.. Weather Update #4 ..

NWS watches/advisories/warnings that have been issued and updated as of 700am CT:

NWS/Austin-San Antonio… a WINTER WEATHER ADVISORY continues for the Texas
Hill Country and IH35 corridor.. including Williamson, Travis, Hays, Bastrop, Caldwell and
Lee Counties.. until 2 pm today for possible ice accumulations to less than 1/10th of an inch.

NWS/San Angelo… a WINTER STORM WARNING continues for Mason County
from now until 12 noon today for possible ice/sleet accumulations of up to 1/4 inch.

NWS/Fort Worth… a WINTER STORM WARNING continues  until 6pm today for large areas
of north Texas.. including the DFW area.. for the likelihood of significant 1/4 to 1/2 inch or more
ice/sleet accumulations with downed trees and power lines possible with power outages already
being reported.
A WINTER WEATHER ADVISORY continues until 6pm today for the area to the
southeast of the warning area above and to including Bell, McLennan and Milam counties..
including the Killeen.. Belton.. Temple.. Waco and Cameron/Rockdale areas for the possibility
of ice/sleet accumulations of up to 1/10th inch.

DISCUSSION

…. Icing Bridges/Overpass Problems Immediate North through West of Austin Area …

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 at times.

An upper level low pressure disturbance has increased lift in the overrunning moisture above the surface
based cold air with light freezing rain and rain in the overnight hours. Freezing temperatures or below
are noted northwest of a line from near Wimberley /Hays County/ northward through the western and
northern parts of the Austin metro area.. then eastward through Pflugerville and then into extreme
southeastern Williamson County to near Thrall.. Thorndale and Rockdale in Milam County.
Radar indicates only patchy precipitation in the area currently but overnight rains have resulted in
some dangerous icing on elevated toll road bridges and overpasses in northwest Austin and into the
Round Rock area.

As the current upper air disturbance moves east northeast of the area by midday today.. precipitation
will taper off and the current winter precipitation threat will diminish.

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.. as predicted.. of the widespread and dangerous winter weather and
ice storm situation that has developed well  to our north over north Texas, Oklahoma into adjoining
Arkansas where WINTER STORM and ICE STORM WARNINGS continue. Widespread power outages
have already been reported in north and far northeast Texas.. including the Dallas/Fort Worth metroplex.