The ridge of high pressure that has been over the southwestern portion of the United States has now shifted farther to the east and has brought some very warm temperatures to the southern plains. For our region, this adjustment in the upper level wind flow will allow a trough of low pressure to form over the Pacific Northwest. This often leads to a more active pattern in the northern plains and that appears to be the case with several rounds of precipitation projected in the next seven days.
The first round of storms (scattered) should be occurring as you read this (Thursday) with more development expected Thursday evening and night as well. After some cooler temperatures as of late, once this first wave of thunderstorms moves through the region, warmer temperatures are expected to return this weekend into early next week. Those warmer temperatures in combination with a much stronger storm system should produce both more widespread rain and higher precipitation totals than what is expected for the first wave today. Plus, that second storm system will send multiple disturbances through the area meaning that at least some part of North Dakota and/or northwestern Minnesota is expected to receive precipitation from Saturday through next Tuesday. The main wave of rain and therefore the period of time with the most storms looks to be Sunday Night through Tuesday morning. As is usually the case, rainfall amounts will vary greatly, but the widespread dry areas will at least have some opportunities for rain that has been lacking in the past few weeks. Yet, this will also mean that the excessively wet locations in northeastern North Dakota and far northwestern Minnesota will likely record at least some rain as well. Specifics in thunderstorms are very difficult to pinpoint beyond a few hours.
Estimated relative humidity (RH) hours are given in Figure 1. With an increase in rain foreseen, plus higher dew points leading to an increase risk of prolong dew on plants during the overnight hours, RH hours above 85% will probably be greater than projected in locations that record the higher rainfall totals. The projected Growing Degree Days (GDDs), base 32°, 44° and 50° for the period July 7 through July 13, 2016 are presented in Figure 2. Although this seven day period starts cool, with the temperatures expected to be a bit above average this weekend into early next week, GDDs should overall be near average for the middle of July.