How meteorologist predict below freezing temperatures
It's no surprise that temperatures have cooled abruptly since Sunday afternoon. A passing cold front has switched winds out of the northwest bringing in cooler Canadian air across Mid-Missouri. These cooler temperatures are expected to continue to dip even further below freezing into the second half of the week, leading meteorologist to turn their attention to the 540 line on their modeling maps.
The 540 line is a derived line using atmospheric heights that help meteorologist find surface freezing temperatures and how far south they have made it. This is not a physical line seen in the atmosphere, but on maps it can be very beneficial. Temperatures at and north of this line are seen as freezing or below. South of this line shows warmer temperatures above 32 degrees.
Beyond just showing the extent of below freezing temperatures, the 540 line also helps identify impactful weather events with winter precipitation. Areas south of this line will produce rain with proper moisture in the lower levels of the atmosphere. Areas along this line could pose anything from rain to sleet, to freezing rain, and snow. This is an area of concern for travel conditions. As you head away from the line and north, snow is the primary threat for winter precipitation.
The 540 line is expected to traverse even further south following a secondary cold frontal passage later this week. This means even cooler temperatures across Mid-Missouri and the majority of the United States. This upcoming Thanksgiving and Black Friday will see highs into the upper 30s meaning winter weather layers will be needed throughout the afternoon hours also.
