Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0753 AM CDT Mon Jul 10 2017 Valid 101300Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDWEST AND SOUTHERN GREAT LAKES VICINITY... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN ROCKIES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN ROCKIES TO THE LOWER GREAT LAKES... ...SUMMARY... Isolated severe thunderstorms are expected mainly this afternoon and evening across portions of the Midwest and southern Great Lakes region, in addition to parts of the northern Rockies. ...Midwest and southern Great Lakes... A generally weakening MCS currently (13Z) extending from central IL northeastward into northern IN and southern Lower MI will continue east-southeastward this morning, with MCS-related outflow continuing to sag south-southeastward today. This outflow, along with differential heating and possibly some MCV influence, should help to refocus thunderstorm redevelopment/intensification this afternoon downstream from northern IN/southern Lower MI into OH. However, the existing early-day cloud canopy is likely to limit overall destabilization especially with eastward extent where low-level moisture will also be more modest. Even so, at least locally damaging winds will be possible this afternoon as storms increase and intensify. Farther west, gradual air mass recovery is anticipated especially on the western flank of the early-day MCS, with the most appreciable late-day destabilization expected from northern MO/southern IA into northern IL in areas just ahead of a southeastward-moving front. Weak large-scale forcing and gradual mid-level warming/capping provides some uncertainty regarding the western extent of late afternoon redevelopment. Overall, surface-based development/intensification appears most likely later today across north-central portions of IL/IN into northern OH. In this corridor, aforementioned buoyancy and 30-40 kt of effective shear, accentuated by relatively strong 2-3 km AGL west-southwesterly winds, could yield some initial supercells this afternoon aside from evolving line segments. Damaging winds should be the primary risk overall, but some of the supercells could yield severe hail, and given the strength of the winds (35-45 kt) within the lowest 1-2 km AGL, some tornado risk may exist as well pending outflow/mesoscale-related details. ...Northern Rockies to northern/central Plains... Gradual height falls will continue to occur across the region today as multiple weak/convectively related disturbances spread generally eastward from the northern Rockies to the north-central Plains and middle MO Valley vicinity. A mid-level impulse over the Pacific Northwest early today and the influence of higher terrain should help focus some strong to severe thunderstorms mainly across parts of southern MT, where moderate combinations of deep-layer shear and buoyancy will exist. Isolated severe hail and damaging winds will be possible. A surface trough may also semi-focus some severe thunderstorms late this afternoon into evening within a modestly moist environment across the western Dakotas, while a few other severe storms could occur in vicinity of a surface low and front extending across NE. ..Guyer.. 07/10/2017Read more
from SPC Forecast Products http://ift.tt/rATNzD
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