Crop and Pest Report Forecast

Maximum temperatures may vary by as much as 30 degrees over the course of the next 7 days.  Today through Saturday the heat that began on Tuesday will continue to be the dominate weather issue.  Although a few locations did record some precipitation Wednesday Night and others this morning, the heat during the next few days will bring little if any moisture as a large ridge of high pressure in the upper atmosphere is expected to keep the storms north and east of North Dakota (Figure 1).

Figure 1. Projected 500 mb (~18,000 feet) Heights/Anomalies from average for Friday, August 14 at 7:00 PM.  Used by Permission of Weatherbell Analytics

Figure 1. Projected 500 mb (~18,000 feet) Heights/Anomalies from average for Friday, August 14 at 7:00 PM. Used by Permission of Weatherbell Analytics

Perhaps the warmest temperatures of 2015 will be recorded during this period with maximums in the 90s with some locations in the low 100s in western North Dakota.  This high heat will mostly come with tolerable dew points (50s and 60s) meaning extremely humid conditions are not expected allowing for some evaporate cooling potential that will offer some heat stress relief for cattle (and humans) and limiting the hours of relative humidity above 85% for disease potential on plants (Figure 4 below).

The well above average temperatures will exasperate the moisture stress already present in many areas, but the heat will come to a quick end on Saturday as a cold front sweeps through the northern plains.   Not only will the front bring cooler temperatures to the region, but also the potential for widespread thunderstorms on Saturday into Saturday Night.  Although there will probably be some severe weather associated with the changeover from well above to below average temperatures, it will bring the best chance of rainfall to the region until the middle of next week.

Temperatures are projected to average between 10 to 15 degrees above normal through Saturday, then behind the cold front from temperatures may be as much as 10 to 15 degrees below normal.  The strong ridge of high pressure currently in place will be replaced by an equally strong, if not stronger, trough of low pressure by the middle of next week (Figure 2).  Maximum temperatures may only reach the mid to upper 60s for some locations for a couple of days during that time period.  Plus, that upper level wind change may induce a storm to form and travel through North Dakota later on Tuesday into Wednesday that would enhance the cooler air that will already be in place.

Figure 2 Projected 500 mb (~18,000 feet) Heights/Anomalies for Wednesday, August 19, 2015 at 7:00 PM.  Used by Permission of WeatherBell Analytics

Figure 2 Projected 500 mb (~18,000 feet) Heights/Anomalies for Wednesday, August 19, 2015 at 7:00 PM. Used by Permission of WeatherBell Analytics

The projected Growing Degree Days (GDDs), base 34°, 44° and 50° for the period August 13 through August 19, 2015 are presented in Figure 3 and the number of hours when the relative humidity is expected to be at or above 85% can be found in Figure 4.

Figure 2. Projected Growing Degree Days from August 13 through August 19, 2015

Figure 2. Projected Growing Degree Days from August 13 through August 19, 2015

 

Figure 3. Projected Hours at/above 85% Relative Humidity from August 13 through August 19, 2015

Figure 3. Projected Hours at/above 85% Relative Humidity from August 13 through August 19, 2015

 

Daryl Ritchison