SPC AC 031755 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1255 PM CDT Mon Apr 03 2023 Valid 041200Z - 051200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM EASTERN IOWA INTO NORTHWEST ILLINOIS...AND FROM SOUTHERN MISSOURI SOUTHWESTWARD TOWARD THE ARKLATEX.... ...SUMMARY... A large area of severe potential will exist from Tuesday afternoon into Wednesday morning, from eastern portions of the Plains into the Missouri and mid/upper Mississippi Valleys. Strong tornadoes and particularly damaging winds are expected. Both afternoon and overnight potential will exist across various regions, including the risk of dangerous nighttime tornadoes. ...Synopsis... A large upper trough will move from the Rockies into the Plains on Tuesday, with an upper low tracking from WY to northern MN by Wednesday morning, deepening after 00Z. Meanwhile, upper ridging will occur over the eastern states. A strong 100 kt midlevel jet max will be positioned from NM into western KS during the day, with an intensifying jet core Tuesday night from KS into IA. Just ahead of the primary upper trough/jet, a leading speed max will strengthen from OK into KS and MO during the day, perhaps with a subtle lobe of cooling aloft. At the surface, low pressure will exist over eastern CO Tuesday morning, and will shift eastward across KS during the day, translating east/northeast along a cold front. This low will shift into IA by evening, and into WI by 12Z Wednesday. Ahead of the low, a prominent warm front will move rapidly north, beginning the day from northeast KS into central IL, and reaching near I-80 from IA into northern IL by 00Z. This boundary will continue north into southern WI and western Lower MI overnight, ahead of the surface low. Behind the low, a cold front will make an eastward push during the late evening and overnight across IA, northwest MO and eastern KS. ...Northeast TX into AR and into MO - OVERNIGHT... Confidence is increasing in the potential for rare and dangerous overnight tornadoes and damaging winds, and a Moderate Risk has been introduced for this region. The air mass will remain capped during the day, as boundary-layer moisture builds. Steep lapse rates will exist above the capping layer, which will not be particularly strong overnight due to robust moisture. As the cold front approaches from the west, the low-level jet will remain strong providing theta-e advection through the night. Nocturnal storms are forecast to erupt after 06Z, and perhaps closer to 08Z from southwest MO into western AR and into northeast TX. Hodographs will strongly favor tornadic supercells with effective SRH near 400 m2/s2. Further, steep lapse rates aloft and ample instability will favor strong tornadoes, and a long tracked tornado cannot be ruled out. This appears to be a rare case where the front may act more like a dryline during the overnight hours, with veering at 850 mb being more gradual. Capping is most likely to limit the eastward extent of the threat for southern areas near LA. ..Jewell.. 04/03/2023