WEATHER BLOG: Arctic front Tuesday, chance for wintry precipitation Tuesday morning

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NEAR-TERM: Cold temperatures are continuing across the area this morning, but expect a warm up this afternoon with highs climbing into the upper 50s under mostly sunny skies. 

WEEKEND: A warming trend is expected Saturday, Sunday, and Monday as readings will be in the 60s each afternoon. Clouds are also expected to increase as moisture increases in our atmosphere with south winds. A few isolated showers possible, but rain chances 20 percent or less each day. 

TUESDAY: The major story will be Monday night and Tuesday, as an Arctic front quickly progresses across the south-central U.S. The high temperature Tuesday will most likely occur right after midnight with temperatures rapidly dropping by Tuesday morning. At the same time, a band of precipitation, accompanying the front, will be working across the state. Both the European and GFS model has the freezing line working into the northern parts of the state by 6am Tuesday morning. The window of precipitation across the state will be from about midnight through Noon Tuesday, so this means winter precipitation will become possible during the morning hours. 

The main thing to analyze is how far south this freezing line gets and the amount of cold air aloft. In this type of event, surface temperatures do matter, but temperatures above the ground also factor in. Even if temperatures are in the 33-38 degree range at ground level, sleet and/or a few wet snowflakes could still be possible if enough cold air is present aloft. Taking a look at the atmosphere at the time, most of the atmospheric column will be below freezing with the exception being a warm tongue of air a few thousand feet above the ground. When this occurs, the precipitaton falls first as snow, melts when it hits the warmer air that’s above freezing, and then refreezes if the air below is below freezing. This warmer air aloft will become more pronounced heading further south towards Acadiana. It’s doubtful temperatures get to the freezing mark along I-10, so the degree of cold air aloft will be important in terms of what kind of precipitation we will see. For snow-lovers, the problem for Acadiana will be the warm air aloft, as our ground-level temperatures should stay above freezing. For Acadiana to see snow, we would need the whole atmospheric column to be below freezing with the exception being right near ground level. 

One thing of note is that consecutive model runs have been trending colder, so it’s something worth watching. Also, this Arctic airmass is expected to be very shallow, which can sometimes cause global models to struggle. I’ve also been monitoring something called “wet-bulb temperature,” which is the temperature that can be achieved from rainfall evaporating in the atmosphere. This can sometimes cause temperatures to decrease further once precipitation begins. Interestingly enough, these wetbulb temperatures are near freezing across the I-10 corridor Tuesday morning, so if the precipitation gets heavy enough and enough evaporation occurs, the freezing line could get a little further south, which is why this event is worth watching. 

BOTTOM LINE…Temperatures both at the surface and aloft will be much colder Tuesday morning across the northern and central parts of the state. I expect mostly wet snow flakes across the I-20 corridor, a band of sleet and a few wet snowflakes across the central parts of the state, and mostly rain with a few sleet pellets south of Highway 190 and across most of Acadiana. Little to no accumulation is expected across Acadiana as temperatures should be too warm, but accumulation could be more likely across the central and northern parts of the state. Of course, this event is still four days away, so slight deviations in precipitation or temperature could change this thinking. At the very least, let’s wishcast for some “wet-bulbing” and for models to trend just a little bit colder, so we could get a nice surprise in the form of a few snowflakes Tuesday morning. Unfortunately, the chance is still pretty low across Acadiana, but it has increased in recent model runs! Stay tuned!

~Meteorologist Trevor Sonnier

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