ACUS11 KWNS 281829
SWOMCD
SPC MCD 281829=20
NVZ000-IDZ000-ORZ000-WAZ000-282100-

Mesoscale Discussion 0882
NWS Storm Prediction Center Norman OK
0129 PM CDT Thu May 28 2026

Areas affected...portions the Northwest and northern Great Basin

Concerning...Severe potential...Severe Thunderstorm Watch likely=20

Valid 281829Z - 282100Z

Probability of Watch Issuance...80 percent

SUMMARY...Scattered to numerous thunderstorms are likely this
afternoon and evening over portions of the Pacific Northwest and
northern Great Basin. Convection should increase in coverage with a
risk for severe/damaging wind gusts, hail and perhaps a tornado or
two. A WW is likely, though timing remains uncertain.

DISCUSSION...As of 1830 UTC, WV imagery showed a deep upper low over
central CA with several prominent shortwave troughs embedded within
the broader cyclonic flow. Visible imagery showed a broad area of
cumuliform clouds in vicinity to the most prominent shortwave
feature rotating northward across central and northern NV.
Unseasonably high surface moisture (dewpoints in the 40s and 50s F)
is in place over OR, WA, and ID. As diurnal heating continues
beneath cool mid-level temperatures, steepening low and mid-level
lapse rates will contribute to moderate destabilization and
thunderstorm development/intensification.

A very complex convective evolution is expected this afternoon. CAM
guidance shows several bands of convection gradually deepening over
northern NV and moving northwestward with the strong shortwave
trough. Additional storms may develop along local terrain features
and across the diffuse synoptic boundary across southern OR. 50+ kt
of east/southerly mid-level flow will overspread the instability,
contributing to moderate/strong effective shear. Initially more
cellular storms may organize into supercells or clusters. Most
guidance shows eventual upscale growth into a more linear structure
with time.

Steep lapse rates and the enhanced flow aloft suggest severe wind
gusts are the most likely hazard. Some hail may also occur, given
cool mid-level temperatures and the degree of buoyancy. Unusually
strong low-level shear beneath the easterly jet aloft may also
support a risk for a tornado or two, especially with any persistent
supercells.

The severe risk is expected to increase from midday into this
evening as the upper trough rotates northward and intersects with
the more unstable air mass. The highest confidence in a sustained
severe risk resides east of the Cascades over much of OR currently.
This will likely necessitate one or more Severe Thunderstorm Watches
this afternoon/evening. However, confidence in the exact timing
remains very uncertain.

..Lyons/Hart.. 05/28/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!9KuWqeg_gaZmhrG1Y18N_vSAziy1QQJ0O-Op0UyiKtBBNQhnTrX_9ckQcHyzE_H-Z0ptZVvBP= vGCb2vEhQF9uX7Uubo$ for graphic product...

ATTN...WFO...BOI...LKN...PDT...REV...MFR...PQR...

LAT...LON 42622108 43462210 45102252 45702170 46271890 45881725
45501690 45021683 43221664 42101631 41761670 41691738
41741872 42312075 42622108=20

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


=3D =3D =3D
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