Mesoscale Discussion

SPC MD 1528

MD 1528 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTHERN CA AND SOUTHERN OR

Mesoscale Discussion 1528
NWS Storm Prediction Center Norman OK
0535 PM CDT Mon Jun 30 2025

Areas affected...portions of northern CA and southern OR

Concerning...Severe potential...Watch unlikely 

Valid 302235Z - 010030Z

Probability of Watch Issuance...20 percent

SUMMARY...Scattered thunderstorm developing over the higher terrain
will gradually expand in coverage/intensity this evening. Isolated
damaging gusts and small hail are possible with the strongest
storms. A WW is not anticipated, though convective trends will
continue to be monitored.

DISCUSSION...As of 2230 UTC, regional satellite and radar imagery
showed initial thunderstorms have increased in cover/intensity
across parts of northern CA and southern OR. Monsoon moisture being
advected ahead of an upper low off the coast of central CA has
resulted in ~1000 J/kg of MUCAPE atop very steep low-level lapse
rates. The warm and unstable air mass will support additional storm
development with continued ascent from a weak upper low, typical
diurnal terrain circulations. As storms mature, southerly deep-layer
shear around 30 kt may allow for some transient organization in the
form of multicell clusters or weak supercells. The dry sub-cloud
layer (deep mixing to near 500 mb) will promote strong downdrafts,
capable of isolated severe gusts. Some small hail will also be
possible with the stronger cores.

Scattered storms will remain possible into this evening and
overnight. Given the increase in convective coverage and the general
environment, some severe risk could materialize. However, the
limited potential for storm organization suggests a WW is not
likely.

..Lyons/Bunting.. 06/30/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...REV...MFR...STO...PQR...EKA...

LAT...LON   41752378 43482322 43642211 42712013 41312017 41122067
            40622184 40502255 41752378 

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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