ACUS11 KWNS 292031
SWOMCD
SPC MCD 292031=20
IDZ000-MTZ000-ORZ000-WAZ000-292230-

Mesoscale Discussion 2059
NWS Storm Prediction Center Norman OK
0331 PM CDT Tue Aug 29 2023

Areas affected...portions of eastern WA/OR...central ID and western
MT

Concerning...Severe potential...Watch possible=20

Valid 292031Z - 292230Z

Probability of Watch Issuance...40 percent

SUMMARY...Scattered high-based convection should develop through the
afternoon with a risk for damaging outflow winds and hail into the
early evening hours. Scattered storm coverage and the potential for
gusts to 70 mph suggests a WW is possible.

DISCUSSION...Across portions of the Pacific Northwest, regional WV
imagery showed a negatively tilted mid-level trough and jet streak
ejecting eastward into portions of the northern Rockies. Ahead of
the trough, broad synoptic ascent was evident in a deepening
convective arc stretching from eastern WA/OR into portions of
central ID. Despite limited surface moisture, (surface dewpoints in
the 30s and 40s F), strong diurnal surface heating and cooling aloft
are supporting 500-1000 J/kg of MLCAPE. As forcing for ascent
continues through the afternoon, the sufficient buoyancy should
allow for continued updraft development off of local terrain
circulations. Scattered high-based storms should mature through the
afternoon and continue into the early evening. As the trough and jet
streak shift eastward, stronger mid-level flow will overspread the
developing storms. Area RAP soundings show deep-layer shear of 30-40
kt which would favor some storm organization. A few longer-lived
updrafts or clusters, including weak supercell structures, may
evolve given the favorable shear and CAPE. With low-level inverted-v
profiles present, strong negatively buoyant downdrafts capable of
damaging gusts to 60-70 mph are possible. Small hail is also
possible with the more sustained storms. As storms continue to
develop, severe potential will likely increase over central and
northeastern ID, into western MT this evening. Uncertainty on the
severity of the threat is still relatively high given the modest
buoyancy, but conditions will be monitored for a possible weather
watch.

..Lyons/Thompson.. 08/29/2023

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-rcYwTQ1ZCdcbUPHpnqawgUhFZ2gBc3uZQ9g-A2I5DY4K_s5HkpgeAdU3GEI4hoQ-x4uOaVNl= j-IvTEOwR5MphTc2Qk$ for graphic product...

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

LAT...LON 44161184 43621273 43531359 44311599 45731761 47051768
48021582 47801386 46711288 45641214 44551173 44161184=20


=3D =3D =3D
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