Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 AM CDT Sun Apr 07 2024
Valid 071630Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS A PORTION
OF THE MID-MISSISSIPPI VALLEY CENTERED FROM THE MISSOURI BOOTHEEL TO
WESTERN PARTS OF KENTUCKY AND TENNESSEE...
...SUMMARY...
Widely scattered strong/isolated severe thunderstorms are possible
during the late afternoon to mid-evening in the lower/mid
Mississippi Valley.
...Mid/lower Mississippi Valley area...
While dewpoints remain in the 30s and 40s across the SLGT risk area
late this morning, low-level moisture advection is ongoing ahead of
the advancing cold front, with low to mid 60s dewpoints now observed
across central and southern portions of Arkansas.
As the front advances eastward, and the more favorable low-level
theta-e airmass continues advecting northward, filtered heating will
support modest destabilization, with afternoon mixed-layer CAPE
values rising into the 500 to 1000 J/kg range.
Stronger ascent will remain just north of the SLGT risk area, as a
lobe of vorticity rotating through cyclonic southwesterly flow aloft
on the southeastern side of closed upper low over Nebraska crosses
Illinois/Indiana this afternoon. Still, scattered convective
development is expected to begin by mid to late afternoon across the
Mid Mississippi Valley, and southward into the Delta region, in
focused low-level ascent near the cold front. While modest CAPE
will likely limit severe potential, the deep-layer wind field
(veering and increasing favorably with height across the pre-frontal
warm sector) will likely augment a few of the stronger updrafts,
suggesting that a few storms will become capable of producing hail
and/or damaging winds. A tornado or two will also be possible, with
hodographs indicating favorable helicity with any right-moving
supercell.
Severe potential should peak through late afternoon, and then
gradually diminish this evening as the boundary layer cools, and the
cold front weakens with time.
...Parts of central/southeastern Iowa and vicinity...
As the weakening/vertically stacked low shifts northeastward out of
Nebraska and across northwestern Iowa this afternoon, continued
daytime heating of a marginally moist (40s dewpoints) boundary
layer, residing beneath rather steep mid-level lapse rates will
continue to facilitate weak destabilization. Thunderstorms have
developed late this morning across portions of northern and central
Illinois, and across north-central Iowa and into adjacent southern
Minnesota. By mid afternoon, new convective development is expected
along the occluded front currently moving northeastward across the
Nebraska/Iowa border/Mid-Missouri Valley at this time, as it shifts
into central and southeastern Iowa. While the evolving, low-topped
storms should remain largely sub-severe, a strong to severe wind
gust or two, and even a brief tornado, will be possible, through
late afternoon/early evening.
..Goss/Gleason.. 04/07/2024
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