Severe Storm Outlook Narrative (AC)
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
ACUS11 KWNS 202038
SPC MCD 202037

Mesoscale Discussion 0198
NWS Storm Prediction Center Norman OK
0237 PM CST Mon Feb 20 2017

Areas affected...Parts of Louisiana and into far southwest

Concerning...Severe potential...Watch unlikely

Valid 202037Z - 202230Z

Probability of Watch Issuance...20 percent

SUMMARY...A slow increase in storm intensity is ongoing, along with
low-probability risk for an isolated damaging wind gust or two, or a
brief tornado.  At this time, it appears that risk will remain
sufficiently limited to preclude the need for WW issuance.

DISCUSSION...Latest surface analysis shows persistent southeasterly
flow off the north-central Gulf of Mexico, contributing to both
onshore advection of upper 60s to low 70s dewpoints, as well as some
enhancement to the low-level shear profile.  As a semi-organized
band of storms continues crossing western Louisiana, a weakly
heating/destabilizing airmass (characterized by around 750 J/kg
mixed-layer cape) is contributing to some increase in updraft
strength -- both within the line, and with isolated showers
developing ahead of the main band of storms.

While potential for additional destabilization is limited, low-level
and deep-layer shear are both sufficient to support a few stronger
cells, and at least weak/mid-level rotation.  Indeed, a few cells
immediately ahead of the main convective band have exhibited weak
rotation per area wsr-88d data, and this will likely continue over
the next several hours.  Overall risk, however, appears likely at
this time to remain marginal, and thus likely not requiring watch

..Goss/Guyer.. 02/20/2017

...Please see for graphic product...


LAT...LON   29749036 29169024 29079132 29409283 30819321 32059330
            32479261 32109152 30889136 29749036 is the U.S. government's official web portal to all federal, state and local government web resources and services.