MD 1489 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PARTS OF SOUTHWEST THROUGH CENTRAL MONTANA
Mesoscale Discussion 1489
NWS Storm Prediction Center Norman OK
0534 PM CDT Mon Jul 10 2023
Areas affected...parts of southwest through central Montana
Concerning...Severe potential...Watch unlikely
Valid 102234Z - 110100Z
Probability of Watch Issuance...20 percent
SUMMARY...A cluster of thunderstorms may continue to develop and
organize while spreading into central Montana near and south of
Lewistown through 7-9 PM MDT.
DISCUSSION...Convection has been consolidating across the mountains
of southwestern Montana into the Helena vicinity during the past
hour or two, likely aided by forcing for ascent downstream of a
short wave trough now progressing northeastward into the Canadian
and northern U.S. Rockies. Embedded with modest (but
strengthening), deep layer west-southwesterly mean flow, largely due
to 30-50 kt speeds in the 500-300 mb layer, the downstream
environment has become characterized by deep boundary-layer mixing.
Although not particularly moist, it may still be characterized by
CAPE in excess of 500 J/kg. And strong vertical shear, due to
pronounced veering with height, might support the evolution of an
increasingly organized system into central Montana near and south of
the Lewistown by 01-03Z. This may be accompanied by a risk for
small to marginally severe hail, and perhaps a developing swath of
strong gusts approaching or occasionally briefly exceeding severe
limits.
..Kerr/Guyer.. 07/10/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BYZ...GGW...TFX...
LAT...LON 47051147 47470904 46840795 45970928 46081109 46051188
47051147
