459
ACUS01 KWNS 092000
SWODY1
SPC AC 091958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Sun Jun 09 2024

Valid 092000Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
ARKANSAS...SOUTHWEST TENNESSEE...NORTHERN MISSISSIPPI...AND
NORTHWEST ALABAMA...

...SUMMARY...
A broad area of isolated severe hail and damaging wind potential
exists today from parts of the Northwest into the High Plains,
southern Plains, and lower Mississippi Valley/Southeast. A
relatively greater severe threat may exist this afternoon and early
evening across parts of Arkansas, southwest Tennessee, northern
Mississippi, and northern/central Alabama.

...20z Update...

No changes are need to the D1 Outlook. Thunderstorm activity has
begun across much of the Marginal Risk area extending from the
Northwest into the High/Southern Plains, and into the lower
Mississippi Valley. Activity is expected to remain widely scattered
with potential for a few instances of damaging winds and hail.

The more concentrated severe risk area remains evident across the
lower Mississippi Valley into the Southeast. Visible satellite shows
initiation ongoing across northwestern Arkansas near a diffuse
surface boundary. This activity will spread east and southeastward
through the afternoon. Ahead of this activity, daytime heating has
allowed a broad region of 2000-3000 J/kg of MLCAPE extending from
Arkansas into northern Mississippi and Alabama. This will support
multi-cell clusters capable of damaging wind and a few instances of
hail. The Slight Risk covers this risk well, with no updates needed
at this time.

..Thornton/Goss.. 06/09/2024

.PREV DISCUSSION... /ISSUED 1120 AM CDT Sun Jun 09 2024/

...Lower Mississippi Valley/Southeast...
A MCV is present over southern MO/northern AR late this morning.
Outflow from this activity has spread south of the remnant ongoing
convection into central AR and far western TN. A very moist
low-level airmass across the lower MS Valley will continue to
destabilize as strong diurnal heating occurs through the afternoon.
Moderate to strong instability will likely develop across parts of
AR, western TN, and northern MS, with MLCAPE values potentially
reaching around 2000-3500 J/kg. Stronger mid-level flow will tend to
remain displaced to the north of the warm sector today across the OH
Valley, Mid-Atlantic, and Northeast in association with an upper
trough/low centered over eastern Canada. Still, some enhancement to
the mid-level flow due to the MCV, with gradually strengthening
west-northwesterly winds at mid/upper levels, should support
sufficient deep-layer shear for thunderstorm organization. Current
expectations are for robust thunderstorms to develop along/near the
outflow boundary in northern/central AR this afternoon, and
subsequently spread east-southeastward over parts of southwest TN,
northern MS, and perhaps northern/central AL through the evening.
Multicell clusters will be capable of producing scattered damaging
winds around 50-70 mph. Isolated hail may also occur with any
marginal supercell structures that can be maintained. Convection
should gradually weaken through the evening across the Deep South as
it encounters a less unstable airmass and increasing MLCIN.

A separate MCV is apparent over the western Carolinas based on
recent visible satellite imagery. As this feature moves eastward, it
may encourage isolated thunderstorms to develop through the day
across parts of NC/SC. While this region will be on the southern
periphery of stronger mid-level flow, sufficient deep-layer shear
should be present to support modest updraft organization. Isolated
hail and strong to damaging winds may occur with the more robust
cores that can develop. But, generally weak instability should keep
the overall severe threat fairly isolated.

...Southern/Central High Plains...
With weak east-northeasterly low-level upslope flow persisting
today, scattered to numerous thunderstorms should develop this
afternoon over the higher terrain of the southern/central Rockies.
Additional convective development is anticipated across parts of the
southern Plains in the vicinity of a convectively reinforced front
extending from parts of west TX into southern/eastern OK. Generally
modest flow is forecast over much of these areas, which should limit
thunderstorm organization to some extent. Still, a moist and
moderately unstable airmass should be in place along/south of the
front, and in a narrow corridor across the High Plains. Where
low-level lapse rates can become steepened though daytime
heating/mixing of the boundary layer, isolated severe wind gusts may
occur with pulse convection and loosely organized multicell
clusters. Hail may also occur with the strongest updrafts.
Deep-layer shear appears too weak to support a more organized severe
threat across these regions.

...Interior Northwest into the Northern High Plains...
An upper-level ridge extends from the Southwest/Four Corners region
into the Great Basin. Scattered thunderstorms are forecast to
develop later today from parts of eastern OR to the northern High
Plains on the periphery of this upper ridge. Modestly enhanced
mid-level flow may support some convective organization. A deeply
mixed boundary layer with inverted-v type soundings should foster an
isolated threat for severe wind gusts with the strongest downdrafts.
With somewhat greater low-level moisture and instability present,
occasional hail may also occur over the northern High Plains as
thunderstorms spread eastward this afternoon and evening.

$$