Crop Concerns Due to Spring Weather - UNL CropWatch, May 20, 2011
May 30, 2011
The intense temperature swings this spring have led to concerns about abnormally cool soil temperatures inhibiting planting and crop emergence. A May 17 review of soil temperature data from the High Plains Regional Climate Center indicates most locations have seven-day average soil temperatures running just 1-2°F below the long-term averages.
1- and 3-Month Temperature and Precipitation Outlooks
For all maps EC means equal chances of above normal, normal, or below normal values; A means above normal; N means normal; and B means below normal chances. (Source: National Weather Service Climate Prediction Center.)
Figure 1. June 2011 temperature probability.
Figure 2. June 2011 precipitation probability.
Figure 3. Three-month temperature probability for June, July, and August.
Figure 4. Three-month precipitation probability for June, July, and August.
Although there have been large fluctuations in daily soil temperatures in the past month, the seven-day averages smooth out much of this variability. We need to remember that even with the recent cool weather, daily highs were well into the 80s and 90s last week and that has offset the last few days of below normal temperatures.
Information from the Nebraska Agricultural Statistics Service indicates that corn emergence is one to two days behind normal at most locations and soybean emergence is two to three days behind normal due to the recent cool weather. With several days of high temperatures of 70°F or more, the crop could easily catch up to normal.
Whether the crop falls further behind normal is highly dependent on how heat or cold develops during the next 30 days. We track crop status by using Growing Degree Day unit accumulations. The standard equation for warm season crops uses an upper threshold of 86°F and a lower threshold of 50°F. By mid-June our normal daily high temperatures will approach 86°F and the only way to accumulate above normal units is for minimum temperatures to be above normal.
It is not until late August when the average daily high drops below 86°F that we have an opportunity to significantly cut into accumulated deficits, if they exist.
Recent atmospheric trends have seen upper air lows ejecting out of the Gulf of Alaska into the central Rockies, then slowly moving through the central Plains. In advance of these systems, above normal temperatures are common before moving to below normal conditions under the influence of extensive cloud cover and rain.
It appears this trend will continue through the next several weeks, increasing chances for above normal moisture and severe weather outbreaks. As we move into the early summer, these upper air lows will gradually weaken and shift north.
There are early signs that this may begin as an upper air ridge is attempting to develop over the central Canadien Prairie Province region. As the surfaces in Canada heat up, this upper air high should strengthen. If the Gulf of Alaska lows are unable to cut underneath of this blocking high, then the Southern Plains dryness will move northward. If these lows continue to undercut the blocking high, as has been the recent trend, then above normal moisture will continue well into the growing season.
The latest 30-day and 90-day outlooks (Figures 1-4) issued by the Climate Prediction Center on May 19 indicate a tendency for below normal temperatures for the northeastern third of Nebraska with equal chances of above normal, normal, or below normal temperatures for the remainder of the state. Precipitation is expected to trend toward above normal across extreme northern Nebraska and most of the Dakotas. The remainder of Nebraska has equal chances for above normal, normal, or below normal precipitation.
The 90-day forecast shifts the below normal temperatures east of the state to cover much of upper and mid Mississippi valley region. The only area of below normal moisture is across the Pacific Northwest. No trends for temperatures and precipitation is indicated for Nebraska so there are equal chances of receiving above normal, normal, or below normal temperatures and precipitation during the June-August period.
Extension State Climatologist