Winter/spring 2012 weather outlook

Dec 30, 2011
by WLJ

As we enter winter, farmers and ranchers are wondering whether the fall’s climate trends are going to continue and which regions of the country are susceptible to production problems in 2012. This is the second consecutive winter with La Ni a conditions in the Equatorial Pacific and there appear to be as many dissimilarities as similarities to the same time in 2011, according to climatologists at the University of Nebraska.

EC = Equal chances of above, below or normal activity B = Below normal activity N = Normal activity A = Above

During fall 2011, drought began to rapidly develop across the southern U.S. Texas bore the brunt of drought which developed into one of, if not, the worst agricultural disasters in history. This drought has now expanded northward and includes Oklahoma and the southern two-thirds of Kansas.

In contrast, the eastern Corn Belt was extremely wet from fall 2010 to spring 2011, leading to planting delays and poor root development. The shallow rooting depth left crops vulnerable to dry conditions during the summer, resulting in significant production declines from Illinois east through Ohio. This fall, excessively wet conditions redeveloped and are forecast to continue into spring.

The northern and western Corn Belt turned excessive ly dry during late August through mid-November. This mostly duplicated conditions a year earlier, with one exception, heavy rainfall that dropped up to 7 inches of moisture across southern Minnesota and northern Iowa in fall 2010 wasn’t repeated this year. A broad area of southern Minnesota, northeast Nebraska, eastern South Dakota and northwest Iowa has received less than a quarter of its normal precipitation during the past 90 days.

This fall, the Dakotas didn’t receive the abundance of snow they did in early 2011 when record runoff led to flooding in the Missouri River Basin. At this point, many locations across eastern Montana and western North Dakota have not received 2 inches of snow this winter. By this time last winter, 20-plus inches of snow was the norm and the average snow depth ranged from 10 to 20 inches.

With the redevelopment of La Ni a conditions this fall, there was considerable banter between climatologists as to whether 2011 winter trends would return in force this winter. So far, the answer is no. First and foremost, equatorial sea surface departures are averaging about 1.5 C below normal, while last year, the basin was nearly 3 C below normal. The current La Ni a is rated as a weak to moderate event, compared to last year’s rating of exceptionally strong.

Because La Ni a was so strong last year, the northern jet stream was especially active and winter storm activity was concentrated across the northern and north-central Rockies eastward through the Great Lakes and northeast. In the last 30-45 days, the jet stream has tended toward a split flow pattern with a portion of the energy moving into the northern Rockies and northern Plains and the remaining energy diving down into the southwest and the southern Great Basin.

What does this really mean? Essentially, the upper air lows moving across Texas are keeping moisture from moving north into the northern Plains. As a result, the upper Plains moisture patterns will depend on moisture from the Pacific Ocean rather than the Gulf of Mexico.

Three-month forecasts

The latest Climate Prediction Center forecast for January-March indicates above normal temperatures for the southern Plains, extending north to the extreme southeastern Nebraska. The precipitation forecast indicates below normal moisture for the southern Plains, extending north to the Kansas- Nebraska border, and moisture for the northern Rockies and eastern Corn Belt.

Nebraska precipitation forecasts for February-April and March-May are more worrisome. Below normal moisture should cover the southern and central Plains region, extending north to include much of Nebraska. This scenario would suggest that the northern Plains dryness is not likely to disappear until April or later.

Nebraska climate data also suggests drier than normal moisture (less than 50 percent of normal) in February and March.

It also suggests that the eastern Corn Belt will remain wet and flooding and/ or planting delays likely will occur this spring in the Ohio and mid-Mississippi River valleys. The current snow pack is rated normal to below normal in the headwater region of the Platte and Missouri watersheds because most of the recent snows have been across the southern Rockies.

There is enough reservoir storage space in these two watersheds to handle normal to slightly above normal snowfall without major floods; however, if snowstorms pick up, this could change. — University of Nebraska