ACUS02 KWNS 270600
SWODY2
SPC AC 270559

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Sun Apr 27 2025

Valid 281200Z - 291200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
IOWA INTO SOUTHEAST MINNESOTA AND WESTERN WISCONSIN...

...SUMMARY...
An outbreak of severe weather remains likely across portions of the
Upper Midwest, centered on Monday afternoon and evening. Very large
hail, strong tornadoes, and damaging winds are expected.

...Synopsis...
A strong (~75 knot) mid-level jet streak will advance from the
central Plains to the Upper Midwest on Monday. As this occurs, a
surface low will deepen across the Upper Midwest with an eastward
advancing dryline to its south and a cold front to the
west-southwest. A warm front will extend east of this surface low
and move rapidly north through the day, spreading mid 60s dewpoints
across much of the Upper Midwest.

...MN/IA/WI...
Thunderstorms will likely be ongoing at the beginning of the period
north of a warm front across Minnesota and Wisconsin amid moderate
isentropic ascent. Isolated large hail will be possible from these
storms. A surface low will be located somewhere near eastern South
Dakota and will start to advance east during the morning. This
surface low is expected to deepen somewhat through the day (perhaps
to the low 990s mb range) as it moves toward the Twin Cities. There
is a consistent signal for thunderstorms to develop along the cold
front as it intersects the surface low/dryline in west-central
Minnesota Monday afternoon. After some initial hail threat, these
storms will likely become quickly linear along the front with an
increasing severe wind threat. Strong low-level shear will also
favor some line-embedded tornadoes, particularly if there area any
areas within the line which become more favorably oriented to the
low-level shear vector.

Additional thunderstorms are forecast to develop along the dryline
from southern Minnesota to west-central Iowa during the afternoon on
Monday. 00Z CAM guidance is not overly bullish with convective
development south of the MN/IA border, likely due to relatively weak
convergence along the dryline in western Iowa from most high
resolution guidance. However, the lack of convection from much of
the guidance does not seem realistic considering the overall
pattern. ECMWF/GFS/NAM are fairly consistent with a deepening
surface low across Minnesota and moderate to strong height falls
across the dryline. The southern extent of the previous Day 3
moderate risk corresponds well to the southern extent of the more
favorable height falls, and convective precipitation signal from the
ECMWF/GFS. Therefore, no adjustments to the southern extent of the
moderate risk were deemed necessary. However the moderate risk was
expanded slightly westward to account for the expectation for
earlier convective initiation (19-21Z) than shown by most guidance.
Given very strong effective shear and over 3000 J/kg MLCAPE, expect
any supercells which develop to become quickly severe with a threat
for all severe weather hazards.

As the surface low across Minnesota deepens the low-level jet is
also forecast to strengthen across Iowa, Minnesota and Wisconsin.
This will elongate low-level hodographs and support an increasing
tornado threat during the evening. STP values of 3 to 5 are common
across much of the warm sector ahead of anticipated storms with some
guidance indicating values of 7 to 10. Therefore, any mature,
discrete supercells which can form and maintain within the open warm
sector on Monday late afternoon/evening will pose a threat for
strong to potentially intense tornadoes.

...Eastern Kansas and northern Missouri to West Texas...
Overall forcing will be weaker farther south along the dryline, but
subtle height falls across a mostly uncapped warm sector could
result in isolated to scattered supercell development Monday
afternoon. A secondary area of higher severe weather probabilities
may exist from portions of West Texas into southwest Oklahoma where
the nocturnally strengthening low-level jet could support scattered
supercell development Monday evening. However, weak height rises
cast some doubt on storm coverage during the evening, precluding
higher probabilities at this time.

..Bentley.. 04/27/2025

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