LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 PM CDT Tue Jul 29 2025
Valid 292000Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS 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.
...20z Update...
The forecast largely remains on track with the early stages of
convective initiation underway across portions of north/northwest WY
and along the central High Plains per recent satellite imagery and
regional radar composites. The primary change for this forecast
update was the introduction of significant hail/wind areas to
portions of the northern Rockies. Latest GOES imagery shows
convection beginning to develop across northern WY/southern MT ahead
of a shortwave trough over the Great Basin. Regional 18z soundings
continue to sample steep (8-9 C/km) mid-level lapse rates, and GOES
imagery suggests 30-40 knot mid-level winds are overspreading the
region. As such, a favorable environment for a few supercells
appears to be in place and should support the potential for very
large hail. This activity should grow upscale through late evening
with the potential for a few significant (75+ mph) wind gusts. See
MCD #1833 for additional short-term details.
Across the Plains, the significant wind risk area has been adjusted
to better align with recent convective development along a
stationary boundary draped from southwest to northeast across NE and
where boundary-layer mixing appears to be deepest (based on observed
dewpoint depressions), which should favor stronger downdrafts and a
higher potential for significant gusts. See MCD #1834 for additional
short-term details.
..Moore.. 07/29/2025
.PREV DISCUSSION... /ISSUED 1132 AM CDT Tue Jul 29 2025/
...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.
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