SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Sun Oct 24 2021 Valid 241300Z - 251200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE OZARKS AND MIDDLE MISSISSIPPI RIVER VALLEY... ...SUMMARY... Scattered severe thunderstorms associated with damaging wind gusts, isolated large hail and tornadoes are expected from parts of the Ozarks into the middle Mississippi Valley, especially this afternoon into tonight. Other locally severe storms are possible along the coastal Pacific Northwest. ...Ozarks/Mid-South/Middle Mississippi Valley... An eastward-progressive shortwave trough coincident with an amplifying and strengthening belt of cyclonically curved westerlies will spread from the south-central High Plains toward the Ozarks to near the confluence of the Mississippi/Ohio Rivers by daybreak Monday. A considerable coverage of showers/thunderstorms is ongoing early today especially along/north of the warm front. This warm front will continue to develop north-northeastward today across the middle Mississippi River Valley, with a surface low developing east-northeastward from east-central Kansas across northern Missouri, and into central Illinois/north-central Indiana tonight. A surface low-trailing cold front will spread southeastward across the Ozarks and reach the middle Mississippi Valley and Mid-South by evening. Within the warm sector, low/middle 60s F surface dewpoints will become increasingly prevalent from eastern Oklahoma and essentially all of Arkansas/Missouri into central/southern Illinois this afternoon. A plume of steep mid-level lapse rates, in relative proximity to the cyclone and triple point, will overspread Missouri and nearby northern Arkansas/far western Illinois. However, a point of uncertainty is that cloud cover/some precipitation may tend to linger into the afternoon near the surface low and near/just south of the warm front across northern Missouri and central Illinois, although late-day clearing is plausible if not likely. Regardless, a semi-narrow axis of moderate destabilization is expected immediately ahead of the advancing cold front, especially from central/eastern Missouri south-southwestward into far eastern Oklahoma and northern/western Arkansas by late afternoon. Initial surface-based storm development is expected by around mid-afternoon across northeast/central Missouri toward far west-central Illinois, with a subsequent (but somewhat more isolated) southward expansion of deep convective development expected into far eastern Oklahoma and northern/western Arkansas by around sunset. Relatively strong deep-layer/low-level shear will exist across essentially all of the storm-viable warm sector this afternoon into tonight. This will support initial supercells capable of large hail along with a tornado risk, especially across central/eastern Missouri into western Illinois in vicinity of the surface low and effective warm front. A couple of stronger tornadoes could occur. Storms will likely tend to grow upscale in most areas by evening, with a nocturnally intensifying low-level jet being supportive of damaging winds and a QLCS-related tornado risk as storms race east-northeastward this evening. Overall storm intensity is expected to wane overnight as storms quickly move eastward across Indiana and east-southeastward toward the Mid-South/immediate Mississippi River vicinity (south of the Ohio River). ...Coastal Pacific Northwest... Influenced by the upper low off the coastal Pacific Northwest, steepening low/mid-level lapse rates and adequate moisture will support increasing cellular convection and isolated thunderstorms near the coast into this afternoon. Strong deep-layer southwesterly winds could support some semi-organized/sustained storms including a few low-topped supercells. The potential will exist for a brief tornado and convectively enhanced wind gusts mainly from late morning through early evening. ..Guyer/Kerr.. 10/24/2021 Read more LIVE: spc.noaa.gov
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