SPC AC 101712

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1212 PM CDT Mon May 10 2021

   Valid 111200Z - 121200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY AND
   SOUTHEAST...

   ...SUMMARY...
   Isolated strong to severe storms may occur Tuesday across parts of
   the southern Plains into the lower Mississippi Valley and Southeast.
   Large hail and damaging wind gusts should be the main threats.

   ...Synopsis...
   Shortwave trough currently moving through the northern Great Basin
   is forecast to continue southeastward into the Four Corners region
   tonight before then moving more eastward across the central High
   Plains/central Plains on Tuesday. Another shortwave trough is
   currently moving east-northeastward across the Baja Peninsula. This
   shortwave is expected to continue moving eastward across northern
   Mexico and into the southern Plains and Lower MS Valley on Tuesday.

   A relatively moist air mass will precede these shortwaves across the
   southern Plains and Lower MS Valley. A stalled frontal boundary will
   likely extend from southern MS/AL west-southwestward through the TX
   Coast Plains into south TX, and then northwestward across northwest
   Mexico. Some northward movement of this boundary is anticipated
   through Tuesday afternoon before building high pressure over the
   central Plains and mid/upper MS Valley encourages a southward surge
   Tuesday evening through early Wednesday.

   ...Southern Plains into the Lower MS Valley and Southeast...
   Showers and thunderstorms will likely be ongoing across portions of
   the Lower MS Valley early Tuesday morning. Thunderstorm coverage is
   expected to increase throughout the morning as ascent attendant to
   the Baja shortwave trough mentioned in the synopsis spreads across
   the southern Plains and Lower MS Valley. Warm-air advection
   associated with strengthening low-level southerly flow across the
   frontal boundary will also aid in storm development. 

   Widespread thunderstorm activity is anticipated across much
   central/east TX and LA by early Tuesday afternoon, which will then
   spread eastward throughout the remainder of the period. Moderate
   vertical shear and buoyancy suggest a few embedded strong to severe
   storms are possible. Majority of these storms will be north of the
   front, indicating hail should be the primary threat. However, given
   the shallow nature of the low-level stable layer, a few stronger
   gusts are also possible. Additionally, northward motion of the warm
   front could result in interaction between ongoing storms and this
   frontal zone, particularly from east TX across central LA and into
   central/southern MS. This interaction may result in a corridor of
   modestly higher severe potential. Even so, mesoscale nature of this
   interaction precluding introducing any higher severe probabilities
   with this outlook.

   A clustered/multicell storm mode is anticipated with most of the
   activity across the southern Plains, Lower MS Valley, and Southeast.
   The only exception is over southwest TX, where a triple point may
   develop at the intersection of the effective warm front and dryline.
   Convective initiation may occur as a result of convergence along
   these boundaries, resulting in more discrete storms. Environment
   supports a threat for large hail and damaging wind gusts if storms
   do develop.

   ..Mosier.. 05/10/2021

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