SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Thu Sep 19 2024 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN A PART OF THE MIDWEST... ...SUMMARY... Isolated, marginally severe thunderstorms are possible in the late afternoon Friday in parts of Illinois, Indiana, and southwest Lower Michigan. ...Midwest... A low-amplitude shortwave trough will pass across the Upper to Central Great Lakes during the first half of the period. This will outpace a cold front that trails from a cyclone shifting northeast in MB, yielding a largely weakening to stalling front by Friday evening. Most guidance suggests at least isolated thunderstorms should form within a low-level warm conveyor ahead of the front, generally focused on a moderate buoyancy plume emanating northeast from parts of MO/AR. A fast westerly upper jet will further impinge on this portion of the front as well, favorably timed with peak boundary-layer heating. A few marginally severe storms may develop within this regime. Despite weak mid-level lapse rates, elongation of the mid to upper hodograph should support a threat for 1-1.5 inch hail, along with strong to marginally severe gusts from 45-60 mph. These threats should diminish quickly after sunset. ...Southern High Plains... Locally strong gusts are possible during the late afternoon to early evening with high-based, low-topped convection amid a weak buoyancy environment. The region will remain between a stout mid-level anticyclone over the Lower Rio Grande Valley and a southern-stream shortwave trough slowly moving across CA into AZ. Relatively warm mid-level temperatures should preclude appreciable storm intensity, but well-mixed boundary layers could support sporadic gusts approaching severe levels. ...Central Great Plains... Isolated elevated storms may develop overnight into Saturday morning within a strengthening warm theta-e advection regime. Weak mid-level lapse rates should temper elevated buoyancy and limit hail potential to some extent. But sufficient mid to upper-level speed shear could foster small hail production. ..Grams.. 09/19/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1229 AM CDT Thu Sep 19 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM MINNESOTA...IOWA AND WESTERN WISCONSIN SOUTHWARD INTO EASTERN KANSAS AND WESTERN MISSOURI... ...SUMMARY... Scattered severe thunderstorms are possible across central/eastern Minnesota, Iowa, and western Wisconsin. A couple tornadoes, isolated large hail, and damaging winds may occur. An area of locally severe gusts and hail may also develop over parts of eastern Kansas, southwest Missouri, and into northeast Oklahoma. ...Synopsis... A negatively tilted shortwave trough will move across the Dakotas and MN during the day, with veering midlevel winds into western MN by late afternoon. Farther south, moderate west/southwest winds in the midlevels will extend into NE and IA, with weaker west to northwest winds around a southern Plains upper high from KS/OK into MO and AR. In the high levels, flow will be strongest across the central Plains, with weakening winds over the northern Plains/upper MS Valley. At the surface, the primary low will move into southern MB, with a cold front moving into MN and western IA by mid afternoon. A wind shift/surface trough will also extend southward across eastern KS and into northern OK at that time. Southerly surface winds will set up a plume of mid to upper 60s F dewpoints east of the front/surface trough, and this will aid moderate destabilization across the length of the front, with scattered severe storms from MN to perhaps OK. ...Upper MS Valley... Scattered early day elevated storms are likely to dissipate by midday as they move out of MN/IA into WI, with destabilization in their wake. Strong heating near the surface trough/front along with cool temperatures aloft will yield MUCAPE to around 3000 J/kg, beneath 35-40 kt 500 mb winds. A broken line of storms including supercells are expected after 21Z over much of central and eastern MN and into IA. A couple tornadoes are most likely from IA into southern MN and southwest WI where effective SRH may exceed 200 m2/s2. Given the northward lifting of the shortwave trough, and increasing inhibition east of the MS River, the primary threat are may remain relatively narrow. ...Eastern KS into western MO and into OK... A few thunderstorms may be ongoing early this morning from IA into northwest MO, near the 850 mb theta-e plume and beneath subtle height falls. A cell or two may persist into the afternoon, likely translating southeastward across western MO. A greater risk of locally severe wind gusts or hail will then develop near and just west of the early day activity, as a plume of steep lapse rates develops out of OK into KS. While midlevel subsidence may limit instability somewhat, plenty of CAPE will be present at or above 2000 J/kg, with a lengthy mid to upper level hodograph by virtue of northwest flow aloft. As such, hail may still occur with the cellular storm modes, and favorable time of day and hot surface conditions will favor locally strong to damaging gusts. ..Jewell/Weinman.. 09/19/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Wed Sep 18 2024 Valid 190100Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A NARROW ZONE FROM THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY INTO THE CENTRAL PLAINS... ...SUMMARY... Isolated strong storms are possible this evening over parts of the central Plains, and from the Red River into the upper Mississippi Valley overnight. ...Northern Plains/Upper MS Valley... Cooling aloft with an upper trough will continue eastward across the Dakotas and into MN, with a cold front pushing east and providing a focus for possible storm development. Convection is now forming within a narrow instability axis over eastern ND, and some of the cells could eventually produce severe hail. Additional activity may occur farther south as well, although coverage is less certain. Cool air aloft with veering winds with height will tend to favor sporadic hail. For more information see mesoscale discussion 2085. ...Central Plains... Warm temperatures and peak heating has led to isolated storms along a retreating dryline from south-central KS into the eastern TX Panhandle. While capping should eventually result in dissipation in a couple hours, marginal hail or locally strong gusts will be possible in the near term. ..Jewell.. 09/19/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Wed Sep 18 2024 Valid 190100Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A NARROW ZONE FROM THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY INTO THE CENTRAL PLAINS... ...SUMMARY... Isolated strong storms are possible this evening over parts of the central Plains, and from the Red River into the upper Mississippi Valley overnight. ...Northern Plains/Upper MS Valley... Cooling aloft with an upper trough will continue eastward across the Dakotas and into MN, with a cold front pushing east and providing a focus for possible storm development. Convection is now forming within a narrow instability axis over eastern ND, and some of the cells could eventually produce severe hail. Additional activity may occur farther south as well, although coverage is less certain. Cool air aloft with veering winds with height will tend to favor sporadic hail. For more information see mesoscale discussion 2085. ...Central Plains... Warm temperatures and peak heating has led to isolated storms along a retreating dryline from south-central KS into the eastern TX Panhandle. While capping should eventually result in dissipation in a couple hours, marginal hail or locally strong gusts will be possible in the near term. ..Jewell.. 09/19/2024 Read more

No watches are valid as of Wed Sep 18 22:46:02 UTC 2024.

No Mesoscale Discussions are in effect as of Wed Sep 18 22:46:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0430 PM CDT Wed Sep 18 2024 Valid 201200Z - 261200Z An active mid-level flow regime is expected across the CONUS over the next seven days. Troughing over the western US will gradually move eastward as an embedded speed max passes over the Southern Rockies/Plains this weekend with gusty winds and dry conditions. By early next week, troughing will move over the central CONUS favoring cooler and wetter conditions. At the same time, ridging should redevelop to the west. Some potential for easterly offshore winds could develop over parts of CA and OR early next week, but significant forecast uncertainty is present in the medium range. This suggests the threat for fire-weather conditions is relatively low. ...Southern Plains... As troughing gradually moves eastward, stronger southwesterly flow aloft will overspread parts of the Southern Rockies/Plains late this week and into the first half of the weekend. A lee low will quickly deepen over eastern CO supporting periods of gusty downlope winds, with gusts of 25-30 mph. However, moisture return ahead of the low will favor higher RH values. Additionally, recent precipitation has likely tempered fuels somewhat, with more precipitation likely in into this weekend. Thus, while some risk for fire-weather conditions may develop over the Plains, confidence is low. ..Lyons.. 09/18/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0430 PM CDT Wed Sep 18 2024 Valid 201200Z - 261200Z An active mid-level flow regime is expected across the CONUS over the next seven days. Troughing over the western US will gradually move eastward as an embedded speed max passes over the Southern Rockies/Plains this weekend with gusty winds and dry conditions. By early next week, troughing will move over the central CONUS favoring cooler and wetter conditions. At the same time, ridging should redevelop to the west. Some potential for easterly offshore winds could develop over parts of CA and OR early next week, but significant forecast uncertainty is present in the medium range. This suggests the threat for fire-weather conditions is relatively low. ...Southern Plains... As troughing gradually moves eastward, stronger southwesterly flow aloft will overspread parts of the Southern Rockies/Plains late this week and into the first half of the weekend. A lee low will quickly deepen over eastern CO supporting periods of gusty downlope winds, with gusts of 25-30 mph. However, moisture return ahead of the low will favor higher RH values. Additionally, recent precipitation has likely tempered fuels somewhat, with more precipitation likely in into this weekend. Thus, while some risk for fire-weather conditions may develop over the Plains, confidence is low. ..Lyons.. 09/18/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Wed Sep 18 2024 Valid 182000Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEBRASKA INTO FAR NORTHWEST IOWA...EASTERN SOUTH DAKOTA...AND WESTERN MINNESOTA... ...SUMMARY... Thunderstorms capable of producing severe wind gusts and large hail are possible today across parts of the eastern Dakotas and Minnesota into the mid Missouri Valley. A marginal severe threat will also extend southward into parts of the central and southern Plains. ...20Z Update... No changes were made to the ongoing forecast. For mesoscale details concerning eastern South Dakota and vicinity, see MCD 2083. Additional details can be found in the previous discussion below. ..Wendt.. 09/18/2024 .PREV DISCUSSION... /ISSUED 1118 AM CDT Wed Sep 18 2024/ ...Northern Plains/Upper Midwest to the Southern High Plains... A closed upper low centered over eastern MT will continue northeastward during the period, reaching southeast SK by early Thursday morning. Upper-level ridging extending northward from the northwest Gulf Coast into the upper MS Valley will slowly shift eastward to the Upper Great Lakes. A belt of enhanced southwesterly mid-level flow will extend from southern CA through the central High Plains, while also wrapping cyclonically through the eastern Dakotas and into southern Canada. At the surface, a trough/front extends southward from central ND into SD and western NE, before continuing southwestward over the central/southern High Plains. This boundary may serve as a focus for renewed thunderstorm development later today. A band of elevated convection has generally moved northward from northeast ND and northwest MN into southern MB. In the wake of this activity, cloud cover remains prevalent across much of the warm sector across the northern Plains/Upper Midwest. Still, filtered daytime heating of an adequately moist boundary layer should aid in the development of around 1500-2000 J/kg of MLCAPE by late afternoon. Isolated to scattered thunderstorms may form along/east of the surface trough/front within a favorable zone of 30-40 kt of effective bulk shear. But, better large-scale forcing associated with the upper low over the northern High Plains will tend to remain displaced north and west (in southern Canada). Accordingly, 12Z high-resolution guidance continues to vary regarding storm coverage across the Slight Risk (isolated versus scattered) given the weaker forcing aloft. Even with this continued uncertainty, various NAM/RAP forecast soundings still suggest a somewhat conditional risk for organized storms (mix of multicells and supercells). Severe hail/wind may accompany the stronger storms from late afternoon through early evening, before this activity eventually weakens. Further south into the central/southern Plains, low-levels are forecast to be somewhat drier near the surface trough, with surface dewpoints expected to mostly range in the upper 50s to low 60s by late afternoon with pronounced boundary-layer mixing. Warmer mid-level temperatures and limited large-scale ascent across these regions should temper the overall intensity of any updrafts that can form and be sustained, and resultant intensity/coverage of this convection. Still, some guidance shows locally greater thunderstorm coverage and resulting isolated severe wind threat from the eastern TX Panhandle into far northwest OK and southern KS during the late afternoon/early evening, where low-level lapse rates should be maximized with robust daytime heating. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Wed Sep 18 2024 Valid 182000Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEBRASKA INTO FAR NORTHWEST IOWA...EASTERN SOUTH DAKOTA...AND WESTERN MINNESOTA... ...SUMMARY... Thunderstorms capable of producing severe wind gusts and large hail are possible today across parts of the eastern Dakotas and Minnesota into the mid Missouri Valley. A marginal severe threat will also extend southward into parts of the central and southern Plains. ...20Z Update... No changes were made to the ongoing forecast. For mesoscale details concerning eastern South Dakota and vicinity, see MCD 2083. Additional details can be found in the previous discussion below. ..Wendt.. 09/18/2024 .PREV DISCUSSION... /ISSUED 1118 AM CDT Wed Sep 18 2024/ ...Northern Plains/Upper Midwest to the Southern High Plains... A closed upper low centered over eastern MT will continue northeastward during the period, reaching southeast SK by early Thursday morning. Upper-level ridging extending northward from the northwest Gulf Coast into the upper MS Valley will slowly shift eastward to the Upper Great Lakes. A belt of enhanced southwesterly mid-level flow will extend from southern CA through the central High Plains, while also wrapping cyclonically through the eastern Dakotas and into southern Canada. At the surface, a trough/front extends southward from central ND into SD and western NE, before continuing southwestward over the central/southern High Plains. This boundary may serve as a focus for renewed thunderstorm development later today. A band of elevated convection has generally moved northward from northeast ND and northwest MN into southern MB. In the wake of this activity, cloud cover remains prevalent across much of the warm sector across the northern Plains/Upper Midwest. Still, filtered daytime heating of an adequately moist boundary layer should aid in the development of around 1500-2000 J/kg of MLCAPE by late afternoon. Isolated to scattered thunderstorms may form along/east of the surface trough/front within a favorable zone of 30-40 kt of effective bulk shear. But, better large-scale forcing associated with the upper low over the northern High Plains will tend to remain displaced north and west (in southern Canada). Accordingly, 12Z high-resolution guidance continues to vary regarding storm coverage across the Slight Risk (isolated versus scattered) given the weaker forcing aloft. Even with this continued uncertainty, various NAM/RAP forecast soundings still suggest a somewhat conditional risk for organized storms (mix of multicells and supercells). Severe hail/wind may accompany the stronger storms from late afternoon through early evening, before this activity eventually weakens. Further south into the central/southern Plains, low-levels are forecast to be somewhat drier near the surface trough, with surface dewpoints expected to mostly range in the upper 50s to low 60s by late afternoon with pronounced boundary-layer mixing. Warmer mid-level temperatures and limited large-scale ascent across these regions should temper the overall intensity of any updrafts that can form and be sustained, and resultant intensity/coverage of this convection. Still, some guidance shows locally greater thunderstorm coverage and resulting isolated severe wind threat from the eastern TX Panhandle into far northwest OK and southern KS during the late afternoon/early evening, where low-level lapse rates should be maximized with robust daytime heating. Read more

MD 2083 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF EASTERN SOUTH DAKOTA...ADJACENT NORTHEASTERN NEBRASKA AND SOUTHWESTERN MINNESOTA
Mesoscale Discussion 2083 NWS Storm Prediction Center Norman OK 0253 PM CDT Wed Sep 18 2024 Areas affected...parts of eastern South Dakota...adjacent northeastern Nebraska and southwestern Minnesota Concerning...Severe potential...Watch possible Valid 181953Z - 182230Z Probability of Watch Issuance...40 percent SUMMARY...The initiation of one or two strong storms appears possible late this afternoon. Sustained storm development may include the evolution of supercell structures posing a risk for severe hail, and perhaps some potential for a tornado by early evening. Due to the isolated nature, it is not certain that a severe weather watch is needed, but trends are being monitored. DISCUSSION...Although stronger mid-level height falls appear to be shifting to the north, a destabilizing warm sector boundary layer across the eastern South Dakota vicinity will remain beneath weakly difluent cyclonic mid-level flow into early evening. With mixed-layer CAPE now on the order of 1500 J/kg, beneath 30-50 kt southwesterly mid/upper flow, the environment appears at least conditionally supportive of supercells, and low-level hodographs may enlarge with clockwise curvature as southerly flow around 850 mb is forecast to strengthen some (to around 30+ kt) through 22-00Z. Although low-level forcing for sustained convective development remains unclear, weak warm advection to the east of the dryline may be supporting ongoing attempts at deepening convection east of Huron into the Watertown vicinity. And objective analysis has indicated a persistent localized area of enhanced convergence along a confluence zone near/west of Yankton. Model output, including the convection allowing guidance, suggest that probabilities for thunderstorm development are generally low into early evening. However, the initiation of one or two storms appears possible. If this is sustained, this may include the evolution of supercell structures posing a risk for severe hail, and perhaps some potential for a tornado. ..Kerr/Gleason.. 09/18/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...FSD...OAX...ABR...LBF... LAT...LON 45389647 44609622 42819716 42949859 44379830 45219788 45549726 45389647 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Wed Sep 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...20z Update... No changes were made to the prior outlook. Gusty post-frontal winds are possible across parts of the Dakotas, through the Cascade Gaps and parts of northern CA. However, much of the fuels over these areas should remain poorly receptive to fire spread following recent precipitation. See the prior discussion for more info. ..Lyons.. 09/18/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Wed Sep 18 2024/ ...Synopsis... In the wake of a midlevel low moving northeastward from the northern Plains into Canada, an expansive surface high will develop across much of the West. At the same time, a deep midlevel low and strong deep-layer southwesterly flow will overspread southern CA and the Lower CO River Valley. Overall, this pattern will limit the overlap of strong surface winds and warm/dry boundary-layer conditions atop dry fuels. ...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 0229 PM CDT Wed Sep 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...20z Update... No changes were made to the prior outlook. Gusty post-frontal winds are possible across parts of the Dakotas, through the Cascade Gaps and parts of northern CA. However, much of the fuels over these areas should remain poorly receptive to fire spread following recent precipitation. See the prior discussion for more info. ..Lyons.. 09/18/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Wed Sep 18 2024/ ...Synopsis... In the wake of a midlevel low moving northeastward from the northern Plains into Canada, an expansive surface high will develop across much of the West. At the same time, a deep midlevel low and strong deep-layer southwesterly flow will overspread southern CA and the Lower CO River Valley. Overall, this pattern will limit the overlap of strong surface winds and warm/dry boundary-layer conditions atop dry fuels. ...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 0206 PM CDT Wed Sep 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Friday. ...Synopsis... Separate northern-stream and southern-stream mid/upper-level shortwave troughs are forecast to move across parts of the West on Friday, with the northern shortwave reaching the northern Great Plains and Canadian Prairies by Saturday morning. Meanwhile, a stout midlevel anticyclone (with the warmest 500 mb temperatures near or slightly above 0C) will remain anchored over Texas. A weakening mid/upper-level shortwave trough is forecast to move across parts of the Great Lakes and Ohio Valley. At the surface, a weakening cold front will extend somewhere from the south-central Great Plains into parts of the Midwest/Great Lakes by late afternoon. This front may tend to stall with time, and potentially move northward as warm front across the central Plains later Friday night into Saturday morning. A general lack of overlap between favorable moisture/instability and stronger ascent/deep-layer flow is currently expected to limit organized severe potential on Friday. Isolated diurnal storm development will be possible near the weakening front from the Plains into parts of the Great Lakes/Ohio Valley. Elevated storm development will also be possible Friday night into Saturday morning across parts of the central Plains, within a warm-advection regime. It remains uncertain if elevated buoyancy will become sufficient for any hail potential with the stronger storms within this regime. High-based convection that may be capable of localized strong gusts will be possible across parts of the Southwest and southern Rockies, in association with the southern-stream shortwave trough. ..Dean.. 09/18/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0206 PM CDT Wed Sep 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Friday. ...Synopsis... Separate northern-stream and southern-stream mid/upper-level shortwave troughs are forecast to move across parts of the West on Friday, with the northern shortwave reaching the northern Great Plains and Canadian Prairies by Saturday morning. Meanwhile, a stout midlevel anticyclone (with the warmest 500 mb temperatures near or slightly above 0C) will remain anchored over Texas. A weakening mid/upper-level shortwave trough is forecast to move across parts of the Great Lakes and Ohio Valley. At the surface, a weakening cold front will extend somewhere from the south-central Great Plains into parts of the Midwest/Great Lakes by late afternoon. This front may tend to stall with time, and potentially move northward as warm front across the central Plains later Friday night into Saturday morning. A general lack of overlap between favorable moisture/instability and stronger ascent/deep-layer flow is currently expected to limit organized severe potential on Friday. Isolated diurnal storm development will be possible near the weakening front from the Plains into parts of the Great Lakes/Ohio Valley. Elevated storm development will also be possible Friday night into Saturday morning across parts of the central Plains, within a warm-advection regime. It remains uncertain if elevated buoyancy will become sufficient for any hail potential with the stronger storms within this regime. High-based convection that may be capable of localized strong gusts will be possible across parts of the Southwest and southern Rockies, in association with the southern-stream shortwave trough. ..Dean.. 09/18/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Wed Sep 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to mid-evening on Thursday across central/eastern Minnesota, Iowa, and western Wisconsin. A few tornadoes, isolated very large hail, and damaging winds may occur. ...Upper Midwest... A seasonably strong stacked cyclone initially near the ND/SK/MB border region is forecast to move northeastward through the period. An attendant cold front will move eastward through the day across parts of the upper Midwest and central Plains. Diurnal heating of a rather moist airmass along/east of the front will support a relatively narrow zone of moderate to large MLCAPE (1500-3000 J/kg) by peak heating. Moderate midlevel flow will support sufficient effective shear for storm organization, with shear vectors generally aligned perpendicular to the front. This will support supercell potential from central/eastern MN into western WI and parts of IA, though the timing of initial development and western extent of the primary severe threat remain somewhat uncertain. Favorable instability and an initially discrete storm mode will support large to very large hail as storms mature, along with some potential for isolated damaging wind. Low-level hodographs will also be sufficiently curved/enlarged to support a tornado threat. A tendency toward clustering and perhaps some modest upscale growth is possible later in the storm evolution, with a severe threat likely persisting into the early/mid evening. The threat should begin to wane by late evening into Thursday night, as instability weakens with time and eastward extent. ...Eastern KS/northern OK into southeast NE/western MO... A conditionally favorable storm environment is also expected to develop from southeast NE into eastern KS/western MO and northern OK, along/ahead of the approaching front. While storm coverage will generally be less compared to areas farther north (due to weaker large-scale ascent), isolated supercells and/or stronger clusters will be possible from late afternoon into the evening. Increasingly warm midlevel temperatures will tend to limit updraft intensity with southward extent, but an isolated severe threat could extend as far south as northern OK. ..Dean.. 09/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Wed Sep 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEBRASKA INTO FAR NORTHWEST IOWA...EASTERN SOUTH DAKOTA...AND WESTERN MINNESOTA... ...SUMMARY... Thunderstorms capable of producing severe wind gusts and large hail are possible today across parts of the eastern Dakotas and Minnesota into the mid Missouri Valley. A marginal severe threat will also extend southward into parts of the central and southern Plains. ...Northern Plains/Upper Midwest to the Southern High Plains... A closed upper low centered over eastern MT will continue northeastward during the period, reaching southeast SK by early Thursday morning. Upper-level ridging extending northward from the northwest Gulf Coast into the upper MS Valley will slowly shift eastward to the Upper Great Lakes. A belt of enhanced southwesterly mid-level flow will extend from southern CA through the central High Plains, while also wrapping cyclonically through the eastern Dakotas and into southern Canada. At the surface, a trough/front extends southward from central ND into SD and western NE, before continuing southwestward over the central/southern High Plains. This boundary may serve as a focus for renewed thunderstorm development later today. A band of elevated convection has generally moved northward from northeast ND and northwest MN into southern MB. In the wake of this activity, cloud cover remains prevalent across much of the warm sector across the northern Plains/Upper Midwest. Still, filtered daytime heating of an adequately moist boundary layer should aid in the development of around 1500-2000 J/kg of MLCAPE by late afternoon. Isolated to scattered thunderstorms may form along/east of the surface trough/front within a favorable zone of 30-40 kt of effective bulk shear. But, better large-scale forcing associated with the upper low over the northern High Plains will tend to remain displaced north and west (in southern Canada). Accordingly, 12Z high-resolution guidance continues to vary regarding storm coverage across the Slight Risk (isolated versus scattered) given the weaker forcing aloft. Even with this continued uncertainty, various NAM/RAP forecast soundings still suggest a somewhat conditional risk for organized storms (mix of multicells and supercells). Severe hail/wind may accompany the stronger storms from late afternoon through early evening, before this activity eventually weakens. Further south into the central/southern Plains, low-levels are forecast to be somewhat drier near the surface trough, with surface dewpoints expected to mostly range in the upper 50s to low 60s by late afternoon with pronounced boundary-layer mixing. Warmer mid-level temperatures and limited large-scale ascent across these regions should temper the overall intensity of any updrafts that can form and be sustained, and resultant intensity/coverage of this convection. Still, some guidance shows locally greater thunderstorm coverage and resulting isolated severe wind threat from the eastern TX Panhandle into far northwest OK and southern KS during the late afternoon/early evening, where low-level lapse rates should be maximized with robust daytime heating. ..Gleason/Moore.. 09/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Wed Sep 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEBRASKA INTO FAR NORTHWEST IOWA...EASTERN SOUTH DAKOTA...AND WESTERN MINNESOTA... ...SUMMARY... Thunderstorms capable of producing severe wind gusts and large hail are possible today across parts of the eastern Dakotas and Minnesota into the mid Missouri Valley. A marginal severe threat will also extend southward into parts of the central and southern Plains. ...Northern Plains/Upper Midwest to the Southern High Plains... A closed upper low centered over eastern MT will continue northeastward during the period, reaching southeast SK by early Thursday morning. Upper-level ridging extending northward from the northwest Gulf Coast into the upper MS Valley will slowly shift eastward to the Upper Great Lakes. A belt of enhanced southwesterly mid-level flow will extend from southern CA through the central High Plains, while also wrapping cyclonically through the eastern Dakotas and into southern Canada. At the surface, a trough/front extends southward from central ND into SD and western NE, before continuing southwestward over the central/southern High Plains. This boundary may serve as a focus for renewed thunderstorm development later today. A band of elevated convection has generally moved northward from northeast ND and northwest MN into southern MB. In the wake of this activity, cloud cover remains prevalent across much of the warm sector across the northern Plains/Upper Midwest. Still, filtered daytime heating of an adequately moist boundary layer should aid in the development of around 1500-2000 J/kg of MLCAPE by late afternoon. Isolated to scattered thunderstorms may form along/east of the surface trough/front within a favorable zone of 30-40 kt of effective bulk shear. But, better large-scale forcing associated with the upper low over the northern High Plains will tend to remain displaced north and west (in southern Canada). Accordingly, 12Z high-resolution guidance continues to vary regarding storm coverage across the Slight Risk (isolated versus scattered) given the weaker forcing aloft. Even with this continued uncertainty, various NAM/RAP forecast soundings still suggest a somewhat conditional risk for organized storms (mix of multicells and supercells). Severe hail/wind may accompany the stronger storms from late afternoon through early evening, before this activity eventually weakens. Further south into the central/southern Plains, low-levels are forecast to be somewhat drier near the surface trough, with surface dewpoints expected to mostly range in the upper 50s to low 60s by late afternoon with pronounced boundary-layer mixing. Warmer mid-level temperatures and limited large-scale ascent across these regions should temper the overall intensity of any updrafts that can form and be sustained, and resultant intensity/coverage of this convection. Still, some guidance shows locally greater thunderstorm coverage and resulting isolated severe wind threat from the eastern TX Panhandle into far northwest OK and southern KS during the late afternoon/early evening, where low-level lapse rates should be maximized with robust daytime heating. ..Gleason/Moore.. 09/18/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Wed Sep 18 2024 Valid 181700Z - 191200Z ...NO CRITICAL AREAS... ...17z Update... Morning observations show widespread precipitation greater than 0.1 inches, with pockets as high as 1-1.25 inches, has fallen over much of western SD and western NE in the last 72 hours. While some drier pockets remain, fuel guidance shows a notable decrease in dryness as a result. Meteorological conditions may still support some localized fire-weather concerns with strong southwesterly winds expected behind the surface low this afternoon. However, the strongest winds are likely to remain farther northwest where the heaviest precipitation has fallen. Gusty winds and humidity below 20% may support some drying today, but fuel recovery is expected to be modest such that no areas will be introduced. See the prior discussion for more information. ..Lyons.. 09/18/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Wed Sep 18 2024/ ...Synopsis... A deep low-pressure system will move slowly east-northeastward over the northern High Plains through the period. On the backside of this system, a tight pressure gradient, and boundary-layer mixing into a belt of strong flow aloft, will yield strong post-frontal surface winds and 15-20 percent RH from eastern WY into the central Dakotas. While this would ordinarily support fire-weather concerns, precipitation over the past 24 hours should limit fuel receptiveness and the overall fire-weather threat. ...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 1118 AM CDT Wed Sep 18 2024 Valid 181700Z - 191200Z ...NO CRITICAL AREAS... ...17z Update... Morning observations show widespread precipitation greater than 0.1 inches, with pockets as high as 1-1.25 inches, has fallen over much of western SD and western NE in the last 72 hours. While some drier pockets remain, fuel guidance shows a notable decrease in dryness as a result. Meteorological conditions may still support some localized fire-weather concerns with strong southwesterly winds expected behind the surface low this afternoon. However, the strongest winds are likely to remain farther northwest where the heaviest precipitation has fallen. Gusty winds and humidity below 20% may support some drying today, but fuel recovery is expected to be modest such that no areas will be introduced. See the prior discussion for more information. ..Lyons.. 09/18/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Wed Sep 18 2024/ ...Synopsis... A deep low-pressure system will move slowly east-northeastward over the northern High Plains through the period. On the backside of this system, a tight pressure gradient, and boundary-layer mixing into a belt of strong flow aloft, will yield strong post-frontal surface winds and 15-20 percent RH from eastern WY into the central Dakotas. While this would ordinarily support fire-weather concerns, precipitation over the past 24 hours should limit fuel receptiveness and the overall fire-weather threat. ...Please see www.spc.noaa.gov/fire for graphic product... Read more