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Mesoscale Discussion 1674
NWS Storm Prediction Center Norman OK
0541 PM CDT Fri Aug 12 2022

Areas affected...ID into western MT

Concerning...Severe Thunderstorm Watch 518...

Valid 122241Z - 130015Z

The severe weather threat for Severe Thunderstorm Watch 518
continues.

SUMMARY...The threat for severe hail and wind continues across WW
518. Some threat may extend east of the watch across northern and
central Montana this evening, but the need for new downstream watch
issuance remains uncertain.

DISCUSSION...Scattered strong to potentially severe thunderstorms
are ongoing across much of ID into western MT late this afternoon.
This activity is being fueled by moderate instability (MLCAPE of
generally 1000-1500 J/kg) and effective shear of 35+ kt (as noted in
recent objective mesoanalyses and VWPs from KCBX and KMSX). Storms
have largely been discrete thus far, with occasional supercell
structures noted. Discrete modes will likely be maintained into the
early evening, with a continued threat of large hail, and also a
threat of localized strong/severe wind gusts, especially where
strong diurnal heating occurred prior to storm arrival. 

With time, some upscale growth is possible, as outflows consolidate
and convection tries to propagate eastward into parts of
central/northern MT. With weaker instability and stronger MLCINH
downstream, and stronger large-scale ascent expected to remain
northwest of the area in association with the offshore upper
cyclone, the potential for an organized severe-wind threat to spread
eastward this evening remains uncertain. This in turn renders the
need for new downstream watch issuance uncertain, though at least a
local extension of the WW 518 may be needed as ongoing convection
spreads eastward into this evening.

..Dean/Goss.. 08/12/2022

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

ATTN...WFO...TFX...PIH...MSO...BOI...OTX...

LAT...LON   42801612 43271635 43911610 45111527 45601623 46001610
            46471580 47251511 47951502 48751508 49041373 48891128
            48361021 47931022 47481037 46451174 45781200 44261236
            44161241 43331300 42601517 42801612