SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Aug 09 2021 Valid 091630Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT ACROSS NORTHERN IL AND NORTHWESTERN IN...AND ACROSS EASTERN ND AND VICINITY... ...SUMMARY... Severe storms are expected this afternoon into tonight over parts of the northern Plains and Midwest/Ohio Valley, primarily across eastern North Dakota and northern Illinois. ...Northern IL area this afternoon into early tonight... Clouds and convection have been relatively widespread across WI/IL/IN this morning in association with multiple thunderstorm clusters, though some cloud breaks are becoming apparent from west central into northeast IL. Storms are ongoing along the WI/IL border along the southern/southeastern flank of an MCV, and additional storm development should occur toward the south and southwest as the low levels destabilize from west-to-east this afternoon across northern IL. Enhanced low-level flow/warm advection along the south flank of the MCV will result in substantial hodograph curvature/SRH, while deep-layer shear will be sufficiently strong for supercells. The net result will be a band of convection developing southward across northern IL with embedded supercells capable of producing damaging winds, large hail, and a couple of tornadoes. ...Eastern ND and vicinity this afternoon into early tonight... A pronounced midlevel shortwave trough over MT this morning will progress eastward across ND through tonight. The midlevel trough will be preceded by a surface cyclone and cold front in eastern ND, which will combine with ascent downstream from the midlevel trough to focus thunderstorm development through tonight. Surface heating in the warm sector will contribute to MLCAPE up to 2000 J/kg, while midlevel lapse rates will be relatively steep (close to 8 C/km) and effective bulk shear will reach 35-45 kt in a narrow corridor along the front. A mix of supercells and clusters/line segments is expected along the front late this afternoon through late evening, with an attendant threat for isolated very large hail of 2 to 2.5 inch diameter and severe outflow winds of 60-70 mph. ..Thompson/Bentley.. 08/09/2021 Read more LIVE: spc.noaa.gov
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