386
ACUS01 KWNS 191252
SWODY1
SPC AC 191251

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Thu Sep 19 2024

Valid 191300Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM
MINNESOTA...IOWA AND WESTERN WISCONSIN SOUTHWARD INTO EASTERN KANSAS
AND WESTERN MISSOURI...

...SUMMARY...
Scattered severe thunderstorms are possible across central/eastern
Minnesota, Iowa, and western Wisconsin. A couple tornadoes, isolated
large hail, and damaging winds may occur. An area of locally severe
gusts and hail may also develop over parts of eastern Kansas,
southwest Missouri, and into northeast Oklahoma.

...Synopsis...
Early morning water-vapor imagery shows a slow-moving mid- to
upper-level low near the SK/MB/Dakotas border.  A negatively tilted
shortwave trough will move across the Dakotas and MN through the
day.  A belt of strong (40-50 kt) 500mb flow will extend through the
base of the trough from NE wrapping cyclonically through the Upper
MS Valley into western ON and to the northwest of a flattening ridge
over the mid MS Valley/southwest Great Lakes.  Farther south, weaker
west to northwest winds will encompass an area around a southern
Plains upper high from KS/OK into MO and AR.  In the high levels,
flow will be strongest across the central Plains, with weakening
winds over the northern Plains/upper MS Valley.

In the low levels, a cyclone will develop northeastward from
southeast SK into central MB by early Friday morning, while a cold
front moves into MN/western IA by mid afternoon, with frontolysis
expected during the latter part of the period.  A wind shift/surface
trough will also extend southward across eastern KS and into
northern OK.  Ahead of the aforementioned boundaries, southerly flow
will maintain a plume of mid to upper 60s F dewpoints.

...MN/IA/WI...
Scattered weak, elevated storms from the lower MO Valley northward
into MN/WI will gradually move east this morning and likely
dissipate by midday.  Cloud breaks and clearing in their wake will
contribute to appreciable heating and moderate to strong buoyancy
developing from near the MO River in western IA northward into MN.
Forecast soundings show 2500-3000 J/kg MLCAPE with a veering and
strengthening wind profile into the mid levels.  A broken band of
quasi-discrete storms (including supercells) is forecast to develop
from MN southward into at least northern IA.  The risk for a couple
of tornadoes may be highest from MN into northern IA where effective
SRH may exceed 200 m2/s2.  A couple of stronger supercells may also
develop into western/southwest IA per recent HRRR model trends.
Given the northward lifting of the shortwave trough, and increasing
inhibition east of the MS River, the primary threat should remain
relatively narrow.

...Eastern KS into western MO and into OK...
Widely scattered thunderstorms are ongoing this morning from
south-central into northeast KS.  Much of this activity will likely
dissipate but a few residual storms may continue or regenerate on
outflow over parts of western MO later this afternoon.  Strong
heating and the steepening of 0-3 km lapse rates will favor the
development of other isolated to widely scattered storms later this
afternoon near the wind shift.  12 UTC regional raobs sampled warm
mid-level temperatures (around -1 deg C at 525 mb at Norman, OK).
These warm midlevel temperatures will limit the overall magnitude of
instability.  However, lengthy mid to upper level hodographs will
support storm organization with any robust/established updraft.  The
stronger storms will potentially be capable of a risk for severe
gusts and perhaps large hail.

..Smith/Mosier.. 09/19/2024

$$