Austin / Travis County and South Central Texas Weather Update #2
Prepared by Incident Meteorologist Troy Kimmel (www.troykimmelweather.com)
525am CT – Tuesday / 11 February 2014
…. Not Much Change in My Forecast Thought ….
…. Low Probability Winter Weather Event Possible This Morning into Midday ….
…. Extremely Low Probability Winter Weather Event Possible Tonight ….
…. NWS/Winter Weather Advisory continues for Travis (Metro Austin).. Williamson.. and
Hays Counties and hill country counties to the west until 6pm this evening ….
LCRA Hydromet gauge network (including current temperatures) – a good tool to use this morning:
A shallow wedge of colder arctic air continues to settle southward into Texas.
A low pressure disturbance is approaching the area and then trek overhead west-to-east.. on top
of the cold arctic surface air.. by later today into tonight. It will depart the area by 9pm to 12
As the disturbance moves slowly over our area, it is resulting in an “overrunning” pattern with an
extensive cloud layer moving in and over the top of the surface based cold air with enough atmospheric
lift to give us good rain chances today. Rain chances decrease rapidly by this evening and ending by
9pm to midnight tonight as the system departs the area.
The two possible nighttime freezing rain/drizzle episodes are addressed separately below…
This morning into midday:
Clouds and, although a little slow to start, chance of light overrunning rain will be increasing over the
next few hours and continuing through the daytime hours before rapidly decreasing by the evening
rush hour as the upper air disturbance departs to the east northeast.
According to the LCRA Hydromet and NWS/FAA surface observation sites, temperatures at 5am, as
predicted, are right at or just a degree or so above above the freezing mark. in Travis County.
As precipitation becomes more widespread over the next few hours, temperatures are expected to be
very close or just below the freezing mark. While overall precipitation amounts will remain below
1/10th of an inch, any precipitation that does fall in this environment could cause icing especially to
elevated bridges, overpasses and flyovers as well as exposed objects in areas where the temperatures
are at or below freezing.
Temperatures should climb above freezing my late morning across the area.
My forecast has a 60% probability of rain today with highs around 36F.. the NWS/Austin-San Antonio
is currently calling for a 70% probability with highs in the mid 30s. Most of the atmospheric
model computer guidance.. along with all local broadcast meteorologists and private forecast firms..
shows highs between 35 and 39 F today with all showing at least a 50% chance of precipitation.
I continue to think that the greatest threat of freezing precipitation over the next six hours or so be from
the western and northern parts of the Austin metro area north and westward over Williamson and Burnet
counties as well as to the southwest over northwestern Hays County.
Location will be extremely critical as far as any potential problems over the next few hours…
Potential precipitation types: Mainly light rain.. possible freezing rain/freezing drizzle/sleet
My thought locally: A low probability event with potential moderate to high impacts if it materializes
Tonight night/Wednesday morning:
The clouds and the chance overrunning light precipitation will end quickly with the passage of the upper
air low pressure disturbance by 5pm this evening. Precipitation, as I see it now, will over in the area by
6 pm. Clouds will break overnight with a partly cloudy sky expected after midnight.
Temperatures should cool to near freezing by 9pm this evening, but with precipitation tapering off
before then, the only issue may be patchy pooling of water from precipitation today that might freeze
My forecast is showing precipitation probabilities falling through 20% by 5pm this evening and then dropping
completely by 6pm.. so does the NWS/Austin-San Antonio and other forecast entities.
Potential precipitation types: No additional precipitation after 6pm
My thought locally: An extremely low probability event with low impacts (freezing of pooled water) with
freezing temps in the overnight hours
A couple of reminders…
— With what we’ve seen over the past two months, it is painfully apparent that even a sprinkle or
several hundredths of an inch of rain in a subfreezing surface environment, in the Austin metro area
and the IH35 corridor with our extensive above ground road network (flyovers, upper level of IH35),
can produce a hazardous mess in a hurry. You should be prepared in case the forecast or the on going
weather conditions change expectantly at the last minute. I will do the best I can to keep you informed
during this potential weather event.
— Winter weather episodes are difficult to predict at 30 degrees north latitude.. the latitude
of the Austin metro area and the IH35 corridor. Precipitation types.. i.e., sleet, snow, freezing rain..
are difficult to predict.