Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Aug 27 2024 Valid 272000Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE GREAT LAKES AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail and a tornado or two are possible across the Great Lakes region and portions of the Midwest through tonight. ...20z Update... The prior forecast remains largely on track with minor changes. The Slight and Marginal risk area over parts of WI was trimmed behind extensive convection ongoing over the Lake and northern MI. Ongoing severe storms over parts of the Great Lakes are expected to gradually expand in coverage and intensity over southern lower MI, northern IL and IN through the remainder of the afternoon and into the evening/overnight. The primary risk remains damaging winds associated with organized clusters or bowing segments, but hail and a tornado or two will also remain possible. Farther south into parts of the Mississippi Valley and eastern Plains, additional storm development/intensification is probable this afternoon within a warm and unstable air mass ahead of a weak cold front. Vertical shear is somewhat weaker displaced south of the main shortwave trough, but robust boundary-layer heating should suffice for periodic intensification of multicell storms. At least some damaging wind or hail risk may develop with clusters of strong to severe storms across eastern KS and south-central IA from this afternoon through the evening. ..Lyons.. 08/27/2024 .PREV DISCUSSION... /ISSUED 1142 AM CDT Tue Aug 27 2024/ ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. Read more

WW 0657 Status Updates
STATUS FOR WATCH 0657 HAS NOT BEEN ISSUED YET Read more

WW 0657 Status Updates
STATUS FOR WATCH 0657 HAS NOT BEEN ISSUED YET Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Tue Aug 27 2024 Valid 281200Z - 291200Z An Elevated area was added over portions of southern/central Wyoming with this update. While marginal fuels should largely mitigate the fire-weather threat (as described below), Critical-caliber winds/RH (sustained 20-25 mph amid 10-15 percent RH) will still pose some risk -- especially over any areas that missed out on precipitation during the last few weeks. For additional details, see the previous discussion below. ..Weinman.. 08/27/2024 .PREV DISCUSSION... /ISSUED 0145 AM CDT Tue Aug 27 2024/ ...Synopsis... A pronounced mid-level trough will traverse the Northern Rockies and eject into the northern High Plains tomorrow (Wednesday), supporting robust surface lee troughing across the northern Plains states. Strong isallobaric flow is thus expected over portions of the northern and central Rockies, particularly eastern Montana, as well as central into eastern Wyoming. In both areas, sustained west-southwesterly surface winds exceeding 20 mph amid 15-25 percent RH are expected during the afternoon. Such conditions typically necessitate at least Elevated to perhaps Critical highlights. However, fuel receptiveness in these regions is marginal at best, especially considering rainfall over the past week. As such, fire weather highlights have been withheld this outlook. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Tue Aug 27 2024 Valid 281200Z - 291200Z An Elevated area was added over portions of southern/central Wyoming with this update. While marginal fuels should largely mitigate the fire-weather threat (as described below), Critical-caliber winds/RH (sustained 20-25 mph amid 10-15 percent RH) will still pose some risk -- especially over any areas that missed out on precipitation during the last few weeks. For additional details, see the previous discussion below. ..Weinman.. 08/27/2024 .PREV DISCUSSION... /ISSUED 0145 AM CDT Tue Aug 27 2024/ ...Synopsis... A pronounced mid-level trough will traverse the Northern Rockies and eject into the northern High Plains tomorrow (Wednesday), supporting robust surface lee troughing across the northern Plains states. Strong isallobaric flow is thus expected over portions of the northern and central Rockies, particularly eastern Montana, as well as central into eastern Wyoming. In both areas, sustained west-southwesterly surface winds exceeding 20 mph amid 15-25 percent RH are expected during the afternoon. Such conditions typically necessitate at least Elevated to perhaps Critical highlights. However, fuel receptiveness in these regions is marginal at best, especially considering rainfall over the past week. As such, fire weather highlights have been withheld this outlook. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Tue Aug 27 2024 Valid 281200Z - 291200Z An Elevated area was added over portions of southern/central Wyoming with this update. While marginal fuels should largely mitigate the fire-weather threat (as described below), Critical-caliber winds/RH (sustained 20-25 mph amid 10-15 percent RH) will still pose some risk -- especially over any areas that missed out on precipitation during the last few weeks. For additional details, see the previous discussion below. ..Weinman.. 08/27/2024 .PREV DISCUSSION... /ISSUED 0145 AM CDT Tue Aug 27 2024/ ...Synopsis... A pronounced mid-level trough will traverse the Northern Rockies and eject into the northern High Plains tomorrow (Wednesday), supporting robust surface lee troughing across the northern Plains states. Strong isallobaric flow is thus expected over portions of the northern and central Rockies, particularly eastern Montana, as well as central into eastern Wyoming. In both areas, sustained west-southwesterly surface winds exceeding 20 mph amid 15-25 percent RH are expected during the afternoon. Such conditions typically necessitate at least Elevated to perhaps Critical highlights. However, fuel receptiveness in these regions is marginal at best, especially considering rainfall over the past week. As such, fire weather highlights have been withheld this outlook. ...Please see www.spc.noaa.gov/fire for graphic product... Read more