There will likely be scattered thunderstorms in the area today into tonight, plus some additional rainfall, particularly in southwestern North Dakota on Saturday. Yet, overall this next week is expected to be fairly dry. The exceptions will be the localized spots that get a direct hit from a thunderstorm today, but the odds are that most locations will not record all that much precipitation during this period. The one weather element that will impact all of us will be cooler temperatures for the next several days.
It will still be seasonally mild today, but the scattered thunderstorms that are expected are associated with, what should be, a very noticable cold front. A ridge of high pressure aloft is developing over the Pacific Northwest and in turn a sharp trough will be developing over the northcentral portion of the United States this weekend. This will bring into the northern plains some of the coolest air since May. Some portion of North Dakota is expected to record maximums in the 60s and minimums in the 40s on Friday through Sunday and far eastern North Dakota and/or northwestern Minnesota may experience those types of temperatures even on Monday. Because this cooler air will be impacting different locations on differing days, not all areas will be this chilly on each day, but a true taste of autumn weather is expected in the short term. Some warmer temperatures will temporarily return next week.
Current indications are that this warmer air mass will only last a couple of days and by the end of next week, the cooler air will be returning. In fact, it appears that there will be more below average days than above average days during the second half of August. On a negative note, this will limit the number of growing degree days for the next couuple of weeks, but on the positive side, this Canadian air mass is not only cool, but dry, which will limit the number of days with muggy conditions, meaning fewer hours with high relative humidity (RH).
The projected growing degree days (GDDs) for base temperatures of 32°, 44° and 50° are presented in Figure 1. The estimated hours with RH above 85% is presented in Figure 2.