This morning, between 8 and
10AM, New Orleans, Louisiana had a dusting to about an inch of snow
as a vigorous early season winter storm moving from Louisiana
towards the mid-Atlantic pulled very cold air over the south
central states while abundant moisture was moving in from the Gulf
of Mexico. Snow in New Orleans is of course quite rare, having
occurred only 17 times since 1850. New Orleans' last snow was a
dusting on Christmas 2004, and before that they received 1-2 inches on December 22nd, 1989.
The most in their recorded history was 5 inches on December 22nd, 1963. That
makes this snowfall the earliest ever recorded in New Orleans.
Below are some weather charts that help
explain why this highly unusual weather event occurred. Most
striking is the very deep 500mb trough (Figure 3) with a developing
cutoff low forming directly over southeastern Louisiana. Normally
these troughs would not reach this far south with this strength in
December. Also, note in the last surface chart, that with the
exception of that isolated 31F reading in east central Texas, there
are no freezing or below-freezing
temperatures near the Gulf coast. In this case, there was a very
shallow layer of above-freezing air at the surface, but much colder
temperatures just above it that allowed the snow to reach the ground
without melting.
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