Severe Storms

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 PM CST Sun Dec 15 2024 Valid 160100Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK INTO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a brief tornado may occur tonight through early Monday morning from parts of eastern Oklahoma and the Ozarks. ...Synopsis... Early evening water-vapor imagery shows a pronounced shortwave trough embedded within mostly zonal westerly flow slowly amplifying across the central and northern Plains states. Stronger westerly flow south of the main shortwave is expected to expand eastward this evening, as a subtle perturbation crosses the southern Plains and moves into the Ozarks tonight. This subtle forcing for ascent will allow increasingly strong northward advection of a partially modified Gulf air mass into portions of the southern Plains, Ozarks and lower OH River Valley ahead of a cold front. ...Eastern OK and the Ozark Plateau... Weak low-level warm advection is occurring across the ArkLaTex early this evening as evidenced by showers and several weak thunderstorms from northeast TX into western AR. This should continue before intensifying with the approach of the stronger deep-layer ascent tonight. A 30-45 kt low-level jet will support moderate isentropic ascent centered over eastern OK and western AR mainly after 03z. Low to mid 60s F surface dewpoints should reach as far north as the AR/OK/MO border region supporting moderate destabilization despite poor low-level lapse rates. Delayed by the late arrival of modest large-scale forcing for ascent, convective initiation is expected late this evening into the overnight hours near the cold front from northeast OK into southwest MO, and farther southeast within the warm sector. Initial activity may be supercellullar, given 35-40 kt of deep-layer shear and 1000-2000 J/kg of MUCAPE. This suggests the stronger storms may initially be capable of some severe hail, especially with any persistent rotating updrafts. Strong low-level shear is also suggestive of a non-zero tornado and damaging wind gust threat through early Monday morning. However, this is conditional upon more unstable near-surface based parcels, which, given the poor low-level lapse rates and saturated air mass, is uncertain. Overall, the severe threat with any convection that develops should remain rather isolated, will maintain level 1 Marginal with low-end probabilities for all hazards. ..Lyons.. 12/16/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 PM CST Sun Dec 15 2024 Valid 160100Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK INTO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a brief tornado may occur tonight through early Monday morning from parts of eastern Oklahoma and the Ozarks. ...Synopsis... Early evening water-vapor imagery shows a pronounced shortwave trough embedded within mostly zonal westerly flow slowly amplifying across the central and northern Plains states. Stronger westerly flow south of the main shortwave is expected to expand eastward this evening, as a subtle perturbation crosses the southern Plains and moves into the Ozarks tonight. This subtle forcing for ascent will allow increasingly strong northward advection of a partially modified Gulf air mass into portions of the southern Plains, Ozarks and lower OH River Valley ahead of a cold front. ...Eastern OK and the Ozark Plateau... Weak low-level warm advection is occurring across the ArkLaTex early this evening as evidenced by showers and several weak thunderstorms from northeast TX into western AR. This should continue before intensifying with the approach of the stronger deep-layer ascent tonight. A 30-45 kt low-level jet will support moderate isentropic ascent centered over eastern OK and western AR mainly after 03z. Low to mid 60s F surface dewpoints should reach as far north as the AR/OK/MO border region supporting moderate destabilization despite poor low-level lapse rates. Delayed by the late arrival of modest large-scale forcing for ascent, convective initiation is expected late this evening into the overnight hours near the cold front from northeast OK into southwest MO, and farther southeast within the warm sector. Initial activity may be supercellullar, given 35-40 kt of deep-layer shear and 1000-2000 J/kg of MUCAPE. This suggests the stronger storms may initially be capable of some severe hail, especially with any persistent rotating updrafts. Strong low-level shear is also suggestive of a non-zero tornado and damaging wind gust threat through early Monday morning. However, this is conditional upon more unstable near-surface based parcels, which, given the poor low-level lapse rates and saturated air mass, is uncertain. Overall, the severe threat with any convection that develops should remain rather isolated, will maintain level 1 Marginal with low-end probabilities for all hazards. ..Lyons.. 12/16/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 PM CST Sun Dec 15 2024 Valid 160100Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK INTO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a brief tornado may occur tonight through early Monday morning from parts of eastern Oklahoma and the Ozarks. ...Synopsis... Early evening water-vapor imagery shows a pronounced shortwave trough embedded within mostly zonal westerly flow slowly amplifying across the central and northern Plains states. Stronger westerly flow south of the main shortwave is expected to expand eastward this evening, as a subtle perturbation crosses the southern Plains and moves into the Ozarks tonight. This subtle forcing for ascent will allow increasingly strong northward advection of a partially modified Gulf air mass into portions of the southern Plains, Ozarks and lower OH River Valley ahead of a cold front. ...Eastern OK and the Ozark Plateau... Weak low-level warm advection is occurring across the ArkLaTex early this evening as evidenced by showers and several weak thunderstorms from northeast TX into western AR. This should continue before intensifying with the approach of the stronger deep-layer ascent tonight. A 30-45 kt low-level jet will support moderate isentropic ascent centered over eastern OK and western AR mainly after 03z. Low to mid 60s F surface dewpoints should reach as far north as the AR/OK/MO border region supporting moderate destabilization despite poor low-level lapse rates. Delayed by the late arrival of modest large-scale forcing for ascent, convective initiation is expected late this evening into the overnight hours near the cold front from northeast OK into southwest MO, and farther southeast within the warm sector. Initial activity may be supercellullar, given 35-40 kt of deep-layer shear and 1000-2000 J/kg of MUCAPE. This suggests the stronger storms may initially be capable of some severe hail, especially with any persistent rotating updrafts. Strong low-level shear is also suggestive of a non-zero tornado and damaging wind gust threat through early Monday morning. However, this is conditional upon more unstable near-surface based parcels, which, given the poor low-level lapse rates and saturated air mass, is uncertain. Overall, the severe threat with any convection that develops should remain rather isolated, will maintain level 1 Marginal with low-end probabilities for all hazards. ..Lyons.. 12/16/2024 Read more

No watches are valid as of Sun Dec 15 22:15:02 UTC 2024.

No Mesoscale Discussions are in effect as of Sun Dec 15 22:15:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...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 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...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 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...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 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...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 0310 PM CST Sun Dec 15 2024 Valid 171200Z - 231200Z Zonal upper-level flow across the CONUS will begin to amplify Tuesday into Wednesday. An upper-level ridge will develop across the West with shortwave troughs progressing through areas east of the Divide. With colder air and precipitation potential for many areas east of the Rockies, fire weather concerns will generally remain low. Some portions of the central High Plains vicinity will not observe much precipitation. Dry and windy conditions are possible in both the post-frontal environments as well as when surface lows deepen in the Plains. Given the antecedent cooler temperatures, it is not clear more than locally elevated conditions will occur. Fire weather concerns will primarily be focused in southern California as high surface pressure intensifies in the Great Basin Tuesday into Thursday. ...Southern California... Model guidance remains consistent in an enhanced offshore pressure gradient maximizing Tuesday night into Wednesday morning. There is moderate confidence in at least a low-end critical offshore pressure gradient, though models have tended to back off on the magnitude slightly over the past couple of days. The greatest level of uncertainty exists with how low RH will fall. Available high resolution guidance from the CANSAC WRF suggests 15-20% RH will be most typical. That being said, the most widespread critical fire weather may hold off until Wednesday morning when some heating will occur and winds will still be moderately strong. A brief period of critical fire weather could occur very late Tuesday and trends in guidance will continue to be monitored. Given the remaining uncertainty, 40% critical probabilities will be maintained this outlook. ..Wendt.. 12/15/2024 ...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 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0155 PM CST Sun Dec 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTH TEXAS TO THE OZARKS... ...SUMMARY... Isolated severe hail, strong/gusty winds, and perhaps a tornado may occur tonight through early Monday morning from parts of north Texas to the Ozarks. ...20Z Update... The previous forecast (see below) remains on track, and no changes were needed with this update. The latest guidance indicates some potential for embedded/loosely organized cells tracking northeastward across southeast MO during the early morning hours -- mainly capable of producing small hail and/or locally strong gusts. It is unclear if this activity will be surface-based, and given marginal midlevel lapse rates/instability, severe potential appears too low to expand probabilities. ..Weinman.. 12/15/2024 .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Dec 15 2024/ ...Synopsis... Gradual amplification and consolidation of upper troughing will occur through the period across parts of the northern Plains and Upper Midwest. The southern fringe of this upper trough will begin to influence and overspread portions of the central/southern Plains late this evening and overnight. The primary surface low will develop towards the international border region of northern MN/southern Canada, while partially modified Gulf moisture continues to gradually stream northward over portions of the southern Plains into the Ozarks ahead of a cold front. ...Eastern Oklahoma into Western Arkansas and Southwest Missouri... Convective initiation will likely be delayed until 03Z or later this evening across eastern OK/western AR vicinity, as low-level warm/moist advection aids in the northward transport of a moist low-level airmass. Once convection develops as glancing ascent from the approaching upper trough overspreads the warm sector, convective mode may quickly become messy, as generally southwesterly low/mid-level flow encourages updraft interactions and mergers. Even so, around 1000-2000 J/kg of MUCAPE, aided by modestly steepened mid-level lapse rates, should support robust updrafts. Coupled with sufficient (around 30-40 kt) deep-layer shear, some of this initial development could produce marginally severe hail on an isolated basis. Based on latest guidance trends showing convective initiation farther north across parts of northern OK into southwest MO, the Marginal Risk has been expanded northward to account for this initial hail threat. Poor/neutral low-level lapse rates and a generally saturated boundary-layer shown in various NAM/RAP forecast soundings limit confidence to some extent in the potential for truly surface-based thunderstorms tonight across the warm sector. Still, the presence of a 35-45 kt southwesterly low-level jet, with associated 0-1 km SRH sufficient for low-level updraft rotation, suggests a non-zero threat for a tornado along with some potential for occasional strong/gusty winds as convection spreads eastward across eastern OK into western AR and the Ozarks through early Monday morning. The potential for sustained supercells appears limited by a weakness in the flow/hodograph forecast around 700 mb, with the southward-moving cold front also encouraging a more linear/cluster mode with time. Overall, the severe threat with any convection that develops should remain rather isolated, but within a conditionally somewhat favorable environment. Read more

MD 2268 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF WEST VIRGINIA INTO WESTERN MARYLAND AND SOUTHWESTERN PENNSYLVANIA
Mesoscale Discussion 2268 NWS Storm Prediction Center Norman OK 0930 AM CST Sun Dec 15 2024 Areas affected...portions of West Virginia into western Maryland and southwestern Pennsylvania Concerning...Winter mixed precipitation Valid 151530Z - 152030Z SUMMARY...Freezing rain should gradually increase into the late morning and early afternoon hours, with some sleet or snow also possible. Up to .06/3 hr ice accretion rates cannot be ruled out, especially in higher-terrain areas. DISCUSSION...A pronounced mid-level trough is progressing eastward across the OH Valley, encouraging low-level warm air/moisture advection over portions of the Appalachians. Here, QG ascent is supporting a broad shield of precipitation, which is beginning to approach a wedge of sub-freezing low-level temperatures over higher-terrain areas. Surface observations from Hardy County, WV to Cambria County, PA show temperatures around or below freezing, with wet bulb temperatures well below freezing over several locales. 15Z mesoanalysis continues to show 925-850 mb CAA over the higher terrain, which will further support freezing rain potential, perhaps with some sleet or snow mixed in. The best chance for .06/3hr ice accretion rates, as well as some sleet or snow, will be late this morning into the afternoon hours, as also shown by the latest HRRR and HREF probabilistic guidance. ..Squitieri.. 12/15/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CTP...LWX...PBZ...RLX... LAT...LON 38687964 39297928 39857927 40527896 40647851 40497812 40037806 39357826 38937852 38677891 38547926 38687964 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0134 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 12/15/2024 .PREV DISCUSSION... /ISSUED 0155 AM CST Sun Dec 15 2024/ ...Synopsis... A progressive and mostly zonal mid-level flow pattern is expected over the CONUS D2/Mon. A pronounced shortwave trough within the stronger westerly flow will move quickly eastward over the northern third of the CONUS. At the surface, cyclone associated with the mid-level trough will move along the US/Canadian border, trailing a cold front over the central US. In the wake of the front, a much colder air mass and modest high pressure are likely over the western 2/3rds of the US. This should keep winds relatively light and RH values elevated. Additionally precipitation ahead of the front and from the prior day will augment fuels, such that little or no fire-weather risk is expected. ...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 0134 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 12/15/2024 .PREV DISCUSSION... /ISSUED 0155 AM CST Sun Dec 15 2024/ ...Synopsis... A progressive and mostly zonal mid-level flow pattern is expected over the CONUS D2/Mon. A pronounced shortwave trough within the stronger westerly flow will move quickly eastward over the northern third of the CONUS. At the surface, cyclone associated with the mid-level trough will move along the US/Canadian border, trailing a cold front over the central US. In the wake of the front, a much colder air mass and modest high pressure are likely over the western 2/3rds of the US. This should keep winds relatively light and RH values elevated. Additionally precipitation ahead of the front and from the prior day will augment fuels, such that little or no fire-weather risk is expected. ...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 0134 PM CST Sun Dec 15 2024 Valid 161200Z - 171200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 12/15/2024 .PREV DISCUSSION... /ISSUED 0155 AM CST Sun Dec 15 2024/ ...Synopsis... A progressive and mostly zonal mid-level flow pattern is expected over the CONUS D2/Mon. A pronounced shortwave trough within the stronger westerly flow will move quickly eastward over the northern third of the CONUS. At the surface, cyclone associated with the mid-level trough will move along the US/Canadian border, trailing a cold front over the central US. In the wake of the front, a much colder air mass and modest high pressure are likely over the western 2/3rds of the US. This should keep winds relatively light and RH values elevated. Additionally precipitation ahead of the front and from the prior day will augment fuels, such that little or no fire-weather risk is expected. ...Please see www.spc.noaa.gov/fire for graphic product... Read more