Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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FXUS64 KEWX 120339 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
939 PM CST Mon Dec 11 2017

.UPDATE...
A weak cold front is pushing down Central Texas and expected to move
across the Hill Country around midnight tonight. The front will
continue to push to the southeast overnight and early Tuesday. A
cooler airmass will spread across the area later tonight into
Tuesday. No rainfall expected with the passage of the cold front,
however, the cooler airmass will make temperatures to only reach the
60s Tuesday afternoon.

&&

.PREV DISCUSSION... /ISSUED 545 PM CST Mon Dec 11 2017/

AVIATION.../00Z_TAFS/
VFR conditions are expected at all TAF sites throughout the entire
TAF period as we remain in dry northwest flow aloft. Scattered to
broken high clouds will continue at and above 10-15 kft with light
south-southwest winds gradually veering to west-northwest this
evening. A cold front is expected to move through all TAF sites
between 7-9Z to bring persistent north-northwest 10-15 knot winds
with gusts around 20 knots tomorrow afternoon at the I-35 sites.

PREV DISCUSSION... /ISSUED 231 PM CST Mon Dec 11 2017/

SHORT TERM (Today through Tuesday)...
Other than some passing clouds this afternoon Central Texas will see
mostly sunny skies with afternoon high temperatures running about 8
to 10 degrees above normal. Relative Humidity values back in Central
Texas have dropped into the teens across the Hill Country leading to
elevated fire weather concerns, but winds are and should remain
light through the afternoon and evening hours. The afternoon water
vapor continues to show the low pressure system diving southeast
across the Upper Midwest and Great Lakes Region embedded in a larger
trough across the Eastern U.S. A cutoff low pressure off of Baja
California will be the culprit that provides the high clouds later
today. A weak ridge can be seen in the synoptic pattern with the next
weather system approaching the West Coast.

A weak cold will slip through South Central Texas late tonight into
Tuesday morning. Behind the front winds will switch around to the
north and temperatures tomorrow and for the rest of the week will be
about 10 degrees cooler, right around seasonal normals. No
precipitation is expected with the front as conditions at the surface
are far too dry. Northwest flow will continue today through Tuesday
as the large trough continues across the Eastern U.S.

LONG TERM (Tuesday Night through Sunday)...
The two highlights of the long term forecast are a second cold front
on Thursday and what happens with the cutoff low across Baja
California. In general though mostly sunny skies are expected with
highs around normal through the weekend, with lows in the 30s and
40s. High pressure which is leading to the sunny skies will shift
eastward for the second half of the week.

The Thursday front will rotate through the large scale trough across
the Eastern U.S. It will move through during the day and reinforce
the cooler air across the area, maintaining the seasonal
temperatures. The front will again switch winds out of the north for
Thursday and Friday. Enough southerly flow will be in place to keep
relative humidity values above 30 percent behind the next front.

For days 6 and 7 the two long term models diverge. The ECMWF
dissolves the cutoff low into the zonal flow across Texas, keeping
the atmosphere and the precipitation forecast dry. The GFS on the
other hand pulls the cutoff low into the trough ahead of the next
front producing rain over the coastal plains for Sunday thanks to
plentiful Gulf moisture pulled ahead of the trough. Have sided with
the drier ECMWF for this forecast package and the weaker southerly
flow keeping South Central Texas dry through the next 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              43  62  37  67  44 /   0   0   0   0   0
Austin Bergstrom Intl Airport  39  61  35  65  42 /   0   0   0   0   0
New Braunfels Muni Airport     40  62  35  65  42 /   0   0   0   0   0
Burnet Muni Airport            39  60  35  67  41 /   0   0   0   0   0
Del Rio Intl Airport           40  65  38  65  42 /   0   0   0   0   0
Georgetown Muni Airport        39  60  36  66  42 /   0   0   0   0   0
Hondo Muni Airport             37  66  35  66  41 /   0   0   0   0   0
San Marcos Muni Airport        40  62  36  65  42 /   0   0   0   0   0
La Grange - Fayette Regional   41  62  36  65  42 /   0   0   0   0   0
San Antonio Intl Airport       42  65  38  65  44 /   0   0   0   0   0
Stinson Muni Airport           42  65  38  65  44 /   0   0   0   0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Mesoscale/Aviation...LH
Synoptic/Grids...17
Public Service/Data Collection...33



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