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 43 44 45 46 47 48 49 50
000
ACUS01 KWNS 250056
SWODY1
SPC AC 250055

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 PM CDT Fri Mar 24 2017

Valid 250100Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS PARTS OF SOUTHEAST TEXAS INTO THE OZARK PLATEAU AND LOWER
MISSISSIPPI VALLEY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
SURROUNDING PORTIONS OF THE PLAINS AND MISSISSIPPI VALLEY...

...SUMMARY...
A risk for severe thunderstorms continues, mainly across parts of
eastern Texas into the Ozark Plateau this evening, perhaps spreading
into the lower Mississippi Valley overnight.

...Plains/Mississippi Valley...
Although a significant lower/mid tropospheric cyclone is in the
process of weakening across the south central Plains, deep layer
mean wind fields and vertical shear within/above the surface warm
sector remain potentially supportive of substantive severe weather
potential as the center of circulation turns east northeast of
central Oklahoma toward the Ozarks tonight.  The lack of a broad
deep low-level moisture return off the Gulf of Mexico appears the
primary factor limiting destabilization and convective potential.
However, mid-level cooling to the south and east of the circulation
center has cut off the northeastward advection of elevated
mixed-layer air from the Mexican Plateau region.  And a pre-frontal
band of convective cloud cover and precipitation has stabilized
boundary layer conditions ahead of the dryline, across much of
western Arkansas into the Sabine Valley.  Furthermore, downward
mixing of dry lower/mid tropospheric air has slowed boundary layer
moistening across a large portion of the lower Mississippi Valley.

Still, attempts at vigorous thunderstorm development are underway
near and just ahead of the dryline, within a narrow corridor of more
substantive moistening, from near the Oklahoma/Arkansas border
south/southwestward into parts of southeastern Texas.  An
intensifying line segment northeast/east of Fayetteville and Fort
Smith AR likely has been aided by stronger forcing for ascent ahead
of the mid-level low.  This is expected to continue to spread
northeastward  across parts of southern Missouri and northern
Arkansas through this evening, with at least some risk for
potentially damaging wind gusts, but severe weather potential, in
general, may be limited by weak boundary layer instability.

Somewhat better severe weather potential appears to exist from
portions of eastern/southeastern Texas through central/northern
Louisiana and southeastern Arkansas.  Forcing for ascent associated
with an impulse pivoting around the southeastern periphery of the
south central Plains mid-level low may contribute to consolidation
of initially discrete storm development into a progressive
organizing line of storms.  This could be aided by some increase in
low-level moisture off the Gulf of Mexico, but even this is not
certain.  Given sizable clockwise curved low-level hodographs near a
40-50 kt southerly 850 mb jet, a risk for tornadoes exists,
particularly this evening across parts of southeast Texas into the
Ark-La-Tex region.  However, potentially damaging wind gusts may
become the more prominent threat, and could continue into the lower
Mississippi Valley overnight.

..Kerr.. 03/25/2017

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.