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KEY MESSAGES

- Isolated to scattered severe storms are possible this evening through early Sunday morning, mainly over southwestern North Dakota.

- Cooler temperatures are forecast today and Sunday, with another chance (40 to 60 percent) for showers and thunderstorms on Sunday.

- Temperatures will trend warmer again through the middle of next week, along with daily chances for showers and storms.

DISCUSSION

Issued at 237 PM CDT Sat Jul 5 2025

As of early this afternoon, a weak shortwave was moving through the mean ridge aloft. This wave has led to a narrow line of diminishing showers across the west with an occasional rumble of thunder south. This activity will continue to diminish over the next couple of hours, giving way to a mostly sunny sky through the rest of the afternoon. Highs will be cooler than the past couple of days, ranging from the mid 70s northwest, to the lower 80s south central and southeast.

Attention then turns to tonight as chances for thunderstorms increase in the evening across the west, especially the southwest. Storms will develop this afternoon across the higher terrain over western and central Montana and then track towards the western North Dakota border. Most of the CAMs suggest an organized line of convection (or multiple lines) approaching the state border in the 00z to 03z Sunday time frame, weakening fairly quickly as the move into North Dakota. Forecast RAP soundings do suggest much weaker instability on the North Dakota side with MUCAPE mainly ranging from 300 to 800 J/kg. That being said, deep layer shear will be strong in the 45 to 55 knot range so a few strong to severe storms cannot be ruled out, especially across the southwest where instability will be maximized. It is important to note that the threat has shifted significantly south and west so there is some possibility that North Dakota will end up seeing little to no severe weather. However, given the impressive shear profile, we will continue to advertise the potential for ping pong ball size hail and damaging winds to 70 mph as a worst case scenario.

Several other little waves will continue moving through the nearly zonal flow aloft through the day on Sunday, keeping chances of showers and storms (40 to 60 percent) in the forecast, mainly early in the day. Once again, shear will be descent (but not as strong as tonight), but instability will be limited. Thus a stronger storm or two cannot be ruled out but severe weather is not anticipated. Sunday will also be cooler, with highs in the upper 60s to upper 70s.

The next wave moves in on Monday as active zonal flow continues. We will see low to medium chances (20 to 40 percent) for showers and storms across much of the west and central with the best chances in the vicinity of the Devils Lake Basin and James River Valley. By the afternoon hours here, some guidance has MLCAPE reaching into the 1000 to 2000 J/kg range with deep layer shear in 45 to 55 knot range. That being said, confidence in stronger instability is rather low given the potential for some ongoing convection, cloud cover, and less than favorable wave timing. A few storms could be strong to severe around the James River Valley if everything falls into place, but the threat appears fairly conditional at the moment.

A more substantial ridge starts to build in Monday night through mid-week, promoting another big warmup. Highs on Monday will range from the mid 70s to the lower 80s and then by Wednesday we will see widespread highs back in the 90s. Another cooldown is then possible by the end of the workweek, but large ensemble spread suggests some pattern uncertainty still. Some more weak waves are forecast to move through the region as the ridge axis pushes east, only leading to low chances (20 to 30 percent) for showers and storms here and there Tuesday night through Friday. CSU Machine Learning severe weather guidance is starting to pick up on some low chances for severe storms in the Wednesday/Thursday time frame but we still have quite a ways to go with plenty of time for things to change.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1226 PM CDT Sat Jul 5 2025

The current showers over western North Dakota should continue to diminish over the next hour or two. Another storm system will bring chances of showers and thunderstorms, mainly to the west in the evening and into portions of the central overnight. Brief MVFR visibilities will be possible under any of the heavier storms as well as gusty and erratic winds. KDIK could also see a period of MVFR ceilings Sunday morning. Precise timing and specific location of thunderstorms remain a bit uncertain so we are relying heavily on PROB30 groups for now.

BIS WATCHES/WARNINGS/ADVISORIES

None.