Aggregator

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z Only minor adjustments were made to the D2 Fire Outlook Isolated Dry Thunderstorm area to expand into north-western Arizona in alignment with recent hi-res guidance. See previous discussion below for more information. ..Thornton.. 08/11/2025 .PREV DISCUSSION... /ISSUED 0135 AM CDT Mon Aug 11 2025/ ...Synopsis... Isolated dry thunderstorms will remain the primary fire weather concern for Tuesday across the country. Latest forecast guidance hints that a deeply-mixed, but adequately buoyant, environment will remain in place across central AZ on the northern fringe of deeper monsoonal moisture. Forcing for ascent will be fairly weak and largely driven by orographic ascent along the Mogollon Rim. However, several deterministic CAM and recent HREF guidance hints at the potential for at least a few thunderstorms. This thermodynamic environment has yielded a mixture of wet and dry thunderstorms over the past 24 hours, so a similar combination appears probable for Tuesday. Fine fuels largely remain dry across the region, and recent lightning-caused fires hint that the fuel environment should support at least some fire starts. ...Pacific Northwest... A weak mid-level trough is forecast to move across the Pacific Northwest on Tuesday. While flow aloft will be fairly modest, the zonal flow over the Cascades and northern Sierra Nevada will likely induce a downslope flow regime within an antecedent dry environment with receptive fuels. Ensemble support was too limited to warrant additional highlights, but localized elevated fire weather conditions appear possible across far northwest NV, eastern OR, and southern WA Tuesday afternoon. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Mon Aug 11 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF THE GREAT PLAINS... ...SUMMARY... The evolution of an organized cluster of thunderstorms accompanied by strong to severe wind gusts appears possible across parts of central through eastern South Dakota by Wednesday evening. ...Discussion... Models indicate that the stronger westerlies will remain confined to the northern mid-latitudes, mostly to the north of the Canadian/U.S. border through this period. One significant embedded short wave trough shifting across Ontario through Quebec may become sheared while becoming absorbed within an increasingly confluent regime, preceded in lower latitudes by northeastward accelerating mid-level troughing offshore of the Canadian Maritimes. Upstream, another significant short wave perturbation, initially digging near the Canadian Rockies, is forecast to turn eastward across the Canadian Prairies and provide support for significant lower/mid-tropospheric cyclogenesis across southern Alberta through central/northern Saskatchewan by late Wednesday night. In lower latitudes ahead of this feature, there appears a consensus among latest model output that a much more subtle perturbation will dig east-southeast of the northern U.S. Rockies late Wednesday through Wednesday night, within weaker flow on the northern periphery of modest mid-level ridging. ...Northern Great Plains... The NAM, with support from other model output, including the latest ECMWF, depicts the evolution of a notable convective perturbation Wednesday evening into Wednesday night across the central/eastern South Dakota vicinity. This appears focused where lower/mid-tropospheric warm advection may become enhanced, near the leading edge of a plume of warm, elevated mixed layer air advecting eastward across the middle Missouri Valley, supported by a strengthening nocturnal low-level jet. Low-level moisture return to the vicinity of deepening lee surface troughing may be seasonably modest, but it still appears that sizable CAPE may develop across parts of central South Dakota by late afternoon, near the nose of a corridor of seasonably strong boundary-layer heating and deep mixing, south through east of the Black Hills. It remains unclear whether stronger convective development will initiate from late afternoon high-based thunderstorm development near/north of the Black Hills, or perhaps an initial supercell forming near a focused area of low-level convergence across central South Dakota. However, large-scale forcing for ascent probably will lead to upscale growing convection by Wednesday evening, in an environment conducive to a few strong downbursts, and a consolidating, strengthening surface cold pool with potential to produce a swath of strong to severe gusts. It is possible that severe probabilities may still need to be increased further in later outlooks for this period. ..Kerr.. 08/11/2025 Read more

077
ABPZ20 KNHC 111733
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Mon Aug 11 2025

For the eastern and central North Pacific east of 180 longitude:

Active Systems:
The National Hurricane Center is issuing advisories on Hurricane
Henriette, located in the Central Pacific basin several hundred
miles north of the Hawaiian Islands, and has issued the last
advisory on Post-Tropical Cyclone Ivo, located in the Eastern
Pacific basin several hundred miles west of the southern tip of the
Baja California peninsula.

Tropical cyclone formation is not expected during the next 7 days.

$$
Forecaster Berg

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Mon Aug 11 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF EASTERN WISCONSIN...UPPER AND LOWER MICHIGAN...AND PARTS OF NORTHEASTERN ILLINOIS...NORTHERN INDIANA...NORTHWESTERN OHIO... ...SUMMARY... Strong thunderstorms may impact parts of the upper Great Lakes region Tuesday into Tuesday evening, accompanied by at least some risk for severe wind and hail. ...Discussion... The westerlies will remain confined to the northern mid-latitudes, but models suggest that flow near/north of the Canadian/U.S. border will trend a bit more zonal, as an initially prominent mid-level high centered offshore of the Pacific Northwest continues to become suppressed west-southwestward across the northeastern Pacific. Within this regime, models continue to indicate the consolidation of several short wave perturbations into larger-scale mid-level troughing across Ontario into Quebec by late Tuesday night, accompanied by significant surface cyclogenesis across far northern Ontario into the southern Hudson/James Bay vicinity. In lower levels, a modest initial intrusion of cooler/drier air may overspread much of the Dakotas and portions of the Upper Midwest and adjacent Great Lakes region by 12Z Tuesday, before slowly advancing east-southeastward across the upper Great Lakes and eventually being overtaken by a more substantive cool intrusion later Tuesday through Tuesday night. Complicating matters with respect to destabilization, guidance continues to indicate that the lead front will be preceded by a stalled lingering remnant frontal zone, which may still be reinforced by convective precipitation/outflow across parts of southern Lower Michigan and northern Illinois, into the lower Missouri Valley and the southern Great Plains, at the outset of the period. ...Upper Great Lakes... Short wave developments within the evolving pattern remain unclear due to spread within the various model output, but guidance continues to indicate that one notable short wave impulse will continue digging across parts of the Upper Midwest and adjacent Great Lakes region during the day Tuesday, before pivoting across and east-northeast of Lake Huron/Georgian Bay. It appears that this may be preceded by one or two convectively generated perturbations which will become increasing sheared while merging into the southwesterly cyclonic mid-level regime overspreading the Great Lakes vicinity. As this occurs, various model output (notably including calibrated thunderstorm probability guidance from the High Resolution Ensemble system) suggests that destabilization and forcing for ascent will become supportive of a couple of corridors of increasing thunderstorm development by late Tuesday afternoon. These generally coincide with the stalled remnant frontal zone across parts of southeastern Lower Michigan into northeastern Illinois and the initial cold front advancing across Upper Michigan/eastern Wisconsin. Along the southern boundary, which may strengthen some with differential surface heating, mid-level thermodynamic profiles may be relatively warm with weak lapse rates. However, it still appears that seasonably high boundary-layer moisture content, coupled with daytime heating, will contribute to sizable CAPE. Coinciding with a belt of strengthening southwesterly lower/mid-level flow (including 30-40 kt in the 700-500 mb layer), the environment may become conducive to organized convection, including evolving supercell structures and upscale growing clusters with potential to produce strong to severe wind gusts by late Tuesday afternoon into evening. Across Upper Michigan into eastern Wisconsin, pre-frontal destabilization remains more unclear due to the possible influence of convective cloud cover and/or outflow. But, with breaks in cloud cover allowing for a narrow corridor of heating, cooling aloft and strengthening shear along the frontal zone might contribute to an environment conducive to strong thunderstorm development with potential to produce marginally severe hail and localized strong surface gusts late Tuesday afternoon. ...Southwest... Forecast deep-layer mean wind fields are generally light, but include a west-northwesterly upslope component to the low-level flow beneath north-northeasterly mid-level flow. This may aid propagation of convection off the higher terrain of southwestern New Mexico and southeastern Arizona, into lower elevations with a warm and deeply mixed boundary layer characterized by modest potential instability by late Tuesday afternoon. As this occurs, a few strong to severe downbursts and gusts along strengthening outflows appears possible. ..Kerr.. 08/11/2025 Read more