SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0148 PM CST Sat Mar 05 2022
Valid 052000Z - 061200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN IA AND
FAR NORTHERN MO...
...SUMMARY...
Severe thunderstorms are expected this afternoon through tonight
across the lower Missouri Valley into southern portions of the Great
Lakes region. A few tornadoes, damaging winds, and large hail will
be likely in portions of Iowa and northern Missouri. Isolated
damaging gusts will be possible through tonight toward the Great
Lakes.
...Midwest/Lower MO Valley to Great Lakes...
Previous forecast reasoning remains largely on-track with somewhat
greater confidence in the number of discrete supercells developing
along and just east of the MO River into southern IA and northern
MO. Increasingly agitated CU/CB development is ongoing near the
surface cyclone across southeast NE and northeast KS with around 100
miles of clearing immediately east. Further destabilization through
boundary-layer heating and cooling mid-level temperatures will
support a narrow corridor of MLCAPE reaching 1000 J/kg. Despite
boundary-layer dew points only in the mid to locally upper 50s, low
to mid-level lapse rates greater than 8 C/km and enlarging low-level
hodographs suggests a few tornadoes appear likely. See MCD 194 for
additional near-term discussion.
Only other change is to expand lower tornado probabilities eastward
across northern IL to southern Lower MI. Environment should remain
favorable for a conditional tornado threat in addition to damaging
winds, although the bulk of CAMs still suggest convection should
nocturnally weaken later this evening.
..Grams.. 03/05/2022
.PREV DISCUSSION... /ISSUED 1029 AM CST Sat Mar 05 2022/
...Midwest/Lower Missouri Valley to Great Lakes...
A negatively tilted shortwave trough and attendant 70-80 kt H5 jet
streak visible across the central High Plains on morning water vapor
imagery are forecast to rapidly eject northeastward reaching the
upper Midwest/Great Lakes over the next 12-16 hours. Strong dynamic
lift associated with this trough/jet and a 40-50 kt low-level jet
have advected modest (50-55 F) dewpoints across eastern KS, northern
MO and far southern IA. As the trough continues northeastward during
the day, a deepening surface cyclone will continue pulling moisture
northward, toward a slowly advancing warm front stretching from the
low northeastward into central IA.
North of the warm front, a band of elevated convection is ongoing
within the strong warm advection regime at the nose of the low-level
jet. Modest buoyancy aloft may favor some potential for isolated
severe hail trough the morning, before these storms move far enough
north and eastward away from the jet and into more stable
conditions.
Behind the initial convection, strong dynamic lifting from the
approaching trough and isolated cloud breaks should work to
destabilize the boundary-layer ahead of a fast moving cold
front/dryline near the low across northeastern KS and southeastern
NE. With the modest surface moisture in place, destabilization
should remain mostly weak to moderate, with regional model soundings
showing between 500 and 1000 J/kg of MLCAPE developing beneath -20 C
500 mb temps by early afternoon. Some uncertainty exists regarding
destabilization in the wake of early-day convection, though clearing
evident across northeastern KS this morning lends some confidence to
at least patchy sunshine through the early afternoon. Strong
convection appears likely to initiate near the triple point in
vicinity to the Missouri River between 19 and 21z, and track
northeastward across south-central IA and northern MO. Wind profiles
near and southeast of the low and the warm front strongly favor
supercells with enhanced low-level curvature (200-250 0-1km SRH)
evident on model hodographs. Aloft, more straight line structure
suggests some potential for left splits and upscale growth resulting
in a mixed storm mode of broken/semi discrete bands of convection.
Fast storm motions and the potential development of small but
moderately strong low-level mesocyclones will support all severe
hazards including a few tornadoes. Steep lapse rates, both low and
in the mid-levels will facilitate efficient transfer of strong winds
aloft to the surface with scattered damaging gusts likely,
especially after the initial cellular development. Some potential
for damaging gusts will also extended farther south along the cold
front across eastern KS and southwestern MO and into the western
Great Lakes later tonight. Displaced from the stronger ascent,
convective organization is less certain, but the strong wind fields
suggests some threat for damaging wind gusts and small hail.
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