The Storm Prediction Center convective weather outlook is part of the National Weather Service (NWS) and the National Center for Environmental Prediction (NCEP). Their mission is to provide accurate forecasts and monitor the timing of thunderstorms and severe storms in the United States. The SPC provides convective outlooks on Day 1, Day 2, and Day 3 that reflect the overall level of severe weather hazard outlooks through a list of forecast statistics. This data identifies areas at risk of mild thunderstorms and severe thunderstorms. For more information on how to read this map, please see the bottom of this page.
Convective Outlook Day 1
SPC Day 1 Outlook Discussion
ACUS01 KWNS 091239 SWODY1 SPC AC 091237 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0737 AM CDT Sun Aug 09 2026 Valid 091300Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE MIDWEST... ...SUMMARY... Scattered damaging winds may occur today into this evening from southern Minnesota and eastern Iowa eastward across parts of northern Illinois, southern Wisconsin, southern Lower Michigan, northwest Ohio, and northern Indiana. Damaging wind and hail are also expected across portions of the Dakotas. ...Midwest... Radar/satellite composite shows a corridor of showers/thunderstorms from northern MO into southern MN and western WI associated with isentropic lift on the nose of a 40-kt southwesterly LLJ. A localized risk for hail/wind may accompany this activity this morning as it shifts eastward across the MS River towards Lake MI through midday. Considerable uncertainty remains regarding the severe forecast for the eastern IA into the southern Great Lakes portion of the Slight Risk. Showers/thunderstorms and related convective debris/outflow will be influential on airmass recovery later this afternoon. It seems plausible a warm front draped over the Corn Belt this morning will slowly advance northward into the southwest Great Lakes with an increasingly unstable airmass developing to the south/west of this convectively augmented baroclinic zone. Model forecast soundings show ample CAPE aided by the northern rim of lower to mid 70s F surface dewpoints into northern portions of IL/IN. Adequately strong and vertically veering wind profiles will support 30-40 kt effective shear magnitudes. Low-level SRH may also be locally boosted in the vicinity of the warm front/effective boundary, which could then play a role in severe potential if a supercell or linear segments were to develop and favorably interact within this corridor. Rather poor depiction of this morning's thunderstorm evolution (i.e., 00z HREF members) casts large uncertainty where a couple of more intense thunderstorm clusters will ultimately develop. It seems the greatest potential for severe will be centered over northern IL later this afternoon through the evening, but confidence remains low regarding details and the need for spatial refinements of the severe risk area and the need for potential higher probabilities. ...Dakotas and western NE... A surface front is expected to push southward across the central Plains, becoming oriented across northern KS by tonight. Low-level warm advection atop the boundary, and surface winds becoming south/southeasterly with time will maintain 60s dewpoints across the region. Within this post-frontal upslope regime, a reservoir of mainly 60s F dewpoints will reside beneath moderate northwesterly flow aloft. Supercell wind profiles and steep low-level lapse rates will support initial storms capable of large hail and severe gusts, especially as this activity over the western Dakotas moves southeastward into richer moisture. A small cluster may eventually evolve during the overnight with an attendant risk for severe gusts and perhaps large hail. ...Southern Appalachians... Scattered thunderstorm development is expected over higher terrain within a seasonally moist and unstable airmass. Steepening low-level lapse rates and high PW values may support locally strong gusts with wet microbursts through early evening. ...AZ... Modest easterly mid/upper flow will persist across the region on the southern periphery of an upper high over the Four Corners. Another day of hot conditions will promote steep lapse rates and modest destabilization. As convection develops over higher terrain and spread westward, strong outflow gusts may occur. ..Smith/Kerr.. 08/09/2026 $$ |
Convective Outlook Day 2
SPC Day 2 Outlook Discussion
ACUS02 KWNS 090544 SWODY2 SPC AC 090542 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Sun Aug 09 2026 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN GREAT LAKES... ...SUMMARY... Thunderstorms with severe wind gusts will be possible Monday afternoon and evening from northern Illinois eastward into western Pennsylvania. Isolated severe gusts and hail will also be possible from parts of the central and northern Plains into the Midwest. ...Southern Great Lakes... At mid-levels, west-northwesterly flow will be in place on Monday from the northern Plains into the Great Lakes. A subtle mid-level shortwave trough and an associated jet streak will move through the Great Lakes. To the south of the jet streak, a cold front is forecast to advance southward into northern Illinois, northern Indiana and northern Ohio by mid afternoon. Low-level convergence along the front will be a focus for convective development. To the south of the front, surface dewpoints in the 70s F will contribute to moderate to strong destabilization by afternoon, with MLCAPE likely peaking in the 2000 to 3500 J/kg range. Thunderstorms are expected to develop near the front and move east-southeastward into the stronger instability during the afternoon and evening. Along the instability axis in the late afternoon from Lincoln, Illinois to Pittsburgh, Pennsylvania, the ECMWF has 0-6 km shear around 30 knots. This should support a mixed mode, with short intense line segments and embedded rotating storms possible. The primary threat will damaging wind gusts, with the maximum threat located ahead of any cold pool that can organize. The severe threat could persist into the early to mid evening, especially if MCS development takes place, maintained by increasing low-level flow. ...Central and Northern Plains/Midwest... West-northwesterly mid-level flow will be in place over the north-central U.S. on Monday. A subtle shortwave trough is forecast to move east-southeastward across the northern Plains. At the surface, a cold front is forecast to advance southward across western South Dakota during the day, with a dryline extending southward into western Nebraska. To the east of the dryline, surface dewpoints in the 60s and 70s F will contribute to moderate to strong instability by afternoon. Isolated thunderstorms appear likely to develop near the dryline during the mid to late afternoon. Additional isolated storms are expected to develop further east along the moist axis from eastern Nebraska into Iowa. Forecast sounding along the moist axis in the late afternoon have MLCAPE peaking in the 3000 to 4000 J/kg range with 0-6 km shear around 30 knots. This environment, combined with steep low to mid-level lapse rates, will support isolated potential for severe wind gusts and hail. ..Broyles.. 08/09/2026 $$ |
Convective Outlook Day 3
SPC Day 3 Outlook Discussion
ACUS03 KWNS 090725 SWODY3 SPC AC 090724 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0224 AM CDT Sun Aug 09 2026 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OHIO VALLEY AND CENTRAL APPALACHIANS... ...SUMMARY... Thunderstorms with severe wind gusts will be possible on Tuesday over parts of the Ohio Valley and central Appalachians. Isolated severe gusts and hail will also be possible from parts of the central and northern Plains into the Midwest. ...Ohio Valley/Central Appalachians.... At mid-levels, west-northwesterly flow will be in place on Tuesday from the northern Plains to the central and northern Appalachians. Along the southern edge of the stronger mid-level flow, a west-northwest to east-southeast corridor of moderate to strong instability is forecast to develop by afternoon. It appears that an outflow boundary from the previous day's storms will be located from approximately north-central Illinois east-southeastward into southern Ohio. Low-level convergence along this boundary will be a focus for convective initiation. In the afternoon, thunderstorms are expected to develop near the boundary and move east-southeastward into the stronger instability over the Ohio Valley. A cluster of strong to severe storms is expected, and MCS development will be possible across the region. Instability is forecast to be similar to the previous day, with MLCAPE peaking in the 2000 to 3500 J/kg range. According to the ECMWF, deep-layer shear may be a bit stronger with 0-6 km shear in the 30 to 40 knot range. This would support supercells and short intense line segments capable of severe wind gusts. The wind-damage threat would become maximized if a cold pool can develop during the late afternoon and early evening. The current thinking is that the ECMWF has a better handle on where the outflow boundary will be than other solutions, and the Slight Risk area has been placed favoring the ECMWF scenario. ...Central and Northern Plains/Midwest... West-northwesterly mid-level flow will remain over the north-central U.S. on Tuesday. At the surface, dewpoints in the 60s and 70s F from South Dakota and Nebraska eastward into Iowa will contribute to strong destabilization by afternoon. MLCAPE is forecast to peak above 4000 J/kg along parts of the moist axis by late afternoon. In spite of the instability, large-scale ascent is forecast to remain relatively weak. Isolated to scattered storms could still develop along zones of low-level convergence. The strong instability along with moderate deep-layer shear should support an isolated severe threat from mid afternoon to mid evening. Severe wind gusts and hail will be the primary threats. Due to the weak forcing, there is some uncertainty as to where the greatest convective coverage will be. ..Broyles.. 08/09/2026 $$ |
Convective Outlook Day 4-8
SPC Day 4-8 Outlook Discussion
ACUS48 KWNS 090900 SWOD48 SPC AC 090858 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sun Aug 09 2026 Valid 121200Z - 171200Z ...DISCUSSION... ...Wednesday/Day 4 to Friday/Day 6... From Wednesday to Friday, a broad mid-level cyclonic flow pattern is forecast to remain in place across the Great Lakes and the Northeast, as a ridge moves eastward from the northern Rockies into the upper Mississippi Valley. At the surface, a cold front is forecast to become quasi-stationary from the central and northern Plains into the mid Missouri and Ohio Valleys. Low-level convergence near this front will be a focus for convective development each day. On Wednesday, model forecasts suggest that scattered thunderstorms will most likely develop Wednesday afternoon along an axis of moderate instability from western Nebraska into southwestern South Dakota. The storms will be supported by a mid-level shortwave trough moving across the north-central U.S. Moderate deep-layer shear near the instability axis should support a severe threat during the afternoon and evening. The models also suggest that a convective cluster will form within a very moist and unstable airmass in the central Appalachians Wednesday afternoon, where a wind-damage threat will be possible. On Thursday, the most favored corridor for convective development is forecast from eastern Nebraska into central Illinois. However, the models suggest that scattered convective coverage could be concentrated overnight as low-level flow increases across the region. A severe threat could develop during the day but would remain relatively isolated due to a lack of storm coverage. An isolated severe threat could also develop across parts of the central and northern High Plains during the afternoon. However, storms there will also likely be isolated due to a shortwave ridge aloft. On Friday, thunderstorm swill also be possible from the central Plains eastward into the Ohio Valley during the afternoon and evening. However, the most favored locations are likely to be determined by outflow boundaries associated with the previous day's convection. For this reason, uncertainty is substantial on Friday. ...Saturday/Day 7 and Sunday/Day 8... Over the weekend, a mid-level shortwave ridge is forecast to move across the north-central U.S., as west-northwesterly flow remains in the Northeast. An axis of instability is forecast from the central Plains into the Ohio Valley, which will be a focus for thunderstorm development. It appears that an isolated severe threat could develop along and near the instability axis each afternoon and evening. However, uncertainty is considerable concerning the details of any potential scenario. ..Broyles.. 08/09/2026
Convective Weather Outlook Legend Data
- TSTMÂ (light green) – General or non-severe thunderstorms – Delineates, to the right of a line, where a 10% or greater probability of thunderstorms is forecast during the valid period.
- 1-MRGL (dark green) – Marginal risk – An area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity.
- 2-SLGT (yellow) – Slight risk – An area of organized severe storms, which is not widespread in coverage with varying levels of intensity.
- 3-ENHÂ (orange) – Enhanced risk – An area of greater (relative to Slight risk) severe storm coverage with varying levels of intensity.
- 4-MDT (red) – Moderate risk – An area where widespread severe weather with several tornadoes and/or numerous severe thunderstorms is likely, some of which should be intense. This risk is usually reserved for days with several supercells producing intense tornadoes and/or very large hail. Or an intense squall line with widespread damaging winds.
- 5-HIGH (magenta) – High risk – An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes. Also, a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe. (i.e., violent tornadoes or very damaging convective wind events).
This data is courtesy from the Storm Prediction Center