Subj : MESO: Mesoscale Discussion 0833 To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 21 2023 19:42:35 ACUS11 KWNS 211942 SWOMCD SPC MCD 211942=20 IDZ000-ORZ000-212145- Mesoscale Discussion 0833 NWS Storm Prediction Center Norman OK 0242 PM CDT Sun May 21 2023 Areas affected...portions of eastern Oregon and western Idaho Concerning...Severe potential...Severe Thunderstorm Watch likely=20 Valid 211942Z - 212145Z Probability of Watch Issuance...80 percent SUMMARY...Isolated to widely scattered thunderstorms will gradually evolve off of the higher terrain this afternoon. A few supercells capable of severe hail and winds are possible. A Severe Thunderstorm Watch is likely. DISCUSSION...Early this afternoon, regional WV imagery showed a mid-level trough and associated cold front shifting eastward over portions of the northwestern CONUS. Ahead of the front, forcing for ascent and afternoon heating were supporting the gradual destabilization of the air mass across portions of eastern OR and western ID. Low 50s to upper 40s F surface dewpoints and mid-level lapse rates near 8 C/km were supporting ~500 J/kg of MLCAPE from SPC mesoanalysis. Further heating should aid destabilization with peak MLCAPE values of 1000-1250 J/kg while inhibition is diminished. As the front slowly advances eastward, forcing for ascent and local terrain circulations should result in the development of scattered thunderstorms from eastern OR into ID this afternoon. Enhanced southwesterly flow ahead of the approaching trough was supporting a broad area of 35-40 kt of 0-6km shear over much of the Northwest. As storms develop this afternoon, a few high-based supercells or multi-cell clusters will likely become organized and track northeastward. The favorable mid-level shear profiles and lapse rates will favor large hail, especially with sustained supercells. Dry sub-cloud layers may also support a risk for severe wind gusts as cells merge or cluster together later this evening as strong downdrafts are established. While the coverage of severe storms may remain isolated to widely scattered, confidence in storm organization is relatively high across parts of northeastern OR and western ID. The favorable CAPE/shear space and storm coverage suggest that conditions may warrant a Severe Thunderstorm Watch this afternoon. ...Lyons/Grams.. 05/21/2023 ....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!6sove-pk1rX12KqmZaDMbiE53riCktduf47PovwNjfj5N4JxEzbXsq7u4gnGn64GIijn-VUdl= Ycte6tcB8jxTpEi7bc$ for graphic product... ATTN...WFO...MSO...BOI...OTX...PDT...MFR... LAT...LON 42011973 43831641 45411542 46161519 46361569 46091666 45501785 44361946 43302079 42332078 42011973=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .