Day 4-8 Convective Outlook
Issued: · Valid: –
Summary
Severe storms are possible across parts of the northern and central Plains and the Mid-Missouri Valley on Sunday, with the potential for more widespread severe weather moving into the Mississippi and Upper Great Lakes valleys on Monday.
Product Text
000 ACUS48 KWNS 090729 SWOD48 SPC AC 090727 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Wed Sep 09 2026 Valid 121200Z - 171200Z ...DISCUSSION... ...Day 4/Sat - Central Plains... A cold front will stall across the central Plains on Saturday. Low-level east/southeasterly flow will maintain rich boundary layer moisture across KS and into eastern CO. Early day convection may be ongoing in the vicinity of the stalled boundary within the low-level warm advection regime. It is uncertain if airmass recovery and renewed thunderstorm development will occur within the unstable warm sector given nebulous large-scale ascent and modest vertical shear. While low severe potential may eventually evolve, probability appears less than 15 percent at this time. ...Days 5-6/Sun-Mon -- Central Plains to the Great Lakes... An upper trough is forecast to move from the northern Rockies to the Great Lakes through early Day 7/Tuesday. This will bring enhanced southwesterly flow to portions of the northern/central Plains into the Great Lakes, particularly on Monday. With the approach of the trough, lee low development is forecast across the northern/central High Plains on Sunday. Increasing southerly low-level flow will transport moisture northward to NE/SD ahead of a southeastward-advancing cold front. This could support some severe risk across parts of the northern/central Plains and Mid-MO Valley vicinity on Sunday. However, large spread exists among forecast guidance with regards to the surface low placement, northward extent of moisture return, and frontal position. As a result, corridors of greater severe potential are uncertain on Sunday. As the upper trough continues to lift east/northeast through the Great Lakes on Monday, severe potential could develop eastward into parts of the Mid/Upper MS Valley and upper Great Lakes vicinity. Stronger deep-layer flow may become displaced to the north of better instability, and similarly large model spread continues into this time frame. Depending on trends, severe probabilities could eventually be needed for Sunday and/or Monday. ...Days 7-8/Tue-Wed... Lower amplitude, quasi-zonal flow is expected to develop by the end of the forecast period as the early-week uppers shortwave trough lifts into eastern Canada and the sub-tropical high begins to rebuild over the southern U.S. This should largely limit severe potential, though abundant moisture will reside from the southern Plains into the Southeast and Mid-Atlantic and daily sporadic strong storms could still occur. ..Leitman.. 09/09/2026