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Mesoscale Discussion 641
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   Mesoscale Discussion 0641
   NWS Storm Prediction Center Norman OK
   0250 AM CDT Mon Jun 04 2018

   Areas affected...west Texas

   Concerning...Severe Thunderstorm Watch 154...

   Valid 040750Z - 040915Z

   The severe weather threat for Severe Thunderstorm Watch 154

   SUMMARY...Brief/isolated hail and gusty winds may continue for a few
   more hours, especially to the east of San Angelo.

   DISCUSSION...Thunderstorms that developed across New Mexico last
   evening have congealed into a north-south mesoscale convective
   system (MCS) that is slowly working its way east. Radar trends
   suggest that a weak mesoscale convective vortex (MCV) has developed
   within the trailing precipitation region of the aforementioned MCS.
   The circulation around this MCV appears to be lifting a surface
   front northward as a warm front just ahead of the leading edge of
   the MCS. Radar imagery suggests that the intersection of the MCS
   outflow and the lifting warm front is somewhere near the general
   vicinity of where thunderstorm intensity has increased the last 1-2
   hours, currently near Coke County, TX.

   Farther east, thunderstorms developed last night across southeast
   Texas along said front and have been propagating westward through
   the morning hours, with periodic bouts of hail likely occurring. As
   these thunderstorms continue to develop westward along the old
   front, the general propagation component of movement should shift
   from westerly to northwesterly as the new updrafts develop along the
   warm front ahead of the eastward moving MCS. 

   The overall environment across the area remains weakly sheared, but
   unstable, with most-unstable CAPE values between 1000-2000 J/kg
   ahead of both the eastward- and westward-moving thunderstorm
   complexes. Although weak deep-layer shear will not contribute much
   to thunderstorm longevity, low-level circulations associated with
   the remnant front and various outflows should produce enough
   convergence to overcome convective inhibition and the realization of
   the elevated CAPE reservoir. Periodic bouts of hail and gusty
   thunderstorm outflows will remain possible for another few hours.

   A brief uptick in hail and wind potential will occur when the
   outflows from the two separate thunderstorm clusters merge in the
   vicinity of the triple point (front-MCS intersection). Here, the
   increase in low-level convergence should help initiate more vigorous
   updrafts -- at least temporarily -- before an overall weakening
   trend occurs as low-level convergence weakens, amidst an
   increasingly chaotic low-level flow field as the MCS moves
   across/through the westward-moving convection.

   ..Marsh.. 06/04/2018

   ...Please see for graphic product...


   LAT...LON   30960175 32210093 33730030 33509890 31479734 30799722
               30179778 30239859 30720035 30960175 

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