Why does Missouri experience frequent and noticeable changes in weather?
If you have lived in Missouri for even a short amount of time, you know how much of a roller coaster it can be. For example, last week, to start the month of February, afternoon high temperatures only got into the low to mid 30s from the 1st through the 4th. Then, the 5th through the 8th, afternoon temperatures suddenly jumped into the 40s and 50s before reaching the highest temperature of the month so far, near 70 degrees on the 9th. Have you ever wondered why such significant changes can happen in such a short amount of time in the state?
Geography in the United States plays a large role in the amount of variability seen for a specific area when it comes to weather. For example, much of the West Coast and Western United States has the Rocky Mountains stretching throughout many of the states. This mountain range acts like a "wall" that most of the frigid air from the north can't pass over, so most of the air masses that they deal with are air masses that originate from the Pacific that consist of more moisture and slightly warmer air. This is why areas like San Francisco, CA, do not see much change in the temperatures that are experienced on a yearly basis.
This is a similar story for the Eastern United States and the East Coast. The "wall" they have is the Appalachian Mountains, and although it is a smaller range compared to the Rockies, it still plays a large role in blocking most of the cold, dry air from the north.
Since there is no mountain range or terrain to act like a blockade for Missouri, not only does the frigid air from the north have free range on the state, but so does the warm, moist air from the Gulf. This often creates a clash of completely different air masses, and depending on the setup, one is bound to win, even if it is short lived.
The thing that drives these air masses into the area and determines what kind of weather the state is going to experience is the jet stream. This is a fast-flowing river of air in the upper-levels of the atmosphere, and it can either drive frigid air from the north into Missouri, or guide warm, moist air from the south into the area. Currently, the polar jet stream, the river of air that most commonly brings these changes, is in its transition phase as it shifts back into the Northern United States and Canada. As it transitions from February to March, it is most commonly positioned over Missouri. This means that if any major changes occur in this jet stream, the weather or noticeable differences will be delivered right to your doorstep.
As for what kind of changes can be expected over the next 7 days, it is pretty easy to tell which air mass will be winning. Afternoon high temperatures Monday through Wednesday are expected to continue to stay in the mid to upper 60s, which is over 20 degrees above the average temperature for this period of February.
