Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 221259
SWODY1
SPC AC 221258

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0758 AM CDT Mon May 22 2017

Valid 221300Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN NM
AND WEST/WEST-CENTRAL TX...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
CENTRAL/SOUTHERN HIGH PLAINS TO THE UPPER MIDWEST...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF
COAST/SOUTHEAST STATES...

...SUMMARY...
Severe thunderstorms will be possible this afternoon and evening
from parts of eastern New Mexico into west Texas. Other strong to
briefly severe storms may occur across the western/central Gulf
Coast region, as well as the central Plains and Upper Midwest.

...Synopsis...
A longwave trough will continue to evolve over the CONUS to the east
of the Rockies, with multiple embedded low-amplitude disturbances
crossing the Plains and Gulf Coast into the Southeast States through
tonight.

...Southern High Plains...
Beneath a plume of steep mid-level lapse rates noted in 12Z observed
soundings, weak low-level upslope trajectories will maintain modest
boundary layer moisture across west TX into eastern NM today. This
scenario should result in as much as 1000-1500 J/kg of MLCAPE by
peak heating especially across east-central/southeast NM into
west/southern TX including the TX south Plains and Permian Basin
vicinities. Storms are likely to initially develop and intensify
through early/mid-afternoon across eastern NM.

In the presence of strengthening west-northwesterly mid/high-level
winds, more than adequate buoyancy and vertical shear will exist for
supercells capable of large hail. These storms are likely to spread
east/southeastward into west/southwest TX by late afternoon, with a
continued large hail risk and an increasing potential for
severe-caliber wind gusts as storm mergers occur. These storms may
reach parts of the Edwards Plateau and Low Rolling Plains by late
evening.

...Western/central Gulf Coast region to Southeast States...
A cluster of persistent eastward-moving thunderstorms exist along
and off the middle TX coast to coastal LA early this morning, with
other showers and a few thunderstorms noted across other parts of
east TX to the lower MS River Valley. Focused generally near a
west/southwest to east/northeast-oriented frontal boundary
(modulated by outflow), this convection appears to be aided by a
weak southern-stream disturbance. While deep-layer/low-level winds
are forecast to gradually strengthen through the afternoon and
evening atop the frontal corridor, the widespread nature of
near-coastal convection contributes to uncertainty regarding the
degree of destabilization in inland areas. Even so, some potential
for locally damaging winds, marginally severe hail and possibly a
brief tornado (near-coastal areas) will exist today. Should greater
inland destabilization become more apparent, areas such as southern
LA/far southern MS could warrant a Slight Risk upgrade.

Farther east, other more isolated strong to locally severe
thunderstorms could occur this afternoon and evening across other
parts of the Southeast States into the Carolinas.

...Central Plains and Upper Midwest...
Low-level moisture will be limited in advance of a pre-frontal
trough and weak southeastward-moving front today, although diurnally
steepening lapse rates and modest moisture will yield weak buoyancy
mainly across far southeast SD and east-central NE into IA/southern
MN. Isolated to widely scattered thunderstorm development is
expected this afternoon. While updraft intensities will be tempered
by weak overall buoyancy, strong mid-level winds across the area
could contribute to a few stronger storms capable of strong gusty
winds and possibly some marginally severe hail this afternoon into
evening.

Farther west, other southeastward-moving high-based storms are
expected across the central High Plains this afternoon/evening with
some potential for severe-caliber winds and perhaps some hail.

..Guyer/Jewell.. 05/22/2017

$$



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