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

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FXUS64 KEWX 061142
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
542 AM CST Tue Dec 6 2016

.AVIATION DISCUSSION...FOR 12Z TAF PERIOD...
Ground fog has been the complicating factor for terminals this
morning resulting in briefly IFR VIS. For the most part, this fog
has remained very isolated and have only resulted in brief
obstructions so far this morning. KDRT appears to have some fog
developing on or near the Lake Amistad area and impacting the
terminal at TAF issuance. Expecting this to linger through mid
morning.

An advancing cold front will reach KAUS by shortly after the noon
time hour and may contain some MVFR CIGs with -DZ. This will keep
KAUS likely at MVFR throughout the majority of the TAF period.
Should reach KSAT with MVFR CIGS as well by early evening.


&&

.PREV DISCUSSION... /ISSUED 354 AM CST Tue Dec 6 2016/

SHORT TERM (Today through Wednesday)...

Near to slightly below normal temperatures will occur through
mid-week with clouds returning this afternoon and lingering through
Wednesday. There will be a slight chance of light drizzle this
afternoon for northern I-35 corridor areas and a 20-30% of light
showers Wednesday across the Coastal Plains ahead of a strong
front early Thursday morning.

For this morning, localized and transient pockets of ground fog
are occurring across portions of the Hill Country, into the I-35
corridor, the Coastal Plains. Just enough variant wind stirring
and slowly increasing dewpoint depressions is allowing the shallow
ground fog develop quickly and then dissipate out. The trend
through the dawn hours should be a decreasing risk of ground fog
despite the saturated ground from all the recent rainfall.
Observational trends have matched well with the RAP/HRRR output
and will follow such for the short-term forecast through 10am.
Will keep a close watch however, if trends alter and patchy dense
fog does develop across the Coastal Plains or I-35 corridor.
Confidence in dense fog occurrence remains low at this time.

A weak boundary will shift through the region this afternoon that
will help bring more clouds and northerly winds. With weak to
neutral CAA, temperatures should be able to rise to near normal
conditions but the clouds will temper it down a few degrees. NAM
BUFR soundings suggest enough low-level saturation this afternoon
across far northern I-35 corridor locations that light drizzle
could occur. Accumulations will be negligible with only a trace
to 0.02" at best. By Wednesday, weak return moisture flow will
commence as winds shift back to the S/SE. Weak isentropic upglide
could provide just enough vertical lift for light showers across
the Coastal Plains. Accumulations again, will be light across this
area.

LONG TERM (Wednesday Night through Monday)...

A strong cold front with Canadian origins is expected to arrive
early Thursday morning. Much colder temperatures of 20-25 degrees
below normal will be felt through the day Thursday into Saturday.
A widespread freeze is expected Friday morning and likely again
Saturday morning. A slow warm up is expected by late weekend
before yet another front moves through Sunday.

A longwave trough across the Great Lakes in conjunction with a
strong surface high pressure system over the Great Plains will
usher in a strong cold front early Thursday morning. Precipitation
at this time looks to be light along and ahead of the front.
However, temperature profiles across northern and central Edwards
Plateau could support a light change over to a rain/snow mix.
Profiles for Hill Country and Southern Edwards Plateau still
appear slightly too warm for this change over to occur. Soundings
also suggest dry layering that could reduce the overall
precipitation probabilities as well. Will continue to monitor if
temperature profiles cool or saturate further for any possibility
of a rain/snow mix shifting towards the Hill Country/Southern
Edwards Plateau. Any winter mix chances at this time for South-
Central Texas remains quite low to near zero. The other big story
will be the temperatures Thursday through Saturday. Highs Thursday
behind the front will be quite cold with readings 20-25 degrees
below normal with values only managing the upper 30s in the Hill
Country and 40s most other locations. A widespread freeze and
even hard freeze is likely for many, if not all, areas Friday
morning. A freeze warning will be highly likely for this time-
frame. Friday`s highs again will be 15-20 degrees below normal
with another good freeze Saturday morning.

Temperatures will rebound Sunday just before another front moves
through in association with a trough passage through the Central
Plains. 20-30% light rain showers will be possible for central and
eastern locations where the limited moisture return and depth are
co-located. This front will not have Canadian origins and thus
temperatures will remain higher and closer to seasonal normals
into early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              63  43  62  38  44 /  10  -   10  20  10
Austin Bergstrom Intl Airport  64  42  61  40  44 /  10  -   10  20  10
New Braunfels Muni Airport     65  42  60  41  45 /  -    0  10  20  10
Burnet Muni Airport            58  41  60  35  39 /  10  -   -   20  10
Del Rio Intl Airport           68  44  63  42  44 /   0   0   0  10  10
Georgetown Muni Airport        59  42  61  37  41 /  10  -   -   20  10
Hondo Muni Airport             69  41  62  42  48 /   0   0  -   20  10
San Marcos Muni Airport        64  42  61  41  45 /  -   -   10  30  10
La Grange - Fayette Regional   67  45  63  43  46 /  -   -   20  30  10
San Antonio Intl Airport       68  43  61  42  45 /   0   0  10  20  10
Stinson Muni Airport           69  43  61  44  46 /   0   0  10  20  10

&&

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

$$

Mesoscale/Aviation...TB3
Synoptic/Grids...Allen



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