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ACUS11 KWNS 271712
SPC MCD 271712

Mesoscale Discussion 0343
NWS Storm Prediction Center Norman OK
1212 PM CDT Mon Mar 27 2017

Areas affected...Northern/Central MS...Far northeast LA

Concerning...Severe potential...Watch possible

Valid 271712Z - 271915Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorm coverage is expected to increase over the
next several hours. Some severe is possible and trends will be
monitored for possible watch issuance.

DISCUSSION...Moisture continues to advect northward across the
region ahead of the approaching shortwave trough. Current surface
observations reveal low 60 dewpoints as far north as southern
portions of western TN with mid-60s dewpoints reaching into central
MS. 12Z sounding sampled steep mid-level lapse rates (i.e. 7.8 deg C
per km between 700-500 mb at JAN) advecting into the region. These
steep lapse rates atop gradually improving low-level moisture will
support at least moderate instability. Recent mesoanalysis already
suggests MLCAPE at or greater than 1500 J per kg for much of the
region. Modifying the 12Z JAN sounding with current conditions
validates the mesoanalysis estimates and also suggest little
convective inhibition remains. As such, thunderstorm coverage is
expected to increase as forcing for ascent provided by both
low-level confluence and shortwave trough increases.

Strong mid-level flow also exists across the region (i.e. 500 mb
flow around 40 to 50 kt), which will help organize any thunderstorms
that do develop. Given the steep lapse rates and strong mid-level
flow, the primary severe threat appears to be hail and damaging wind
gusts. The tornado threat will be mitigated somewhat by gradually
veering low-level flow and generally modest surface winds. However,
an isolated tornado threat may exist, particularly if storms
interact with any mesoscale boundaries and/or if locally backed
surface winds exist. Trends across the area will be monitored for
possible watch issuance later this afternoon.

..Mosier/Guyer.. 03/27/2017

...Please see for graphic product...


LAT...LON   33619069 33969007 34268902 34058818 33078845 31969042
            32459176 33619069 is the U.S. government's official web portal to all federal, state and local government web resources and services.