Austin / Travis County and South Central Texas Weather Update #1
Prepared by Incident Meteorologist Troy Kimmel (www.troykimmelweather.com)
555pm CT – Tuesday / 4 February 2014

…. Very Low Probability Winter Weather Event Possible Late Thursday into Early Friday ….
…. A Slim Chance of Freezing Rain and Freezing Drizzle ….

Another strong cold front.. with modified arctic air.. will make its way southward across the
area in the overnight hours tonight into the predawn hours tomorrow.

While skies will generally be mostly clear tonight into Wednesday.. a series of weak low
pressure disturbances will trek overhead west-to-east late Wednesday night into Thursday
and Friday. As they do, it will result in an “overrunning” pattern with an extensive cloud layer
moving in and  over the top of the fairly shallow layer surface based cold air with enough
atmospheric lift to give us some very slim rain chances. However, based on the latest computer
guidance and manual data, I am seeing a very “moisture starved” atmosphere and wonder
whether the system will have enough available moisture to produce much more than a low/mid
level cloud deck (at least initially). If this system does produce precipitation, I don’t see it before
midday on Thursday when we potentially could moisten the atmosphere enough for any rain
chances. I do expect temperatures below freezing for tomorrow night into Thursday midday but,
again, precipitation, based on my thoughts above, should not occur before noon on Thursday
when temperatures rise to slightly above freezing.

With below freezing temperatures after 7 to 8pm Thursday night into the morning hours on
Friday and with the possibility of a more moist atmospheric column, the slim rain/freezing rain
chances look possible but, again, I still don’t think there will be enough moisture for anything much
more than a few sprinkles. Even so, with what we’ve seen over the past two months, we know
what a sprinkle or even several hundredths of an inch of rain, in the Austin metro area and the
IH35 corridor,  can produce in a freezing/subfreezing surface environment. As a result, we must
continue to monitor model precipitation trends over the next 24 to 48 hours and then monitor
the disturbances in real time as they pass overhead.

As far as current precipitation forecast probabilities, I’m maintaining my 20 to 30% chance of
precipitation Thursday night and Friday (but getting close to shaving that back to 20%).. compared
to NWS Austin forecasts showing 20%.. local broadcast meteorologists showing 20 to 30% probabilities..
with private sector weather company forecasts, at best, carrying 10 to 20% probabilities locally. Only
one computer model.. the NAM model.. is showing probabilities much more than 20% for the Thursday
night into Friday morning; it is showing a 29% probability for the 6 hours ending at 6am CT Friday.

Bottom line.. my forecast thought is that this is a very low probability event with, if it materializes,
a high potential impact.

I’ll continue to keep you informed.

tk