Austin / Travis County and South Central Texas Weather Update #3
Prepared by Incident Meteorologist Troy Kimmel (www.troykimmelweather.com)
500pm CDT – Thursday / 5 December 2013
.. Weather Update #3 ..
NWS watches/advisories/warnings that have been issued and updated as of 500pm CT:
NWS/Austin-San Antonio… a WINTER WEATHER ADVISORY will be in effect for the Texas
Hill Country and IH35 corridor.. including Williamson, Travis, Hays, Bastrop, Caldwell and
Lee Counties.. from 8pm tonight through 2 pm Friday for possible ice accumulations to 1/10th
of an inch by tomorrow morning.
NWS/San Angelo… a WINTER STORM WARNING is now in effect for Mason County
from now until 12 noon Friday for possible ice/sleet accumulations of up to 1/4 inch.
NWS/Fort Worth… a WINTER STORM WARNING is or will shortly be in effect until
6pm Friday for areas northwest of a line from Goldthwaite to Canton line for the likelihood
of significant 1/4 to 1/2 inch ice/sleet accumulations with downed trees and power lines possible
with lengthy power outages possible.
A WINTER WEATHER ADVISORY will be in effect 6am Friday until 6pm Friday for the area
southeast of the warning above and to include Bell and McLennan counties.. including
the Killeen.. Belton.. Temple and Waco areas for the possibility of ice/sleet accumulations of
up to 1/10th inch.
DISCUSSION
…. Increasing Likelihood of Freezing Rain Overnight ….
The unseasonably cold arctic air mass continues to slide southward out of Canada into the through the
western two thirds of the USA. As this cold air continues to move southeastward through Texas, it, as
usual, is in a relative shallow layer close to the ground. This is combining with an active subtropical
jet stream to cause moisture to overrun the cold air and then upper air disturbances embedded in the
subtropical jet stream to move by between now and Sunday, create lift in the atmosphere and, as a result,
cause precipitation.
The front arrived in the Austin area about 4 to 5am this morning with rain showers and light rain along
and just behind the front. Although we haven’t seen any precipitation today, clouds have held temperatures
in the upper 30s to near 40 all day long.
By later tonight, the leading edge of a low pressure disturbance will begin to increase lift in the overrunning
moisture above the surface based cold air with light rain beginning.. with temperatures just above freezing..
later tonight. After midnight tonight, our surface temperatures will approach the freezing mark and
precipitation will transition to freezing rain with ice accumulations beginning to form on higher bridges
and overpasses as well as exposed objects. As this rain falls into the early morning hours tomorrow, please
understand that if temperatures remain a degree or two warmer that we’re expecting, this will be a simple
cold rain event locally. On the other hand, if temperatures fall several degrees lower than anticipated, we could
rapidly find ourselves in a full winter storm situation. I would love to be able to tell you which of these
scenarios will play out… but I can’t at this point as there is just too much uncertainty. The NWS Austin-
San Antonio has mentioned that it is possible that the winter weather advisory may have to be upgraded to
a winter storm warning over parts of our area later tonight into Friday but it’s just simply too soon to tell.
This means that this may be more “last minute” as whether we have ice accumulations locally from
this system.. we’ll need to watch the 12 midnight to 7am period overnight tonight to get a real idea about this
winter storm and whether it will directly affect our area.
This arctic cold air will hang in here for the next week or so with another winter weather risk existing for the
local area for Saturday into Saturday night and into early Sunday morning time period as another upper air
low pressure disturbance moves by.. these time periods will be dealt with by the NWS with possible later
watches/advisories/warnings.
A continued reminder to let you know of the potentially widespread and dangerous winter weather (ice storm)
situation that map develop to our north over north Texas, Oklahoma into adjoining Arkansas where
WINTER STORM and ICE STORM WARNINGS are already in effect. This could cause widespread
and long lasting power outages in north and northeast Texas.. including the Dallas/Fort Worth metroplex
as well as the Longview/Tyler/Kilgore as well as Texarkana areas over the coming days.
Another note… this cold arctic air will continue to be reinforced from the north through the weekend and
into next week. Based on the guidance I’m seeing now, I would be surprised if we’re back above
50 degrees F for high temperatures until about 7 or 8 days from now. More importantly, overnight lows
next week, assuming a clearing sky, will result in hard freezes in the overnight areas with some areas to
around 20 degrees F for overnight lows on Monday/Tuesday/Wednesday nights of next week. The good news..
at this time.. is that no precipitation is expected for this time period.
In conclusion, even as the winter storm is already directly affecting other parts of the state, there is still much
uncertainty about this potential winter weather event locally for our south central Texas area tonight into
tomorrow. On the other hand, please understand and appreciate the very high impact that this system could
have on our area with very little notice if temperatures turn out being even slightly colder over our area than
we’re currently forecasting now. It is so very important that all interests pay close attention to the latest
weather conditions over the coming days and for the latest NWS watches/advisories and/or warnings that may be
issued.
I’ll continue to monitor this situation.
tk