Austin / Travis County and South Central Texas Weather Statement #2
Prepared by UT University/Incident Meteorologist Troy Kimmel
845pm CT – Sunday / 22 February 2015
… Winter Weather Advisories Will Go In Effect Overnight into Monday …
… Initial Disturbance with Precipitation Chances Tonight into Monday …
… Another Disturbance with Winter Precipitation Tomorrow Night into Early Tuesday …
AREA NWS WATCHES / ADVISORIES / WARNINGS:
NWS / Winter Weather Advisory
(Valid 3am CT Mon 23Feb2015 until 6pm CT Mon 23Feb2015)
Counties Included.. Williamson, Hays, Travis and Hill Country counties to northwest
Ice accumulations up to 1/10th inch.. but primarily limited to bridges, overpasses and
elevated roadways/structures in western Hays, western Travis and north and western
Williamson county and counties to north and west from there.
NWS / Winter Weather Advisory
(Valid 9pm CT Tonight until 6pm CT Mon/23Feb2015)
Counties Included.. Milam (Rockdale/Cameron)
Ice accumulations up to 1/10th Inch
Sleet accumulations up to 1/4 inch
SYNOPTIC/FORECAST REASONING:
Arctic high pressure is centered over eastern North Dakota /1046mb/ and is
building southward into Texas.
The depth of the cold air over south central Texas.. based on NWS Doppler
radar and upper air data.. is about 4,000 feet deep. Low.. middle and high level
moisture is “overrunning” the surface based arctic air as disturbances, being
ejected by an upper level low pressure area located south of San Francisco, CA,
traverse the area tonight through Monday into Monday night into early Tuesday.
Given the relatively shallow nature of the surface based arctic air.. my current
thinking is that the main threats will be freezing drizzle, freezing rain and a lower
probability of ice pellets/sleet mainly north of our area.
The last disturbance is forecast to move through the area tomorrow night into
early Tuesday with precipitation tapering off thereafter.
THREAT(S) FOR AUSTIN METRO AND IH35 CORRIDOR COUNTIES:
Tonight into Monday: Chilly rain metro areas, freezing drizzle, freezing rain and some
possible sleet in north and western areas of IH35 counties.
(50-60% probability of precipitation)
Geographic area for freezing precipitation: Northwest of line from Wimberley..
Dripping Springs.. Lake Travis.. Georgetown and Jarrell.
Time Period: 3am CT Mon/23Feb2015 to 6pm CT Mon/23Feb2015.
MY FORECAST CONFIDENCE:
Weather system evolution: Very high
Precipitation chances: High to very high
Liquid precipitation (rain) chances: Medium tonight.. high tomorrow
Freezing precipitation (freezing rain/freezing drizzle) chances: Low to moderate (to NW)
Frozen precipitation (snow/ice pellets-sleet) chances: Very low
Thunderstorm/lightning chances: Very low chance over northern hill country overnight
Severe thunderstorm chances: None
LATEST OBSERVATIONS AND MY THOUGHTS:
At 8pm.. the freezing line is along a line from the southeast part of the DFW metroplex
southwestward to just northwest of Hamilton to just north of Junction. Temperatures along
the IH35 corridor counties at 9pm are in the low to mid 40s.
Again, we find ourselves right on the border line as far as potential weather problems are
concerned. A few degrees colder than anticipated and problems will develop quickly.. especially
in areas north and west of Austin. Please note that the NWS has us in the WINTER WEATHER
ADVISORY predawn tomorrow into the day tomorrow primarily because of the potential problems
in western areas of Hays and Travis counties and north and western Williamson county.. not so much,
at least at this point, in the IH35 metro areas. I caution you, though, that this could change and it is
everyone’s responsibility to remain weather aware and to be ready to act in case things turn worse
than currently expected.
Temperatures tomorrow will only rise a degree or so and remain in the 30s all day with
precipitation continuing.
We can thank the highs in the 70s over the last few days for the fact that, unless it gets colder than
currently anticipated, that, at least tonight into early Monday, any ice accumulations should be on
bridges, overpasses and elevated objects (trees, etc) and elevated roadways.
By tomorrow night, another final upper air disturbance will move eastward through the area and then
depart to the east. I feel as though tomorrow night may be the best chance of problems deeper into
the IH35 metro areas.. but, at the same time, precipitation chances will be trending downward by then.
I do believe that the NWS Austin-San Antonio may have to reissue or extend some type of winter
weather product after 6pm tomorrow night into early Tuesday so please be aware of this possibility.
Weather conditions improve Tuesday with temperatures warming back to near 40 degrees during
the day.
AVIATION INFORMATION FOR THE AUSTIN/BERGSTROM
INTERNATIONAL AIRPORT (KAUS) AERODROME:
The NWS Austin-San Antonio has the mention of freezing drizzle in the KAUS TAF
(see below) from 2000z to 2359z tomorrow. Although it doesn’t meet their criteria and is
not mentioned below, I would consider there to be a freezing precipitation threat for tomorrow
night into early Tuesday as well.
Current KAUS Terminal Aerodrome Forecast (TAF) – Issued 232332z ..
KAUS 222332Z 2300/2406 01020G30KT 6SM BR OVC008
FM230600 01022G32KT 3SM -DZ BR OVC004
FM231800 01018G28KT 5SM BR VCSH OVC005 PROB30 2320/2324 -FZDZ
FM240000 01017KT 4SM -DZ BR OVC007
FM240500 01014KT 3SM BR OVC007=
. For Our DAL/DFW Hub Aerodromes ..
Current NWS public forecasts continues the WINTER STORM WARNING for the DFW
and DAL aerodromes. Please be aware of potential cancellations and diversions as weather
conditions are currently deteriorating at the DFW/DAL aerodromes. At 8pm.. freezing rain
has been reported in last hour at DFW with light rain at DAL with temps just above freezing.
This will be a rather extended winter storm situation in the DFW area.. even into tomorrow
night into early Tuesday (but with lower precipitation probabilities).. so please be aware.
For Our HOU/IAH Hub Aerodromes ..
Current NWS public forecasts do not have any mention of winter precipitation for the IAH
and HOU aerodromes at this time as the threat should remain north of the area.
Current FAA National Airspace Status
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, please let me know at tkimmel@austin.utexas.edu
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
tk