Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1132 AM CDT Sat Sep 21 2019 Valid 211700Z - 221200Z ...Portions of the Southwest and Central/Southern High Plains... 16Z surface observations indicate that spotty elevated conditions have already developed across portions of northwest AZ and also across southern CO/northern NM. Elevated conditions will become more widespread this afternoon, with locally critical conditions possible. The previous Elevated delineations have been maintained in this update -- see the previous discussion below for more information. ..Dean.. 09/21/2019 .PREV DISCUSSION... /ISSUED 1242 AM CDT Sat Sep 21 2019/ ...Synopsis... A highly amplified upper-level trough located over much the Intermountain West will shift eastward into the central/northern Plains today while ridging develops in its wake across the northern Great Basin. Within the base of the trough, a mid-level short-wave trough, accompanied by enhanced mid-level flow, will quickly move across portions of the Southwest into the central/southern High Plains. ...Portions of the Southwest and Central/Southern High Plains... As the aforementioned enhanced mid-level flow overspreads the area in combination with diurnal heating, vertical mixing will allow winds near the surface to reach sustained speeds of 15-20 mph during the afternoon. A dry, post frontal airmass resides over much of the region, and thus RH values will fall into the teens amidst fuels that remain receptive to large-fire spread. Two areas have been highlighted for delineating elevated fire-weather potential, the first being a continuation of the previous forecast over portions of southern Colorado and northeastern New Mexico, with a minor expansion made to account for greater areal coverage of wind/RH threshold exceedance. A second area was added farther west across portions of northwest New Mexico into east-central Arizona, where better agreement exists in the wind/RH combo among the latest high-resolution deterministic- and ensemble-based guidance. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sat Sep 21 2019 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF MINNESOTA AND WISCONSIN...AND OVER PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of central Minnesota into northwest Wisconsin. ...MN/WI... Morning surface analysis shows a weak low over northwest MN, with a trailing cold front extending southward across the eastern Dakotas. This front will move eastward today into central MN by mid-afternoon, where a combination of daytime heating and forcing associated with an upper trough tracking across the northern Plains will lead to the development of widely scattered thunderstorms. 12z model solutions are inconsistent on coverage of storms in this area, but forecast soundings suggest a conditional risk of rotating storms and the potential for hail and damaging wind in the strongest cells that form. An isolated tornado or two is also possible, given the presence of remnant outflow boundaries and ample low-level moisture. Storms will move into central WI and weaken this evening. ...Central Plains... The aforementioned surface cold front extends southward into central NE/KS. Strong heating is expected this afternoon ahead of the front from central/eastern KS into southeast NE, with MLCAPE values approaching 3000 J/kg. Convective initiation is expected during the late afternoon over central KS. Storms will build northeastward across the SLGT risk area during the evening, with the potential for large hail and damaging winds. Shear profiles will promote initial supercell structures with a risk of very large hail. Persistent clouds limit confidence in severe threat extending into central/eastern IA. ..Hart/Bentley.. 09/21/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sat Sep 21 2019 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF MINNESOTA AND WISCONSIN...AND OVER PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of central Minnesota into northwest Wisconsin. ...MN/WI... Morning surface analysis shows a weak low over northwest MN, with a trailing cold front extending southward across the eastern Dakotas. This front will move eastward today into central MN by mid-afternoon, where a combination of daytime heating and forcing associated with an upper trough tracking across the northern Plains will lead to the development of widely scattered thunderstorms. 12z model solutions are inconsistent on coverage of storms in this area, but forecast soundings suggest a conditional risk of rotating storms and the potential for hail and damaging wind in the strongest cells that form. An isolated tornado or two is also possible, given the presence of remnant outflow boundaries and ample low-level moisture. Storms will move into central WI and weaken this evening. ...Central Plains... The aforementioned surface cold front extends southward into central NE/KS. Strong heating is expected this afternoon ahead of the front from central/eastern KS into southeast NE, with MLCAPE values approaching 3000 J/kg. Convective initiation is expected during the late afternoon over central KS. Storms will build northeastward across the SLGT risk area during the evening, with the potential for large hail and damaging winds. Shear profiles will promote initial supercell structures with a risk of very large hail. Persistent clouds limit confidence in severe threat extending into central/eastern IA. ..Hart/Bentley.. 09/21/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sat Sep 21 2019 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF MINNESOTA AND WISCONSIN...AND OVER PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of central Minnesota into northwest Wisconsin. ...MN/WI... Morning surface analysis shows a weak low over northwest MN, with a trailing cold front extending southward across the eastern Dakotas. This front will move eastward today into central MN by mid-afternoon, where a combination of daytime heating and forcing associated with an upper trough tracking across the northern Plains will lead to the development of widely scattered thunderstorms. 12z model solutions are inconsistent on coverage of storms in this area, but forecast soundings suggest a conditional risk of rotating storms and the potential for hail and damaging wind in the strongest cells that form. An isolated tornado or two is also possible, given the presence of remnant outflow boundaries and ample low-level moisture. Storms will move into central WI and weaken this evening. ...Central Plains... The aforementioned surface cold front extends southward into central NE/KS. Strong heating is expected this afternoon ahead of the front from central/eastern KS into southeast NE, with MLCAPE values approaching 3000 J/kg. Convective initiation is expected during the late afternoon over central KS. Storms will build northeastward across the SLGT risk area during the evening, with the potential for large hail and damaging winds. Shear profiles will promote initial supercell structures with a risk of very large hail. Persistent clouds limit confidence in severe threat extending into central/eastern IA. ..Hart/Bentley.. 09/21/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sat Sep 21 2019 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF MINNESOTA AND WISCONSIN...AND OVER PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of central Minnesota into northwest Wisconsin. ...MN/WI... Morning surface analysis shows a weak low over northwest MN, with a trailing cold front extending southward across the eastern Dakotas. This front will move eastward today into central MN by mid-afternoon, where a combination of daytime heating and forcing associated with an upper trough tracking across the northern Plains will lead to the development of widely scattered thunderstorms. 12z model solutions are inconsistent on coverage of storms in this area, but forecast soundings suggest a conditional risk of rotating storms and the potential for hail and damaging wind in the strongest cells that form. An isolated tornado or two is also possible, given the presence of remnant outflow boundaries and ample low-level moisture. Storms will move into central WI and weaken this evening. ...Central Plains... The aforementioned surface cold front extends southward into central NE/KS. Strong heating is expected this afternoon ahead of the front from central/eastern KS into southeast NE, with MLCAPE values approaching 3000 J/kg. Convective initiation is expected during the late afternoon over central KS. Storms will build northeastward across the SLGT risk area during the evening, with the potential for large hail and damaging winds. Shear profiles will promote initial supercell structures with a risk of very large hail. Persistent clouds limit confidence in severe threat extending into central/eastern IA. ..Hart/Bentley.. 09/21/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sat Sep 21 2019 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF MINNESOTA AND WISCONSIN...AND OVER PORTIONS OF THE CENTRAL PLAINS... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of central Minnesota into northwest Wisconsin. ...MN/WI... Morning surface analysis shows a weak low over northwest MN, with a trailing cold front extending southward across the eastern Dakotas. This front will move eastward today into central MN by mid-afternoon, where a combination of daytime heating and forcing associated with an upper trough tracking across the northern Plains will lead to the development of widely scattered thunderstorms. 12z model solutions are inconsistent on coverage of storms in this area, but forecast soundings suggest a conditional risk of rotating storms and the potential for hail and damaging wind in the strongest cells that form. An isolated tornado or two is also possible, given the presence of remnant outflow boundaries and ample low-level moisture. Storms will move into central WI and weaken this evening. ...Central Plains... The aforementioned surface cold front extends southward into central NE/KS. Strong heating is expected this afternoon ahead of the front from central/eastern KS into southeast NE, with MLCAPE values approaching 3000 J/kg. Convective initiation is expected during the late afternoon over central KS. Storms will build northeastward across the SLGT risk area during the evening, with the potential for large hail and damaging winds. Shear profiles will promote initial supercell structures with a risk of very large hail. Persistent clouds limit confidence in severe threat extending into central/eastern IA. ..Hart/Bentley.. 09/21/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Sat Sep 21 2019 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM KS TO IA...AND ACROSS PARTS OF MN AND NORTHWEST WI... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of Minnesota and northwest Wisconsin. ...MN/northwest WI this afternoon/evening... A midlevel shortwave trough over the northern High Plains this morning will progress to northern MN by early tonight, as an associated surface cyclone develops east-northeastward from ND to western ON, and a trailing cold front moves eastward across MN late this afternoon into tonight. Widespread overnight convection has produced a cold pool across northwest MN, and convection to the south near the SD/MN border is expected to weaken this morning. Additional storm development is possible in advance of the cold front and southeast of the remnant cold pool this afternoon as modest surface warming occurs in cloud breaks, with MLCAPE up to 2000-3000 J/kg in the warm sector. Modest forcing for ascent suggests storm coverage may remain rather isolated, while effective shear greater than 40 kt and storm motions off the front also support semi-discrete modes. The main uncertainty will be the degree of cloud breaks/surface heating and storm coverage. Will maintain the Slight risk area for the conditional threat of damaging winds/large hail. A tornado or two will also be possible in the moist low-level environment with 0-1 km SRH of 100-150 m2/s2, though low-level flow will tend to veer and reduce hodograph curvature in closer proximity to the cold front this afternoon. ...KS to IA through tonight... A trailing shortwave trough over southern NV/UT will move eastward to the central High Plains by Sunday morning. In the wake of the separate shortwave trough over the northern Plains, a surface cold front will move southeastward across NE/KS, though the front should slow by late afternoon/evening in response to lee cyclogenesis across southeast CO. A narrow corridor of stronger surface heating is expected across KS along the front and to the northwest of the thicker cloud band with the subtropical moisture plume from OK into MO, and storm development will become more probable after about 22z. Boundary-layer dewpoints at or above 70 F, steep midlevel lapse rates, and strong deep-layer shear with long hodographs will favor supercells initially, capable of producing isolated very large hail, damaging winds, and perhaps a tornado or two. Storms should grow upscale into more cluster/linear modes overnight, with a gradual decrease in the hail/wind threat. ..Thompson/Leitman.. 09/21/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Sat Sep 21 2019 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM KS TO IA...AND ACROSS PARTS OF MN AND NORTHWEST WI... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of Minnesota and northwest Wisconsin. ...MN/northwest WI this afternoon/evening... A midlevel shortwave trough over the northern High Plains this morning will progress to northern MN by early tonight, as an associated surface cyclone develops east-northeastward from ND to western ON, and a trailing cold front moves eastward across MN late this afternoon into tonight. Widespread overnight convection has produced a cold pool across northwest MN, and convection to the south near the SD/MN border is expected to weaken this morning. Additional storm development is possible in advance of the cold front and southeast of the remnant cold pool this afternoon as modest surface warming occurs in cloud breaks, with MLCAPE up to 2000-3000 J/kg in the warm sector. Modest forcing for ascent suggests storm coverage may remain rather isolated, while effective shear greater than 40 kt and storm motions off the front also support semi-discrete modes. The main uncertainty will be the degree of cloud breaks/surface heating and storm coverage. Will maintain the Slight risk area for the conditional threat of damaging winds/large hail. A tornado or two will also be possible in the moist low-level environment with 0-1 km SRH of 100-150 m2/s2, though low-level flow will tend to veer and reduce hodograph curvature in closer proximity to the cold front this afternoon. ...KS to IA through tonight... A trailing shortwave trough over southern NV/UT will move eastward to the central High Plains by Sunday morning. In the wake of the separate shortwave trough over the northern Plains, a surface cold front will move southeastward across NE/KS, though the front should slow by late afternoon/evening in response to lee cyclogenesis across southeast CO. A narrow corridor of stronger surface heating is expected across KS along the front and to the northwest of the thicker cloud band with the subtropical moisture plume from OK into MO, and storm development will become more probable after about 22z. Boundary-layer dewpoints at or above 70 F, steep midlevel lapse rates, and strong deep-layer shear with long hodographs will favor supercells initially, capable of producing isolated very large hail, damaging winds, and perhaps a tornado or two. Storms should grow upscale into more cluster/linear modes overnight, with a gradual decrease in the hail/wind threat. ..Thompson/Leitman.. 09/21/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Sat Sep 21 2019 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM KS TO IA...AND ACROSS PARTS OF MN AND NORTHWEST WI... ...SUMMARY... Large hail, damaging winds, and perhaps a couple of tornadoes are possible this afternoon/evening from Kansas to Iowa, and across parts of Minnesota and northwest Wisconsin. ...MN/northwest WI this afternoon/evening... A midlevel shortwave trough over the northern High Plains this morning will progress to northern MN by early tonight, as an associated surface cyclone develops east-northeastward from ND to western ON, and a trailing cold front moves eastward across MN late this afternoon into tonight. Widespread overnight convection has produced a cold pool across northwest MN, and convection to the south near the SD/MN border is expected to weaken this morning. Additional storm development is possible in advance of the cold front and southeast of the remnant cold pool this afternoon as modest surface warming occurs in cloud breaks, with MLCAPE up to 2000-3000 J/kg in the warm sector. Modest forcing for ascent suggests storm coverage may remain rather isolated, while effective shear greater than 40 kt and storm motions off the front also support semi-discrete modes. The main uncertainty will be the degree of cloud breaks/surface heating and storm coverage. Will maintain the Slight risk area for the conditional threat of damaging winds/large hail. A tornado or two will also be possible in the moist low-level environment with 0-1 km SRH of 100-150 m2/s2, though low-level flow will tend to veer and reduce hodograph curvature in closer proximity to the cold front this afternoon. ...KS to IA through tonight... A trailing shortwave trough over southern NV/UT will move eastward to the central High Plains by Sunday morning. In the wake of the separate shortwave trough over the northern Plains, a surface cold front will move southeastward across NE/KS, though the front should slow by late afternoon/evening in response to lee cyclogenesis across southeast CO. A narrow corridor of stronger surface heating is expected across KS along the front and to the northwest of the thicker cloud band with the subtropical moisture plume from OK into MO, and storm development will become more probable after about 22z. Boundary-layer dewpoints at or above 70 F, steep midlevel lapse rates, and strong deep-layer shear with long hodographs will favor supercells initially, capable of producing isolated very large hail, damaging winds, and perhaps a tornado or two. Storms should grow upscale into more cluster/linear modes overnight, with a gradual decrease in the hail/wind threat. ..Thompson/Leitman.. 09/21/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0244 AM CDT Sat Sep 21 2019 Valid 241200Z - 291200Z ...DISCUSSION... On Tuesday/D4, a broad upper trough is forecast to dive southeastward across northern Rockies and Plains, with substantial cooling aloft and increasing wind fields. A cold front will accompany this system, and should extend roughly from MN into NE. Models differ on timing of the leading shortwave, with the ECMWF relatively slow with the development of precipitation along the front. As such, predictability is too low for D4 but severe probabilities for hail and wind may be added in later outlooks. A continuation of scattered storms is expected into Wednesday/D5 as the cold front progresses east, with a lesser threat of severe storms from KS into IL. For the D6-D8 period, the upper low over the Southwest will eventually eject northeast across the Plains, and may provide a focus for a few severe storms on D6 or D7, though predictability is quite low. Beyond this time frame, a large-scale trough amplification over the West is likely, with warm and moist conditions over much of the Plains. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0244 AM CDT Sat Sep 21 2019 Valid 241200Z - 291200Z ...DISCUSSION... On Tuesday/D4, a broad upper trough is forecast to dive southeastward across northern Rockies and Plains, with substantial cooling aloft and increasing wind fields. A cold front will accompany this system, and should extend roughly from MN into NE. Models differ on timing of the leading shortwave, with the ECMWF relatively slow with the development of precipitation along the front. As such, predictability is too low for D4 but severe probabilities for hail and wind may be added in later outlooks. A continuation of scattered storms is expected into Wednesday/D5 as the cold front progresses east, with a lesser threat of severe storms from KS into IL. For the D6-D8 period, the upper low over the Southwest will eventually eject northeast across the Plains, and may provide a focus for a few severe storms on D6 or D7, though predictability is quite low. Beyond this time frame, a large-scale trough amplification over the West is likely, with warm and moist conditions over much of the Plains. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0244 AM CDT Sat Sep 21 2019 Valid 241200Z - 291200Z ...DISCUSSION... On Tuesday/D4, a broad upper trough is forecast to dive southeastward across northern Rockies and Plains, with substantial cooling aloft and increasing wind fields. A cold front will accompany this system, and should extend roughly from MN into NE. Models differ on timing of the leading shortwave, with the ECMWF relatively slow with the development of precipitation along the front. As such, predictability is too low for D4 but severe probabilities for hail and wind may be added in later outlooks. A continuation of scattered storms is expected into Wednesday/D5 as the cold front progresses east, with a lesser threat of severe storms from KS into IL. For the D6-D8 period, the upper low over the Southwest will eventually eject northeast across the Plains, and may provide a focus for a few severe storms on D6 or D7, though predictability is quite low. Beyond this time frame, a large-scale trough amplification over the West is likely, with warm and moist conditions over much of the Plains. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Sat Sep 21 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL ARIZONA... ...SUMMARY... Scattered storms, some severe with damaging wind and hail, are expected over much of Arizona Monday. ...Synopsis... An upper low will drop south across the Great Basin and into AZ, providing large-scale lift and increasing shear from the CO Valley across much of AZ. A surface low and wind shift will exist over southwest AZ, with a cold front pushing through the state overnight. Ahead of the upper low, gulf moisture will be in place, with 60s F dewpoints over much of southern and central AZ fueling storms. To the east, a potent shortwave trough will move across the northeastern states, along with a weak cold front. Shear will be strong in this region, but instability will be weak. ...Arizona... Models have been consistent for several days now showing a favorable combination of lift, instability and shear over AZ with the approach of the upper low. Low-level winds are expected to be weak, but mid to high level flow will be strong, which will result in elongated hodographs favorable for discrete storms or small bows capable of hail and wind. Strong heating will lead to 1000-1500 J/kg MUCAPE with storms forming over western AZ near the moisture gradient, and along the Rim where weak upslope flow will aid lift. Given continued cooling aloft, a long duration of thunderstorm activity is possible, with heavy rain, locally damaging wind gusts and hail. Isolated strong storms may also persist overnight, spreading into parts of southwest NM. ...Northeastern states... A strong shortwave trough will progress across the Northeast on Monday, providing large-scale lift and strong deep-layer wind fields. A cold front will move across NY and PA during the day, and will clear all but Maine by 12Z Tuesday. Despite the favorable synoptic setup, forecast soundings indicate instability will be very weak, with only a few hundred J/kg MUCAPE possible. By the time the more significant cooling aloft arrives, low-level winds will be veered to westerly. While a strong wind gust cannot be ruled out, severe potential appears low at this time. Instability trends will continue to be monitored in subsequent outlooks. ..Jewell.. 09/21/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Sat Sep 21 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL ARIZONA... ...SUMMARY... Scattered storms, some severe with damaging wind and hail, are expected over much of Arizona Monday. ...Synopsis... An upper low will drop south across the Great Basin and into AZ, providing large-scale lift and increasing shear from the CO Valley across much of AZ. A surface low and wind shift will exist over southwest AZ, with a cold front pushing through the state overnight. Ahead of the upper low, gulf moisture will be in place, with 60s F dewpoints over much of southern and central AZ fueling storms. To the east, a potent shortwave trough will move across the northeastern states, along with a weak cold front. Shear will be strong in this region, but instability will be weak. ...Arizona... Models have been consistent for several days now showing a favorable combination of lift, instability and shear over AZ with the approach of the upper low. Low-level winds are expected to be weak, but mid to high level flow will be strong, which will result in elongated hodographs favorable for discrete storms or small bows capable of hail and wind. Strong heating will lead to 1000-1500 J/kg MUCAPE with storms forming over western AZ near the moisture gradient, and along the Rim where weak upslope flow will aid lift. Given continued cooling aloft, a long duration of thunderstorm activity is possible, with heavy rain, locally damaging wind gusts and hail. Isolated strong storms may also persist overnight, spreading into parts of southwest NM. ...Northeastern states... A strong shortwave trough will progress across the Northeast on Monday, providing large-scale lift and strong deep-layer wind fields. A cold front will move across NY and PA during the day, and will clear all but Maine by 12Z Tuesday. Despite the favorable synoptic setup, forecast soundings indicate instability will be very weak, with only a few hundred J/kg MUCAPE possible. By the time the more significant cooling aloft arrives, low-level winds will be veered to westerly. While a strong wind gust cannot be ruled out, severe potential appears low at this time. Instability trends will continue to be monitored in subsequent outlooks. ..Jewell.. 09/21/2019 Read more

MD 1995 CONCERNING SEVERE THUNDERSTORM WATCH 655...656... FOR PORTIONS OF ND...SD AND NORTHWEST MN
Mesoscale Discussion 1995 NWS Storm Prediction Center Norman OK 0122 AM CDT Sat Sep 21 2019 Areas affected...portions of ND...SD and northwest MN Concerning...Severe Thunderstorm Watch 655...656... Valid 210622Z - 210745Z The severe weather threat for Severe Thunderstorm Watch 655, 656 continues. SUMMARY...Overall severe threat is expected to be limited the remainder of the night. Additional watches are not expected and WW 655 and 656 likely will be allowed to expire as scheduled. DISCUSSION...Convection associated with earlier bowing segment across central and eastern ND into northwest MN continues to weaken as outflow has surged ahead of the line. Thunderstorms continue to develop just behind the outflow atop the cold pool in a warm advection regime aided by a 40-50 kt southwesterly low level jet as evident in region VWP data. Overall severe threat is expected to remain limited with this line as vertical shear becomes increasingly veered with time as the upper trough shifts eastward overnight and as midlevel lapse rates become increasingly less favorable with continued heavy rain/training thunderstorm activity. Further south, an MCV has shifted northward into south-central ND. This area could continue to see some marginally better organized storms the next couple of hours, but remains on the western fringe of stronger low level jet and the eastern fringe of stronger effective shear. And with the aforementioned weakening midlevel lapse rates, this convection also is expected to struggle to produce severe gusts of hail the remainder of the night. An additional line of convection is moving into south-central SD and along the NE border. While this convection will be moving into a more pristine airmass that has not been contaminated by earlier convection, this activity will likely remain somewhat elevated and eventually will merge with the outflow from the line of storms across central/eastern ND. Overall, the severe threat is expected to be limited overnight and a downstream watch into central/eastern SD is not expected at this time. Furthermore, Severe Thunderstorm Watches 655 and 656 will likely be allowed to expire as scheduled. ..Leitman.. 09/21/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...FGF...FSD...ABR...BIS...UNR... LAT...LON 47290021 47379920 47329835 47509765 47899692 48389599 48629552 48589489 48309474 47779492 46969532 45399609 44859635 44149666 43559737 43319814 43109931 43040033 43100086 43310115 43730114 44900132 45990142 46830099 47290021 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1243 AM CDT Sat Sep 21 2019 Valid 221200Z - 231200Z ...NO CRITICAL AREAS... ...Synopsis... A large upper-level trough located over the central/northern Plains will shift east into the Great Lakes region, while another deep/amplifying trough enters the West Coast. An upper-level ridge located between these features, to go along with a lack of appreciable mid-level flow should result in low fire-weather concerns. Breezy conditions could momentarily develop over central portions of Nevada during the afternoon, however disagreement among various sources of mid-range guidance in the placement/magnitude of the wind/RH combo precludes the introduction of any highlights at this time. ..Karstens.. 09/21/2019 ...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 1243 AM CDT Sat Sep 21 2019 Valid 221200Z - 231200Z ...NO CRITICAL AREAS... ...Synopsis... A large upper-level trough located over the central/northern Plains will shift east into the Great Lakes region, while another deep/amplifying trough enters the West Coast. An upper-level ridge located between these features, to go along with a lack of appreciable mid-level flow should result in low fire-weather concerns. Breezy conditions could momentarily develop over central portions of Nevada during the afternoon, however disagreement among various sources of mid-range guidance in the placement/magnitude of the wind/RH combo precludes the introduction of any highlights at this time. ..Karstens.. 09/21/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CDT Sat Sep 21 2019 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA TO OHIO... ...SUMMARY... Scattered storms, some severe with damaging winds, are expected from Oklahoma to northwest Ohio on Sunday. ...Synopsis... A potent shortwave trough will move east across the northern Plains and upper MS valley during the day on Sunday, and across the Great Lakes Sunday night, with a broad area of strong southwest flow aloft. At the surface, a cold front will stretch from Lake Michigan to eastern KS to northwest TX by 00Z, with a moist and marginally unstable air mass ahead of it. Southwesterly 850 mb winds of 40-50 kt will maintain a theta-e plume along the front, and will support rain and storms throughout the period, some of which may become severe as deep-layer shear will be strong. ...OK to OH... Substantial thunderstorm activity is expected to be ongoing Sunday morning along and ahead of the cold front which may be complex and reinforced by outflow boundaries. Some of the early storms may be capable of strong wind gusts as deep-layer shear will be parallel to the front, but instability will be weak early in the day. Gradual destabilization is possible by afternoon ahead of the front, with at least isolated severe storms producing wind damage. Warm air advection may result in sufficient instability as far north as IN, Lower MI and OH Sunday night. Predictability is low given the amount of ongoing storms early in the period, but a small Slight Risk corridor cannot be ruled out in later outlooks, mainly for wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Jewell.. 09/21/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CDT Sat Sep 21 2019 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA TO OHIO... ...SUMMARY... Scattered storms, some severe with damaging winds, are expected from Oklahoma to northwest Ohio on Sunday. ...Synopsis... A potent shortwave trough will move east across the northern Plains and upper MS valley during the day on Sunday, and across the Great Lakes Sunday night, with a broad area of strong southwest flow aloft. At the surface, a cold front will stretch from Lake Michigan to eastern KS to northwest TX by 00Z, with a moist and marginally unstable air mass ahead of it. Southwesterly 850 mb winds of 40-50 kt will maintain a theta-e plume along the front, and will support rain and storms throughout the period, some of which may become severe as deep-layer shear will be strong. ...OK to OH... Substantial thunderstorm activity is expected to be ongoing Sunday morning along and ahead of the cold front which may be complex and reinforced by outflow boundaries. Some of the early storms may be capable of strong wind gusts as deep-layer shear will be parallel to the front, but instability will be weak early in the day. Gradual destabilization is possible by afternoon ahead of the front, with at least isolated severe storms producing wind damage. Warm air advection may result in sufficient instability as far north as IN, Lower MI and OH Sunday night. Predictability is low given the amount of ongoing storms early in the period, but a small Slight Risk corridor cannot be ruled out in later outlooks, mainly for wind. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Jewell.. 09/21/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Sat Sep 21 2019 Valid 211200Z - 221200Z ...Synopsis... A highly amplified upper-level trough located over much the Intermountain West will shift eastward into the central/northern Plains today while ridging develops in its wake across the northern Great Basin. Within the base of the trough, a mid-level short-wave trough, accompanied by enhanced mid-level flow, will quickly move across portions of the Southwest into the central/southern High Plains. ...Portions of the Southwest and Central/Southern High Plains... As the aforementioned enhanced mid-level flow overspreads the area in combination with diurnal heating, vertical mixing will allow winds near the surface to reach sustained speeds of 15-20 mph during the afternoon. A dry, post frontal airmass resides over much of the region, and thus RH values will fall into the teens amidst fuels that remain receptive to large-fire spread. Two areas have been highlighted for delineating elevated fire-weather potential, the first being a continuation of the previous forecast over portions of southern Colorado and northeastern New Mexico, with a minor expansion made to account for greater areal coverage of wind/RH threshold exceedance. A second area was added farther west across portions of northwest New Mexico into east-central Arizona, where better agreement exists in the wind/RH combo among the latest high-resolution deterministic- and ensemble-based guidance. ..Karstens.. 09/21/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more