025
ACUS01 KWNS 202048
SWODY1
SPC AC 202047

Day 1 Convective Outlook AMEND 1
NWS Storm Prediction Center Norman OK
0347 PM CDT Mon May 20 2024

Valid 202000Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL HIGH PLAINS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTHERN ILLINOIS AND SOUTHERN WISCONSIN...

AMENDED FOR LOWER MICHIGAN

...SUMMARY...
The primary threat for severe thunderstorms today will be over parts
of the central Plains, with large hail, damaging wind gusts, and a
few tornadoes possible.

...20z Update...
No changes to forecast reasoning and outlook thresholds for the
Plains severe risk -- see previous discussion below. Some spatial
adjustments made across southern Wisconsin and northern Illinois for
an eastward-shifting severe risk, which includes upward-adjusted
probabilities (Slight Risk) across parts of Lower Michigan.

..Guyer.. 05/20/2024

.PREV DISCUSSION... /ISSUED 1133 AM CDT Mon May 20 2024/

...Central High Plains...
A large upper trough will slowly deepen across the western United
States today, with strengthening southwesterly mid/upper level flow
spreading across the Plains states.  A band of mid-level moisture
and instability will result in scattered high-based thunderstorms
across northern CO/southern WY by mid-afternoon, capable of locally
damaging wind gusts.  Other discrete supercell storms may form in
vicinity of the DCVZ as southeasterly low-level winds and elevated
terrain aid in initiation.  These storms will track
east-northeastward into a progressively more moist/unstable air
mass, with the risk of very large hail and a few tornadoes through
the evening.  By mid-evening, coverage of storms will increase over
southwest NE as a southerly low-level jet strengthens, with storms
progressing across the central Plains overnight with a continued
risk of large hail and damaging winds.

...IL/WI...
A well-defined remnant MCV from overnight convection over KS is
currently over northeast IA.  A surface boundary extends eastward
from the low across northern IL.  Broken clouds and partial
afternoon heating will aid in the development of thunderstorms near
the MCV later today as it tracks across southern WI/northern IL.
Any storm that can interact with the boundary would have the
potential to become a supercell and pose a risk of a tornado or two.
 Otherwise, hail and gusty winds could occur with the strongest
cells.

...Southeast FL...
Widely scattered afternoon thunderstorms are possible across
southeast FL.  Ample low-level moisture, strong heating, cyclonic
midlevel flow, and relatively steep lapse rates could result in a
strong storm or two capable of gusty winds and hail.

$$