Mesoscale Discussion 1208
NWS Storm Prediction Center Norman OK
0525 AM CDT Sat Jul 01 2017
Areas affected...TX Big Country
Concerning...Severe Thunderstorm Watch 387...
Valid 011025Z - 011230Z
The severe weather threat for Severe Thunderstorm Watch 387
SUMMARY...Locally strong/damaging wind gusts cannot be ruled out
through early this morning across the Texas Big Country as a solid
band of storms advances to the east-southeast. The need for a new
severe-thunderstorm watch is unlikely, at this time, for areas
downstream across the southwest portion of the FWD county warning
area and the adjacent part of the EWX county warning area.
DISCUSSION...At 0950Z, mosaic radar imagery showed a solid band of
storms extending from Haskell County to northwest Coke and southeast
Mitchell counties, with the southern extent of this band having the
fastest movement to the southeast at 40 kt. This faster storm
motion is likely due to better proximity to stronger 2-hourly
surface pressure rises of 4-mb within the attendant cold pool. In
addition, early morning surface and radar imagery analysis detected
a composite convective outflow boundary extending from northeast TX
(25 SE GGG) westward to 40 E SEP to near MKN and BWD, then
west-northwestward to northeast Coke County and southwest to 35 S
MAF. The main band of storms has remained north of the outflow
boundary, and should continue to move the southeast through the
eastern part of WW 387, given northwesterly shear vectors remaining
perpendicular to the convective band.
Recent surface observations with the passage of the band of storms
have remained sub-severe. Although a strong/damaging wind gust
cannot be ruled out, given the strong surface pressure rises,
warming cloud tops with this MCS and weakening/veering low-level jet
suggest the overall severe-weather threat is likely waning.
Meanwhile, higher theta-e air near and south of the composite
convective outflow boundary across the southwest portion of FWD
county warning area into adjacent counties of EWX county warning
area suggest more favorable inflow air to sustain any remaining
thunderstorms that reach those areas. However, the weakening
low-level jet should limit ascent into the southern part of the MCS
and preclude a greater severe-weather threat this morning that would
warrant a new WW. This scenario is supported by the last several
HRRR runs, showing the stronger storms weakening by 15Z from SJT to
BWD to near FTW.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 32030099 32320016 32949980 33129970 33159944 32869880
32509876 31949829 31379839 31229890 31249961 31440024