ACUS48 KWNS 130859
SWOD48
SPC AC 130857
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Wed May 13 2026
Valid 161200Z - 211200Z
...DISCUSSION...
...Saturday/Day 4 to Monday/Day 6...
At mid-levels, a shortware trough will move eastward across the
western U.S. on Saturday, as flow becomes west-southwesterly over
much of the central U.S. In response, moisture advection is forecast
to increase over the central U.S. as a pocket of 65 to 70 F
dewpoints moves northward into the lower and mid Missouri Valley. A
dryline is forecast on the western edge of the moist airmass.
Isolated to scattered storms appear likely to initiate to the east
of the dryline in the afternoon. Additional storms may form eastward
across the lower to mid Missouri Valley. Moderate deep-layer shear
is forecast over the instability axis, which should support a
potential for supercells with large hail and severe wind gusts.
On Sunday, an upper-level trough is forecast to develop over the
western U.S. Mid-level flow is expected to become southwesterly over
the Great Plains, where model forecasts show a surge of low-level
moisture. In response, surface dewpoints are forecast to increase
into the mid to upper 60s F over much of the north-central U.S. A
series of subtle shortwave troughs moving through the Great Plains
will likely support scattered to numerous thunderstorms in the
afternoon and evening. The greatest severe threat may develop over
eastern Nebraska and western Iowa, along the northern edge of a
low-level jet. A potential for supercells with large hail, wind
damage and a tornado threat is expected.
On Monday, the upper-level trough is forecast to move across the
Intermountain West, as multiple shortwave impulses move
northeastward across the Great Plains. A cold front is forecast to
move southeastward across the central U.S. Ahead of the front,
surface dewpoints in the lower to mid 70s F are forecast to be in
place by afternoon. In response, strong instability is expected to
develop in parts of the moist airmass. In addition, a mid-level jet
is forecast to eject northeastward across the central U.S. Moderate
to strong deep-layer shear associated with the jet will support a
potential for severe storms across a broad area from the southern
Plains northeastward into the Upper Midwest. Supercells and bowing
line segments with large hail, severe wind gusts and tornadoes will
be possible.
...Tuesday/Day 7 and Wednesday/Day 8...
On Tuesday and Wednesday, a cold front is forecast to move from the
Upper Midwest southeastward into the Appalachians. A moist and
unstable airmass will likely be in place ahead of the front, with
scattered to numerous thunderstorms likely developing each afternoon
and evening. The greatest severe threat could materialize over the
mid Mississippi and lower Ohio Valley on Tuesday, and in the
Northeast on Wednesday, adjacent to a mid-level jet passing through.
However, uncertainty is substantial at this time concerning the
timing of the upper-level trough and cold front.
..Broyles.. 05/13/2026
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