119
ACUS01 KWNS 021942
SWODY1
SPC AC 021941

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0241 PM CDT Wed Jul 02 2025

Valid 022000Z - 031200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER NORTH CENTRAL
MONTANA...

...SUMMARY...
Scattered severe thunderstorm gusts are possible across Montana this
afternoon into the evening.  Isolated severe thunderstorms may occur
today across parts of the Great Basin and Upper Midwest/Great Lakes.

...20z Update...
There are no changes are needed to the D1 Convective Outlook. See
previous discussion below for more information.

..Thornton.. 07/02/2025

.PREV DISCUSSION... /ISSUED 1132 AM CDT Wed Jul 02 2025/

...Northern Rockies into the Northern High Plains...
Recent satellite imagery shows expansive upper ridging extending
from the southern Plains into central AB/SK. An upper low is slowly
drifting eastward into southern CA, impinging on the western
periphery of this upper ridging. This upper low is forecast to stay
well south of the region throughout the day, but a modest vorticity
maximum, generated by convection east of this upper low, is forecast
to move into the northern Rockies this afternoon. Ascent associated
with this vorticity max coupled with orographic ascent, and perhaps
additional large-scale ascent ahead of weak shortwave trough moving
across OR, is expected to result in thunderstorms over the high
terrain as the airmass diurnally destabilizes this afternoon.
Persistent southwesterly flow aloft will then take these storms
north/northeastward into more of the MT High Plains. Highest storm
coverage is expected from central ID into western MT during the
afternoon, before transition to more of central MT this evening.
Vertical shear is strong enough for occasionally organized storm
structures. The high cloud bases and steep low-level lapse rates
will contribute to the potential for strong to severe wind gusts,
particularly across central MT as storms become outflow dominant.

...Western Great Basin...
Increasing thunderstorm coverage is anticipated this afternoon and
evening east of a slow-moving upper low currently moving into
central/southern CA. Moderate mid-level flow through the eastern
periphery of the upper low combined with modest buoyancy and high
LCLs will result in an environment favorable to isolated to
scattered strong to severe wind gusts. Highest overall thunderstorm
coverage and relatively greater chance for strong/severe gusts is
over southern NV.

...AZ...
12Z PHX sounding sampled a precipitable water of 1.4" this morning
and the expectation is that this moisture will support the
development of numerous thunderstorms across the region this
afternoon/evening. Development is anticipated over the higher
terrain first, before then slowly moving westward toward lower
elevations. This overall pattern generally favors strong to severe
gusts across central AZ. However, very weak mid-level flow suggests
the westward push off the terrain will be slow, if it occurs at all,
which should limit the overall severe potential.

...Upper Midwest/Great Lakes...
A weak cold front is forecast to move into northern MN, northern WI,
Upper MI this afternoon. Thunderstorms are anticipated along this
front as it interacts with the modest buoyancy (i.e. MLCAPE around
1000 J/kg) over this region. Isolated pre-frontal storms are
possible across Lower MI as well. Moderate mid-level flow will
support the potential for damaging gusts with any of the stronger
storms.

Additional thunderstorms are possible later this evening farther
west from far southeast SD into southern MN and northern IA. There
is some chance development occurs along the front during the
afternoon, but low-level convergence will likely be too weak to
overcome the convective inhibition. Later, isolated coverage appears
more likely as warm-air advection, supported by modest low-level
jet, increases. Given the expected combination of buoyancy and
vertical shear, one or two more organized storms capable of large
hail are possible.

...Eastern NC...
Weak upper troughing and attendant surface cold front will advance
eastward today across the southern Mid-Atlantic and Carolinas.
Widespread thunderstorm development is anticipated ahead of these
features. However, poor lapse rates aloft will likely limit updraft
strength, with deep-layer shear limiting storm organization as well.
A few water-loaded downbursts are possible within the strongest
storms.

$$