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SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Sat Sep 13 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST... ...SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies to the northern Great Plains and a portion of the Midwest, mainly today into early tonight. ...Southwest/southern Rockies/High Plains... The basal portion of the broad mid/upper trough from the northern Rockies to the Lower CO Valley will progress more quickly east, yielding an elongated trough enveloping the entire High Plains by early Sunday. Widespread thunderstorm development is anticipated by midday to early afternoon across western NM/CO as cooling mid-level temperatures become favorably timed with moderate diurnal heating of a seasonably moist airmass. Lower-level instability should be tempered by remnants of early morning convection and the quick redevelopment cycle by afternoon. Nevertheless, a broad belt of moderate southwesterly speed shear should support transient mid-level updraft rotation within the deepest updrafts. These should tend to become focused across southern/eastern NM later in the afternoon, but this region will be on the fringe of greater mid-level cooling centered on the Four Corners. As such, mid-level lapse rates will be weak where boundary-layer heating is more pronounced. A broad swath of sporadic strong to marginally severe hail/wind is anticipated before convection subsides after sunset. ...NE/SD/ND... Overall severe wind/hail potential appears low across multiple regimes through the period, amid a persistent meridional mid-level flow regime. Ongoing convection over the western Dakotas, tied to a minor MCV, should progress north-northeast towards the Canadian border this morning. Residual cloudiness/overturning should limit the northern extent of more substantial diurnal destabilization in ND. Late afternoon to evening storm development appears more likely to emanate out of the central High Plains north-northeastward across western/central NE within a modestly sheared and weakly buoyant airmass. This activity may foster another MCV that drifts north into SD, which could impinge on a confined corridor of recovered moderate buoyancy and sustain a marginal severe wind/hail threat tonight. ...IL/IN/WI... Low-probability severe hail/wind potential remains evident, but seems likely to be rather isolated. An MCV over central WI will drift south-southeast this morning. An increase in convective vigor is possible towards sunrise along the MUCAPE gradient in southern WI to northern IL. Within a belt of moderate mid-level northwesterlies, transient/weak updraft rotation is possible in a cell or two. Guidance differs greatly on the degree of boundary-layer heating downstream of the morning elevated activity. The more aggressively warm guidance suggests a conditional threat of diurnal intensification with potential for locally strong gusts. ..Grams/Dean.. 09/13/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Sat Sep 13 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST... ...SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies to the northern Great Plains and a portion of the Midwest, mainly today into early tonight. ...Southwest/southern Rockies/High Plains... The basal portion of the broad mid/upper trough from the northern Rockies to the Lower CO Valley will progress more quickly east, yielding an elongated trough enveloping the entire High Plains by early Sunday. Widespread thunderstorm development is anticipated by midday to early afternoon across western NM/CO as cooling mid-level temperatures become favorably timed with moderate diurnal heating of a seasonably moist airmass. Lower-level instability should be tempered by remnants of early morning convection and the quick redevelopment cycle by afternoon. Nevertheless, a broad belt of moderate southwesterly speed shear should support transient mid-level updraft rotation within the deepest updrafts. These should tend to become focused across southern/eastern NM later in the afternoon, but this region will be on the fringe of greater mid-level cooling centered on the Four Corners. As such, mid-level lapse rates will be weak where boundary-layer heating is more pronounced. A broad swath of sporadic strong to marginally severe hail/wind is anticipated before convection subsides after sunset. ...NE/SD/ND... Overall severe wind/hail potential appears low across multiple regimes through the period, amid a persistent meridional mid-level flow regime. Ongoing convection over the western Dakotas, tied to a minor MCV, should progress north-northeast towards the Canadian border this morning. Residual cloudiness/overturning should limit the northern extent of more substantial diurnal destabilization in ND. Late afternoon to evening storm development appears more likely to emanate out of the central High Plains north-northeastward across western/central NE within a modestly sheared and weakly buoyant airmass. This activity may foster another MCV that drifts north into SD, which could impinge on a confined corridor of recovered moderate buoyancy and sustain a marginal severe wind/hail threat tonight. ...IL/IN/WI... Low-probability severe hail/wind potential remains evident, but seems likely to be rather isolated. An MCV over central WI will drift south-southeast this morning. An increase in convective vigor is possible towards sunrise along the MUCAPE gradient in southern WI to northern IL. Within a belt of moderate mid-level northwesterlies, transient/weak updraft rotation is possible in a cell or two. Guidance differs greatly on the degree of boundary-layer heating downstream of the morning elevated activity. The more aggressively warm guidance suggests a conditional threat of diurnal intensification with potential for locally strong gusts. ..Grams/Dean.. 09/13/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Sat Sep 13 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST... ...SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies to the northern Great Plains and a portion of the Midwest, mainly today into early tonight. ...Southwest/southern Rockies/High Plains... The basal portion of the broad mid/upper trough from the northern Rockies to the Lower CO Valley will progress more quickly east, yielding an elongated trough enveloping the entire High Plains by early Sunday. Widespread thunderstorm development is anticipated by midday to early afternoon across western NM/CO as cooling mid-level temperatures become favorably timed with moderate diurnal heating of a seasonably moist airmass. Lower-level instability should be tempered by remnants of early morning convection and the quick redevelopment cycle by afternoon. Nevertheless, a broad belt of moderate southwesterly speed shear should support transient mid-level updraft rotation within the deepest updrafts. These should tend to become focused across southern/eastern NM later in the afternoon, but this region will be on the fringe of greater mid-level cooling centered on the Four Corners. As such, mid-level lapse rates will be weak where boundary-layer heating is more pronounced. A broad swath of sporadic strong to marginally severe hail/wind is anticipated before convection subsides after sunset. ...NE/SD/ND... Overall severe wind/hail potential appears low across multiple regimes through the period, amid a persistent meridional mid-level flow regime. Ongoing convection over the western Dakotas, tied to a minor MCV, should progress north-northeast towards the Canadian border this morning. Residual cloudiness/overturning should limit the northern extent of more substantial diurnal destabilization in ND. Late afternoon to evening storm development appears more likely to emanate out of the central High Plains north-northeastward across western/central NE within a modestly sheared and weakly buoyant airmass. This activity may foster another MCV that drifts north into SD, which could impinge on a confined corridor of recovered moderate buoyancy and sustain a marginal severe wind/hail threat tonight. ...IL/IN/WI... Low-probability severe hail/wind potential remains evident, but seems likely to be rather isolated. An MCV over central WI will drift south-southeast this morning. An increase in convective vigor is possible towards sunrise along the MUCAPE gradient in southern WI to northern IL. Within a belt of moderate mid-level northwesterlies, transient/weak updraft rotation is possible in a cell or two. Guidance differs greatly on the degree of boundary-layer heating downstream of the morning elevated activity. The more aggressively warm guidance suggests a conditional threat of diurnal intensification with potential for locally strong gusts. ..Grams/Dean.. 09/13/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Sat Sep 13 2025 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST... ...SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies to the northern Great Plains and a portion of the Midwest, mainly today into early tonight. ...Southwest/southern Rockies/High Plains... The basal portion of the broad mid/upper trough from the northern Rockies to the Lower CO Valley will progress more quickly east, yielding an elongated trough enveloping the entire High Plains by early Sunday. Widespread thunderstorm development is anticipated by midday to early afternoon across western NM/CO as cooling mid-level temperatures become favorably timed with moderate diurnal heating of a seasonably moist airmass. Lower-level instability should be tempered by remnants of early morning convection and the quick redevelopment cycle by afternoon. Nevertheless, a broad belt of moderate southwesterly speed shear should support transient mid-level updraft rotation within the deepest updrafts. These should tend to become focused across southern/eastern NM later in the afternoon, but this region will be on the fringe of greater mid-level cooling centered on the Four Corners. As such, mid-level lapse rates will be weak where boundary-layer heating is more pronounced. A broad swath of sporadic strong to marginally severe hail/wind is anticipated before convection subsides after sunset. ...NE/SD/ND... Overall severe wind/hail potential appears low across multiple regimes through the period, amid a persistent meridional mid-level flow regime. Ongoing convection over the western Dakotas, tied to a minor MCV, should progress north-northeast towards the Canadian border this morning. Residual cloudiness/overturning should limit the northern extent of more substantial diurnal destabilization in ND. Late afternoon to evening storm development appears more likely to emanate out of the central High Plains north-northeastward across western/central NE within a modestly sheared and weakly buoyant airmass. This activity may foster another MCV that drifts north into SD, which could impinge on a confined corridor of recovered moderate buoyancy and sustain a marginal severe wind/hail threat tonight. ...IL/IN/WI... Low-probability severe hail/wind potential remains evident, but seems likely to be rather isolated. An MCV over central WI will drift south-southeast this morning. An increase in convective vigor is possible towards sunrise along the MUCAPE gradient in southern WI to northern IL. Within a belt of moderate mid-level northwesterlies, transient/weak updraft rotation is possible in a cell or two. Guidance differs greatly on the degree of boundary-layer heating downstream of the morning elevated activity. The more aggressively warm guidance suggests a conditional threat of diurnal intensification with potential for locally strong gusts. ..Grams/Dean.. 09/13/2025 Read more

Issued at 1130 PM CST Fri Sep 12 2025 000 WTPZ63 KNHC 130532 TCUEP3 Remnants of Mario Tropical Cyclone Update NWS National Hurricane Center Miami FL EP132025 1130 PM CST Fri Sep 12 2025 ...MARIO IS NO LONGER A TROPICAL CYCLONE... ...LAST ADVISORY WILL BE ISSUED SHORTLY... Recent satellite-derived wind data and satellite imagery indicate that Mario no longer has a well-defined center of circulation. Therefore, a special, final, advisory will be issued by 1200 AM CST...0600 UTC, in lieu of the 0900 UTC advisory. SUMMARY OF 1130 PM CST...0530 UTC...INFORMATION ---------------------------------------------- LOCATION...18.3N 105.3W ABOUT 85 MI...135 KM SW OF MANZANILLO MEXICO MAXIMUM SUSTAINED WINDS...30 MPH...50 KM/H PRESENT MOVEMENT...WNW OR 290 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...1009 MB...29.79 INCHES $$ Forecaster Reinhart

...MARIO IS NO LONGER A TROPICAL CYCLONE... ...LAST ADVISORY WILL BE ISSUED SHORTLY... As of 11:30 PM CST Fri Sep 12 the center of Mario was located near 18.3, -105.3 with movement WNW at 15 mph. The minimum central pressure was 1009 mb with maximum sustained winds of about 30 mph.

5-Day Uncertainty Track last updated Sat, 13 Sep 2025 02:35:17 GMT


Wind Speed Probabilities last updated Sat, 13 Sep 2025 03:22:13 GMT

MD 2069 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF WESTERN/CENTRAL SD INTO SOUTHWEST ND
Mesoscale Discussion 2069 NWS Storm Prediction Center Norman OK 0949 PM CDT Fri Sep 12 2025 Areas affected...Parts of western/central SD into southwest ND Concerning...Severe potential...Watch possible Valid 130249Z - 130445Z Probability of Watch Issuance...40 percent SUMMARY...A threat for isolated hail and strong to locally severe gusts will continue into late tonight. DISCUSSION...Earlier slow-moving supercells have largely weakened across northwest SD/southwest ND, but recent vigorous development has been noted across southwest SD along a northeastward-moving outflow emanating out of the northern High Plains. Additional strong to potentially severe storms may develop along this outflow as it impinges upon a favorable thermodynamic environment (as observed in the 00Z BIS/ABR soundings). While ascent along the outflow may encourage some tendency toward development of clusters or small line segments, favorable deep-layer shear combined with weak low-level flow may continue to favor isolated or semi-discrete cells with a continued threat of large hail. While MLCINH will continue to increase with time, favorable lapse rates above the stabilizing near-surface layer will also support some potential for strong to locally severe gusts. The severe threat may continue to remain rather isolated, but watch issuance is possible if trends support maintenance of multiple sustained supercells or organized clusters/line segments into late tonight. ..Dean/Gleason.. 09/13/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR... LAT...LON 43090282 45430394 46220400 46870179 46960058 45700028 44990023 44380026 43670055 43250087 43090282 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN Read more

5-Day Uncertainty Track last updated Sat, 13 Sep 2025 02:35:17 GMT


Wind Speed Probabilities last updated Sat, 13 Sep 2025 02:35:17 GMT

Issued at 900 PM CST Fri Sep 12 2025 000 WTPZ43 KNHC 130233 TCDEP3 Tropical Depression Mario Discussion Number 6 NWS National Hurricane Center Miami FL EP132025 900 PM CST Fri Sep 12 2025 The low-level center of Mario was apparent this afternoon near the convective mass just off of the coast of southwestern Mexico. Since that time, satellite imagery shows that a large low-pressure area is developing to the south of Mario, with vorticity centers noted near 17N 106W and 15N 103W. This is causing the small circulation of Mario to lose its identity as it seems to be becoming a part of the larger circulation. In addition, the convection near the center has decreased during the past several hours, and there has been a corresponding decrease in satellite intensity estimates. Based on these developments, Mario is downgraded to a tropical depression with an initial intensity of 30 kt. The dynamical models show several possible scenarios for the evolution of Mario during the next few days. The ECMWF and Canadian models show the system dissipating as it becomes absorbed into the larger low during the next day or two. The UKMET does not absorb Mario into the low, but shows it degenerating into a trough and moving northwestward and then westward around the north side of the low. The GFS, in contrast, uses the Mario circulation to become the center of the larger low, although it keeps the winds below 35 kt through the forecast period. The regional hurricane models show the possibility of a tropical storm re-forming near or west of Socorro Island in a few days, although it is unclear whether this development is related to the current Mario circulation. Given these scenarios, the current trends, and the previous forecast, the new intensity forecast calls for Mario to continue as a depression for 36 h before dissipating inside the larger low. However, an alternative scenario is that the circulation could degenerate to a trough at any time. The initial motion is 290/13. If Mario manages to maintain its identity, it should turn more westward during the next 36 h as it moves around the north side of the larger low. Key Messages: 1. Heavy rainfall associated with Mario will impact Jalisco and nearby areas into Saturday morning, which could result in flash flooding, particularly in areas of higher terrain. 2. While all coastal watches have been discontinued for Mexico, gusty winds are possible elsewhere along the coasts of western Guerrero, Michoacan, and Colima through tonight. Interests in these areas should continue to monitor the progress of Mario. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 18.1N 104.6W 30 KT 35 MPH 12H 13/1200Z 18.8N 106.3W 30 KT 35 MPH 24H 14/0000Z 19.2N 108.0W 30 KT 35 MPH 36H 14/1200Z 19.7N 109.7W 30 KT 35 MPH 48H 15/0000Z...DISSIPATED $$ Forecaster Beven

Issued at 0300 UTC SAT SEP 13 2025 000 FOPZ13 KNHC 130233 PWSEP3 TROPICAL DEPRESSION MARIO WIND SPEED PROBABILITIES NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132025 0300 UTC SAT SEP 13 2025 AT 0300Z THE CENTER OF TROPICAL DEPRESSION MARIO WAS LOCATED NEAR LATITUDE 18.1 NORTH...LONGITUDE 104.6 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 30 KTS...35 MPH...55 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) PACIFIC DAYLIGHT TIME (PDT)...SUBTRACT 7 HOURS FROM Z TIME HAWAIIAN STANDARD TIME (HST)...SUBTRACT 10 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 00Z SAT AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 00Z SAT 12Z SAT 00Z SUN 12Z SUN 00Z MON 00Z TUE 00Z WED PERIODS TO TO TO TO TO TO TO 12Z SAT 00Z SUN 12Z SUN 00Z MON 00Z TUE 00Z WED 00Z THU FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT 20N 110W 34 X X( X) 7( 7) X( 7) X( 7) X( 7) X( 7) $$ FORECASTER BEVEN

Issued at 900 PM CST Fri Sep 12 2025 000 WTPZ33 KNHC 130233 TCPEP3 BULLETIN Tropical Depression Mario Advisory Number 6 NWS National Hurricane Center Miami FL EP132025 900 PM CST Fri Sep 12 2025 ...MARIO WEAKENS TO A TROPICAL DEPRESSION AS IT STARTS MOVING AWAY FROM SOUTHWESTERN MEXICO... ...TROPICAL STORM WATCH DISCONTINUED FOR THE COAST OF MEXICO... SUMMARY OF 900 PM CST...0300 UTC...INFORMATION ---------------------------------------------- LOCATION...18.1N 104.6W ABOUT 65 MI...105 KM SSW OF MANZANILLO MEXICO ABOUT 175 MI...280 KM SSE OF CABO CORRIENTES MEXICO MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H PRESENT MOVEMENT...WNW OR 290 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Government of Mexico has discontinued the Tropical Storm Watch for the coast of Mexico. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: There are no coastal watches or warnings in effect. Interests along the coast of southwestern Mexico should continue to monitor the progress of Mario. DISCUSSION AND OUTLOOK ---------------------- At 900 PM CST (0300 UTC), the center of Tropical Depression Mario was located near latitude 18.1 North, longitude 104.6 West. The depression is moving toward the west-northwest near 15 mph (24 km/h), and this motion is expected to continue for the next several hours. A slower motion toward the west-northwest is forecast later tonight through the weekend. On the forecast track, the center of Mario should gradually move away from the coast of Mexico tonight and Saturday. Maximum sustained winds are now near 35 mph (55 km/h) with higher gusts. Little change in strength is expected through Saturday night, and Mario is forecast to dissipate on Sunday. The estimated minimum central pressure is 1007 mb (29.74 inches). HAZARDS AFFECTING LAND ---------------------- RAINFALL: Tropical Depression Mario will lead to additional rainfall of 1 to 3 inches for Jalisco, with storm total amounts up to 6 inches locally through Saturday morning. This brings a risk of flash flooding, especially in areas of higher terrain. For a complete depiction of forecast rainfall and flash flooding associated with Mario, please see the National Weather Service Storm Total Rainfall Graphic, available at hurricanes.gov/graphics_ep3.shtml?rainqpf WIND: Gusty winds are possible along coastal portions of the states of Guerrero, Michoacan, and Colima through tonight. NEXT ADVISORY ------------- Next complete advisory at 300 AM CST. $$ Forecaster Beven

...MARIO WEAKENS TO A TROPICAL DEPRESSION AS IT STARTS MOVING AWAY FROM SOUTHWESTERN MEXICO... ...TROPICAL STORM WATCH DISCONTINUED FOR THE COAST OF MEXICO... As of 9:00 PM CST Fri Sep 12 the center of Mario was located near 18.1, -104.6 with movement WNW at 15 mph. The minimum central pressure was 1007 mb with maximum sustained winds of about 35 mph.

Issued at 0300 UTC SAT SEP 13 2025 191 WTPZ23 KNHC 130232 TCMEP3 TROPICAL DEPRESSION MARIO FORECAST/ADVISORY NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132025 0300 UTC SAT SEP 13 2025 TROPICAL DEPRESSION CENTER LOCATED NEAR 18.1N 104.6W AT 13/0300Z POSITION ACCURATE WITHIN 20 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 13 KT ESTIMATED MINIMUM CENTRAL PRESSURE 1007 MB MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 18.1N 104.6W AT 13/0300Z AT 13/0000Z CENTER WAS LOCATED NEAR 17.9N 104.0W FORECAST VALID 13/1200Z 18.8N 106.3W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 14/0000Z 19.2N 108.0W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 14/1200Z 19.7N 109.7W MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 15/0000Z...DISSIPATED REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 18.1N 104.6W NEXT ADVISORY AT 13/0900Z $$ FORECASTER BEVEN

MD 2068 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTHEAST WYOMING INTO WESTERN SOUTH DAKOTA AND SOUTHWEST NORTH DAKOTA
Mesoscale Discussion 2068 NWS Storm Prediction Center Norman OK 0601 PM CDT Fri Sep 12 2025 Areas affected...northeast Wyoming into western South Dakota and southwest North Dakota Concerning...Severe potential...Watch possible Valid 122301Z - 130130Z Probability of Watch Issuance...40 percent SUMMARY...Storms may increase in coverage this evening, with strong wind gusts in addition to sporadic large hail. Trends are being monitored for watch potential. DISCUSSION...Widely scattered cells, some with hail, persist this evening over parts of MT, WY, and the Dakotas, where peak heating has led to an uncapped air mass and moderate instability. Thus far, clusters of cells have been slow moving. However, a gradual uptick in coverage has been noted recently over northeast WY, western SD and now into south-central ND. Also of note is an apparent outflow surge associated with a larger area of convection over east-central WY. Indications are that new cell development may keep developing along the leading edge of the outflow/baroclinic zone as it pushes northeastward across northeast WY, southeast MT, and the western Dakota through the evening. Such a propagating storm regime could result in an increased wind risk, specially as the activity interacts with an increasingly moist/unstable air mass to the northeast. ..Jewell/Gleason.. 09/12/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR...CYS...BYZ...RIW... LAT...LON 44160672 45880482 46250406 46920201 46920104 46770055 46520033 46200042 45740103 44020176 43480215 43140289 43010407 43170493 43670641 44160672 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Fri Sep 12 2025 Valid 130100Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN WESTERN SD AND FAR SOUTH-CENTRAL ND... ...SUMMARY... Large hail and isolated severe gusts remain possible tonight across parts of the northern Great Plains and Black Hills. ...Northern Great Plains... Despite limited severe hail reports thus far, a few supercells along the south-central ND/north-central border area had impressively large MRMS MESH signatures. These supercells have remained anchored along a southwest/northeast-oriented surface trough amid weak low-level winds but around 40-kt effective bulk shear. This nearly straight-line hodograph structure conducive for splitting supercells, coincident with MLCAPE near 3000 J/kg per the 00Z BIS sounding, should support large hail potential over the next couple hours. An arc of convective outflow spreading north to east across northeast WY to far southwest SD will eventually impinge on the MLCAPE gradient that runs southwest to northeast across western SD. Cells along the outflow should intensify as they spread northeast of the Black Hills and north of the Badlands later this evening. 15Z and later CAMs indicate potential for a few sporadic supercells, which would yield a large hail threat. Severe gusts are also possible, but these may remain localized and transient given the modest motion of the outflow and supercell wind profile. ...Southeast AZ/Southwest NM... Earlier severe wind/hail storms across southeast AZ should diminish over the next hour or two as they attempt to spread into southwest NM where prior overturning has occurred. A cooler downstream boundary layer and weaker tropospheric lapse rates will further marginalize storm intensity after dusk. ..Grams.. 09/13/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Fri Sep 12 2025 Valid 130100Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN WESTERN SD AND FAR SOUTH-CENTRAL ND... ...SUMMARY... Large hail and isolated severe gusts remain possible tonight across parts of the northern Great Plains and Black Hills. ...Northern Great Plains... Despite limited severe hail reports thus far, a few supercells along the south-central ND/north-central border area had impressively large MRMS MESH signatures. These supercells have remained anchored along a southwest/northeast-oriented surface trough amid weak low-level winds but around 40-kt effective bulk shear. This nearly straight-line hodograph structure conducive for splitting supercells, coincident with MLCAPE near 3000 J/kg per the 00Z BIS sounding, should support large hail potential over the next couple hours. An arc of convective outflow spreading north to east across northeast WY to far southwest SD will eventually impinge on the MLCAPE gradient that runs southwest to northeast across western SD. Cells along the outflow should intensify as they spread northeast of the Black Hills and north of the Badlands later this evening. 15Z and later CAMs indicate potential for a few sporadic supercells, which would yield a large hail threat. Severe gusts are also possible, but these may remain localized and transient given the modest motion of the outflow and supercell wind profile. ...Southeast AZ/Southwest NM... Earlier severe wind/hail storms across southeast AZ should diminish over the next hour or two as they attempt to spread into southwest NM where prior overturning has occurred. A cooler downstream boundary layer and weaker tropospheric lapse rates will further marginalize storm intensity after dusk. ..Grams.. 09/13/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Fri Sep 12 2025 Valid 130100Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN WESTERN SD AND FAR SOUTH-CENTRAL ND... ...SUMMARY... Large hail and isolated severe gusts remain possible tonight across parts of the northern Great Plains and Black Hills. ...Northern Great Plains... Despite limited severe hail reports thus far, a few supercells along the south-central ND/north-central border area had impressively large MRMS MESH signatures. These supercells have remained anchored along a southwest/northeast-oriented surface trough amid weak low-level winds but around 40-kt effective bulk shear. This nearly straight-line hodograph structure conducive for splitting supercells, coincident with MLCAPE near 3000 J/kg per the 00Z BIS sounding, should support large hail potential over the next couple hours. An arc of convective outflow spreading north to east across northeast WY to far southwest SD will eventually impinge on the MLCAPE gradient that runs southwest to northeast across western SD. Cells along the outflow should intensify as they spread northeast of the Black Hills and north of the Badlands later this evening. 15Z and later CAMs indicate potential for a few sporadic supercells, which would yield a large hail threat. Severe gusts are also possible, but these may remain localized and transient given the modest motion of the outflow and supercell wind profile. ...Southeast AZ/Southwest NM... Earlier severe wind/hail storms across southeast AZ should diminish over the next hour or two as they attempt to spread into southwest NM where prior overturning has occurred. A cooler downstream boundary layer and weaker tropospheric lapse rates will further marginalize storm intensity after dusk. ..Grams.. 09/13/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Fri Sep 12 2025 Valid 130100Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN WESTERN SD AND FAR SOUTH-CENTRAL ND... ...SUMMARY... Large hail and isolated severe gusts remain possible tonight across parts of the northern Great Plains and Black Hills. ...Northern Great Plains... Despite limited severe hail reports thus far, a few supercells along the south-central ND/north-central border area had impressively large MRMS MESH signatures. These supercells have remained anchored along a southwest/northeast-oriented surface trough amid weak low-level winds but around 40-kt effective bulk shear. This nearly straight-line hodograph structure conducive for splitting supercells, coincident with MLCAPE near 3000 J/kg per the 00Z BIS sounding, should support large hail potential over the next couple hours. An arc of convective outflow spreading north to east across northeast WY to far southwest SD will eventually impinge on the MLCAPE gradient that runs southwest to northeast across western SD. Cells along the outflow should intensify as they spread northeast of the Black Hills and north of the Badlands later this evening. 15Z and later CAMs indicate potential for a few sporadic supercells, which would yield a large hail threat. Severe gusts are also possible, but these may remain localized and transient given the modest motion of the outflow and supercell wind profile. ...Southeast AZ/Southwest NM... Earlier severe wind/hail storms across southeast AZ should diminish over the next hour or two as they attempt to spread into southwest NM where prior overturning has occurred. A cooler downstream boundary layer and weaker tropospheric lapse rates will further marginalize storm intensity after dusk. ..Grams.. 09/13/2025 Read more