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.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 30960175 32210093 33730030 33509890 31479734 30799722
30179778 30239859 30720035 30960175