ACUS03 KWNS 171853
SWODY3
SPC AC 171852

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CDT Tue Sep 17 2024

Valid 191200Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
UPPER MIDWEST...

...SUMMARY...
Scattered severe thunderstorms are possible from mid-afternoon to
early evening on Thursday across central to eastern Minnesota and
north-central Iowa.

...Upper Midwest...

Minor adjustments (mainly eastward expansion) to severe
probabilities have been made based on latest forecast guidance for
the Day 3/Thursday period, but overall forecast philosophy remains
unchanged from the previous outlook.

A negatively tilted upper shortwave trough will shift east/northeast
from the northern Plains/Canadian Prairies toward the Upper Midwest
and western Ontario. Mid/upper west/southwesterly flow will remain
somewhat enhanced (around 30-40 kt 850-700 mb flow) through around
00z before the system as a whole weakens. At the surface, a cold
front will extend roughly north to south/southwest from western MN
into southeast NE at midday. Ahead of this feature, southerly
low-level flow will maintain 60s F dewpoints across IA into eastern
MN/western WI. The warm sector will remain rather narrow due to
generally high pressure and a drier boundary layer over much of the
Midwest east of the MS River. Nevertheless, within the axis of
greater moisture/low-level theta-e, around 1000-2000 J/kg MLCAPE is
forecast. Organized thunderstorm clusters and line segments will
pose a risk of isolated severe gusts and hail through early evening.
The severe risk should rapidly diminish beyond 00z with loss of
daytime heating, limited moisture/instability with eastward extent,
and weakening deep-layer flow.

..Leitman.. 09/17/2024

$$

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