Day 3 Convective Outlook
Issued: · Valid: –
Summary
Widely scattered thunderstorms are possible across the Upper Midwest through the Mid-Atlantic region on Friday, though organized severe weather is not currently expected. Additional thunderstorms may develop along a cold front across the Upper Great Lakes from late Friday into early Saturday.
Product Text
000 ACUS03 KWNS 150732 SWODY3 SPC AC 150730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Wed Jul 15 2026 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible across much of the country on Friday. Although a few strong storms may occur, areas of organized severe weather are not currently forecast. ... Synopsis ... Enhanced mid-level flow will persist across the Pacific Northwest and the Great Lakes/Northeast US along the periphery of a large mid-level anticyclone centered across the central US. Across the Northwest, strong southwesterly mid-level flow and embedded vorticity/speed maxima will contribute to shower and thunderstorm development during Friday afternoon and evening. Farther east, northwesterly mid-level flow will be in place across the Upper Midwest into the Mid-Atlantic and Northeast regions. A strong trough will be departing the Northeast at the start of the forecast period, and several smaller mid-level waves will be traversing the enhanced mid-level flow during the day. A stronger mid-level wave is forecast to approach the Upper Great Lakes overnight Friday into Saturday. At the surface, a residual synoptic boundary will stretch from the Upper Peninsula of Michigan southeast toward the vicinity of Washington D.C. early on Friday. By late morning, this boundary will begin lifting northeast across the Great Lakes region in response to the approaching mid-level trough. Farther southeast, this boundary will still be slowly sagging southward during the morning before stalling during the afternoon and quickly lifting northeast during Friday night into Saturday morning. A weak surface low will develop along this boundary across northern Minnesota by Friday morning. This low will slowly move east-southeast during the day, dragging a secondary cold front southeast across the Dakotas and into Wisconsin/southern Minnesota by Saturday morning. ... Upper Midwest southeast into the Mid-Atlantic ... Subtle/small vorticity maxima moving through the mid-level flow will yield modest large-scale ascent along portions of the frontal boundary. Strong diurnal heating of the moist airmass along and south of the boundary should support at least widely scattered thunderstorms. The surface boundary will be on the southwest fringe of the better mid-level flow, with effective-layer shear being generally less than 30 knots. This should limit any sustained/organized severe threat. One complicating factor/unknown will be the extent smoke plumes from northern Minnesota are advected into/across the region and their density. A thicker smoke plume may limit the degree of surface heating and impact the overall number of thunderstorms. There is a secondary potential for thunderstorms to develop along the secondary cold front late Friday into early Saturday as stronger large-scale ascent overspreads the Upper Great Lakes. The uncertainty as to whether this convection will be able to produce severe weather is quite large owing to the impacts of both smoke plumes and the cooler waters of Lake Superior. At this time the uncertainty associated with afternoon convection and the overnight convection is too great to introduce unconditional severe weather probabilities with this outlook, however, this region will be evaluated further with subsequent forecasts. ..Marsh.. 07/15/2026 $$