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

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

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0216 PM CDT Tue Aug 27 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN MINNESOTA...WESTERN/CENTRAL IOWA...AND FAR EASTERN NEBRASKA... ...SUMMARY... Severe thunderstorms are possible on Thursday across portions of the Upper/Middle Mississippi Valley and the central Plains. A few strong storms also will be possible over portions of southern West Virginia, Virginia and North Carolina. ...Upper Midwest into the central Plains... An upper trough will progress eastward from the northern/central Plains to the Upper Midwest/Great Lakes vicinity on Thursday. Strong deep-layer southwesterly flow will remain near/north of the International border closer to the compacted closed low over the Canadian Prairies/western Ontario, but modestly enhanced southwesterly flow will extend over portions of the region. At the surface, a cold front will develop east/southeast across the Upper Midwest and central Plains through the period. South/southeasterly low-level flow will maintain 60s F dewpoints, with a corridor of 70s F dewpoints across southern MN to the mid-MS Valley. Strong heating and low-level warm advection ahead of the front should allow for a corridor of strong surface-based instability across parts of the Mid/Upper MS Valley into eastern portions of the central Plains. Thunderstorms are expected along the front during the day and into the evening hours. Vertical shear will remain somewhat modest, and decrease with southward extent. Forecast soundings suggest supercells may be possible, especially across parts of MN/WI/IA where effective shear magnitudes around 30 kt will be present amid vertically veering low-level wind profiles. Linear forcing along the front and marginal shear may favor more rapidly developing line segments however. Regardless, a risk for all severe hazards may accompany this activity. With southward extent into the central Plains, forecast soundings show weaker deep-layer southwesterly flow. Nevertheless, strong instability and inverted-v sub-cloud thermodynamic profiles/steep low-level lapse rates ahead of the southeast-advancing front suggest strong wind gust potential. ...Mid-Atlantic vicinity... Weak deep-layer flow is expected across the region in the wake of a departing upper trough over the Northeast and Canadian Maritimes. However, a very moist and hot airmass is forecast, support moderate to strong destabilization during the day. As a cold front sags south across the region, isolated thunderstorms producing locally strong/damaging gusts will be possible. This risk should quickly diminish with loss of daytime heating. ..Leitman.. 08/27/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0216 PM CDT Tue Aug 27 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN MINNESOTA...WESTERN/CENTRAL IOWA...AND FAR EASTERN NEBRASKA... ...SUMMARY... Severe thunderstorms are possible on Thursday across portions of the Upper/Middle Mississippi Valley and the central Plains. A few strong storms also will be possible over portions of southern West Virginia, Virginia and North Carolina. ...Upper Midwest into the central Plains... An upper trough will progress eastward from the northern/central Plains to the Upper Midwest/Great Lakes vicinity on Thursday. Strong deep-layer southwesterly flow will remain near/north of the International border closer to the compacted closed low over the Canadian Prairies/western Ontario, but modestly enhanced southwesterly flow will extend over portions of the region. At the surface, a cold front will develop east/southeast across the Upper Midwest and central Plains through the period. South/southeasterly low-level flow will maintain 60s F dewpoints, with a corridor of 70s F dewpoints across southern MN to the mid-MS Valley. Strong heating and low-level warm advection ahead of the front should allow for a corridor of strong surface-based instability across parts of the Mid/Upper MS Valley into eastern portions of the central Plains. Thunderstorms are expected along the front during the day and into the evening hours. Vertical shear will remain somewhat modest, and decrease with southward extent. Forecast soundings suggest supercells may be possible, especially across parts of MN/WI/IA where effective shear magnitudes around 30 kt will be present amid vertically veering low-level wind profiles. Linear forcing along the front and marginal shear may favor more rapidly developing line segments however. Regardless, a risk for all severe hazards may accompany this activity. With southward extent into the central Plains, forecast soundings show weaker deep-layer southwesterly flow. Nevertheless, strong instability and inverted-v sub-cloud thermodynamic profiles/steep low-level lapse rates ahead of the southeast-advancing front suggest strong wind gust potential. ...Mid-Atlantic vicinity... Weak deep-layer flow is expected across the region in the wake of a departing upper trough over the Northeast and Canadian Maritimes. However, a very moist and hot airmass is forecast, support moderate to strong destabilization during the day. As a cold front sags south across the region, isolated thunderstorms producing locally strong/damaging gusts will be possible. This risk should quickly diminish with loss of daytime heating. ..Leitman.. 08/27/2024 Read more

WW 0655 Status Updates
STATUS REPORT ON WW 655 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 10 WSW RFD TO 15 SSE JVL TO 35 NW BEH. ..JEWELL..08/27/24 ATTN...WFO...LOT...MKX... STATUS REPORT FOR WS 655 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-097-111-272040- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE LAKE MCHENRY LMZ740-777-272040- CW . ADJACENT COASTAL WATERS INCLUDED ARE WINTHROP HARBOR TO WILMETTE HARBOR IL LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5NM OFFSHORE TO MID LAKE THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 0655 Status Updates
STATUS REPORT ON WW 655 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 10 WSW RFD TO 15 SSE JVL TO 35 NW BEH. ..JEWELL..08/27/24 ATTN...WFO...LOT...MKX... STATUS REPORT FOR WS 655 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC007-097-111-272040- IL . ILLINOIS COUNTIES INCLUDED ARE BOONE LAKE MCHENRY LMZ740-777-272040- CW . ADJACENT COASTAL WATERS INCLUDED ARE WINTHROP HARBOR TO WILMETTE HARBOR IL LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5NM OFFSHORE TO MID LAKE THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Tue Aug 27 2024 Valid 281200Z - 291200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE DAKOTAS...AND FROM OHIO TO THE NORTHERN MID-ATLANTIC COAST... ...SUMMARY... Severe thunderstorms are expected on Wednesday from parts of Ohio to the northern Mid-Atlantic coast, and across parts of North and South Dakota. ...Mid-MS/OH Valleys to the Mid-Atlantic... Uncertainty remains this forecast cycle, particularly from around central PA eastward to the northern Mid-Atlantic Coast/Chesapeake Bay vicinity. Severe thunderstorm probabilities have been focused along and just ahead of a southward sagging cold front and instability gradient from central OH to the NJ coast. Rich boundary-layer moisture (dewpoints in the upper 60s to mid 70s F) will contribute to a corridor of MLCAPE around 2000-4000 J/kg from the Mid-MS Valley eastward to the NJ coast. Warm midlevel temperatures may lead to lingering inhibition, particularly across eastern portions of the Slight and Marginal risk areas. Height falls associated with troughing over eastern Canada will remain well north of the region, and resulting in somewhat nebulous large-scale ascent amid very modest vertical shear (effective shear magnitudes generally less than 25 kt). Convection from the Day 1/Tue period may be ongoing Wednesday morning across parts of the Great Lakes vicinity and shift east along the instability gradient/southward-sagging surface front through the afternoon. Vertical shear may be locally enhanced with any MCV that may be present with this activity, and damaging winds are possible as the downstream boundary layer destabilizes. Additional isolated thunderstorm development is possible from central PA/northern VA eastward to the coast. This activity could produce locally damaging gusts and perhaps small hail if capping can be overcome and longer-lived updrafts develop. Weak shear further west toward the Mid-MS Valley vicinity will likely preclude a more organized severe risk. However, strong heating amid the very moist/unstable airmass will support isolated strong/locally damaging gusts during the afternoon. ...Northern Plains... A robust upper cyclone will spread east from the northern Rockies to the northern Plains on Wednesday. Enhanced mid/upper southwesterly flow ahead of this feature will overspread the Dakotas, in conjunction with stronger height falls, from late afternoon into the overnight hours. At the surface, low pressure will deepen over the northern High Plains during the day, resulting in an increasing baroclinic zone across the northern Plains. Southeasterly low-level flow will transport 60s F dewpoints northwest ahead of a westward-advancing cold front. Steepening midlevel lapse rates and favorable boundary-layer moisture will support a corridor of strong instability (MLCAPE 2000-3000 J/kg). Forecast soundings indication supercell wind profile, with greater than 40 kt effective shear magnitudes and elongated/straight hodographs. Large hail, some potential to 3 inch diameter, will be possible in addition to severe wind gusts beginning near 00z and lingering into the nighttime hours. ..Leitman.. 08/27/2024 Read more

MD 2013 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHEAST WISCONSIN...NORTHERN ILLINOIS...WESTERN LOWER MICHIGAN
Mesoscale Discussion 2013 NWS Storm Prediction Center Norman OK 1125 AM CDT Tue Aug 27 2024 Areas affected...southeast Wisconsin...northern Illinois...western Lower Michigan Concerning...Severe potential...Watch possible Valid 271625Z - 271900Z Probability of Watch Issuance...60 percent SUMMARY...Storms may continue to increase in coverage and intensity along a weak boundary, from eastern WI into northern IL. Scattered strong to severe gusts will be possible. DISCUSSION...Storms which formed in a semi-elevated regime over central WI have continued to expand north-south in coverage, with recently reported gusts just below severe limits (40-50 kt range). Addition convection is now forming southward along a subtle wind shift into southern WI, and additional storms are anticipated into northern IL. The air mass is quite moist and unstable over the entire area, and low-level lapse rates will continue to steepen over the next several hours. Although shear is weak, the ample precipitable water, MUCAPE, and existing forcing mechanisms (outflow boundary and wind shift to the southwest) suggest additional strong to severe gusts will develop later this afternoon. While convection near Green Bay will soon move offshore, westerly 925/850 mb winds may maintain an unstable feed of air above the cooler lake surface. If storms can maintain composure over Lake MI, the heated air over western Lower MI may then support severe gusts. Farther south into northern IL and extending into southwest Lower MI, the severe risk will is conditional on enough convection forming along the weak boundary. Given a very moist air mass with mid to upper 70s F dewpoints, and current satellite trends, the thinking is that this may indeed be the case, and trends will be closely monitored. A severe thunderstorm watch may be needed over parts of the region this afternoon. ..Jewell/Guyer.. 08/27/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...APX...IWX...GRR...GRB...LOT...MKX...DVN... LAT...LON 43208515 42298568 41618640 41358725 41308782 41318876 41508937 41958963 42568925 43128882 43898837 44458817 44638796 45138567 45038503 44558471 43978474 43208515 Read more

WW 0655 Status Updates
STATUS FOR WATCH 0655 HAS NOT BEEN ISSUED YET Read more

WW 655 SEVERE TSTM IL WI LM 271705Z - 272100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 655 NWS Storm Prediction Center Norman OK 1205 PM CDT Tue Aug 27 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Illinois Southeast Wisconsin Lake Michigan * Effective this Tuesday afternoon from 1205 PM until 400 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of severe storms will continue to move across southeast Wisconsin early this afternoon, with additional development possible into northern Illinois. The severe thunderstorm watch area is approximately along and 50 statute miles east and west of a line from 50 miles northeast of Milwaukee WI to 40 miles east of Rockford IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 28025. ...Guyer Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Tue Aug 27 2024 Valid 271630Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT LAKES AND MIDWEST... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail are possible across the Great Lakes region and portions of the Midwest through tonight. ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. ..Guyer/Wendt.. 08/27/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Tue Aug 27 2024 Valid 271630Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT LAKES AND MIDWEST... ...SUMMARY... Severe thunderstorms capable of damaging thunderstorm winds and occasional large hail are possible across the Great Lakes region and portions of the Midwest through tonight. ...Great Lakes/Midwest/Central Plains... A rather complex mesoscale scenario exists particularly across the Great Lakes region, influenced by multiple MCSs/outflows since last evening. Multiple MCVs are apparent across the region including western Upper Michigan, potentially including an MCV with evolving asymmetric quasi-linear convection across east-central Wisconsin late this morning. Within a zone of pre-frontal confluence/augmented outflow, MCS persistence and further upscale/southward peripheral growth is possible into Lower Michigan/northern Illinois into a very unstable air mass, but this is far from certain. For additional short-term information, see Mesoscale Discussion 2013. Where storm clusters do develop and intensify regionally, ample buoyancy, particularly south of the aforementioned late-morning MCS, and sufficient deep-layer shear will support damaging wind and isolated large hail potential. The severe threat could reach as far as the Lake Ontario vicinity late tonight/early Wednesday. Farther southwest, nearer to the cold front and potentially augmented by residual outflow, CAPE and especially vertical shear will be weaker from southeast Iowa/western Illinois into northern Missouri and eastern Kansas/southeast Nebraska. A few organized multicells are possible atop a strongly heated boundary layer, with strong wind gusts and severe hail possible. ..Guyer/Wendt.. 08/27/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1145 AM CDT Tue Aug 27 2024 Valid 271700Z - 281200Z The previous forecast (see below) remains on track, and no changes were needed with this update. ..Weinman.. 08/27/2024 .PREV DISCUSSION... /ISSUED 0144 AM CDT Tue Aug 27 2024/ ...Synopsis... A mid-level trough will amplify while traversing the northwestern U.S. today, encouraging strong surface lee troughing over the northern Rockies. In turn, strong and dry downslope flow is anticipated to the lee of the Cascades, where surface meteorological conditions will be conducive to wildfire spread. By afternoon, 15-20 mph sustained westerly surface winds will coincide with 15-25 percent RH for at least a few hours in the Columbia Basin in eastern Washington. Fuels experiencing these dry and windy meteorological conditions will be modestly receptive to wildfire spread, warranting Elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1145 AM CDT Tue Aug 27 2024 Valid 271700Z - 281200Z The previous forecast (see below) remains on track, and no changes were needed with this update. ..Weinman.. 08/27/2024 .PREV DISCUSSION... /ISSUED 0144 AM CDT Tue Aug 27 2024/ ...Synopsis... A mid-level trough will amplify while traversing the northwestern U.S. today, encouraging strong surface lee troughing over the northern Rockies. In turn, strong and dry downslope flow is anticipated to the lee of the Cascades, where surface meteorological conditions will be conducive to wildfire spread. By afternoon, 15-20 mph sustained westerly surface winds will coincide with 15-25 percent RH for at least a few hours in the Columbia Basin in eastern Washington. Fuels experiencing these dry and windy meteorological conditions will be modestly receptive to wildfire spread, warranting Elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Tue Aug 27 14:05:02 UTC 2024.

No Mesoscale Discussions are in effect as of Tue Aug 27 14:05:02 UTC 2024.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Tue Aug 27 2024 Valid 271300Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT LAKES REGION AND PORTIONS OF THE MIDWEST... ...SUMMARY... Clusters of damaging thunderstorm winds and occasional large hail are possible across the Great Lakes region and portions of the Midwest. ...Synopsis... The mid/upper-level pattern temporarily will become less amplified over the CONUS, as an anticyclone now over the mid Mississippi Valley region weakens, and a nearly zonal northern stream takes shape across most of the northern tier of states. This will occur downstream from a strong synoptic-scale cyclone -- evident in moisture-channel imagery over southwestern/near-coastal BC. The 500-mb low should move east-southeastward to the northern Rockies by 12Z tomorrow, with trough and cyclonic flow southward to the northern Great Basin. Downstream, a strong shortwave trough was apparent over the western Dakotas to the NE Panhandle, with embedded circulation center near DIK. This perturbation is forecast to deamplify gradually, but still remain a well-defined shortwave trough, as it moves eastward to the Lake Superior/northern Lake Michigan region by the end of the period. At the surface, 11Z analysis showed a low near the end of the Keweenaw Peninsula in Upper MI, with cold front extending diffusely southwestward through post-outflow air across northern WI, southern MN, central NE, to parts of western KS and eastern CO. The Great Lakes low should migrate eastward along the front to ME by 12Z tomorrow. The front is expected to reach Lake Huron, central Lower MI, southeastern WI, northern MO, central KS, and southwestern CO by 00Z, preceded by several outflow boundaries. By 12Z, the front should extend from the ME low across central/western NY, Lake Ontario, northern IN, and central MO, becoming quasistationary from there to central KS, and a warm front over eastern CO. The latter will occur in response to return flow setting up ahead of the Northwest cyclone aloft, with strengthening lee troughing between the front and a low over eastern MT. That low will be attached to another, stronger cold front emerging from the Rockies, and moving eastward over central/southwestern MT by 12Z. ...Great Lakes to central Plains... Widely scattered to locally numerous thunderstorms (in episodic clusters) are expected to cross the outlook area through the period, offering damaging to severe gusts, occasional large hail, and a marginal tornado threat. Within the broader 15%/"slight risk" area, one or more corridors of greater severe-wind threat may develop in concert with the best-organized portions of any cold-pool-driven, forward-propagational complex(es) that may develop. However, specific tracks of such axial maxima are still too uncertain at this time, due to dependence on iterative mesoscale factors. A residual arc of thunderstorms over Lake Huron and southeastern Lower MI has left an outflow boundary across southern Lower MI to south-central WI to near the southeast tip of MN, where it is being intercepted from the west by fresh outflow from another complex moving northeastward over western WI. The relatively stable airmass north of the first MCS' outflow boundary is shallow and subject to destabilization from both warm advection and (later this morning) diurnal heating, lending some potential for expansion or intensification of any part of the WI complex that still is present and extends into the increasingly favorable theta-e. Meanwhile, the outflow in/from the second ongoing complex may: 1. Produce isolated severe gusts through the shallow stable outflow layer over WI in the near term, 2. Modify favorably across parts of WI/IL/lower MI today (the latter assuming it reaches Lower MI to reinforce the first outflow pool) and 3. Focus additional development an uncertain distance farther south -- possibly including upscale growth into more complex(es), today into this evening. Overall, the environment along and south of the outflow boundaries should be favorable thermodynamically, with strong diabatic heating and rich moisture (70s F surface dewpoints being common). In satellite imagery, a plume of moisture with origins in the Southwest monsoon -- and still connected to MCS activity in western MX -- extends near an ELP-CAO-GLD-FSD axis. A residual EML to the east of this, and around the northwestern quadrant of the anticyclone, results in a plume of warmer 700-mb temperatures (per last night's 00Z charts and available soundings so far this morning), as well as somewhat steeper midlevel lapse rates and slightly stronger capping atop the moist boundary layer. This contributes to the potential for areas of 3000-4500 J/kg MLCAPE along and south of the boundary(s) from parts of WI and Lower MI southwestward into northern MO. While such strong buoyancy will support upscale growth, longevity of clusters also is uncertain due to lack of a supportive LLJ. This far southeast of the main mid/upper-level shortwave trough, flow aloft and deep shear will be rather weak, so steering flow will be less of an influence on convective motion than internal cold pools and foregoing mesoscale boundary alignment. Farther southwest, nearer to the cold front over the lower Missouri Valley into KS, shear and CAPE both will be weaker, but still with enough instability to support isolated to scattered afternoon development. A few organized multicells are possible atop a strongly heated boundary layer, with pulse gusts and hail near severe limits possible. ..Edwards/Bentley.. 08/27/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Tue Aug 27 2024 Valid 271300Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT LAKES REGION AND PORTIONS OF THE MIDWEST... ...SUMMARY... Clusters of damaging thunderstorm winds and occasional large hail are possible across the Great Lakes region and portions of the Midwest. ...Synopsis... The mid/upper-level pattern temporarily will become less amplified over the CONUS, as an anticyclone now over the mid Mississippi Valley region weakens, and a nearly zonal northern stream takes shape across most of the northern tier of states. This will occur downstream from a strong synoptic-scale cyclone -- evident in moisture-channel imagery over southwestern/near-coastal BC. The 500-mb low should move east-southeastward to the northern Rockies by 12Z tomorrow, with trough and cyclonic flow southward to the northern Great Basin. Downstream, a strong shortwave trough was apparent over the western Dakotas to the NE Panhandle, with embedded circulation center near DIK. This perturbation is forecast to deamplify gradually, but still remain a well-defined shortwave trough, as it moves eastward to the Lake Superior/northern Lake Michigan region by the end of the period. At the surface, 11Z analysis showed a low near the end of the Keweenaw Peninsula in Upper MI, with cold front extending diffusely southwestward through post-outflow air across northern WI, southern MN, central NE, to parts of western KS and eastern CO. The Great Lakes low should migrate eastward along the front to ME by 12Z tomorrow. The front is expected to reach Lake Huron, central Lower MI, southeastern WI, northern MO, central KS, and southwestern CO by 00Z, preceded by several outflow boundaries. By 12Z, the front should extend from the ME low across central/western NY, Lake Ontario, northern IN, and central MO, becoming quasistationary from there to central KS, and a warm front over eastern CO. The latter will occur in response to return flow setting up ahead of the Northwest cyclone aloft, with strengthening lee troughing between the front and a low over eastern MT. That low will be attached to another, stronger cold front emerging from the Rockies, and moving eastward over central/southwestern MT by 12Z. ...Great Lakes to central Plains... Widely scattered to locally numerous thunderstorms (in episodic clusters) are expected to cross the outlook area through the period, offering damaging to severe gusts, occasional large hail, and a marginal tornado threat. Within the broader 15%/"slight risk" area, one or more corridors of greater severe-wind threat may develop in concert with the best-organized portions of any cold-pool-driven, forward-propagational complex(es) that may develop. However, specific tracks of such axial maxima are still too uncertain at this time, due to dependence on iterative mesoscale factors. A residual arc of thunderstorms over Lake Huron and southeastern Lower MI has left an outflow boundary across southern Lower MI to south-central WI to near the southeast tip of MN, where it is being intercepted from the west by fresh outflow from another complex moving northeastward over western WI. The relatively stable airmass north of the first MCS' outflow boundary is shallow and subject to destabilization from both warm advection and (later this morning) diurnal heating, lending some potential for expansion or intensification of any part of the WI complex that still is present and extends into the increasingly favorable theta-e. Meanwhile, the outflow in/from the second ongoing complex may: 1. Produce isolated severe gusts through the shallow stable outflow layer over WI in the near term, 2. Modify favorably across parts of WI/IL/lower MI today (the latter assuming it reaches Lower MI to reinforce the first outflow pool) and 3. Focus additional development an uncertain distance farther south -- possibly including upscale growth into more complex(es), today into this evening. Overall, the environment along and south of the outflow boundaries should be favorable thermodynamically, with strong diabatic heating and rich moisture (70s F surface dewpoints being common). In satellite imagery, a plume of moisture with origins in the Southwest monsoon -- and still connected to MCS activity in western MX -- extends near an ELP-CAO-GLD-FSD axis. A residual EML to the east of this, and around the northwestern quadrant of the anticyclone, results in a plume of warmer 700-mb temperatures (per last night's 00Z charts and available soundings so far this morning), as well as somewhat steeper midlevel lapse rates and slightly stronger capping atop the moist boundary layer. This contributes to the potential for areas of 3000-4500 J/kg MLCAPE along and south of the boundary(s) from parts of WI and Lower MI southwestward into northern MO. While such strong buoyancy will support upscale growth, longevity of clusters also is uncertain due to lack of a supportive LLJ. This far southeast of the main mid/upper-level shortwave trough, flow aloft and deep shear will be rather weak, so steering flow will be less of an influence on convective motion than internal cold pools and foregoing mesoscale boundary alignment. Farther southwest, nearer to the cold front over the lower Missouri Valley into KS, shear and CAPE both will be weaker, but still with enough instability to support isolated to scattered afternoon development. A few organized multicells are possible atop a strongly heated boundary layer, with pulse gusts and hail near severe limits possible. ..Edwards/Bentley.. 08/27/2024 Read more

MD 2012 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN MINNESOTA AND WESTERN WISCONSIN
Mesoscale Discussion 2012 NWS Storm Prediction Center Norman OK 0557 AM CDT Tue Aug 27 2024 Areas affected...eastern Minnesota and western Wisconsin Concerning...Severe potential...Watch unlikely Valid 271057Z - 271230Z Probability of Watch Issuance...20 percent SUMMARY...A locally greater severe wind threat will persist across eastern Minnesota and western Wisconsin for a few hours this morning. DISCUSSION...A line of mostly sub-severe storms moved across Minnesota this morning. On the southern extent of this line, a more organized severe wind threat developed with measured wind gusts of 50 to 60 knots in portions of the Minneapolis/St. Paul metro area after several hours of minimal evidence of severe winds prior. The environment across western Wisconsin is somewhat cooler, upper 60s vs lower 70s temperatures. This may weaken this portion of the line as it moves east. However, it is also possible that this southern extent of the main line remains anchored to the instability gradient and access to more favorable theta-e and is able to produce additional isolated severe wind through the morning across western Wisconsin. A watch is not anticipated due to the confined nature of the threat at this time. ..Bentley/Edwards.. 08/27/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ARX...MPX... LAT...LON 45159339 45459241 45499088 45119057 44749111 44639229 44579281 44649329 45159339 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0402 AM CDT Tue Aug 27 2024 Valid 301200Z - 041200Z ...DISCUSSION... Latest runs of the global models suggest that the general pattern evolution over the U.S. through the medium range will be characterized by a slowly progressive upper flow field, trending toward amplification of troughing over the eastern U.S. and ridging over the West. Late in the period, as the pattern continues to progress, a Pacific trough is progged to approach and then move into the western states, while the western U.S. ridge shifts gradually toward the central states. Still farther upstream, the eastern U.S. trough will likewise continue shifting eastward, into/across New England and the Canadian Maritimes. Through the first half of the period, as the upper trough moves across the Great Lakes region and adjacent Ontario and is then reinforced by a second feature digging southeastward out of Canada, a series of surface cold fronts will shift eastward/southeastward across the central and eastern CONUS. On Day 4/Friday, at least some severe threat will likely evolve over the Upper Great Lakes/Midwest, ahead of the initial cold front. By Day 5/Saturday, convection -- and possibly limited severe risk -- may spread across the Lower Lakes and Ohio Valley area. A continued, eastward shift should persist through Day6/Sunday, as the next front accelerates eastward across the Great Lakes/Midwest, with most substantial strong convective potential evolving from New England into the Mid-Atlantic region. Overall however, with low-level moisture begin suppressed gradually southward by Canadian frontal intrusions, and the surface baroclinic zone settling south of the stronger flow aloft, overall risk should remain limited, and gradually decreasing through the period. As such, no risk areas are being included in the medium-range outlook at this time. Read more