365
ACUS01 KWNS 291633
SWODY1
SPC AC 291632

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1132 AM CDT Tue Jul 29 2025

Valid 291630Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO TONIGHT FROM PARTS OF THE NORTHERN HIGH PLAINS INTO THE CENTRAL
PLAINS...

...SUMMARY...
Severe thunderstorms are expected from southern Montana into the
central High Plains, and across much of Nebraska and western Iowa.
Areas of severe gusts will be possible, with hail most likely over
western areas.

...CO/NE/IA...
Surface analysis indicates a frontal zone draped from IA
west-southwestward into the central High Plains.  Moist conditions
either side of the boundary and ample heating will promote a very to
extremely unstable airmass as temperatures continue to warm through
the mid afternoon.  Initial storms are progged over the central High
Plains with perhaps other activity continuing across the mid MS
Valley through the afternoon.  Hail/wind will be possible with the
earlier storms, but a gradual increase in storm coverage is forecast
this evening into the overnight near/north of the boundary.  Severe
gusts will tend to be the main severe hazard tonight.

...WY/MT...
Water-vapor imagery late this morning shows a prominent shortwave
trough over the northern Great Basin moving into eastern ID/WY this
afternoon.  A moist (dewpoints in the 50s to lower 60s) and
destabilizing boundary layer near/northeast of a residual frontal
zone, coupled with orographic and large-scale ascent, will lead to
scattered afternoon thunderstorms.  Easterly flow beneath moderate
westerlies will yield effective shear supporting organized storms,
including a few supercells and organized clusters.  Hail/wind will
be the primary severe hazards before a tendency for upscale growth
into linear clusters during the evening.

...Southeast OR...
A mid-level trough over the Sierra into the northern Great Basin,
embedded within larger-scale trough over the West Coast, will move
northward through this evening across the northern Great Basin into
southern OR/ID.  Scattered high-based thunderstorms will probably
focus along the leading edge of ascent as low to mid tropospheric
lapse rates exceed 9 deg C/km.  A relatively dry sub-cloud layer
will promote evaporatively cooled downdrafts capable of isolated
severe gusts (60-70 mph) with the stronger cores/clusters, mainly
during the 22-04 UTC period.

..Smith/Halbert.. 07/29/2025

$$