Mesoscale Discussion 0313
NWS Storm Prediction Center Norman OK
1136 AM CDT Wed May 02 2018
Areas affected...Eastern TX/OK Panhandles western OK to parts of
southwest and south-central KS
Concerning...Severe potential...Tornado Watch likely
Valid 021636Z - 021900Z
Probability of Watch Issuance...95 percent
SUMMARY...Development of additional thunderstorms is expected
between 17-19Z across portions of the Texas Panhandle into the
eastern Oklahoma Panhandle into southwest and south-central Kansas.
Severe storms will be likely by early afternoon, with all severe
hazards possible, including very large hail and a tornado threat.
DISCUSSION...Trends in morning surface analyses and visible
satellite imagery showed a quasistationary boundary extending from
extreme southeast NE to southwest KS into the OK Panhandle (east of
KGUY) to far northern TX Panhandle. In KS this boundary was
analyzed at 15Z to the south of KCNK and south of KGBD. Although
surface heating, given breaks in high-level clouds, is resulting in
mixing, persistent southerly low-level winds are compensating to
maintain surface dew points in the middle-upper 60s from the eastern
TX Panhandle into western and central OK to southern and eastern KS.
Moisture return has also spread farther westward this morning into
more of the TX Panhandle. This moisture combined with diabatic
heating will further weaken inhibition, resulting very strong
instability (MUCAPE of 2500-3500 J/kg) this afternoon.
Recent lightning data, satellite and radar imagery showed a storm
had developed near the intersection of the quasistationary boundary
and dry line in Hansford County TX (extreme northern TX Panhandle).
A 70-75 kt southwesterly 500-mb jet accompanying a shortwave trough
will move through the southern High Plains early this afternoon and
proceed downstream into western OK to central KS by late afternoon.
Forcing for ascent attendant to this trough and exit region of the
500-mb jet are expected to reach western portions of the discussion
area between 17-19Z supporting additional storm development into the
afternoon. This scenario is suggested by the last several runs of
the operational HRRR and the 12Z HREF. These initial storms will
continue to form from the northern TX Panhandle to part of southwest
and adjacent south-central KS where low-level convergence is the
strongest, given strengthening low-level winds into the
quasistationary boundary. Storms will also develop equatorward
along and east of the dryline, as it mixes eastward this afternoon
into the eastern TX/OK Panhandles, and into western OK. The
available MUCAPE and increasing effective bulk shear will be
favorable for supercells producing tornadoes, very large hail, and
damaging winds. Storms that develop along the dryline and into
western OK will have a greater likelihood to be discrete, given
shear vectors crossing the initiation boundary. Shear vectors in
vicinity of the boundary in KS may tend to be more parallel
resulting in bows with embedded supercells.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 34580139 35800143 37050058 38399882 39269745 38879669
38139647 37029768 35289889 34409920 34380083 34580139