening.  Storms
   will likely develop first over the mountains of northern Mexico and
   northward along the dryline into the Ft Stockton area, and
   spread/develop eastward through the evening.  Vertical shear is
   sufficient for organized multicell or a few supercell storms capable
   of large hail and damaging winds.  

   ...West TX into KS...
   The dryline will also activate this afternoon across much of West TX
   and the Panhandle region - and possibly as far north as
   central/western KS.  Storms should initiate after 3pm along this
   corridor and spread eastward into western OK through the evening. 
   MLCAPE values of 2000-3000 J/kg, steep lapse rates, and sufficient
   vertical shear will pose another risk of large/very large hail and
   damaging winds with storms across this region today.

   ...KS into IA...
   Visible satellite imagery shows a well-defined MCV over southern KS,
   and several remnant outflow boundaries over portions of eastern KS,
   northern MO, and southern IA.  All of these factors may help to
   initiate scattered thunderstorms this afternoon across this broad
   region.  Ample low level moisture and considerable heating will
   yield MLCAPE values approaching 3000 J/kg, and flow around the
   northward moving MCV may result in a localized favorable environment
   for supercells.  Details are uncertain, but have maintained the
   ongoing SLGT risk across the region for this afternoon and evening.

   ...Southeast CO into Western KS...
   Northeasterly upslope flow is occurring today over southeast CO,
   with dewpoints in the upper 40s.  This will likely be sufficient for
   the development of a few thunderstorms over the Raton ridge this
   afternoon - spreading/developing east-northeastward into western KS
   after dark. A weakening cap and favorable vertical shear profiles
   will support a risk of rotating storms capable of large hail and
   locally damaging wind gusts.

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