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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0300 PM CDT Mon Jul 15 2024

Valid 152000Z - 161200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF EASTERN IOWA...EXTREME SOUTHERN WISCONSIN...NORTHERN
ILLINOIS...AND FAR NORTHWEST INDIANA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL PLAINS...AND ACROSS PARTS OF NEW YORK...PENNSYLVANIA AND
FAR NORTHERN NEW JERSEY...

...SUMMARY...
Severe thunderstorms are expected through this evening across
portions of the Midwest, central High Plains, lower Great Lakes, and
Arizona.  The greatest potential for severe gusts is over eastern
Iowa into Illinois and Indiana.

...Midwest...

Both tornado and wind probabilities have been increased with the 20z
update to 10 percent, and 45 percent SIG, respectively. Latest
satellite imagery shows a modified outflow boundary draped across
far eastern IA into northern IL. A very moist airmass with dewpoints
in the mid/upper 70s amid strong heating is resulting in a corridor
or strong to extreme instability across the region. Favorable
vertical shear will support initial supercells, organizing into a
bowing MCS with time as low-level flow remains orthogonal to the
developing band of storms. The greatest severe wind potential is
expected along the instability gradient in the vicinity of the
remnant outflow boundary, extending from far eastern IA into extreme
southern WI, northern IL, and far northwest IN into this evening.
Widespread gusts of 60-70 mph are expected, with some gusts to 85
mph possible. Given favorable low-level shear, mesovortex tornadoes
are likely along and near the apex of the developing bow late this
afternoon into evening. 

For short term details on severe potential across this area,
reference MCD 1630.

...NY/PA and the Central High Plains...

No changes have been made with the 20z update. Reference Severe
Thunderstorm Watch 538 regarding severe potential across NY/PA, and
previous outlook discuss for more details.

..Leitman.. 07/15/2024

.PREV DISCUSSION... /ISSUED 1131 AM CDT Mon Jul 15 2024/

...Midwest...
A broad upper trough is digging southeastward across northwest
Ontario and MN today, with strengthening mid level flow across much
of the Midwest.  Rapid thunderstorm development is expected to occur
by mid afternoon across portions of WI/northeast IA, with storms
tracking rapidly east-southeastward into northern IL and eventually
parts of IN/Lower MI.  12z CAM guidance remains in general agreement
that a large bowing co*plex is likely, although details of the
corridor of greatest risk vary between solutions.  Regardless, an
active severe event is expected for this region, with the potential
for isolated instances of significant damaging winds.

...NY/PA...
Thunderstorms have begun to intensify over eastern Lake Erie, ahead
of a strong upper trough and remnant MCVs.  These storms are
expected to increase in coverage and spread eastward through the
day, possibly as far east as southeast NY and northern NJ by
evening.  Damaging winds and hail are the main concerns with these
storms.

...Central High Plains...
Scattered high-based thunderstorm development is expected this
afternoon from western NE southward into parts of northeast CO and
western KS.  The co*bination of a deeply mixed boundary layer,
sufficient CAPE, and 30+ knots of westerly mid level flow will pose
a risk of locally damaging wind gusts in the stronger cells.