Spring Outlook for the Sioux Empire

Spring Started Over 2 Weeks Ago... So What Can We Expect For Spring?

March 20th marked the start of Spring which was, believe it or not, over 2 weeks ago. Instead of seeing our first 70 degree day, the Sioux Empire continued to see not only cooler than normal temperatures but snow as well. Now that Spring has officially begun, what does the outlook look like for Spring (March 20th through June 21st)? We’ll look take a look at the temperature and precipitation outlook is and any other weather phenomenons that could potentially effect our Spring.

Let’s first take a look at what our temperatures are expected to look like as we go into the rest of April and then the rest of Spring. According to our friends at the Climate Prediction Center, temperatures are expected to remain cooler than normal throughout the month of April across much of the Northern Plains (shown below). Meteorologists have also been looking at long range models, specifically the CFS otherwise known as the Climate Forecast System. Predominantly used by NCEP (National Centers for Environmental Prediction) the CFS is run once a day by NCEP for different time lengths; the shortest forecast time overlaps or is equivalent to the same time length as the GFS (which goes out 16 days) while the longest forecast time 3 months out. Over the last 9 runs of the CFS, and for each forecasted time length, the Northern Plains have consistently been underneath cooler than normal air. This cooler than normal air trend looks to linger throughout April, May and June but the cooler air isn’t expected to be as far south. Further down in the blog, it’s explained why.

Another reason why the Northern Plains will see cooler than normal air is because Madden-Julian Oscillation (MJO) located well off to our South, along the Equator. Taken from the NOAA website, “Tropical rainfall exhibits strong variability on time scales shorter than the seasonal El Nino-Southern Oscillation (ENSO). These fluctuations in tropical rainfall often go through an entire cycle in 30-60 days, and are referred to as the Madden-Julian Oscillation or intraseasonal oscillations. The intraseasonal oscillations are a naturally occurring component of our coupled ocean-atmosphere system. They significantly affect the atmospheric circulation throughout the global Tropics and subtropics, and also strongly affect the wintertime jet stream and atmospheric circulation features over the North Pacific and western North America. As a result, they have an important impact on storminess and temperatures over the United States.” You can see a visual, provided by the National Weather Service Boulder office, of what the MJO is below.

Current conditions show more convection, or thunderstorm activity, over western portions of the Pacific and it’s expected to continue into western parts of Africa into the second week of April. That uptick in thunderstorm activity means that much of the northern CONUS (Continental United States) will experience cooler than normal temperatures. In fact, those temperatures are expected to be between 10 and 25 degrees below normal.

However, as I talked about in a previous blog the La Nina setup in the Pacific is expected break down through March to May and return to neutral phase ENSO. Over the last two weeks, sea-surface temperatures across eastern portions of the Pacific have been warming by about 1-3°C. During neutral phase, sea surface temperatures, atmospheric winds as well as tropical rainfall typically are close averages seen over the long term. As stated in an earlier blog, forecasts suggest that ENSO will remain in neutral-phase through the second half of the year. An update on the fading La Nina and the forecast moving forward will be made available on April 12th.

Precipitation wise, what can the Sioux Empire expect over the Spring months? Even though parts of the Northern Plains, including central and western South Dakota, still are underneath drought conditions (the worst being severe drought conditions just west of the Missouri River) the Sioux Empire also needs to dry out and allow that moisture to soak into the ground before receiving another round of rain/snow. Unfortunately, as we go further into Spring, especially April, it looks as though there’s going to be an increased chance for precipitation. This is most likely due to the jetstream still in a La Nina type set up with a ridge over the west coast and a trough located to our southeast. Temperatures will play a huge factor in what type of precipitation we do receive as well as where the low pressure system originates and move through; if the low originates from the southwest and moves into the forecast area, it’ll most likely have more moisture to use/fall versus a low pressure system that originated to our northwest.

Though severe weather activity does start to pick up until early May, during the month of April the KDLT forecast area starts to see severe weather begin. Though the number of events are small, a few tornadoes are possible during the month of April whereas hail events are much more frequent… almost 8 times more frequent in fact. In May, as stated earlier, the severe weather activity really starts to pick up as more energy (CAPE) and warmth air move out of south and sit overhead. So we’ll have to wait and see if conditions improve for severe weather going into April and May until then… we’ll have to deal with cooler than normal temperatures. Normal day time high temperatures will start to increase though; from the 50s in April to the 70s by the time we go into mid/late June.

Blaise Keller
KDLT News Morning Meteorologist
Twitter – @blaisekellerr

Categories: Weather, Weather Blog