The Storm Prediction Center (SPC) 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 through a list of forecast statistics that identify areas at risk of mild thunderstorms and severe thunderstorms across the contiguous United State. 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 180549 SWODY1 SPC AC 180548 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Mon Aug 18 2025 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Strong to severe storms capable of damaging winds are possible in parts of the Upper Midwest today. Isolated to widely scattered storms with large hail and severe winds are possible in parts of the central/northern Plains through tonight. ...Central High Plains... A broad upper trough over the northern Plains will move east today with an attendant surface low and cold front also moving east. Behind the departing surface low, weak upslope flow is expected across portions of western SD, northeastern WY. Strong heating and steep mid-level lapse rates should allow for diurnal destabilization with widely scattered thunderstorms expected along a lee trough by the afternoon. Elongated hodographs, courtesy of 30-40 kt of westerly flow aloft, will allow for some organized storms including supercells or clusters. Steep mid-level lapse rates, and moderate buoyancy will support a hail risk. Farther south, stronger heating and mixing will limit low-level moisture across southeastern WY and northeastern CO. Still, enough CAPE should be present for scattered high-based storms near peak heating. The steep low-level lapse rates and any clustering that develops should support damaging winds as storms spread eastward into northeast CO and western NE. Some potential exists for a longer-lived cluster to spread eastward into central/eastern NE and northern KS overnight. Should this occur, damaging winds and some hail would be the primary concerns, though this scenario remains highly uncertain given weaker forecast low-level jet. ...Midwest... One or more clusters of thunderstorms or an MCV is expected to be ongoing at the start of the period in the vicinity of the warm front across portions of IA/MN, casting significant uncertainty on the overall convective evolution for the day. Filtered diurnal heating and nebulous ascent from the broad trough over the northern Plains could support continuation of these storms and additional development into southern WI and northern IL this afternoon. While complications abound, substantial buoyancy (3000-4000 J/kg of MLCAPE) and dewpoints in the mid 70s F south of the composite front/remnant outflow will be supportive of occasional vigorous updrafts. Modest enhancement of the mid and upper-level flow could support a few semi-organized clusters or transient supercells with damaging wind potential. Given the potential for outflow or thunderstorm clusters to significantly alter the environment, confidence in higher wind probabilities is low. ...Southwest into central Montana... Despite a strong ridge building into the northern Rockies, sufficient moisture may promote thunderstorm development in the higher terrain this afternoon. 20-30 kt of flow aloft will be sufficient to support at least marginally organized storms. However, strong mixing during the afternoon could limit buoyancy and storm coverage. Occasional strong, gusty outflow winds are possible with any high-based storms, but confidence in severe potential remains low. ..Lyons/Kerr.. 08/18/2025 $$ |
Convective Outlook Day 2
SPC Day 2 Outlook Discussion
ACUS02 KWNS 180555 SWODY2 SPC AC 180553 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Mon Aug 18 2025 Valid 191200Z - 201200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A severe threat is not expected across the continental U.S. on Tuesday or Tuesday night. ...DISCUSSION... A mid-level ridge will build northward across the central Rockies and northern High Plains on Tuesday, as a subtle shortwave trough moves through the Great Lakes region. At the surface, a cold front will advance southward into the Ohio and mid Mississippi Valleys, extending westward into the southern Plains. As surface temperatures warm during the day, low-level convergence near the front will be favorable for isolated to scattered thunderstorm development. Limited large-scale ascent and weak deep-layer shear will be unfavorable for severe storms. Further northwest into the north-central states, moderate instability will be possible by Tuesday afternoon, mainly in the Dakotas. However, a severe threat is not expected due to limited large-scale ascent, minimal low-level convergence, and weak deep-layer shear. Elsewhere across the continental U.S., a severe threat is not expected Tuesday and Tuesday night. ..Broyles.. 08/18/2025 $$ |
Convective Outlook Day 3
SPC Day 3 Outlook Discussion
ACUS03 KWNS 180714 SWODY3 SPC AC 180713 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Mon Aug 18 2025 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... No severe threat is expected across the continental U.S. on Wednesday or Wednesday night. ...DISCUSSION... A large area of mid-level high pressure will remain over the Intermountain West and Rockies on Wednesday, as an associated ridge moves eastward across the northern Plains. At the surface, a moist airmass will be in place over much of the eastern two-thirds of the nation. In spite of this, convective development will be isolated over much of this airmass during the day on Tuesday. The greatest convective coverage is expected near a front from the southern Plains east-northeastward into the southern Appalachians Wednesday afternoon. Within this corridor, deep-layer shear and large-scale ascent will remain weak, suggesting that conditions will not be favorable for severe storms. Further to the east, Hurricane Erin is expected to remain in the far western Atlantic, and convective potential is expected to be minimal along the Atlantic Seaboard. Elsewhere, a severe threat is not expected to develop across the continental U.S. Wednesday or Wednesday night. ..Broyles.. 08/18/2025 $$ |
Convective Outlook Day 4-8
SPC Day 4-8 Outlook Discussion
ACUS48 KWNS 170855 SWOD48 SPC AC 170854 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Sun Aug 17 2025 Valid 201200Z - 251200Z ...DISCUSSION... ...Wednesday/Day 4 to Friday/Day 6... On Wednesday, a mid-level ridge will likely be in place across the northern Plains. At the surface, a front is forecast to be located over the Ozarks and lower Ohio Valley. Moderate instability is expected to develop to the south of the front, and over parts of the north-central states. In areas where storms are expected, deep-layer shear should be weak, suggesting a severe threat is unlikely. On Thursday, a mid-level shortwave trough and an associated cold front are forecast to move eastward into the northern Plains. An axis of moderate instability is forecast ahead of the front. This combined with moderate deep-layer shear could be enough for an isolated severe threat during the afternoon and evening, mainly over eastern North Dakota and northwestern Minnesota. The front and its associated shortwave trough are forecast to move into the upper Mississippi and mid Missouri Valleys on Friday. Moderate instability appears likely to develop ahead of the front during the afternoon. Along and near the instability axis, the greatest potential for thunderstorm development could occur in the central Plains within northwest mid-level flow. An isolated severe threat will be possible during the late afternoon and early evening. ...Saturday/Day 7 and Sunday/Day 8... On Saturday and Sunday, an upper-level trough is forecast to remain over the Great Lakes region. Ahead of the trough, an axis of instability is forecast to develop in the central Appalachians, where isolated to scattered thunderstorms will be possible each afternoon. Moderate deep-layer shear could be sufficient for an isolated wind-damage threat, mainly in the late afternoon as low-level lapse rates become steep. ..Broyles.. 08/17/2025
Convective Weather Outlook Legend Data
- TSTM (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-ENH (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 or 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