SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Thu Jul 10 2025
Valid 102000Z - 111200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
THE MID-MISSOURI VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
COLORADO INTO THE CENTRAL PLAINS AND PORTIONS OF IOWA...
...SUMMARY...
Severe thunderstorms capable of large hail, damaging winds, and
perhaps a couple of tornadoes are possible late this afternoon into
tonight across parts of the central Great Plains to the Midwest,
particularly across the Middle Missouri Valley. Additional severe
storms are expected across parts of the Northeast and Southeast.
...20Z Update...
In the wake of MCV moving into western Wisconsin, a belt of stronger
shear is evident where modest northwesterly flow aloft is positioned
over surface southeasterly winds in central/eastern Iowa.
Furthermore, temperatures have risen into the upper 80s/low 90s F.
Given the potential for widely scattered to scattered storms to
develop on the southwestern flank of the MCV, the Slight risk has
been expanded into more of eastern Iowa. The remainder of the
outlook is unchanged. See the previous discussion for additional
details.
..Wendt.. 07/10/2025
.PREV DISCUSSION... /ISSUED 1133 AM CDT Thu Jul 10 2025/
...Central High Plains through the Central Plains into IA...
Recent surface analysis places a low near the NE/CO border, with a
moist airmass ahead of it over the central Plains. Satellite imagery
also shows a shortwave trough moving through the Great Basin towards
the central High Plains. Both of these features are expected to move
eastward throughout the day, with the surface low contributing to
eventual convective initiation over far southeast SD/northeast NE
and northwest IA this afternoon. The shortwave is expected to result
in numerous thunderstorms over the high terrain, with these storms
then moving eastward into the central High Plains.
The thunderstorms that develop near the surface low will encounter a
strongly unstable and moderately sheared environment supportive of
initial supercells capable of all severe hazards, including very
large hail and tornadoes. This activity should quickly grow upscale,
with the resulting convective line pushing southeastward into more
of northeast NE and western IA. Given ample buoyancy downstream,
some significant wind gusts are possible as this line moves
eastward/southeastward.
Farther west, the thunderstorms moving into the central High Plains
will initially be high-based and capable of strong wind gusts as
they move into the very deeply mixed airmass downstream. Some
amalgamation along cold pools is possible here over time, with the
resulting convective line likely moving eastward across
south-central NE and central KS. Damaging gusts will be possible as
this line moves eastward.
...Mid MS Valley...
A well-defined MCV is currently moving across southern MN, with the
expectation that it will continue gradually eastward throughout the
day. Daytime heating along the southern/southeastern periphery of
this vorticity max will likely result in airmass destabilization and
moderate buoyancy from eastern IA into southern WI and northern IL
this afternoon. Mesoscale ascent attendant to the MCV will interact
with this airmass, likely resulting in thunderstorm development. Low
to mid-level flow enhanced by the MCV will result in moderate
vertical shear and the potential for a few supercells. Given the
mesoscale nature of this scenario, overall storm coverage, including
the supercell coverage, is uncertain. Any supercells that do develop
could result in a threat for all severe hazards, including large
hail and a brief tornado. Conditionality of the overall scenario
merits only low severe probabilities for now, but higher
probabilities maybe needed for the 20Z if trends merit.
...New England and Upper Ohio Valley...
A shortwave trough currently is moving through the base of the
larger cyclone over central/eastern ON. This shortwave is forecast
to continue eastward throughout the day, resulting in broad ascent
from the Upper OH Valley into New England. Scattered thunderstorm
development is probable during peak afternoon heating, as this wave
interacts with moderate buoyancy and vertical shear. A predominantly
multicellular mode is anticipated, with damaging winds and isolated
hail as the primary risks. A corridor of slightly better low-level
moisture is expected over the Champlain Valley vicinity, which could
result in both greater storm coverage and stronger, more long-lived
updrafts. As a result, there is a small area where higher severe
coverage is possible.
...Southeast/Southern Atlantic Seaboard...
A very moist airmass is in place across the Southeast and southern
Atlantic Seaboard. Recent surface analysis reveals dewpoints in the
low to mid 70s areawide. 12Z soundings at FFC, JAX, and CHS sampled
PW values of 1.91", 1.97", and 2.14", respectively. This ample
low-level moisture will help support airmass destabilization and
moderate to strong buoyancy as temperatures increase into the upper
80s and low 90s this afternoon. Subtle ascent along the southern
periphery of broad upper troughing will interact with this unstable
and buoyant airmass to support scattered strong to severe
thunderstorms this afternoon through early/mid-evening.
Vertical shear across the region will be very weak, resulting in an
outflow-dominant storm mode, with new development then occurring
along these outflows. Water-loaded downbursts will be the primary
hazard as these clusters gradually move southeastward over time.
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