Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 AM CDT Fri Mar 21 2025
Valid 211630Z - 221200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not forecast today.
...Iowa Vicinity...
An upper shortwave trough will move across the Midwest today and
tonight, with increasing deep-layer west/northwest flow associated
with this feature overspreading the region. Boundary layer moisture
will remain scant ahead of an east/southeast moving cold front
sweeping across the Lower MO/Mid-MS Valley this afternoon and
evening. Nevertheless, very cold temperatures aloft (near -25 C at
500 mb, as sampled by 12z regional balloon observations), will
support steep midlevel lapse rates. Additionally, surface heating
into the mid 50s to low 60s will support steepening low-level lapse
rates. These steep lapse rates amid cold temperatures aloft should
be sufficient for SBCAPE values up to 300 J/kg. As such, isolated
high-based, low-topped thunderstorms are expected this afternoon and
evening from the Mid-MO Valley into the Mid-MS Valley. Given the dry
boundary layer and near 30-40 kt flow between 850-700 mb, convection
may locally enhance already gusty surface winds, and a few stronger
gusts near 40-45 kt may occur, especially across southeast Iowa into
northwest IL. A couple instances of small hail/graupel also could
accompany this activity.
...Pacific Northwest/Northern Rockies...
An upper shortwave trough will move across the region tonight.
Cooling aloft will support steepening lapse rates and sufficient
destabilization to support isolated lightning flashes.
..Leitman/Halbert.. 03/21/2025
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