Austin / Travis County and South Central Texas Weather Update #6
Prepared by UT University/Incident Meteorologist Troy Kimmel
735am CT – Monday / 15 January 2018
… UPDATE TO A WINTER STORM WARNING …
.. NWS Issued Winter Storm Warning for all of South Central Texas from 12 Midnight Tonight
Until 6PM Tomorrow (Tuesday) …
.. Ice / Sleet / Snow Accumulations Likely Monday Night Through Tuesday ..
On this Monday morning, the arctic air mass has advanced southward into northwest Texas and
northern Oklahoma. The arctic air mass is forecast to move southward into our area by late tonight
into Tuesday. After a brief warm up today with highs in the 60s, we’ll see northerly winds increase
and temperatures fall following the surface cold frontal passage which I am expecting in the 8pm to
11pm time period tonight for the IH35 corridor. In the hours before and around the forecast time
of the surface cold frontal passage, an upper air low pressure disturbance is forecast to track
eastward over our area with clouds picking up today with light rain and drizzle starting sometime
around the dinner hour with the precipitation persisting as the front passes and continuing as much
as 18 hours after the frontal passage as moisture overruns the much colder surface air moving into
the area.
Surface temperatures, following the cold frontal passage, will fall into the 30s quickly with freezing
temperatures likely by 1am tomorrow morning then into the mid to upper 20s by daybreak with
daytime highs on Tuesday (with the associated cloud cover) staying primarily in the 20s with a strong
northerly wind and impressive wind chill in the low to mid teens.
As temperatures fall following the frontal passage, any precipitation that is occurring locally would
transition over to freezing rain, freezing drizzle and sleet (ice pellets) as we make our way into
post midnight hours tonight/tomorrow morning. As the atmospheric column aloft continues to cool,
although we will see some freezing drizzle/freezing rain beginning by 1am to 2am tomorrow morning, I still
think that precipitation would transition over to a little more sleet (ice pellets) and light snow after daybreak
tomorrow that will continue through day tomorrow. Ice accumulations will average a tenth to one quarter
inch with additional sleet (ice pellets) and snow accumulation possible on top of this. As mentioned above,
temperatures will likely fall below freezing by a little after midnight tonight and remain below freezing
tomorrow and tomorrow night into Wednesday morning. As a result, hazardous/dangerous road conditions
will result throughout the IH35 corridor and south central Texas for the period from shortly after midnight
tonight through tomorrow and tomorrow night into Wednesday morning given this forecast scenario.
As it appears now, any precipitation associated with this first passing disturbance will end, with the departure of
the disturbance, by tomorrow night into Wednesday. Clouds may break a bit on Wednesday.
However, another secondary upper air low pressure disturbance is now seen in the Wednesday night into Thursday
time period with clouds increasing and precipitation chances returning for the period. Current thinking is
that we could see some freezing rain, freezing drizzle, sleet (ice pellets) and snow once again but timing and
amounts as well as exact temperature profiles are uncertain and forecast confidence is lower particularly with
exact surface temperatures and precipitation type. Temperatures during the day Thursday will rise above freezing
by mid to late morning.
At this point locally, regarding the initial system tonight into tomorrow, my forecast confidence regarding the
arrival of the much colder air continues to be very high (although it could trend a few degrees colder) with high to
very high confidence that precipitation will occur. However, being able to forecast exact precipitation type, at any
given time in the forecast, is a lower confidence proposition although I have very high confidence that we’ll see
overall freezing/frozen precipitation locally. As with any winter weather episode around here, please understand
that the timing of the individual ingredients (of colder air arrival, atmospheric column temperatures aloft and the
upper air disturbance) is indeed everything when you consider the forecast given this potential winter weather
event for south central Texas. In other words, if one of our ingredients or timing changes, the forecast can and
will change.
I’ll continue to keep you advised on both of these potential winter weather events.
tk
CALL TO ACTION:
Please remain “weather aware” and listen for the latest weather statements,
advisories, watches and warnings from the National Weather Service.
Make sure that your NOAA All Hazards Weather Radio is operational and are
set to alarm in case of severe and inclement weather watches and/or warnings.
FOLLOWUP STATEMENTS:
I will continue to keep you informed regarding this severe/inclement weather
event. Any questions or if you have a storm report that I can forward on your behalf
to the National Weather Service, please let me know at tkimmel@troykimmelweather.com
GENERAL WEATHER INFORMATION LINKS:
NWS/Austin-San Antonio Current Statements/Advisory/Watches/Warnings
NWS/Austin-San Antonio Web Page
NWS/Storm Prediction Center (Outlooks)
NWS/Storm Prediction Center (Mesoscale Discussions – Severe Weather & Snow)
NWS/Storm Prediction Center (Severe Thunderstorm/Tornado Watches)
NWS/Weather Prediction Center (Mesoscale Discussions – Heavy Rain & Flooding)
NWS/National Hurricane Center