Austin / Travis County and South Central Texas Weather Update #2
Prepared by UT University/Incident Meteorologist Troy Kimmel
135pm CT – Wednesday / 26 December 2018
.. Severe Thunderstorm Threat Increasing for the IH35 Corridor by Later this Afternoon
into the Evening Hours ..
.. Threats Will be Strong Straight Line Thunderstorm Winds, Large Hail and Tornadoes ..
There has been little change in the overall weather pattern affecting our area. A strong upper level low pressure storm system is approaching the area from the west currently.. low level moisture continues to increase over the IH35 corridor counties with scattered rain showers and even a few isolated thunderstorms currently over the area.
As the upper level low pressure system moves overhead and an associated cold front/dry line moves southeastward across the area by later this afternoon into tonight, we’ll see dynamic atmospheric lift combine with a very unstable air mass to produce strong to severe thunderstorms over the area. All severe weather hazards… hail.. damaging straight line thunderstorm winds.. and tornadoes.. are possible.
The NWS/Storm Prediction Center has increased the risk of severe thunderstorms to “enhanced” for the local area over the next 12 hours (see outlook graphic below). The risks are about the same as yesterday although the damaging straight line thunderstorm wind risk may have increased a bit based on the latest NWS/Storm Prediction Center outlook.
As mentioned previously, beginning now and continuing over about the next 12 hour period, thunderstorms will need to be watched for a tornado risk in thunderstorms that show signs of rotation. This rotation can be found in thunderstorms that develop ahead of the squall line that is likely to develop along the cold front/dry line to the west of the IH35 corridor but can also be found in individual thunderstorms within the north-to-south oriented squall line that moves eastward over the area tonight. In addition, there is an increased risk that any thunderstorm in the developing squall line that exhibits a “bowing out” structure will have an associated damaging straight line thunderstorm wind threat.
The greatest risk for these stronger thunderstorms in the Austin metro area and the IH35 corridor will be in the 5pm to 11pm time frame today into tonight.
This system will be quite progressive.. that is, it will move quickly through the area. I will increase the rainfall amounts slightly, but still expect rainfall amounts, based upon NWS/Weather Prediction guidance, to be in the one to two inch range with heavier amounts possible especially northeast of the Austin metro area. As a result, flood problems with this system will be mainly limited to urban/small stream areas.
Rain should end in the area by daybreak tomorrow with sunshine returning for Austin and the IH35 corridor by morning into midday.
… Authority / NWS Storm Prediction Center …
… Wednesday / 26 December 2018 Severe Thunderstorm Outlook …
Let’s continue to be weather aware as this system approaches and moves overhead and to the east of the area by late tonight. You should ALWAYS have at least two methods of receiving weather information.. the NWS/Austin-San Antonio (particularly their Twitter account) is ALWAYS a good first choice… https://twitter.com/NWSSanAntonio . A good second source.. NWS All Hazard Weather Radios.. which should be set to alarm with the liklihood of watches and warnings over the next 12 hours.
As usual.. I’ll do my best continue to keep you informed.