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

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FXUS64 KEWX 091135
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
535 AM CST Fri Dec 9 2016

.AVIATION...
VFR flying conditions with BKN-OVC clouds prevail today through
tonight with some areas becoming FEW-SCT this afternoon and
evening. CIGs lower to MVFR Saturday as moisture deepens and have
included at KSAT at 10/13Z and KAUS at 10/15Z. Surface ridge
drifts off to the east. Nly winds 10 to 15 KTS turn to NEly at 5
to 10 KTS this afternoon, become VRBL less than 5 KTS tonight, and
then SEly Saturday most areas. Except out west, Nly winds 5 to 10
KTS become SEly this afternoon into tonight.

&&

.PREV DISCUSSION... /ISSUED 358 AM CST Fri Dec 9 2016/

SHORT TERM (Today through Saturday)...
Temperatures tonight range from the upper 20s in parts of the Hill
Country to lower 40s in the Rio Grande Plains with most spots in
the 30s. Northerly 10-15 knot winds and an overcast cloud deck at
6-9 kft have created enough mixing and trapped enough outgoing IR
radiation to keep temperatures from dropping as fast as forecast.
However, winds are continuing to subside and with 3-4 hours left
before sunrise, so a freeze near and north of a Del Rio to San
Antonio to Halletsville line is still anticipated. Therefore, a
Freeze Warning remains in effect for those counties that have not
experienced their first freeze of the season until 9 am this
morning. However, locations in the southern fringe of the Freeze
Warning area may remain above freezing if winds do not subside
over the next few hours as overcast clouds should persist.

Skies should begin to clear later this morning as winds become
light and variable during the afternoon as surface high pressure
moves over the region. High temperatures will only warm up into
the mid 40s this afternoon just a few degrees above our average
low temperatures this time of year. Light winds and clear skies
should allow for strong radiational cooling for at least the first
half of the evening tomorrow to allow temperatures to cool back
into the lower to mid 30s with a light freeze expected in the Hill
Country and lower-lying areas along the Interstate 35 corridor.
Low clouds should return from south to north tomorrow night as
weak isentropic ascent develops ahead of a weak shortwave trough
to prevent temperatures from falling into the 20s. However, a
delay in these overcast skies may allow temperatures to fall a few
degrees more than forecast to result in a more widespread freeze.
Highs should warm up into the lower 50s on Saturday under cloudy
skies with light drizzle and very isolated showers as isentropic
ascent strengthens and E/SE flow returns over the region.

LONG TERM (Saturday Night through Thursday)...
Temperatures on Saturday night should remain steady in the upper
40s and lower 50s as warm air advection and southerly flow
strengthens while isolated light showers continue over the
region. Skies should clear and isolated showers end from west to
east on Sunday afternoon to allow temperatures to climb into the
mid to upper 60s just above seasonal normals. Winds briefly shift
to the north on Monday morning as a weak front associated with the
weak shortwave pushes into the region, but this front should
dissipate and have no effect on temperatures as they warm up into
the lower 70s across most of the region.

Temperatures on Tuesday should once again warm up into the lower
70s as a stronger front approaches the region, but models differ
substantially on the timing and strength of this feature. The
ECMWF pushes a modest front through the region Tuesday afternoon
with a reinforcing shot of cold air on Wednesday similar to what
occurred this week, but the GFS remains warm through Wednesday
evening when a much stronger front moves through the region.
Considering the operational GFS is ~10 degrees warmer on Wednesday
and ~10-15 degrees cooler on Thursday than its ensemble mean, for
now have sided more with the ECMWF and the GFS ensemble in causing
a more gradual cooling trend for Wednesday and Thursday. However,
zonal flow regimes are typically not very persistent, so would not
be surprised to see a slower progression of a much stronger front
like the GFS pan out or for the front to stay north of the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              46  34  51  49  68 /   0   0  10  20  20
Austin Bergstrom Intl Airport  45  32  52  49  68 /   0   0  10  20  20
New Braunfels Muni Airport     46  34  51  49  67 /   0  -   10  20  20
Burnet Muni Airport            43  31  50  47  68 /   0   0  10  20  10
Del Rio Intl Airport           46  32  53  43  67 /   0   0  -   -    0
Georgetown Muni Airport        44  31  51  49  67 /   0   0  10  20  10
Hondo Muni Airport             47  33  51  46  67 /   0  -   10  10  -
San Marcos Muni Airport        46  34  51  49  67 /   0  -   10  20  20
La Grange - Fayette Regional   47  35  54  51  70 /   0  -   10  30  20
San Antonio Intl Airport       47  35  51  48  66 /   0  -   10  20  10
Stinson Muni Airport           47  36  51  49  67 /   0  -   10  20  10

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 9 AM CST this morning for the following
counties: Bandera...Bastrop...Bexar...Caldwell...Comal...Edwards...
Fayette...Gonzales...Guadalupe...Hays...Kinney...Lavaca...Lee...
Medina...Real...Travis...Uvalde...Val Verde...Williamson...Wilson.

&&

$$

Mesoscale/Aviation...04
Synoptic/Grids...LH


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