The Forecast Looks A Bit Hazy
May 15, 2012 8:30 PM
A cold front moving through the region Tuesday sure did cool things off with highs closer to more seasonal normals. But after the one-day break from some of the warmer weather, looks like temperatures will begin to rise once again. But there are many questions that remain about the upcoming few days because of computer model discrepancies and fairly normal forecasting “close calls.” Let me explain…
As you may know, nothing in weather is a guarantee. There are many times where we are certain our forecast is accurate, then we get to the advertised time period and the picture has changed quite a bit. (It would be like forecasting a Van Gogh and ending up with a Picasso) But what can make forecasting even more complicated is when our computer models either don’t agree with each other OR have incorrect information in their processor which can make the model unreliable for days at a time. For example, the cold front we experienced Tuesday was originally supposed to arrive Tuesday afernoon and evening, which would have had little affect on high temperatures making for a very warm day. This looked realistic just 24 hours prior on Monday morning. But analyzing the situation Monday afternoon, I realized that the current position of the front and the location that the forecast model had put it in didn’t line up. In fact, they were off by almost 200 miles. This meant that the cold front would come in much faster then expected and therefore, we ended up having a cooler day Tuesday then Monday as you can see in the high temperatures above. Now look at the pictures below. These are temperatures at 850mb, or about 5000 feet. Remember that the majority of the time, cooler air comes from higher levels of the atmosphere and not just areas to your north.
Now the leading edge of the front is in blue on both maps, but notice the subtle differences in temperatures between pictures. In many cases its only 2-4 degrees Celsius, but a subtle difference like that could mean a high of 80 versus a high of 70, much like we saw in the southeast on Tuesday. This is just one of the many reasons why forecasting the high temperature down to the degree is so incredibly difficult.
Looks like temperatures will be climbing the next couple of days with highs back to the 80’s and possibly the 90’s for some of us. Check out the 850mb temperatures for Thursday on two different computer models.
Notice the slight differences in them yet again with one model showing 16-22°C across the area versus 20-24°C. This is a subtle difference but could once again mean the difference between 85 and 95. But its not really the warm air above the surface that’s concerning, it’s the models showing a good deal of cloud cover over the area Thursday and some leftover Friday.
I realize that this is pretty difficult to read so let me explain. The two pictures are once again from 2 different models. The gray scale is total percentage of the sky that is covered with some form of low, mid, or high-level clouds. Notice in the left, there is a reasonably thick blanket of clouds in the south and east and on the right there are partly to mostly cloudy skies across much of the area. Now this may not be widely known, but there can be HUGE differences in temperatures when there are clouds present versus clear skies. Thursday still looks like a warm day with highs into the low 80’s in most cases, regardless of clouds. But if we have full sunshine on Thursday and mixing is occurring reasonably well in the atmosphere, the would be nothing standing in the way of some places topping 90 and even closing in on 100 degrees. So cloud cover can be an enormous question mark when trying to forecast temperatures.
Here is a quick look at our current forecast highs for Thursday. Keep in mind, that these will likely change before Thursday as we know more information.
Even though a couple isolated storms are possible Wednesday night, it looks like more widespread rain will hold off until the weekend. Here’s the rainfall forecast from Friday night through Sunday night.
Now this will continue to get updated as we get closer, but widespread rain is looking more likely with locally heavy rain a possibility so stay tuned to KDLT and KDLT.com for the very latest. Stay cool!