|Mesoscale Discussion 77|
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Mesoscale Discussion 0077
NWS Storm Prediction Center Norman OK
1111 AM CST Tue Feb 20 2018
Areas affected...Northwest TX...North-Central TX...Far South-Central
Concerning...Severe potential...Watch unlikely
Valid 201711Z - 201845Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated small hail and damaging wind gusts are possible
across portions of northwest TX, north-central TX, and far
south-central OK over the next few hours.
DISCUSSION...A line of thunderstorms has developed along a dryline
extending southwestward from just west of SPS to SWW. Atmospheric
profiles are moist and largely void of steep lapse rates but warm
and moist conditions just ahead of the dryline (i.e. temperatures in
the upper 60s/lows and dewpoints in the mid 60s) still support
modest instability. Latest mesoanalysis estimates MLCAPE around 500
to 800 J/kg. Kinematics are a bit more favorable for a few stronger
storms with vertical veering wind profiles shown on regional VADs
sampling 20-35 kt of 0-1 km shear and around 40 kt of 0-6 km shear.
Given these wind field, some updraft rotation is possible with the
more persistent updraft.
Marginal thermodynamics and favorable kinematics will likely keep
strong updrafts predominantly short-lived. Additionally, storm
persistence will be limited by the southward progressing cold front
currently intersecting the dryline just northwest of SPS. Some
brief/localized enhancement of updrafts is possible as frontal
circulations augment lift, but northeastward storm motions will then
result in an undercutting of updrafts. Overall expectation is for
isolated small hail and occasional damaging wind gust across the
region for the next few hours.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 32730008 33939892 34339809 34379709 33379713 32279895
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