Dennis Todey, South Dakota's state meteorologist, says the lack of precipitation during the fall over most of the state, particularly the eastern quarter, has left soils very dry and in need of moisture recharge in the spring.
Large parts of the east and northwest have received less than 50% of average precipitation during the critical soil moisture recharge period, he says. This will leave soils several inches short of moisture starting the spring.
"The US Drought Monitor map reflects this issue with much of the east and northwest in some level of moisture shortage. The worst is reflected in the east central where mid-late summer dryness added to the fall shortfall has placed areas in a D2 – Severe Drought situation," Todey says.
NOAA recently released winter outlook indicating increased chances for below average temperatures and increased chances of above average precipitation over South Dakota due a resurgence of La Nina – cooling of waters along the equatorial Pacific, Todey says.
"One thing to remember is that these outlooks are based on probabilities indicating chances of temperature and precipitation conditions. For example on temperature, northeast SD has a better than 40% chance of being below average temperature. That leaves about a 33% chance of being near average and a 27% chance of being above average. Because of volatility in the system, outlooks cannot be overly specific in the chances."
While the indications are for above average chances for precipitation across the northern tier of states, this volatility is one reason NOAA mentions a wildcard, according to Todey.
"How this other wildcard, called the Arctic Oscillation (AO), behaves can greatly influence conditions. The AO cannot be forecast more than a few weeks in advance introducing more of the uncertainty in the outlooks," he says. "While the outlooks indicate above average chances for precipitation there are several differences from last year. These include pre-existing conditions of the soil. Much of the state is going in to winter with much drier soils than we have seen in some time. Another factor is a difference in the forecast strength of the La Nina, predicted to be weaker than last year."
"There are several extreme stories about forecast precipitation amounts for the winter," Todey continues. "While above average chances for precipitation are likely, these extreme amounts should be viewed somewhat skeptically as the severity of winter is difficult to be determined specifically at this point in the year."Source: SDSU