554
ACUS11 KWNS 202043
SWOMCD
SPC MCD 202042
NDZ000-MTZ000-202215-

Mesoscale Discussion 2092
NWS Storm Prediction Center Norman OK
0342 PM CDT Fri Sep 20 2024

Areas affected...portions of northern Montana and North Dakota

Concerning...Severe potential...Watch unlikely

Valid 202042Z - 202215Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated strong to severe gusts are possible with
convection near an upper low this afternoon/evening. Storm coverage
and the lack of broader organization should keep the threat limited.

DISCUSSION...As of 2040 UTC, regional observations showed low-topped
showers and thunderstorms ongoing beneath an upper low over parts of
northern MT. Cold temperatures aloft (H5 temps ~ -20C) with the
upper low are supporting steep low and mid-level lapse rates.
Despite poor surface moisture, (dewpoints in the 30s and 40s F) weak
buoyancy (~500 J/Kg MUCAPE) should be sufficient to support isolated
convection this afternoon and into the early evening hours. The
steep lapse rates, and momentum transfer from strong flow aloft will
support a risk for strong to severe damaging wind gusts with any
storms able to persist. Storm coverage may gradually expand eastward
with the upper low as it spreads into northwestern ND. Moisture
there is slightly deeper, but buoyancy remains weak. A few strong to
severe gusts are possible through the remainder of the afternoon and
into the early part of this evening. Given the lack of deeper
surface moisture and instability, a WW appears unlikely.

..Lyons/Guyer.. 09/20/2024

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

ATTN...WFO...BIS...GGW...TFX...

LAT...LON   48611213 49141268 49341059 49200676 49140335 48760310
            48030422 47780567 47750777 48131048 48611213