Frigid Monday... Cold Week
January 21, 2013 8:50 PM
Even though overnight lows were only 10 degrees or so below normal and some 20 or 25 degrees shy of records, it was dangerously cold. With winds topping 30mph overnight, wind chills, or what it feels like outside, dropped to 40 below zero in a few cases. These are the coldest wind chills we have seen in nearly 2 years. So cold in fact, frostbite can occur in less than 10 minutes with exposed skin. The picture to the left has a few of the coldest wind chills found across our area Monday morning.
Actual air temperatures can be very deceiving on a cold and windy day because the stronger the wind, the faster your body heat is released into the atmosphere. This will decrease the amount of time it takes for the body temperature to drop to life threatening levels as well as the amount of time it takes to get frostbite. Because of this phenomenon, wind chill was developed and was given a scale all of us understand… temperature. So even though the lows you see above are cold, they don’t accurately describe the atmosphere when you walk outside. The numbers below however, do just that.
Now THESE numbers are ridiculously low. Not the lowest South Dakota has ever experienced, but not far off in some locations with wind chills in the northeast exceeding 40 below zero. The low temperatures Monday morning were also no where close to record setting, however but much like the wind chills, they are some of the coldest readings we have seen in a while. The coldest high temp in nearly 2 years in Sioux Falls, and the coldest high temp in over 4 years in the Twin Cities.
Here’s the good news for those that don’t like the bitter cold… temperatures will be on the rise over the next few days. However, in most cases, they will stay below average until the end of the weekend. But there is one big question mark in the forecast…
Another clipper system will charge out of Canada and into the Upper Midwest on Wednesday. This has the chance to bring some more arctic air along with it and keep our area significantly colder than we would be otherwise through the end of the week. But our computer forecasting models are showing very separate outcomes with that cold front. The two images below show surface temperatures on two different computer models for Wednesday afternoon.
Notice that the first one shows chilly temperatures and a persistent northerly breeze. But the second image is warmer. In many cases, 10 to 15 degrees warmer because the cold front didn’t make it as far south or have as much impact on the region as the other model. This can present a HUGE problem when trying to forecast high temperatures because in this case, it can literally mean the difference of a fairly common cool January day, or another cold, well below average January day.
If you are having a tough time seeing the difference on those two images, then try the one below. This is a singular image of the high temperatures on Wednesday for all of the “larger” cities across the northern high plains.
Now, if you look at the same location in both the top and bottom set of numbers, you can see a very large difference in temperature. I have circled Sioux Falls in red as an example. The top one is 9° and the bottom one is 26°. This means that the computer model on top (called the AVN) has a forecast high temperature in Sioux Falls at 9° on Wednesday and the bottom model (called the NAM) has a forecast high temperature in Sioux Falls of 26° on Wednesday. Are you seeing the complications???? This can make it very difficult to accurately forecast what’s going to happen on Wednesday and they are obviously drastically different. The good news is when you have cases like this (that happen more often than you might think) the computer models each pick up on different pieces of that same puzzle, so to speak. This will often result in the actual high temperature landing somewhere in the middle. But when it doesn’t, those are the days that give meteorologists a bad rap because those are the days we are pretty far off from the forecast.