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000
ACUS01 KWNS 131608
SWODY1
SPC AC 131606

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1106 AM CDT Sat Apr 13 2024

Valid 131630Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM FAR
NORTHEAST CALIFORNIA INTO CENTRAL OREGON...

...SUMMARY...
Thunderstorms with isolated severe hail and strong wind gusts will
be possible this afternoon and early evening across parts of Oregon.

...Far Northeast California into Oregon...

An upper low off the northern/central CA coast will continue to
slowly migrate east through tonight. Deep-layer south/southeasterly
flow on the northeast periphery of this cyclone will advect a plume
of midlevel moisture and steep lapse rates over the area. Heating
through broken cloud cover will allow temperatures to warm into the
60s F by mid-afternoon and MLCAPE around 500-1000 J/kg is forecast.
Moderate deep shear, with 0-6km effective shear magnitudes near 35
kt will support organized clusters, or perhaps a supercell,
developing in the 20-22z time frame. Isolated large hail around 1 to
1.5 inches in diameter will be possible with the strongest cells
given steep lapse rates and favorable shear in the 4-6 km layer. In
addition to hail, a deeply-mixed sub-cloud layer will result in
inverted-v thermodynamic profiles, and isolated strong gusts may
occur.

While low-level moisture will remain a limiting factor for tornado
potential, a brief spin-up can not be ruled out. Enlarged low-level
hodographs are evident in forecast soundings and effective SRH will
increase to 100-200 m2/s2 by 22-00z amid 0-3km MLCAPE near 100 J/kg.
Have added a 2 percent tornado probability to reflect this low, but
non-zero potential.

Uncertainty in storm coverage will preclude an upgrade to Slight
risk at this time.

...Great Lakes...

A low-amplitude shortwave trough migrating through large-scale
northwesterly flow regime will foster elevated thunderstorm
development during the evening/overnight. Weak instability (MUCAPE
generally less than 500 J/kg) will limit storm intensity, though
steep midlevel lapse rates and cool temperatures aloft may be
sufficient for a few instances of small hail.

..Leitman/Bentley.. 04/13/2024

$$