Trading Highs for Lows...Explaining An Uncommon Setup
by Angela Schilling, Meteorologist
January 14, 2012 9:06 PM
This has for sure been an odd last few months with temperatures starting off the winter season well above average. Over the last couple of days we have also seen an unusual set up as far as lows are concerned. Typically you reach your low temperature in the morning, around 7am. Friday night into Saturday morning temperatures rose throughout the night instead of dropping. During the day the sun heats the surface and during the night the heat escapes through long wave radiation. Clouds can act as a blanket and keep us from cooling off overnight, high winds can do the same. Friday night we did have quite a bit of cloud cover in place, but as warm air continued to build in from the west temperatures actually rose instead of dropping or staying put.
The image below shows a timeline of temperatures over the past 24 hours or so. Notice how we reached our low in Sioux Falls around 2am and then continued to warm as the night went on. What’s odd about Friday night is how we randomly dropped around four degrees to reach our low set at 2am and then jumped another 4 degrees in the opposite direction the following hour.
Many locations throughout the region started the first half of the weekend well above average with temperatures in the 20’s but had lows closer to average, into the teens…but keep in mind they were set around 2am.
Temperatures continued to warm throughout the afternoon on Saturday with many of us reaching the upper 30’s and lower 40’s. In 2011, the warmest temperature we saw in Sioux Falls during the month of January was 39. We’re expecting a similar set up Saturday evening with overnight lows being set around 2am and temperatures rising well into the morning. The image below is a real time map from 8:30pm Saturday and shows warmer air in western South Dakota. The lines represent temperatures found just above the surface, at around 850mb…the lines in red show the warmer temperatures.
As we head into the later half of the weekend highs are expected to be a good 10 to 15 degrees above average. Cold front swings through the I-29 corridor Sunday evening, dropping temperatures closer to average by Tuesday…stay tuned to KDLT and KDLT.com for further updates.