This
winter has been a wild one for temperatures in South Carolina. There have been big swings from hot to cold
and back again. Now that meteorological
spring has begun (March 1st) the pattern continues.
A
dramatic change to our weather is about to take place. Cold arctic air is already in place across
much of the central U.S. Normally a cold
front moving in from the west would bring the cold air to our state. However, occasionally it comes in through the
“back door”.
High
pressure builds east and the cold air slides down the eastern seaboard faster
than it can come in from the west. It
becomes trapped between the ocean to the east and the Appalachians to the west. The cold front that surges south is known as
a “back door” cold front.
Typically
a wedge of cold air stays in place until something comes along to move the cold
air out, which is a very difficult thing to do.
The result can be days of overcast skies and chilly northeast winds.
This
time the back door cold front will be accompanied by a dramatic temperature
drop. When the front passes the
temperatures will likely drop 20-25° F in an hour or two. The front will be preceded by a band of rain
which will begin the temperature drop.
Winds will shift from a westerly direction to a northerly direction as
the front passes. The winds will
increase and there will be a wind chill to worry about in the late afternoon.
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| The RPM model forecast for 1:30 p.m. EST on Monday, March 3, 2014. This is from the 21z run of the model using the 12 km grid. Click on the image for a larger version. Image Credit: WLTX-TV\WSI. |
The
Regional Precision Model (RPM), that we use, captures the dramatic change in
temperature. In the panels below it
starts at 1:30 p.m. and ends at 3 p.m.
Notice the sharp drop in temperature in Columbia, SC. It is a change of 21° F in 90 minutes. Furthermore, by 7 p.m. the model projects a
temperature of 32° F with a wind chill temperature of 21° F. High temperatures will likely occur in the
late morning or early afternoon in the mid to upper 60s.
 |
| The RPM temperature forecast for Monday afternoon March 3. 2014. You can tell where the front is from the contour color of temperatures. Note the precipitous drop in temperatures as the front passes. Click on the image for a larger version. Image Credit: WLTX-TV\WSI. |
Don’t
get too “hung up” on the time. The model
could be off by an hour either way. The
important thing to take from this is the large temperature drop. It is highly advisable to take a warm coat
when you leave in the morning for work or school, because it will be
dramatically colder when you come home.
Temperatures
will likely be near or below freezing by early evening. There could be some light freezing rain or
freezing drizzle as the clouds will remain overnight Monday. It will not be enough to cause any travel
problems and there will be little accumulation.
This
weather event is more of a temperature event than a precipitation one. So there will be no snow or ice storm for
this part of the country. However, the
change of temperature can be a problem.
The high temperature in Columbia, SC on Sunday was 76° F, but the
temperature just 24 hours later will be in the mid-30s. Fortunately the warm spell was brief and
plants have not begun to flower. The
pollen season has begun, but the growing season has not.
It
is not often that we see back door cold fronts with temperature gradients of
this strength. When we do they tend to
be in late winter or early spring. This
latest one may have the strongest temperature gradient in recent memory. In addition, temperatures will drop into the
mid to upper 20s Tuesday morning with wind chill temperatures in the upper
teens.
This
may not be winter’s last gasp. I have
been advising everyone to delay planting this year. Don’t be in a hurry. The weather pattern we have been seeing since
late October suggests the possibility of a late freeze. This could happen in the first half of April. Until then we are likely to continue to see
wild swings in temperature.
