Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 290558
SWODY1
SPC AC 290556

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Mon May 29 2017

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM DEEP SOUTH
TEXAS TO THE MID-ATLANTIC...

...SUMMARY...
Strong to severe thunderstorms will be possible from the Texas Gulf
Coast to the Carolinas, with the highest potential likely from
northern Georgia eastward. The primary threat with these severe
storms will be damaging winds, with a few instances of large hail
possible as well.

...Synopsis...
Surrounding a rather large closed cyclone centered over the upper
Great Lakes and western Ontario, broad cyclonic flow will encompass
much of the northern/central Plains and Midwest. To its south, a
series of impulses, some convectively enhanced, will be embedded in
a corridor of west/southwesterly flow from northern Mexico to the
Mid-Atlantic. Farther west, an amplified ridge will remain
positioned over much of the Intermountain West.

...Portions of the Southeast...
While upstream convection may spread cloud cover across parts of the
region today, portions of northern Georgia and points east will
likely realize adequate boundary-layer heating. With surface dew
points generally in the mid/upper 60s, this heating will promote
modest mixed-layer CAPE, upwards of 1000 J/kg or so.  Furthermore,
this area will be on the fringe of stronger west/southwesterly
mid-level flow stretching from the Tennessee Valley to the
Mid-Atlantic, resulting in effective shear around 30-40 kt. While
synoptic-scale forcing for ascent will likely be nebulous at best,
guidance suggests the potential for an MCV/weak impulse to eject
eastward from overnight/morning convection, reaching northern
Alabama/Georgia near peak heating. As such, thunderstorms may be
focused along/ahead of such a feature during the afternoon/evening
hours. With the aforementioned shear profile, these storms will
likely take the form of multicells (with perhaps brief updraft
rotation), capable of a few damaging winds gusts and large hail.
Over time, relatively straight hodographs will likely promote an
evolution to small bowing segments, with the primary hazard becoming
strong/damaging winds.

...South Texas to the central Gulf Coast...
Widespread convection is evolving across the region late this
evening, with a slow east/southeastward propagation towards the
coast. Despite this convection, surface dew points generally remain
in the mid/upper 60s to lower 70s behind ongoing storms. Thus,
weak/modest boundary layer heating will likely be sufficient for
pockets of thunderstorm re-development during the day, with cells
focused along residual outflow boundaries. While deep-layer shear
will be quite marginal, the warm/moist environment may favor strong
wind gusts and a few instances of small to near-severe hail.

..Picca/Dean.. 05/29/2017

$$



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