Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
720 PM CST Friday Dec 19 2014
Update...overcast cloud deck across the northern County Warning Area has expanded
south this evening...along and east of U.S. 281. There may be
additional expansion to the southwest overnight. Minor updates
made to sky grids to reflect current 11-3.9u satellite trends as
well as output from the WRF abi synthetic 10.35-3.9u imagery.
Minor adjustments also made to hourly T grids. Rest of forecast
remains on track.
Previous discussion... /issued 542 PM CST Friday Dec 19 2014/
Aviation... /update for 00z tafs/
a deck of MVFR ceilings covers Austin early this evening...and should
expand southwest to impact Sat/ssf terminals in the next 2-3
hours. A light but steady nearly wind overnight should keep most
areas from seeing significant visibility restrictions...but ceilings are
likely to gradually fall to borderline LIFR/IFR levels toward
daybreak. Gentle surface ridging continues to be overrun by zonal
winds aloft through Saturday...so models are trending toward
overcast skies in the MVFR category all day into Saturday evening.
Previous discussion... /issued 346 PM CST Friday Dec 19 2014/
Short term (tonight through Saturday night)...
as of 3 PM...skies were beginning to clear up on the Escarpment
and Rio Grande Valley. Temperatures were able to reach the middle 60s
in that area with the i35 corridor still only in the upper 50s
with cloud cover persistent. Believe this gradual sky cover trend
will play a role in overnight lows and fog potential in the
A light northerly wind and cloud cover off the Escarpment will
probably be enough to inhibit much in the way of fog. However from
the i35 corridor west...decent radiational cooling and T over
values of -2 to -6 were indicated in MOS guidance.
Therefore...included patchy fog for these locations.
Long term (sunday through friday)...
a series of cold frontal passages between now and next weekend
will be the focus for the long term periods. Our first of which
will be Monday night into Tuesday morning. While this cold front
is prognosticated to be a quick one...it looks like it will be passing
through too dry of an air mass set up across the southern half of
the state. The dry conditions Tuesday night and high surface pressure
in place will make next Wednesday morning the coldest of the week
most likely. Opted to decrease the lows a couple degrees for this
period due to pretty significant ensemble variation lending to the
idea that the guidance values may not be too accurate. But with a
surface high pressure center over the Rio Grande Valley keeping winds
at a northerly component...strong northerly 850 mb winds...and a
dry column...would imagine the colder side of the fence is the
best way to lean for Wednesday morning.
Christmas day is shaping up to look quite pleasant...unless you
were hoping for cold and snowy. It should begin rather
chilly...lows in the middle to upper 30s...but certainly not snowy.
In fact...clear skies and weak ridging should allow highs to reach
the 70s in some locations.
The next frontal passage has been slower to arrive with each model
run the last couple days. While the GFS would have the front
through our area by Saturday...the Euro doesnt have it clearing
ewx until Tuesday morning. The upper level patterns of both models
begin significant Christmas day on handling the next possible
upper level system so it is unclear which outcome holds more
water at this point.
Preliminary point temps/pops...
Austin Camp Mabry 46 56 43 60 48 / - - - - -
Austin Bergstrom international Airport 45 56 41 59 46 / - - - 10 -
New Braunfels Muni Airport 46 56 44 61 48 / - - - 10 -
Burnet Muni Airport 42 54 39 58 46 / - - - - -
del Rio International Airport 46 60 45 63 46 / - - - - -
Georgetown Muni Airport 44 54 39 58 47 / - - - - -
Hondo Muni Airport 41 59 44 62 46 / - - - 10 -
San Marcos Muni Airport 45 57 42 61 46 / - - - - -
La Grange - Fayette regional 48 57 44 61 48 / - - - 10 -
San Antonio International Airport 46 57 44 61 49 / - - - - -
Stinson Muni Airport 46 58 45 62 49 / - - - - -
public service/data collection...12