Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1144 PM CST Sat Dec 20 2014
Update...06z aviation below.
Aviation...widespread MVFR ceilings across the County Warning Area late this
evening...along with patchy 5-6sm visibility in br around aus.
00z model guidance has trended slightly lower with ceilings and
visibility early Sunday morning. Generally expecting IFR ceilings
developing between 06z-09z out near drt and LIFR ceilings possible
around 12z. IFR ceilings developing 10z-12z at aus/Sat/ssf. IFR
ceilings then persisting until 16z-18z...becoming MVFR for the
afternoon along and east of I-35 and VFR out west near drt. East to
southeast wind around 5-10 kts this late evening becoming less than
5 kts at aus/Sat/ssf overnight. S wind 4-8 kts developing Sun
Previous discussion... /issued 912 PM CST Sat Dec 20 2014/
taking a look at latest observation/guidance/hi res models...all are
trending towards fog development across much of the area tonight.
Areas in our northeast including Travis and Williamson counties
are already seeing visible down to 6 sm as of 03z. With wind fields
light or calm at most ob sites...think visible will be decreased
throughout the evening. Not high enough confidence to go with
areas yet but will keep monitoring and will update with more
precision if warranted.
Previous discussion... /issued 720 PM CST Sat Dec 20 2014/
only update for the evening shift was a tweaking of the min T grid
and hourly T grids to encompass some Micro climate effects in the
County Warning Area. Locations on the periphery of the Escarpment are seeing some
accelerating cooling due to topographic effects and tried to mimic
that in the hourly grids. Since a couple locations just off the
Escarpment are already within a degree or two of their forecast
lows...attempted to add a little more precision to the min T grid
to account for this Micro climate effects. Maybe an exercise in
futility but an exercise nonetheless.
Previous discussion... /issued 329 PM CST Sat Dec 20 2014/
Short term (tonight through Sunday night)...
not much to talk about in the short term as the weather is
expected to stay mostly quiet. Cloud cover continues to encompass
most of south central Texas except for The Hill Country. Light
northerly winds are continuing with temperatures in the 50s across
much of the area. Southerly flow will return tomorrow after
morning lows reach the lower 40s to upper 40s. We should have more
clearing tomorrow afternoon and with continued southerly flow...we
should see temperatures around 5 to 7 degrees warmer than today.
Lows Sunday night will reach the 40s and 50s with partly to mostly
Long term (monday through saturday)...
things will be changing beginning Monday as a strong trough of low
pressure begins to build and dive south across the northern
plains. In response to this system...a surface low is expected to
develop across North Texas during the day. Most of our County Warning Area will
see south-southwest winds at the surface with strong SW winds at 850 mb. This
will create downsloping conditions which will lead to a further
increases to the afternoon highs which will range from the upper
70s in the southwest to the lower 70s in the northeast.
A strong piece of energy in association with the main trough axis
will rotate through Texas Tuesday. This will allow a strong cold
front to push south through the County Warning Area by Tuesday afternoon. There
could be enough moisture for light showers mainly across the
eastern zones as this front moves through but precipitation amounts are
expected to be light. The main story with this front will be the
colder temperatures and gusty northerly winds behind the front.
Wind speeds Wednesday afternoon will be around 20 to 25 miles per hour with
higher gusts. Lows on Wednesday morning will be in the lower 30s
to upper 30s. Many areas in The Hill Country will likely be at
freezing but surface winds will remain around 10 miles per hour which should
limit a more widespread freeze.
The next upper system will begin to approach the area by Thursday
morning which will bring the flow back from a southerly direction.
This will equate to lows Christmas morning in the upper 30s to
lower 40s...warming into the middle 60s to near 70 degrees. As
that next trough moves through the area Friday night...it will
send another front through the area. Little to no rain is
expected with this system.
Preliminary point temps/pops...
Austin Camp Mabry 43 60 51 70 50 / 0 0 - - 10
Austin Bergstrom international Airport 43 60 48 70 49 / 0 0 - - 10
New Braunfels Muni Airport 42 61 50 72 51 / 0 0 - - 10
Burnet Muni Airport 41 59 47 71 46 / 0 0 0 - 10
del Rio International Airport 43 64 45 74 49 / 0 0 0 0 -
Georgetown Muni Airport 42 59 49 70 48 / 0 0 - - 10
Hondo Muni Airport 40 62 48 73 47 / 0 0 - - -
San Marcos Muni Airport 42 61 49 70 50 / 0 0 - - 10
La Grange - Fayette regional 43 62 51 72 54 / - - 10 - 10
San Antonio International Airport 44 61 51 72 50 / 0 0 - - -
Stinson Muni Airport 44 62 50 73 50 / 0 0 - - -