What Happened to Saturday’s Snow?

Waking Up... You May Have Noticed A Lack of Snow...

Waking up Saturday, you might have noticed that there wasn’t a lot of heavy snow falling across the Sioux Empire. Even though a Colorado Low was moving through the KDLT forecast area, and the KDLT meteorologists had been forecasting heavy snow, it wasn’t there. That might have you asking why? The answer laid to our southeast.

Wednesday AM Futurecast Showing Heavy Snow on Saturday

Early last week, our long range models started to pick up on a strong low pressure system, known as a Colorado Low, developing Friday and pushing through southeastern parts of the forecast area on Saturday. The low was expected to become more organized throughout the day. With this low being a Colorado Low, heavy snow was expected across southeastern parts of the forecast area. Early last week, we wrote a blog about what we were anticipating as two rounds of snow, including this second round, grew near. As the day of the event got closer, our short range models, the North American Model (NAM) and the Rapid Refresh (RAP), picked up on the low. However, the short range models showed a different scenario than what the longer range GFS and EURO showed. As Saturday grew near, both the NAM and the RAP, and eventually later runs of the GFS and EURO, showed less intense snow across the forecast area. What were they picking up on that they hadn’t previously seen?

MSLP on Saturday Afternoon (2/24) between the GFS (right) and NAM (left)

The atmosphere likes to be in balance, neutral if you will. For example, after heating up throughout the morning and early afternoon hours, storms, sometimes strong, develop and use up all that energy to reset the atmosphere. Another example is after a strong low pressure system moves through an area, an equally strong high pressure system moves overhead. On Saturday, the atmosphere was unbalanced across portions of the Mississippi and Ohio River Valley. As a result moisture from our area was going to be transported to the south to create balance.

Four days before Saturday’s snow, the Storm Prediction Center (SPC) was eyeing an area extending from portions of northeast Texas into the Ohio River Valley that could see severe weather on the 24th. Meteorologists were calling for a line of strong storms to develop along a cold front, strong vertical shear along with deep amplification (allowing for strong storms to develop), and the low pressure system taking more of a negative tilt in the upper layers. A negatively tilted trough allows for strong shear, or turning in the atmosphere, which increases instability and indicates that the low has reached maturity. That was four days out (left image below), which meant that there were still some uncertainties about how Saturday would play out, but that was an area of concern.

The Day One Convective Outlook (image on the right above) showed a wide area that could see severe weather, along with an area that was especially under the threat. The area within the enhanced risk. Forecasters at SPC were still forecasting a negatively tilted trough along with strong storms to develop in the afternoon. Around 9am Saturday, a large cluster of storms had developed across portions of Missouri and Arkansas. The cluster of storms pushed to the east which did not limit the convective potential ahead of the storms, in parts of the enhanced risk. However, the large area of storms was using moisture that would have otherwise been used for snow production back at home.

Satellite and Radar Saturday Morning, 2/24

As we said, the morning storms did not limit convection and severe storms developed later in the afternoon and evening across the south. Unfortunately, three people lost their lives, and several more were injured, as a result of the powerful storms. The strongest tornadoes recorded were several EF-2 tornadoes. There were also a number of wind reports found along the eastward moving cold front, and a handful of hail reports found in Texas, based on preliminary reports.

Preliminary Storm Reports from Storm Prediction Center

Although some of us were hoping for larger snow amounts over the weekend, like Joe, parts of the Sioux Empire did pick up a couple inches, which even set new records. Aberdeen and Sisseton set new records for accumulating 4.90″ in Aberdeen and nearly 7.50″ in Sisseton. Other totals included 3.50″ in Watertown, around 3.00″ in Brookings, 4.50″ in Huron, 1.50″ in Mobridge, 1.60″ in Sioux Falls and 3.50″ in Marshall. Friday morning we had made two snowfall accumulation graphics. One where the storms started later in the day and the other with the storms starting early in the day. Unfortunately, or fortunately depending on who you ask, the latter came true.

Two Snowfall Scenarios Explained Friday Morning, 2/23

Interactive Snowfall Accumulation Map via National Weather Service Aberdeen

Blaise Keller
KDLT News Morning Meteorologist
Twitter – @blaisekellerr

Categories: Weather, Weather Blog