April 24, 2013

What a difference a year makes. One year ago we were basking in a second consecutive month of abnormally warm weather that promoted rapid planting across the state. This year, April temperatures are more reminiscent of conditions we typically experience in March. As of April 21, less than 1% of the corn crop had been planted, compared to the five-year average of 12%.

Figure 1 indicates that the first three weeks of April have been exceptionally cold with average temperatures more than 8 degrees (Fahrenheit) below normal across the northern third of the state. Temperatures 4-8 degrees below normal are common across southern Nebraska. These cold temperatures have dramatically extended vegetative dormancy in trees and resulted in minimal growth of cool season grasses. It is likely that April 2013 will be one of the top five coldest on record dating back to 1895.

Precipitation has been nothing short of remarkable across eastern Nebraska (Figures 2 and 3). Liquid equivalent moisture exceeded 2.5 inches for the eastern third of the state, with portions of northeast and southeast Nebraska receiving over 5 inches. Moisture totals for the western two-thirds of the state generally ranged from 1-3 inches outside of a small pocket of west central Nebraska where 0.50-1.00 inch was reported.

Only the southwestern Sandhills and western half of the southwest climate district experienced below normal moisture through April 23. Surplus moisture of 1.5-3.5 inches was common across eastern Nebraska, with 0.75-1.50 inches across central Nebraska and the Panhandle. The combination of cold temperatures and abundant moisture has helped recharge surface moisture across the state.

The High Plains Regional Climate Center soil moisture monitoring network indicates that field capacity has been reached at the 4-foot level at Beatrice and Falls City. Soil moisture has reached field capacity at the 2-foot level for most areas east of a line from Hastings to Yankton, South Dakota; however, little if any response has been noted at the 4-foot depth. Central and western Nebraska have reached field capacity at the 1-foot depth and most stations are nearing field capacity at the 2-foot depth.

Snowpack Effect

The central Rocky Mountain snowpack has also responded to the cold, wet April with a dramatic jump in snow depth during the past three weeks. The upper Platte River basin which feeds snow melt into Seminoe and Pathfinder reservoirs jumped to 95-100% of normal. The lower North Platte basin which flows into Glendo Reservoir and Lake McConaughy jumped up to 85-90% of normal.

Runoff estimates have likely increased from 60% of normal flow on April 1 to 75-80% of normal on April 19.
The snowpack increase is welcome news, but ultimately the snow melt and longevity of the snowpack will be determined by air temperature and subsequent storm systems. If additional storm systems hit the central Rockies during May, snowpack will likely remain into June. If temperatures remain above normal and storms bypass this region, the snowpack could easily disappear before the end of May.

Forecast: Warmer Temps and Scattered Showers

Forecast models strongly hint that the exceptionally cold temperatures experienced during April will finally break with temperatures soaring into the 70s to end the month. A few pockets of low 80s are entirely possible across portions of southern Nebraska by this Sunday. If wind forecasts are correct, sufficient soil drying should occur to provide near term planting opportunities.

Weather models indicate that a frontal system will slide through the state April 30 - May 1 and generate scattered showers and isolated thunderstorms across western Nebraska and more widespread thunderstorm activity across eastern Nebraska. Models indicate a moderate possibility of a severe weather outbreak. If the models verify, we may see planting delays lasting two to four days. Current models indicate another extended period of dry weather following this event.

Producers to the north and east are not so fortunate This week Iowa reported topsoil moisture that was 31% surplus, 60% adequate, and 9% short to very short and subsoil moisture levels that were 14% very short, 32% short, 48% adequate, and 6% surplus. Illinois reported topsoil moisture at 35% adequate and 65% surplus with subsoil moisture rated at 5% short, 68% adequate, and 27% surplus. Nebraska reported topsoil moisture that was 10% very short, 31% short, 56% adequate, and 3% surplus. Subsoil moisture was rated at 49% very short, 41% short, 10% adequate, and 0% surplus.

Al Dutcher
Extension State Climatologist