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Issued by NWS Nashville, TN

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NOUS44 KOHX 201530

930 AM CST Tue Dec 20 2016


Freezing Fog and Spontaneous Snow Showers Return to the Mid State

As low stratus clouds and dense freezing fog developed over
Middle Tennessee early this morning, some folks in the Mid State
witnessed an unusual, though not rare, event...spontaneous snow
production. A similar event was documented three years ago on the
morning of December 11, 2013 in Millersville. On that particular
morning, a National Weather Service employee was headed to work
and had driven into an area of dense fog when he noticed that a
very thin layer of snow was on the ground. When he stopped to get
gas, he noticed that the air was filled with millions of very
small grainy type snowflakes. Even the interstate had developed a
very thin coat of snow...and just enough to show tire tracks.
Shortly thereafter, the sun came out and the freezing fog and
spontaneous snow shower were nothing but a memory.

A similar event occurred this morning at various spots around
Middle Tennessee, when conditions were very similar to those from
December 11, 2013. Dense freezing fog and low hanging stratus
clouds developed in the presence of very cold temperatures in the
teens to around 20 degrees. Thanks to social media, more pictures
were available of the event this morning than the one that
occurred in 2013. Eventually, we may find that this type event is
not quite as unusual as we first thought, but only under reported
in earlier times.

Freezing fog is a dangerous phenomenon since it can produce
patchy black ice that is very difficult to see. In addition, the
patchy nature of freezing fog can be very deceiving to drivers.
You may be driving along in a fog free area with hardly any concern
at all...and then pass into an area of freezing fog, where patchy
ice exists and where, perhaps, an accident may have already
occurred. The accident may be shrouded in the fog, out of sight.
So, unless you slow down before traveling into the fog, you may
not have sufficient braking distance to maneuver around such
problems. This is exactly how accident pile ups can occur in areas
of dense fog, freezing or otherwise.

So, the main lesson to be learned about driving in dense fog of
any sort is to remain vigilant and slow down when passing through
foggy areas. In addition, you should remember that it only takes
a single patch of ice to cause an accident.

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