SPC Apr 10, 2025 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0300 PM CDT Thu Apr 10 2025

Valid 102000Z - 111200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST...

...SUMMARY...
Scattered strong to severe thunderstorms are expected from portions
of the lower Ohio Valley into the Southeast through this afternoon
and evening. Large hail and damaging winds should be the main
threats.

...20z Update...
Ahead of the cold front moving across the OH/MS Valleys, strong
heating has promoted gradual destabilization and multiple corridors
of storm formation this afternoon. 70s and 80s F surface
temperatures indicate the air mass is well-mixed with dewpoints
generally in the 40s F. The relatively dry boundary layer should
support efficient downward momentum transfer of stronger
tropospheric winds, and a threat for scattered damaging winds. Some
clustering and a stronger cold pool currently becoming established
may focus this threat across the lower OH Valley into parts of
TN/KY. Otherwise, isolated damaging gusts and some hail are
possible.

Across parts of the mid to lower MS valley, predominately cellular
storms are expected late this afternoon continuing through the
evening. Hail appears likely with these storms given the very
favorable lapse rates aloft (8-9 C/km) and elongated hodographs
favoring supercells. Some significant hail near 2 inches in diameter
cannot be ruled out with the more robust rotating storms. Upscale
growth overnight may foster a wind threat as one or more
clusters/line segments spread east across AL and GA with damaging
gusts.

..Lyons.. 04/10/2025

.PREV DISCUSSION... /ISSUED 1126 AM CDT Thu Apr 10 2025/

...Lower Ohio Valley into the Southeast...
Large-scale upper troughing is forecast to further amplify today
over the eastern CONUS, as multiple embedded shortwave troughs
rotate through its base. A lead shortwave trough will advance
eastward over the upper OH Valley and central Appalachians through
the day, while a trailing shortwave trough is expected to move
southeastward across the mid MS Valley, lower OH Valley, and TN
Valley through this evening. A weak/diffuse cold front is likewise
forecast to develop southeastward across these regions through the
day, providing some focus for thunderstorm development later this
afternoon and evening.

12Z soundings across the Southeast indicate shallow/limited
low-level moisture in place, but also relatively steep mid-level
lapse rates. Strong daytime heating, gradual low-level moistening
from the southwest, and cooling mid-level temperatures associated
with the trailing shortwave trough should all aid in the development
of around 1000-1500 J/kg of MLCAPE ahead of the front by mid
afternoon. Weak low-level westerly winds are forecast to gradually
veer and strengthen with height through the mid/upper levels, which
will likely foster relatively long/straight hodographs and 40-55+ kt
of effective bulk shear. This should easily support organized
updrafts, including the potential for supercells.

Current expectations are for robust thunderstorm development to
occur over the lower OH Valley/Mid-South region by 18-20Z. This
initial activity will likely be supercellular, with an associated
threat for large hail given steep lapse rates aloft and strong
deep-layer shear. Additional strong to severe thunderstorms should
develop through the rest of the afternoon and early evening across a
larger portion of the lower OH Valley into the TN Valley and
Southeast. Any convection which can remain at least semi-discrete
should pose a continued hail threat. Some tendency for upscale
growth into multiple bowing clusters seems likely by late
afternoon/early evening. A well-mixed boundary layer should support
efficient downward momentum transfer and a threat for scattered
damaging winds, before convection eventually weakens by mid/late
evening with the loss of daytime heating.

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