SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0310 PM CDT Sat Apr 30 2022
Valid 302000Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING FROM ARKANSAS TO ILLINOIS AND WESTERN INDIANA...
...SUMMARY...
Scattered severe thunderstorms are anticipated this afternoon and
evening across portions of the Mid-Mississippi Valley/Midwest
towards the Ark-La-Tex. A few tornadoes, damaging winds, and large
hail will be possible.
...AR to IL area this afternoon/evening...
An occluded low near the northwest IA/southwest MN border will move
slowly northeastward toward northwest WI by Sunday morning. To its
south and east, a weakening cold front will move eastward across
MO/IL and southeastward across AR the remainder of this afternoon.
Thunderstorm development is expected through the remainder of the
afternoon along and east of the front in the warm sector, where
weak forcing for ascent coincides with minimal convective
inhibition. Buoyancy and vertical shear profiles are sufficient for
supercells from AR to IL, and the more favorable low-level shear
profiles for rotating storms and couple of tornadoes will be near
the northeast edge of the warm sector across northern IL.
Otherwise, occasional damaging gusts and isolated large hail will be
the main threats through late evening.
...Central TX area this afternoon/evening...
The cold front is in the process of stalling across central TX.
Ascent will remain shallow/weak and be confined to the front itself,
and vertical shear is on the lower margins for supercells (somewhat
stronger with westward extent across central TX). Thus, only
isolated storm development is expected this afternoon/evening, but
hodograph length and MLCAPE near 3000 J/kg with steep midlevel lapse
rates will support isolated large hail with storms forming and
propagating west-southwestward along the boundary. An isolated
tornado cannot be ruled out with storm-boundary interactions. See
MD #596 for additional information.
..Thompson.. 04/30/2022
.PREV DISCUSSION... /ISSUED 1210 PM CDT Sat Apr 30 2022/
A deep occluded low is present today over IA, with the associated
cold front sweeping eastward across MO/AR, and the warm front
extending southeastward into parts of northern IL, IN, and eastern
KY. The warm sector of the low is somewhat moist and marginally
unstable with dewpoints in the 50s to lower 60s. Visible satellite
shows scattered breaks in the cloud cover, which will help to
further warm/destabilize the air mass and lead to multiple bands of
thunderstorms along/ahead of the front.
...WI/IL/IN...
Backed surface winds will likely be maintained through the afternoon
from southern IL northward into southern WI, where forecast
soundings show sufficient low/deep layer shear profiles for discrete
and semi-discrete convective modes. This would favor the
development of a few supercells capable of hail, damaging winds, and
a few tornadoes. The main limiting factor for a more significant
tornado event appears to be limited moisture/CAPE. These storms
will spread quickly northeastward today into a progressively more
stable environment, but locally damaging winds may continue to be a
threat into western IN this evening.
...AR/LA/TX...
Substantial low-level moisture is in place over the Arklatex region
today with dewpoints in the upper 60s and lower 70s. Scattered
afternoon thunderstorms are expected to develop, with coverage
decreasing with southwestern extent along the cold front. Low-level
winds are more veered in this area than farther north, and mid-level
flow decreases rapidly south of central AR. Nevertheless, strong
multicell or isolated supercell storms may form, capable of damaging
winds and hail through the evening.
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