A look at the surface analysis shows a strong area of low pressure currently in Wyoming moving to the northeast. The word strong and low pressure at the end of July is almost an oxymoron as usually low pressure centers this time of year are fairly weak. But this is an impressive storm for this time of year in terms of surface pressure. This storm will have a noticeable impact on the weather in the northern plains over the next three days.
Today, the main impact on the weather will be redevelopment of thunderstorms in western and central North Dakota that will then move east and impact a high percentage of the state.
The High Resolution Rapid Refresh Computer guidance above has a simulation of possible radar returns through the day. Storms developing late afternoon that will then move easterly. The storms will be in western and central North Dakota this evening, then move into the Red River Valley and then through Minnesota mostly after midnight.
With dew points projected to be near or above 70 degrees today, before the storms form it will be a warm and humid day by North Dakota and northwestern Minnesota standards. But the abundant low level moisture will mean localized 1 inch plus rain amounts in localized areas as the storm move overhead.
The thunderstorms that do develop today will likely have some severe weather associated with it. The Storm Prediction Center has a Slight Risk of Severe in eastern North Dakota into far western Minnesota and an Enhanced Risk in western North Dakota.
Once the storms pass through the Red River Valley late tonight and shift east, the eastern part of North Dakota into northwestern Minnesota will likely get into the “dry slot” of this strong summer storm. Meaning, a dry, albeit windy Tuesday (West at 20-35 mph), cooler and far less humid with maximum temperatures in the upper 70s to around 80 degrees.
But western North Dakota and Montana will be in the “comma head” of the storm and have a very cool (for late July) day with rain.
Estimated rainfall of 1 to 2 inches with higher amounts possible, especially in parts of Montana to near far western North Dakota, with widely varying totals with the thunderstorms across the rest of the region.
The rain in Montana will be especially welcomed, as will, probably the temporary relief from the heat.
The next 30 hours will bring the main threat of rain this week. It appears toward the end of the week and the weekend there will be at least some spotty activity in typical summer fashion, but this looks to be the main widespread event. Temperatures will be near seasonal averages the rest of the week, with perhaps a brief warmup on Thursday and Saturday, but no long duration “heat” is expected. Sunday through early next week is looking seasonally “chilly”, so the over all trend after today will be for more “cooler” days than “warmer” days as we move into August.