Severe Storms

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Sat Aug 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN PLAINS EAST-SOUTHEASTWARD INTO THE SOUTHERN GREAT LAKES AND OHIO VALLEY... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and hail will be possible on Sunday across parts of the northern Plains east-southeastward into the Upper Midwest, southern Great Lakes and Ohio Valley. ...Northern Plains/Mid Missouri Valley... At mid-levels, west-southwesterly flow will remain over the northern Plains on Sunday. At the surface, upslope flow will gradually become established over much of the western and central Dakotas, as a low deepens over eastern Montana. An axis of moderate instability is forecast to develop by afternoon from southern South Dakota northwestward into eastern Montana. Large-scale ascent will be weak along this corridor keeping convective coverage isolated. Mid-level lapse rates are forecast to be steep and 0-6 km shear is forecast to be mostly in the 25 to 35 knot range. This may be enough for an isolated threat for hail and severe wind gusts in the late afternoon and early evening. ...Upper Mississippi Valley/Southern Great Lakes/Ohio Valley. A mid-level ridge will remain in place across the upper Mississippi Valley on Sunday. From near the ridge axis and to the east, strong instability is forecast to develop by afternoon from northeast Iowa into northern Illinois and northern Indiana. Large-scale ascent will remain limited, which will keep convective coverage isolated. If a cell or two can initiate and persist, the strong instability could be enough for a few marginally severe gusts. To the west of the mid-level ridge axis across Minnesota, isolated to scattered thunderstorms may develop during the afternoon due to a subtle shortwave trough approaching from the southwest. While moderate deep-layer shear is forecast across much of Minnesota, this convection will likely remain well to the north of the axis of instability. For this reason, any threat for severe wind gusts and hail should be marginal. ..Broyles.. 08/16/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Sat Aug 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN PLAINS EAST-SOUTHEASTWARD INTO THE SOUTHERN GREAT LAKES AND OHIO VALLEY... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and hail will be possible on Sunday across parts of the northern Plains east-southeastward into the Upper Midwest, southern Great Lakes and Ohio Valley. ...Northern Plains/Mid Missouri Valley... At mid-levels, west-southwesterly flow will remain over the northern Plains on Sunday. At the surface, upslope flow will gradually become established over much of the western and central Dakotas, as a low deepens over eastern Montana. An axis of moderate instability is forecast to develop by afternoon from southern South Dakota northwestward into eastern Montana. Large-scale ascent will be weak along this corridor keeping convective coverage isolated. Mid-level lapse rates are forecast to be steep and 0-6 km shear is forecast to be mostly in the 25 to 35 knot range. This may be enough for an isolated threat for hail and severe wind gusts in the late afternoon and early evening. ...Upper Mississippi Valley/Southern Great Lakes/Ohio Valley. A mid-level ridge will remain in place across the upper Mississippi Valley on Sunday. From near the ridge axis and to the east, strong instability is forecast to develop by afternoon from northeast Iowa into northern Illinois and northern Indiana. Large-scale ascent will remain limited, which will keep convective coverage isolated. If a cell or two can initiate and persist, the strong instability could be enough for a few marginally severe gusts. To the west of the mid-level ridge axis across Minnesota, isolated to scattered thunderstorms may develop during the afternoon due to a subtle shortwave trough approaching from the southwest. While moderate deep-layer shear is forecast across much of Minnesota, this convection will likely remain well to the north of the axis of instability. For this reason, any threat for severe wind gusts and hail should be marginal. ..Broyles.. 08/16/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Sat Aug 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN PLAINS EAST-SOUTHEASTWARD INTO THE SOUTHERN GREAT LAKES AND OHIO VALLEY... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and hail will be possible on Sunday across parts of the northern Plains east-southeastward into the Upper Midwest, southern Great Lakes and Ohio Valley. ...Northern Plains/Mid Missouri Valley... At mid-levels, west-southwesterly flow will remain over the northern Plains on Sunday. At the surface, upslope flow will gradually become established over much of the western and central Dakotas, as a low deepens over eastern Montana. An axis of moderate instability is forecast to develop by afternoon from southern South Dakota northwestward into eastern Montana. Large-scale ascent will be weak along this corridor keeping convective coverage isolated. Mid-level lapse rates are forecast to be steep and 0-6 km shear is forecast to be mostly in the 25 to 35 knot range. This may be enough for an isolated threat for hail and severe wind gusts in the late afternoon and early evening. ...Upper Mississippi Valley/Southern Great Lakes/Ohio Valley. A mid-level ridge will remain in place across the upper Mississippi Valley on Sunday. From near the ridge axis and to the east, strong instability is forecast to develop by afternoon from northeast Iowa into northern Illinois and northern Indiana. Large-scale ascent will remain limited, which will keep convective coverage isolated. If a cell or two can initiate and persist, the strong instability could be enough for a few marginally severe gusts. To the west of the mid-level ridge axis across Minnesota, isolated to scattered thunderstorms may develop during the afternoon due to a subtle shortwave trough approaching from the southwest. While moderate deep-layer shear is forecast across much of Minnesota, this convection will likely remain well to the north of the axis of instability. For this reason, any threat for severe wind gusts and hail should be marginal. ..Broyles.. 08/16/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Sat Aug 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN PLAINS EAST-SOUTHEASTWARD INTO THE SOUTHERN GREAT LAKES AND OHIO VALLEY... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and hail will be possible on Sunday across parts of the northern Plains east-southeastward into the Upper Midwest, southern Great Lakes and Ohio Valley. ...Northern Plains/Mid Missouri Valley... At mid-levels, west-southwesterly flow will remain over the northern Plains on Sunday. At the surface, upslope flow will gradually become established over much of the western and central Dakotas, as a low deepens over eastern Montana. An axis of moderate instability is forecast to develop by afternoon from southern South Dakota northwestward into eastern Montana. Large-scale ascent will be weak along this corridor keeping convective coverage isolated. Mid-level lapse rates are forecast to be steep and 0-6 km shear is forecast to be mostly in the 25 to 35 knot range. This may be enough for an isolated threat for hail and severe wind gusts in the late afternoon and early evening. ...Upper Mississippi Valley/Southern Great Lakes/Ohio Valley. A mid-level ridge will remain in place across the upper Mississippi Valley on Sunday. From near the ridge axis and to the east, strong instability is forecast to develop by afternoon from northeast Iowa into northern Illinois and northern Indiana. Large-scale ascent will remain limited, which will keep convective coverage isolated. If a cell or two can initiate and persist, the strong instability could be enough for a few marginally severe gusts. To the west of the mid-level ridge axis across Minnesota, isolated to scattered thunderstorms may develop during the afternoon due to a subtle shortwave trough approaching from the southwest. While moderate deep-layer shear is forecast across much of Minnesota, this convection will likely remain well to the north of the axis of instability. For this reason, any threat for severe wind gusts and hail should be marginal. ..Broyles.. 08/16/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Sat Aug 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE NORTHERN PLAINS EAST-SOUTHEASTWARD INTO THE SOUTHERN GREAT LAKES AND OHIO VALLEY... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and hail will be possible on Sunday across parts of the northern Plains east-southeastward into the Upper Midwest, southern Great Lakes and Ohio Valley. ...Northern Plains/Mid Missouri Valley... At mid-levels, west-southwesterly flow will remain over the northern Plains on Sunday. At the surface, upslope flow will gradually become established over much of the western and central Dakotas, as a low deepens over eastern Montana. An axis of moderate instability is forecast to develop by afternoon from southern South Dakota northwestward into eastern Montana. Large-scale ascent will be weak along this corridor keeping convective coverage isolated. Mid-level lapse rates are forecast to be steep and 0-6 km shear is forecast to be mostly in the 25 to 35 knot range. This may be enough for an isolated threat for hail and severe wind gusts in the late afternoon and early evening. ...Upper Mississippi Valley/Southern Great Lakes/Ohio Valley. A mid-level ridge will remain in place across the upper Mississippi Valley on Sunday. From near the ridge axis and to the east, strong instability is forecast to develop by afternoon from northeast Iowa into northern Illinois and northern Indiana. Large-scale ascent will remain limited, which will keep convective coverage isolated. If a cell or two can initiate and persist, the strong instability could be enough for a few marginally severe gusts. To the west of the mid-level ridge axis across Minnesota, isolated to scattered thunderstorms may develop during the afternoon due to a subtle shortwave trough approaching from the southwest. While moderate deep-layer shear is forecast across much of Minnesota, this convection will likely remain well to the north of the axis of instability. For this reason, any threat for severe wind gusts and hail should be marginal. ..Broyles.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sat Aug 16 2025 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT ACROSS SOUTH DAKOTA AND PERHAPS ADJACENT PORTIONS OF NORTHERN NEBRASKA...NORTHEASTERN WYOMING...SOUTHEASTERN MONTANA...AND SOUTHWESTERN NORTH DAKOTA... ...SUMMARY... Scattered strong thunderstorm development, including a couple of evolving clusters posing a risk for strong to severe wind gusts, are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Discussion... Stronger westerlies in the northern mid-latitudes are forecast to generally remain confined to the north of the Canadian/U.S. border. Within this regime, mid-level ridging, now building across and northeast of the Canadian and adjacent northern U.S. Rockies, is likely to undergo further amplification across and east of the Canadian Prairies later today through tonight, downstream of an initially vigorous short wave trough pivoting northeastward inland of the British Columbia coast. Models indicate that larger-scale troughing across the northeastern Pacific will be maintained, as another vigorous short wave trough digs southeast of the Gulf of Alaska. Downstream of the building ridge, large-scale eastern Canadian mid-level troughing is forecast to undergo amplification, as another notable short wave trough digs across and southeast/east of the northern Ontario/southern Hudson and James Bay vicinities. Even as this occurs, it appears that modest mid-level height rises will develop across eastern portions of the northern U.S. Great Plains through the Upper Midwest and adjacent Great Lakes region later today through tonight, downstream of mid-level troughing within weak, broadly confluent mid-level flow across the Wyoming/Colorado Rockies into the western Dakotas. The remnants of an initially notable convectively generated or enhanced perturbation may dig southeastward within the northeastern periphery of the building ridging, across the Midwest/adjacent Great Lakes vicinity into Ohio Valley. However, there is considerably greater spread evident in model output concerning this feature. ...Northern Great Plains into Great Lakes/Ohio Valley... South of the westerlies, convective potential may depend largely on sub-synoptic developments with still relatively low predictability. The NAM and Rapid Refresh, among other model output, continue to suggest a notable perturbation evolving with a consolidating cluster of storms now across parts of central South Dakota into north central Nebraska. By 12Z this morning, it appears that this may be in the process of spreading east of the mid Missouri through upper Mississippi Valleys, above a boundary-layer stabilized by preceding convective activity. A conglomerate surface outflow boundary currently extends from parts of central Illinois through central Iowa and Minnesota. It seems probable that the southern flank of this boundary will undergo at least some modification/northward return into and beyond daybreak, but the extent remains unclear. Outflow impacted air across eastern Minnesota and northeastern Iowa into Wisconsin will probably be reinforced by the approaching cluster, which probably will tend to weaken while overspreading the Upper Midwest into Great Lakes region. However, depending on how quickly the boundary-layer is able to modify on the trailing flank of the reinforced outflow, it appears possible that renewed thunderstorm development and intensification could occur, and eventually grow upscale into another organizing cluster with a tendency to propagate southeastward toward the Ohio Valley. HREF output suggests that a corridor across southern Wisconsin toward areas near and south of southern Lake Michigan may need to be considered for higher severe probabilities in later outlooks for this period. However, given uncertain boundary-layer destabilization, coupled with a tendency for warming aloft/rising mid-level heights, in the presence of generally weak ambient mean flow, there seems a reasonable possibility that the corridor of higher convective potential evident in the HREF may be displaced, if not overdone. Otherwise, there remains a signal in model output that the approaching mid-level troughing could contribute to another upscale growing cluster of storms with potential to produce strong to severe wind gusts across parts of South Dakota this evening. However, this signal is more tempered than prior days. ..Kerr/Lyons.. 08/16/2025 Read more

MD 1960 CONCERNING SEVERE THUNDERSTORM WATCH 593... FOR SOUTHERN SOUTH DAKOTA AND NORTHERN NEBRASKA
Mesoscale Discussion 1960 NWS Storm Prediction Center Norman OK 1120 PM CDT Fri Aug 15 2025 Areas affected...southern South Dakota and northern Nebraska Concerning...Severe Thunderstorm Watch 593... Valid 160420Z - 160545Z The severe weather threat for Severe Thunderstorm Watch 593 continues. SUMMARY...Damaging thunderstorm wind potential will persist into the overnight hours. A downstream severe thunderstorm watch will likely be needed. DISCUSSION...Thunderstorms continue to slowly move east this evening across Severe Thunderstorm Watch 593. The strongest of these storms have a history of producing winds up to 70 mph. The large-scale environment remains favorable for scattered severe wind reports into the overnight hour. MUCAPE ahead of the storms remains in excess of 5000 J/kg, effective-layer shear is around 25 knots across far northern Nebraska to around 50 knots across central South Dakota, and at least modest large-scale ascent remains atop the area ahead of a subtle short-wave trough riding along the periphery of the southern Plains ridge. Current thinking is that there severe potential -- most likely wind -- will remain at least for the next couple of hours as the thunderstorms move east. At their current speeds, thunderstorms will approach the eastern edge of the ongoing severe thunderstorm watch before the watch expires at 3 AM CT. As such, an additional downstream watch will likely be needed perhaps as soon as within the hour. ..Marsh.. 08/16/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...ABR...LBF...UNR...CYS... LAT...LON 42070275 42980279 42990300 43590301 43830268 43860400 44160408 44140345 44250346 44250358 44600354 44590297 45020299 45020204 45450199 45470037 44910042 44899967 44229966 43959932 43699942 43509930 43489952 42989955 42960018 42060017 42070275 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN Read more

WW 0594 Status Updates
STATUS FOR WATCH 0594 HAS NOT BEEN ISSUED YET Read more