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Area forecast discussion 
National Weather Service Austin/San Antonio Texas
544 am CST Sat Nov 28 2015

isentropic lift and the low level jet maintain areas of -ra with
a few isolated rain showers today through tonight. Greatest impacts are mainly
at the I-35 taf sites...kaus/ksat/kssf and have mentioned -ra or
vcsh through the taf period. Lift is weaker at kdrt and have kept
mention out of tafs. However...may have to update later to mention
based on radar and model trends. A mix of IFR/low end MVFR ceilings
will continue through the taf period with lowest ceilings and IFR/MVFR
visibilities during rain. IFR ceilings become more widespread tonight into
Sunday as the airmass cools. Northerly winds 10 to 20 kts today decrease
to 5 to 10 kts tonight as pressure gradient weakens.


Previous discussion... /issued 408 am CST Sat Nov 28 2015/

Short term (today through sunday)...
as of 330am...the cold front was located around crp keeping the
entire County Warning Area in a north surface wind of 10-20 miles per hour. Despite the thick
low level cloud cover...temperatures have fallen into the middle 30s on
plateau and parts of The Hill Country as well. Some observation have had
intermittent reports of light snow as well. However...other than
the river channels and valleys seeing freezing temperatures...most
other locations are in the 34-37 degree range.

As for the rainfall activity...the bulk of the current activity is
associated with the low level jet still at about 35-40 kts as
indicated by the kewx VAD wind profile. The jet will weaken
gradually over the next 12 hours and also shift slightly eastward
which should result in mostly light and occasionally moderate
rainfall throughout the day. Back to the west...a 250 mb 100+ knots
jet steak will pass over central Texas...and mostly north of our
County Warning Area. Therefore...the dominant lifting mechanism will be mostly
overrunning and isentropic ascent which will be maximized in our
east tonight. With plenty of low level moisture and broad
lift...probability of precipitation will continue to be rather high but quantitative precipitation forecast values should
stay pretty meager. Only expecting between a half inch to an inch
throughout the day today and similar amounts overnight.

Long term (sunday night through friday)...
the bulk of the deep layer moisture begins to clear out Monday as
the next cold front enters West Texas. The speed of the front
through south central Texas is not yet well agreed upon in the
deterministic model guidance. The GFS is notably faster with a
more robust Post frontal surface high behind it. It appears that
the Euro and Canadian are more gradual with the frontal passage
and the exodus of our precipitation chances. The other anomalous outcome
is the GFS producing a deep digging shortwave over the southern
rockies and generating another round of significant quantitative precipitation forecast over our
northern zones and again in the sjt/forward area. The good news is it
appears that the Canadian/dgex/Euro are all in agreement with a
broad upper wave that clears out deep moisture with the passage of
the front this keeping Texas dry through the middle week. So for
now...trended below the superblend probability of precipitation. As the 06z GFS trickles appears its backing off slightly and taking on a more
agreeable depiction of its aforementioned upper low development.
So thats good.

Looking into the long range into the weekend...all models are
showing a deep closed low developing in the western Continental U.S. And
becoming negatively tilted as it begins to move into Texas. Wont
get into the details just yet and will keep an eye on this in
further runs. But it is Worth noting the unusual agreement in the
model synoptic patterns this far out.


Preliminary point temps/pops...
Austin Camp Mabry 44 43 49 45 57 / 80 80 70 30 20
Austin Bergstrom international Airport 45 41 50 44 58 / 80 80 70 30 20
New Braunfels Muni Airport 47 42 51 45 60 / 80 70 60 20 20
Burnet Muni Airport 41 41 47 41 56 / 80 80 70 20 20
del Rio International Airport 48 43 57 47 63 / 60 60 30 - -
Georgetown Muni Airport 43 39 48 42 56 / 80 90 90 30 20
Hondo Muni Airport 49 40 53 45 61 / 80 50 50 10 10
San Marcos Muni Airport 46 41 50 44 59 / 80 70 60 30 20
La Grange - Fayette regional 49 45 53 48 58 / 80 60 60 30 20
San Antonio International Airport 48 43 52 46 61 / 80 70 60 20 20
Stinson Muni Airport 50 45 54 47 61 / 80 70 60 20 20


Ewx watches/warnings/advisories...



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