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SPC AC 311954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Fri Mar 31 2023 Valid 312000Z - 011200Z ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FOR FAR SOUTHEAST IOWA...WEST-CENTRAL ILLINOIS...FAR NORTHEAST MISSOURI AND IN PART OF EASTERN ARKANSAS...NORTHERN MISSISSIPPI...AND SOUTHWESTERN TENNESSEE...... ...SUMMARY... A severe weather outbreak will continue this afternoon and evening across a large portion of the Mississippi Valley. Multiple strong tornadoes are expected, some long tracked. A violent tornado will be possible within the High Risk areas. Swaths of intense damaging wind gusts along with very large hail are expected as well. ...20Z Update... An outbreak of severe weather continues to evolve this afternoon, with numerous storms currently from IA near the surface low southward along a dryline into northeast TX. The air mass will continue to destabilize over this expansive area, with large-scale lift increase as well. Shear will remain extremely favorable for supercell tornadoes within multiple regimes from the surface low/vort max across IA/MO/IL to the trailing dryline over the lower MS Valley where dewpoints and MLCAPE are greater. 0-1 km shear is particularly strong currently from central AR into southeast MO, with increasing values expected through evening to the northeast. As a strong vort max with rapid cooling aloft overspread the IA and northern MO/IL region, existing storms are expected to intensify, with several likely becoming tornadic and producing very large hail. The very steep lapse rates in this region will maximize updrafts, and may support several intense tornadoes. Rising dewpoints would further support the tornado risk later today. For more information, see any of multiple mesoscale discussions that remain in effect, including #397 for NE MO/Central IL, #398 for northern MO, #399 for central AR and #400 for northern IL into far southern WI. ..Jewell.. 03/31/2023 .PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Mar 31 2023/ ...Synopsis... A dangerous severe weather outbreak is likely across a large portion of the central states this afternoon into tonight. Long-track, strong to potentially violent tornadoes are forecast across a broad region of the MS Valley. The propensity of model-supporting evidence and observational trends lends confidence in the upgrade to bimodal High Risks for the mid MS Valley and lower MS Valleys. ...Midwest and the Mid-MS to OH Valleys... Morning water-vapor imagery shows a potent 500-mb speed max ejecting east-northeast across the TX Panhandle/western OK to the south of a mid-level low over northern NE. A 992-mb cyclone over western IA will deepen through this afternoon as it matures into the Upper MS Valley before occluding this evening. Visible-satellite imagery/surface observations show a plume of increasingly rich low-level moisture rapidly advecting northward into the lower MO Valley with surface dewpoints rising into the lower 60s F. Strong heating in combination with low-level moistening and cooling mid-level temperatures, are expected to result in a relatively large corridor featuring 1000-3000 J/kg MLCAPE across a moderate to strongly unstable warm sector. In agreement with prior forecast thinking, it seems the primary severe evolution remains likely to evolve beginning around 19Z to the southeast of the deep cyclone across central IA and broadening in coverage through the late afternoon along the north/south-oriented cold front arcing southward into eastern MO. Very steep mid-level lapse rates and an elongated mid to upper-level hodograph will initially support a broken band of supercells capable of producing very large hail. The risk for tornadoes will likely focus initially with supercells near and southeast of the surface low. As this activity rapidly spreads into an increasingly favorable low-level SRH environment in the eastern half of IA and the MS Valley, several to numerous tornadoes are expected to form. Forecast soundings within the High Risk show large 0-3-km MLCAPE co-located with intense speed shear and large low-level and elongated hodographs. Within this arcing band of quasi-discrete supercells, several long-track strong to potentially violent tornadoes are forecast for this afternoon into the evening. Eventual upscale growth into an intense squall line with embedded cellular elements is expected to evolve during the evening into tonight across IL and rapidly sweep eastward across the OH Valley/southern Great Lakes. Some risk for tornadoes will probably spread east with the squall line coincident with a 70-kt 700-mb speed max overspreading the region. Severe gusts (60-90 mph) are possible with surges/bowing structures and embedded cells within the band of storms. Have expanded the Moderate Risk due to significant wind gusts across eastern IL into IN. By late tonight, the evolving QLCS will outpace weakening surface-based instability around the central OH Valley. Extreme low-level wind fields could support a waning wind/brief tornado threat approaching the central Appalachians. ...Ark-La-Tex to the Lower MS/TN Valleys... Multiple rounds of severe convection are expected to unfold, intensifying this afternoon in AR and Ark-La-Tex, before continuing east across the Lower MS into the TN Valleys through tonight. Rapid airmass modification is currently underway across the lower MS Valley with mid 60s deg F dewpoints surging north-northeast across southern AR and towards the AR/TN/MS region. Initially, a capped warm sector via an EML will act to limit storm development (isolated early afternoon storms with mainly a hail risk). However, as buoyancy increases (1500-2500 J/kg MLCAPE) and shear profiles intensify, very favorable hodographs are forecast to develop by mid-late afternoon across southern/eastern AR into adjacent portions of MS/TN (effective SRH 300-600 m2/s2). Scattered thunderstorms will likely develop by late afternoon with these rapidly evolving into supercells. Strong to potentially violent tornadoes are forecast with a few long-tracked supercells. Upscale growth into a QLCS with embedded supercells appears probable during the late evening and overnight as frontal convergence strengthens. Tornadoes and significant damaging wind swaths will remain possible well into the night across at least into the TN Valley, until warm-sector low-level flow becomes more veered towards the end of the period. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z CURRENT UTC TIME: 2321Z (7:21PM), RELOAD THIS PAGE TO UPDATE THE TIME

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SPC AC 311954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Fri Mar 31 2023 Valid 312000Z - 011200Z ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FOR FAR SOUTHEAST IOWA...WEST-CENTRAL ILLINOIS...FAR NORTHEAST MISSOURI AND IN PART OF EASTERN ARKANSAS...NORTHERN MISSISSIPPI...AND SOUTHWESTERN TENNESSEE...... ...SUMMARY... A severe weather outbreak will continue this afternoon and evening across a large portion of the Mississippi Valley. Multiple strong tornadoes are expected, some long tracked. A violent tornado will be possible within the High Risk areas. Swaths of intense damaging wind gusts along with very large hail are expected as well. ...20Z Update... An outbreak of severe weather continues to evolve this afternoon, with numerous storms currently from IA near the surface low southward along a dryline into northeast TX. The air mass will continue to destabilize over this expansive area, with large-scale lift increase as well. Shear will remain extremely favorable for supercell tornadoes within multiple regimes from the surface low/vort max across IA/MO/IL to the trailing dryline over the lower MS Valley where dewpoints and MLCAPE are greater. 0-1 km shear is particularly strong currently from central AR into southeast MO, with increasing values expected through evening to the northeast. As a strong vort max with rapid cooling aloft overspread the IA and northern MO/IL region, existing storms are expected to intensify, with several likely becoming tornadic and producing very large hail. The very steep lapse rates in this region will maximize updrafts, and may support several intense tornadoes. Rising dewpoints would further support the tornado risk later today. For more information, see any of multiple mesoscale discussions that remain in effect, including #397 for NE MO/Central IL, #398 for northern MO, #399 for central AR and #400 for northern IL into far southern WI. ..Jewell.. 03/31/2023 .PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Mar 31 2023/ ...Synopsis... A dangerous severe weather outbreak is likely across a large portion of the central states this afternoon into tonight. Long-track, strong to potentially violent tornadoes are forecast across a broad region of the MS Valley. The propensity of model-supporting evidence and observational trends lends confidence in the upgrade to bimodal High Risks for the mid MS Valley and lower MS Valleys. ...Midwest and the Mid-MS to OH Valleys... Morning water-vapor imagery shows a potent 500-mb speed max ejecting east-northeast across the TX Panhandle/western OK to the south of a mid-level low over northern NE. A 992-mb cyclone over western IA will deepen through this afternoon as it matures into the Upper MS Valley before occluding this evening. Visible-satellite imagery/surface observations show a plume of increasingly rich low-level moisture rapidly advecting northward into the lower MO Valley with surface dewpoints rising into the lower 60s F. Strong heating in combination with low-level moistening and cooling mid-level temperatures, are expected to result in a relatively large corridor featuring 1000-3000 J/kg MLCAPE across a moderate to strongly unstable warm sector. In agreement with prior forecast thinking, it seems the primary severe evolution remains likely to evolve beginning around 19Z to the southeast of the deep cyclone across central IA and broadening in coverage through the late afternoon along the north/south-oriented cold front arcing southward into eastern MO. Very steep mid-level lapse rates and an elongated mid to upper-level hodograph will initially support a broken band of supercells capable of producing very large hail. The risk for tornadoes will likely focus initially with supercells near and southeast of the surface low. As this activity rapidly spreads into an increasingly favorable low-level SRH environment in the eastern half of IA and the MS Valley, several to numerous tornadoes are expected to form. Forecast soundings within the High Risk show large 0-3-km MLCAPE co-located with intense speed shear and large low-level and elongated hodographs. Within this arcing band of quasi-discrete supercells, several long-track strong to potentially violent tornadoes are forecast for this afternoon into the evening. Eventual upscale growth into an intense squall line with embedded cellular elements is expected to evolve during the evening into tonight across IL and rapidly sweep eastward across the OH Valley/southern Great Lakes. Some risk for tornadoes will probably spread east with the squall line coincident with a 70-kt 700-mb speed max overspreading the region. Severe gusts (60-90 mph) are possible with surges/bowing structures and embedded cells within the band of storms. Have expanded the Moderate Risk due to significant wind gusts across eastern IL into IN. By late tonight, the evolving QLCS will outpace weakening surface-based instability around the central OH Valley. Extreme low-level wind fields could support a waning wind/brief tornado threat approaching the central Appalachians. ...Ark-La-Tex to the Lower MS/TN Valleys... Multiple rounds of severe convection are expected to unfold, intensifying this afternoon in AR and Ark-La-Tex, before continuing east across the Lower MS into the TN Valleys through tonight. Rapid airmass modification is currently underway across the lower MS Valley with mid 60s deg F dewpoints surging north-northeast across southern AR and towards the AR/TN/MS region. Initially, a capped warm sector via an EML will act to limit storm development (isolated early afternoon storms with mainly a hail risk). However, as buoyancy increases (1500-2500 J/kg MLCAPE) and shear profiles intensify, very favorable hodographs are forecast to develop by mid-late afternoon across southern/eastern AR into adjacent portions of MS/TN (effective SRH 300-600 m2/s2). Scattered thunderstorms will likely develop by late afternoon with these rapidly evolving into supercells. Strong to potentially violent tornadoes are forecast with a few long-tracked supercells. Upscale growth into a QLCS with embedded supercells appears probable during the late evening and overnight as frontal convergence strengthens. Tornadoes and significant damaging wind swaths will remain possible well into the night across at least into the TN Valley, until warm-sector low-level flow becomes more veered towards the end of the period. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z CURRENT UTC TIME: 2321Z (7:21PM), RELOAD THIS PAGE TO UPDATE THE TIME