Have you ever wondered why temperatures fluctuate wildly in the winter?
AUSTIN, Texas - The old saying goes "if you don’t like Texas’ weather, wait a minute."
That’s especially true in the winter when temperatures can vary from the mid-80s in the morning to lower-30s by the end of the day.
The cause of these temperature fluctuations is no secret, they’re cold fronts and they happen basically all year. But in the winter they take on new power and happen with greater frequency and intensity.
In 2017, a very strong cold front saw temperatures in the mid-80s ahead of the front and in the upper-30s behind it. These kinds of cold fronts, or arctic intrusions as meteorologists call them, are key components in snow, sleet, or ice storms in Central Texas.
The reason for this temperature whiplash is due to a couple of things.
One is topography. If you were to drive from the Gulf of Mexico to the Arctic Ocean, you wouldn’t run into any mountains or anything to block the wind from moving air around the continent. Mountains – especially very tall ones like the Rockies – act as very effective barriers to cold and warm air masses moving freely north or south.
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North America doesn’t have any east-to-west mountain ranges and therefore the cold arctic air and warm tropical air is free to move wherever it wants.
The second reason is that there is way more cold air available in the winter for the cold fronts to tap into. During the winter, northern parts of the United States can be well below freezing, often well below zero whereas Austin’s average low temperature never dips below 40°.
This massive temperature difference allows for wide temperature fluctuations any time the cold air decides to move to the south.
The third reason is related to the second in that during the winter the jet streams are much more powerful and more active. The jet stream’s winds are actually powered by the temperature difference! With a stronger jet stream, more north-south wiggles in the jet can form, and when that happens cold air gets pulled down from the poles and sometimes can make it to central Texas.
The reason this doesn’t happen in the summer is:
- The really cold air gets forced so far north that it can’t manage to push itself this far south.
- The classic Texas "heat dome" works really hard to keep the cold fronts to the north. Every once in a while a powerful front will manage to sneak under the dome but those fronts typically only bring marginal relief and don’t happen very often.