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 200604 SWODY1 SPC AC 200602 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0102 AM CDT Mon Jul 20 2026 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER MIDWEST AND GREAT LAKES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTH CAROLINA AND FAR SOUTHERN VIRGINIA... ...SUMMARY... Severe thunderstorms are expected across portions of the Upper Midwest and Great Lakes vicinity, especially late this afternoon and tonight. Swaths of damaging winds, large hail, and a few tornadoes will all be possible. Isolated damaging wind gusts may also occur over parts of the Carolinas and southern Virginia. ...Upper Midwest/Great Lakes... A potentially active severe-weather scenario is expected later today into tonight, although some key uncertainties persist related to the potential impacts of early day convection and associated cloud debris. A substantial shortwave trough over southern Manitoba will continue to gradually amplify and spread southeastward to the Lake Superior vicinity through tonight, with a strengthening belt of mid/high-level west-northwesterly flow overspreading the Upper Midwest toward the Lake Michigan vicinity, highlighted by 50-70 kt mid-level winds and 100 kt winds in the upper levels across Minnesota/Wisconsin. An east/southeastward-advecting plume of steep mid-level lapse rates will overspread a warm sector with upper 60s to lower/middle 70s F dewpoints. Initially, a few early day storms could produce hail and perhaps some strong wind gusts across east/southeast Minnesota into western Wisconsin and eastern Iowa, amidst ample elevated instability and effective shear over 50 kt. This activity may continue to spread southeastward this morning but tend to wane during the day, leading to a potential regional break prior to additional/more vigorous development by late afternoon along the cold front as it progresses east-southeastward toward Wisconsin/Upper Michigan and northern/eastern Iowa. The initial storms should primarily be supercells given such strong deep-layer shear. A corridor of large hail and tornado risk is evident east of the instability axis from Iowa across Wisconsin into Upper MI. Even while near-surface winds may tend to veer with time, effective SRH may exceed 300 m2/s2, especially across Wisconsin toward Upper Michigan as supported by the seasonally very-strong 2-3 km AGL winds (700 mb winds in excess of 50 kt). The degree of SRH could support a couple strong tornadoes (EF2+), and somewhat higher tornado probabilities could be warranted in subsequent outlooks as early day convection details are resolved. While supercells will persist for a time, several storm clusters will evolve this evening, with a continued damaging wind and some tornado risk persisting southeastward this evening prior to storm intensity eventually waning overnight. ...Carolinas and southern Virginia... Convection and related cloud debris may persist early today, but a moist air mass will again diurnally destabilize this afternoon along and south of a roughly west/east-oriented front. Daytime heating, 70s F dewpoints and surface convergence will aid storm formation and intensification this afternoon. MLCAPE in excess of 2000 J/kg, PWAT over 2.00", and mid-level westerly flow aloft of 15-20 kt will lead to multicellular storm mode with isolated damaging wind gusts during the afternoon until around sunset. ...Florida... Tropical Depression Two may gradually strengthen across the northeast Gulf of America today and tonight. Reference the National Hurricane Center for the latest development/forecast details. While various global models support the notion of a strengthening of southerly winds in the lowest 2-3km AGL, especially across the western Florida Peninsula, it currently appears that supercell-related tornado potential should remain low, largely attributable to the overall weakness of the Depression and weak wind aloft. ..Guyer/Weinman.. 07/20/2026 $$ |
Convective Outlook Day 2
SPC Day 2 Outlook Discussion
ACUS02 KWNS 200541 SWODY2 SPC AC 200539 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Mon Jul 20 2026 Valid 211200Z - 221200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN INDIANA...NORTHEAST KENTUCKY...SOUTHERN/EASTERN OHIO...WEST VIRGINIA...NORTHERN VIRGINIA...MARYLAND...AND PENNSYLVANIA... ...SUMMARY... Numerous severe thunderstorms are expected across a broad region from the Ohio Valley into the Mid-Atlantic and Northeast on Tuesday. All severe hazards are possible, but swaths of damaging wind gusts should be the primary severe risk Tuesday afternoon into the nighttime hours. ...Ohio Valley to the Mid-Atlantic and Northeast... An upper trough will be oriented over the region on Tuesday, with several shortwave impulses migrating through the larger-scale system. At the surface, low pressure will move across southern Ontario into Quebec. A trailing cold front will move across much of the Midwest through the period, becoming positioned from western PA to TN and northern AR/OK by Wednesday morning. Ahead of the main surface front, surface prefrontal troughing is expected to develop across western/central NY into the Mid-Atlantic vicinity. Rich boundary-layer moisture will overspread much of the area, with dewpoints from the mid-60s to low 70s F commonplace. This will aid in development of moderate to strong instability. Deep-layer flow will be strong for this time of year, with 40-60 kt flow at 500 mb, and 30-50 kt in the 850-700 mb layer. Forecast soundings indicate supercell wind profiles with favorably curved low-level hodographs becoming elongated above 2-3 km across much of the region. Convective evolution remains a bit uncertain, but a mix of supercells and one or more bowing linear segments are expected across the Ohio Valley into the Mid-Atlantic. Significant severe (2+ inch hail, 65+ kt winds, etc) potential is unclear, and will largely depend on storm mode and mesoscale evolution of convection. Temperatures aloft are relatively warm, around -5 to -7 C at 500 mb, and this may inhibit sig hail potential. Meanwhile, 65+ kt gusts could occur if a well-organized bowing structure and stronger cold pool can develop. Given warm/moist low-levels and limited low-level lapse rates, confidence in this scenario is low. As a result, the CIG 1 area from the prior Day 3 outlook has been removed for now. Where supercells can be maintained, a risk for a few tornadoes also is possible. While details regarding storm mode and evolution remain somewhat uncertain, the overall environment will support a severe risk across a broad region on Tuesday/Tuesday evening. Swaths of damaging winds still appear to be the greatest risk, though all hazards are possible. ..Leitman.. 07/20/2026 $$ |
Convective Outlook Day 3
SPC Day 3 Outlook Discussion
ACUS03 KWNS 200722 SWODY3 SPC AC 200721 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0221 AM CDT Mon Jul 20 2026 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTH CAROLINA INTO SOUTHEAST VIRGINIA... ...SUMMARY... Isolated strong to severe thunderstorms will pose a risk for damaging wind gusts across parts of southeast Virginia and North Carolina. ...Mid-Atlantic to New England... Several shortwave impulses will migrate through persistent upper troughing over the East on Wednesday. At the surface, low pressure will lift northeast across Quebec. A trailing cold front will move east/southeast across portions of the region, become positioned from the Mid-Atlantic coast into central NC by Thursday morning. Southerly low-level flow ahead of the front will maintain a seasonally moist airmass. Moderate destabilization is expected across parts of the Mid-Atlantic into NC where boundary-layer moisture is greater and stronger heating may occur. Weak instability will be located over New England. Around 30-40 kt southwesterly flow from 850-500 mb will provide sufficient vertical shear for some organized cells/clusters. Isolated strong to severe storms producing damaging winds are expected across portions of the Mid-Atlantic into New England, with the greatest risk across parts of VA/NC and vicinity. ..Leitman.. 07/20/2026 $$ |
Convective Outlook Day 4-8
SPC Day 4-8 Outlook Discussion
ACUS48 KWNS 200804 SWOD48 SPC AC 200802 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0302 AM CDT Mon Jul 20 2026 Valid 231200Z - 281200Z ...DISCUSSION... Upper troughing will persist across the eastern U.S. through early next week. Meanwhile, a strong, amplified upper ridge will envelop the western half of the CONUS. This should largely limit greater severe potential beneath the upper ridge, though some daily mesoscale-driven strong thunderstorm risk could develop over parts of the Plains as moist southerly low-level flow maintains moisture across the central portions of the country. While any stronger flow aloft will mostly remain north of the international border, some model guidance trends over the last 24 hours indicate strengthening northwesterly flow aloft is possible as a shortwave impulse or two migrates atop the upper ridge and over parts of the northern Plains and Great Lakes. This could support an increasing severe risk across these areas over the weekend, though confidence is too low for any 15 percent probability areas at this time. ..Leitman.. 07/20/2026
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