Mesoscale Discussion 0134
NWS Storm Prediction Center Norman OK
0331 PM CDT Sun Mar 18 2018
Areas affected...parts of Texas from the Hill Country eastward
Concerning...Severe potential...Watch possible
Valid 182031Z - 182230Z
Probability of Watch Issuance...40 percent
SUMMARY...Storms may develop/increase over the next couple of hours,
with attendant severe potential. WW may be needed.
DISCUSSION...Latest surface analysis shows a warm front moving
slowly north across north-central and northeast Texas, and a dryline
mixing east into the Hill Country. While the warm sector airmass
features dewpoints in the upper 60s, the boundary layer has been
somewhat slow to heat/destabilize due to relatively
widespread/multi-layer cloudiness. Clouds are gradually thinning,
however, with resulting insolation helping to push surface-based
CAPE above 1500 J/kg across the area.
While the cu field remains relatively subdued over the discussion
area per the latest visible satellite loop, some deeper cu is noted
just west, near the dryline. With multiple CAM runs, and the
operational GFS/ECMWF all showing convective development across the
area this afternoon/early evening, is would appear possible that
these hints of deeper dryline cumulus may gradually evolve into an
area of thunderstorms in the next couple of hours.
Along with ample CAPE, area VWPs confirm model forecasts of very
strong west-southwest flow at mid levels, atop (rather weak)
low-level southerlies. Resulting long hodographs would support
supercells/splitting storms -- with large hail likely the main risk
(in addition to locally gusty/damaging winds or even a tornado). We
will continue to monitor cumulus evolution, as a cue for timing on
any potential WW issuance.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 29859809 30879796 31789733 32349630 32289485 31799444
31029452 30289484 29729671 29859809