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Severe Storm Outlook Narrative (AC)
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Issued by NWS
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610 ACUS11 KWNS 271819 SWOMCD SPC MCD 271818 MTZ000-272045- Mesoscale Discussion 1445 NWS Storm Prediction Center Norman OK 0118 PM CDT Thu Jun 27 2024 Areas affected...Portions of central and eastern Montana Concerning...Severe potential...Watch likely Valid 271818Z - 272045Z Probability of Watch Issuance...80 percent SUMMARY...The severe-storm threat will gradually increase from west to east across portions of central and eastern Montana this afternoon. Large hail and severe gusts are the main concerns. A watch will likely be needed for parts of the area later this afternoon. DISCUSSION...Latest water-vapor imagery indicates a band of large-scale ascent overspreading west/central MT -- ahead of a midlevel trough/low tracking eastward across the Northwest. At the leading edge of this ascent, isolated to widely scattered thunderstorms are tracking east-northeastward along the higher terrain in west/central MT. Over the next several hours, this activity will continue spreading eastward across central into eastern MT, generally in tandem with the large-scale ascent. Additional development is also possible in areas of differential heating farther east. Ample diurnal heating/destabilization beneath steep midlevel lapse rates (sampled by 12Z regional soundings) will erode remaining low-level inhibition and promote a gradual uptick in updraft intensity through the afternoon. Around 50 kt of effective shear associated with the eastward-advancing trough will support storm organization, and a mostly straight hodograph should favor a mix of splitting supercell structures and organized clusters. Large hail (some potentially 2+ inches) and severe outflow winds are possible with the strongest storms. The risk of severe gusts (some 75+ mph) should increase with eastward extent, especially with any upscale-growing clusters. While a brief tornado cannot be entirely ruled out in this area, the more-favorable tornado environment should generally develop over areas farther east (far eastern MT into the Dakotas), where richer boundary-layer moisture and curved hodographs are expected. A watch is likely for portions of the area later this afternoon, though timing of issuance is a bit uncertain at this time. ..Weinman/Hart.. 06/27/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...GGW...TFX... LAT...LON 46320967 46920906 47200870 47580813 47800768 48110706 48290651 48430569 48330512 47910473 46990450 46390455 45770483 45470550 45220700 45160853 45240924 45430965 45710987 46030989 46320967