Convective Outlook
— Day 4-8
Day 4 5/Tue Wed Ohio Valley To Mid Atlantic Vicinity ?
An upper trough will pivot across the region on Tuesday and Wednesday, bringing enhanced southerly flow aloft as a surface cold front sweeps east/southeast through Wednesday night. Ahead of the surface front, rich boundary layer moisture will be in place, and at least moderate destabilization should occur. Convection could be ongoing Tuesday morning across parts of IL/IN/Lower MI/western OH. The extent of this activity is unclear and will depend on the evolution of any potential MCS in the Day 3 period. Nevertheless, the downstream airmass across parts of the Ohio Valley will become favorable for scattered severe thunderstorms Tuesday afternoon and evening, likely in the form of one or more line segments organizing ahead of the advancing cold front. An additional area of severe storms will be possible on Tuesday across the Mid-Atlantic within a warm advection regime ahead of the approaching system over the Ohio Valley. Some areas could see more than one round of severe thunderstorms on Tuesday/Tuesday night.
By Wednesday, the severe risk should spread east from the Mid-Atlantic into the Carolinas as the upper trough and surface cold front continue to shift east. It is uncertain how far north the severe risk may extend and probabilities may eventually need to be included across parts of the Northeast/New England. Where storms do form, damaging winds will be possible until the cold front moves offshore Wednesday evening/night.
Days 6 8/Thu Sat ?
Upper troughing will persist across the eastern U.S. through the end of the forecast period, but deep-layer flow will weaken. High pressure in the wake of the cold frontal passage will preclude severe potential across the Ohio Valley into the Mid-Atlantic and Northeast Thursday through Saturday.
Across the Plains and western U.S., a strong upper anticyclone will park over the southern Plains, with an amplified upper ridge building into the northern Rockies. Some thunderstorm potential could develop across parts of the Plains as low-level moisture increases beneath the ridge. However, severe potential is uncertain as any potential would be driven by mesoscale features not well defined at this time frame, and as the upper ridge suppresses any large-scale support for organized severe thunderstorms.
000 ACUS48 KWNS 180759 SWOD48 SPC AC 180757 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0257 AM CDT Sat Jul 18 2026 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4-5/Tue-Wed -- Ohio Valley to Mid-Atlantic Vicinity... An upper trough will pivot across the region on Tuesday and Wednesday, bringing enhanced southerly flow aloft as a surface cold front sweeps east/southeast through Wednesday night. Ahead of the surface front, rich boundary layer moisture will be in place, and at least moderate destabilization should occur. Convection could be ongoing Tuesday morning across parts of IL/IN/Lower MI/western OH. The extent of this activity is unclear and will depend on the evolution of any potential MCS in the Day 3 period. Nevertheless, the downstream airmass across parts of the Ohio Valley will become favorable for scattered severe thunderstorms Tuesday afternoon and evening, likely in the form of one or more line segments organizing ahead of the advancing cold front. An additional area of severe storms will be possible on Tuesday across the Mid-Atlantic within a warm advection regime ahead of the approaching system over the Ohio Valley. Some areas could see more than one round of severe thunderstorms on Tuesday/Tuesday night. By Wednesday, the severe risk should spread east from the Mid-Atlantic into the Carolinas as the upper trough and surface cold front continue to shift east. It is uncertain how far north the severe risk may extend and probabilities may eventually need to be included across parts of the Northeast/New England. Where storms do form, damaging winds will be possible until the cold front moves offshore Wednesday evening/night. ...Days 6-8/Thu-Sat... Upper troughing will persist across the eastern U.S. through the end of the forecast period, but deep-layer flow will weaken. High pressure in the wake of the cold frontal passage will preclude severe potential across the Ohio Valley into the Mid-Atlantic and Northeast Thursday through Saturday. Across the Plains and western U.S., a strong upper anticyclone will park over the southern Plains, with an amplified upper ridge building into the northern Rockies. Some thunderstorm potential could develop across parts of the Plains as low-level moisture increases beneath the ridge. However, severe potential is uncertain as any potential would be driven by mesoscale features not well defined at this time frame, and as the upper ridge suppresses any large-scale support for organized severe thunderstorms. ..Leitman.. 07/18/2026