SEVERE WEATHER OUTLOOK
Day 1 Convective Outlook
Forecast Discussion
SPC AC 160518 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1218 AM CDT Thu Jul 16 2026 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF WESTERN MONTANA... ...SUMMARY... Severe thunderstorms will be possible across parts of western Montana, mainly Thursday afternoon and evening. Locally damaging winds may also occur across parts of New England, the Upper Midwest, and the Mid-Atlantic. ...Northern Rockies... An upper low will skim the Pacific Northwest coast as it lifts northward through the period. Meanwhile, upper ridging will persist across much of the Rockies to the Plains. Wedged between the upper low and the western periphery of the upper ridging, a belt of enhanced south/southwesterly deep-layer flow will overspread the northern Rockies. Easterly low-level flow will transport 50s F dewpoints across region beneath steep midlevel lapse rates. This will support moderate destabilization (1000-2000 J/kg MLCAPE). Scattered thunderstorms will develop during the afternoon. Vertically veering wind profiles and increasing flow aloft will result in 30+ kt effective shear magnitudes. Organized cells will pose a risk for strong wind gusts and hail across much of the region. The greatest risk for 1+ inch hail will be across portions of western MT. ...New England... A vigorous upper shortwave trough will move across the region through evening. Strong west/northwest deep-layer flow is evident in forecast soundings, with 40+ kt effective shear magnitudes likely. Boundary layer moisture will be somewhat muted compared to the previous few days, with dewpoints generally in the 50s F. Stronger heating is expected to the north of the more prominent smoke plume across southern New England, aiding in steepening low-level lapse rates. While instability will remain modest, strong flow and steep low-level lapse rates may support isolated strong/locally damaging wind gusts as convection spreads southeast from Quebec and across portions of northern New England through the afternoon. ...Southern PA/Mid-Atlantic vicinity... Strong mid/upper-level flow will overspread the region on the southern periphery of the upper shortwave trough moving across New England. A surface front is expected to drop southward through the day, approaching the PA/MD border vicinity by late afternoon. Rich boundary layer moisture will be in place ahead of the surface front and beneath steep midlevel lapse rates. This will foster a corridor of 2000+ J/kg MLCAPE. Furthermore, forecast soundings show 30-40 kt effective shear magnitudes and steep low-level lapse rates. This environment generally should support organized cells/line segments. However, convective coverage is uncertain given stronger forcing for ascent focused north of the area. Additionally, it is uncertain if smoke will continue to have a deleterious impact on an otherwise favorable severe storm environment. Given conditional potential for at least locally damaging gusts, have included low severe wind probabilities. ...ND/MN... A series of convectively enhanced vorticity maxima will migrate across the Canadian Prairies atop the upper ridge and through northwesterly flow aloft into parts of ND and northern MN this afternoon into tonight. At the surface, a weak low and surface front will move across ND into northern MN during the evening and overnight hours. South/southeasterly low-level flow will maintain a moisture-rich boundary layer, supporting a corridor of modest destabilization. Forecast soundings show supercell wind profiles, but also increasing capping through the late afternoon/evening. Nevertheless, most guidance develops convection across southern Manitoba into northeast ND during the evening, spreading east/southeast across northern MN during the nighttime hours. Some risk for strong gusts and marginal hail appears possible, necessitating low severe probabilities. ...AZ... Thunderstorms are expected once again to develop over higher terrain this afternoon/evening and spread westward across portions of central/southern AZ. Deep layer flow will be weaker compared to previous days, but modest instability and steep lapse rates amid strong heating could support sporadic strong gusts. ..Leitman/Lyons.. 07/16/2026 NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
Updated: Thu Jul 16 05:18:38 UTC 2026 (
Day 2 Convective Outlook
Forecast Discussion
SPC AC 160605 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0105 AM CDT Thu Jul 16 2026 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN IDAHO AND WESTERN MONTANA AS WELL AS PORTIONS OF THE UPPER MIDWEST AND NORTHERN GREAT LAKES... ...SUMMARY... Strong to potentially severe storms are possible on Friday across parts of western Montana and northern Idaho, and also across parts of the Upper Great Lakes region. ... Parts of the Upper Midwest and Great Lakes ... A subtle mid-level vorticity maximum evident in the 16/00 UTC guidance is expected to move southeastward across northern Minnesota and the Upper Great Lakes on Friday morning, supporting ongoing thunderstorms across the Arrowhead of Minnesota. This activity should spread southeastward through the morning with at least a marginal severe hail/wind threat. During the day, a surface frontal zone draped from northern Illinois/Indiana should begin to lift northward, ahead of a surface cold front moving through the northern Plains. To the south of the warm front and ahead of the cold front, diurnal heating may be somewhat muted by smoke and residual cloud cover from morning convection. However, increasing low-level moisture should still support moderate destabilization by the afternoon, especially where stronger diurnal heating occurs. Moderate mid-level northwesterly flow will provide enough vertical shear to support organized storms. As the stronger mid-level wave approaches the region during the late afternoon and evening, some potential exists for surface-based thunderstorm redevelopment -- especially near the intersection of the cold front and effective warm front. Large hail and strong thunderstorm winds will be possible with these storms, and the low-level wind field would support at least some potential for a tornado with any sustained surface-based storm during the evening. With time this activity should evolve into one or more clusters of thunderstorms moving southeast overnight across the northern Great Lakes. ... Western Montana and Northern Idaho ... A relatively favorable thermodynamic environment will once again be in place across parts of western Montana and northern Idaho by Friday afternoon. Relatively steep low- and mid-level lapse rates, sufficient moisture, and diurnal heating should support afternoon SBCAPE values in the 1000-1500 J/kg range, as suggested by the 20260716 00UTC HREF. Mid-/upper-level flow will be less than in previous days as the region becomes increasingly displaced from a mid-/upper-level trough/low moving northward into southwest Canada. That said, effective-layer shear on the order of 25-35 knots will be possible, especially where east/southeasterly surface winds are maintained. Scattered thunderstorms are expected to develop during the afternoon and evening hours. The strongest thunderstorm clusters will be capable of large hail. Strong to severe thunderstorm gusts will be possible as well, especially where convective outflows can consolidate amid the steep low-/mid-level lapse rates. Most 16/00 UTC HREF members show explicit convective outflow gusts approaching 60 mph, supporting a localized severe threat. If convective coverage appears greater than currently forecast, severe probabilities may need to be increased in subsequent outlooks. ... Ohio Valley ... Scattered to numerous thunderstorms are expected to develop during the afternoon within a moist, moderately unstable, and weakly capped environment. Localized downburst winds could occur within this environment, though deep-layer flow/shear appears too weak to support an organized severe threat. Additionally, 16/00 UTC guidance suggests early initiation across the region, which would limit the development of widespread steep low-level lapse rates, which may provide some limit on a more widespread, storm-scale driven wind threat. This region will continue to be evaluated in subsequent outlooks. ..Marsh.. 07/16/2026 NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
Updated: Thu Jul 16 06:05:55 UTC 2026 (
Day 3 Convective Outlook
Forecast Discussion
SPC AC 151928 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Wed Jul 15 2026 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF WESTERN MT/NORTHERN ID...AND ALSO ACROSS THE UPPER GREAT LAKES REGION... ...SUMMARY... Strong to potentially severe storms are possible on Friday across parts of western Montana and northern Idaho, and also across parts of the Upper Great Lakes region. ...Parts of ID/western MT... A relatively favorable thermodynamic environment is again expected to reside across parts of western MT and vicinity by Friday afternoon. Relatively steep lapse rates and sufficient moisture may result in MLCAPE increasing to near/above 1000 J/kg. A modest decrease in mid/upper-level flow is expected compared to D2/Thursday, as the region gradually becomes further removed from a mid/upper-level low moving across southwestern British Columbia. However, effective shear of 25-35 kt may develop where low-level flow remains east-southeasterly. Scattered thunderstorms are expected to develop during the afternoon and continue into at least the early evening. The strongest cells/clusters will be capable of producing isolated hail and strong to severe gusts. ...Parts of the Upper Midwest/Great Lakes... Multiple low-amplitude midlevel vorticity maxima may move southeastward across parts of the Upper Midwest/Great Lakes through early evening, before a stronger shortwave trough approaches the region by late Friday night. A frontal zone initially draped from northern IL/IN into northern MN will begin to shift northward as a warm front, while a cold front will move through parts of the Dakotas and northwest MN. Diurnal heating may be somewhat muted due to the effects of smoke, but increasing low-level moisture will support moderate destabilization. Moderate midlevel northwesterly flow will provide sufficient deep-layer shear for storm organization. Details of storm development and evolution remain uncertain across this region, However, isolated surface-based development will be possible near the cold front and effective warm front during the afternoon/evening, and one or more elevated clusters may continue into Friday night. There is a sufficient signal for storm development within a relatively favorable environment for the addition of 5% severe probabilities, though some adjustment will likely be needed in subsequent updates. ...Parts of the Southeast...southern Appalachians...Ohio Valley... Scattered to numerous thunderstorms are expected to develop Friday afternoon, within a moist, moderately unstable, and weakly capped environment. Localized downburst winds could occur within this environment, though deep-layer flow/shear appears too weak to support an organized severe threat. ..Dean.. 07/15/2026 NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
Updated: Wed Jul 15 19:28:46 UTC 2026 (
