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
000
ACUS01 KWNS 250550
SWODY1
SPC AC 250548

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1248 AM CDT Mon Mar 25 2024

Valid 251200Z - 261200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF EXTREME SOUTHEAST ARKANSAS INTO NORTHEAST LOUISIANA AND CENTRAL
MISSISSIPPI...

...SUMMARY...
Severe thunderstorms with a threat for tornadoes and damaging winds
are possible today through tonight from parts of east Texas through
the Lower Mississippi Valley. An instance of hail or a brief tornado
also cannot be ruled out over parts of the Midwest.

...Synopsis...
A mid-level trough will traverse the central U.S. while progressing
eastward and taking on a negative tilt. During the day, a 100+ kt
500 mb jet streak will overspread the central MS Valley as a 994 mb
surface low tracks from the central Plains toward the Great Lakes.
Deep-layer ascent and strong vertical wind shear ahead of the
mid-level trough/surface low will support strong thunderstorm
development along or immediately ahead of an eastward-advancing
Pacific front. Storms should mature over the Mid-South during the
afternoon and progress toward the Gulf Coast states by evening.
Given adequate low-level moisture and overall buoyancy over the
Mid-South, severe thunderstorms are possible. Closer to the surface
low, and where temperatures are coldest aloft, an isolated severe
threat may materialize, particularly over portions of the Midwest.

...Mid South toward the Gulf Coast Region...
Thunderstorms should be ongoing along or immediately ahead of the
Pacific front at the start of the period over portions of central or
eastern TX. Despite widespread cloud cover likely over the entire
warm sector, strong low-level warm-air/moisture advection (driven
primarily by a 60+ kt southerly 850 mb jet) will contribute to a
moistening boundary layer, as cooler temperatures aloft graze the
Mid-South from the north and west. Mid 60s F dewpoints, overspread
by 6-7.5 C/km mid-level lapse rates, will boost SBCAPE into the
500-1000 J/kg range by afternoon peak heating across portions of
extreme eastern TX and LA into southern and central MS. Here, the
overlapping of the intense low-level and mid-level jets will support
rapidly veering/strengthening vertical wind profiles, contributing
to sizeable clockwise-curved low-level hodographs with mid-level
elongation. Effective SRH exceeding 400 m2/s2 will support the
development of strong mesovortices embedded within a squall line.
Damaging gusts and QLCS tornadoes are possible, especially over
eastern LA into southern and central MS, where the best overlap of
SRH and adequate surface-based buoyancy should precede a
well-organized QLCS. A few strong tornadoes are also possible given
the very strong low-level shear. Otherwise, the squall line should
progress eastward into AL with an isolated damaging gust/tornado
threat, though the severe threat should begin to wane sometime
between 09-12Z as the line outpaces the warm sector.

...Portions of the Midwest...
Near the surface low, very cold temperatures aloft will support 8+
C/km mid-level lapse rates beneath 60 F surface dewpoints, boosting
SBCAPE to over 500 J/kg by late morning or early afternoon. Strong
deep-layer ascent will support the development of several
thunderstorms amid deep-layer southerly flow. Speed shear will
contribute to elongated hodographs, and when considering the colder
temperatures aloft, a couple instances of severe hail may accompany
multicellular clusters. Furthermore, strong low-level convergence
north of the surface low, in the vicinity of abundant surface
vertical vorticity, may result in the development of a landspout or
two with one of the stronger multicells as well.

..Squitieri/Darrow.. 03/25/2024

$$


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