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

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FXUS64 KEWX 231743

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1243 PM CDT Fri Oct 23 2020

A cold front is approaching terminals from the north. FROPA expected
at AUS within the hour. Front will reach DRT then San Antonio sites
by 20Z. Some scattered showers with an isolated chance for thunder at
AUS with decreasing chances for showers near SAT/SSF. DRT should
remain free of precip. Winds behind the front are out of the north
and gusting up to 30kt. Widespread overcast skies behind the front
may keep sites MVFR through the TAF period. Winds begin to shift back
out of the southeast just after the TAF period of the 30 hour TAFs.


PREV DISCUSSION... /ISSUED 326 AM CDT Fri Oct 23 2020/

SHORT TERM (Today through Saturday)...

The story of the short term will be the arrival of the first of a
pair of fronts expected across South Central Texas over the next 7
days. The front is currently located across North Texas and is
producing shower and thunderstorm activity ahead of the front north
of the DFW Metroplex and along the front in North Texas and SW
Oklahoma. When the front arrives today will play a large role in
daytime highs as temperatures should fall behind the front. Current
models have the front through the Austin and San Antonio areas by
mid-afternoon. This would mean that highs in the Hill Country will
only reach the mid 70s, while the I-35 corridor tops out around 80
degrees before the front blows through and begins to cool things
down. The Coastal Plains could still heat up to the mid to upper 80s
before the front arrives later in the day. Gusty northerly winds are
forecast behind the front, sustained around 20 mph, but gusting to as
high as 30 mph through the late afternoon and evening hours.

With precipitation already ongoing due to the lift from the front
and a moist environment in place across South Central Texas
(dewpoints in the upper 60s and lower 70s), isolated to scattered
showers and a few thunderstorms are possible this afternoon as the
front moves through. Based on some of the late night and early
morning runs of the HRRR and other high resolution models have
expanded the slight chance PoPs slightly. Not everyone will see rain
from this front, and those who do should generally see a quarter
inch or less, but it will be welcome and lucky rain for those who
get precipitated on later today.

The front should be through the area by this evening leaving behind
mostly cloudy skies and cooling temperatures. Overnight lows tonight
will drop into the upper 40s across the Hill Country, with low to
mid 50s elsewhere. The sun returns late in the day tomorrow with
afternoon highs in the low to mid 70s. Other than the lingering
cloud cover it should be a pleasant Fall Saturday.

LONG TERM (Saturday Night through Thursday)...
Saturday evening dew points level off early and creep back up
slightly as south winds return. Thus min temps Sunday should rebound
5 to 10 degrees over those of Saturday. Daybreak dewpoints could
catch up to the mins in spots as some areas are showing near 100
percent RH. Will hold off mentioning fog for now and look closer at
this potential in later updates. Machine numbers generate some areas
of morning low clouds which is well reflected in the gridded
forecast. After a nice warm-up to above normal temps Sunday, humidities
will again run high Sunday night in advance of a cold front that hits
our northern counties in the pre-dawn hours Monday. Again will need
to look at light fog potential ahead of the front as RH values reach
near 100 percent.

Monday`s stronger cold front will bring a more important element to
the area--much needed rain. All the deterministic runs are depicting
a weak shortwave to be well timed with the shallow post-frontal
environment late Monday morning, and that is enough reason to show an
uptick in most of the rain chances into the low chance category. QPF
amounts remain low, but the wetter trend is certainly welcome
considering our very dry start to October. SW flow aloft remains over
the frontal inversion with scattered light showers and or drizzle to
continue into Tuesday. The SW flow pattern is due to a low latitude
trough cutting off from the polar flow into a mostly symmetric upper
low as it crosses N TX Wednesday. The timing of the upper low Track
is slowly gaining some consistency in looking at the ensembles for
comparison, but the CMC 00Z run continues to run the track over TX
several hours later than the consensus. Thus will keep the highest
rain chances dampened and spread over the period midnight Tuesday
night to midnight Wednesday night when a slightly more convective and
widespread rain event may occur. It is also worth noting that the
track of the upper low center passing north of the area (roughly
along US Hwy 67 in the period late Tuesday through late Wednesday)
could result in areas near the Rio Grande to be left with little or
no rain to show from the system. Cloudy skies and mostly north winds
will probably keep the convection from becoming strong, but a few
pockets of rainfall totals over an inch might be a possibility. Given
our short-term drought, little concern is given toward runoff
potential. By Thursday morning most of the models clear rain chances
west to east leaving a fair and mild pattern for late next week into
Halloween weekend.


Austin Camp Mabry              50  70  59  83  62 /  -   -    0   0  10
Austin Bergstrom Intl Airport  50  70  58  85  63 /  -    0   0   0  10
New Braunfels Muni Airport     52  73  60  88  67 /  -    0   0   0  -
Burnet Muni Airport            47  68  58  83  55 /  -    0   0   0  10
Del Rio Intl Airport           54  75  60  89  61 /  -    0   0   0  -
Georgetown Muni Airport        47  69  57  83  57 /  -    0   0   0  10
Hondo Muni Airport             52  75  59  88  66 /  -   -    0   0   0
San Marcos Muni Airport        51  72  58  86  63 /  -   -    0   0  -
La Grange - Fayette Regional   53  71  61  86  68 /  10  -    0   0  -
San Antonio Intl Airport       53  72  60  86  67 /  -   -    0  -   -
Stinson Muni Airport           54  72  61  86  69 /  -   -    0   0  -




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