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

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FXUS64 KEWX 200600 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
100 AM CDT Tue Oct 20 2020

.AVIATION...
/06Z TAFS/
MVFR cigs are already affecting the I-35 terminals and this trend
will continue through at least 16Z/17Z time frame. KDRT enjoys VFR
as of this writing but MVFR cigs are expected to begin at 09Z. Some
models suggest for even IFR cigs for few hours across all area
airports around 11Z/12Z period and therefore included. VFR cigs are
expected to return by 18Z across all area terminals this afternoon.
Southerly winds will be in control through the period with speeds
ranging from 5 to 10 knots along the I-35 corridor and 10 to 15 knots
with gusts up to 22 knots across KDRT for most of the day. MVFR cigs
return once again late tonight for all sites. Can`t rule out a
passing shower or two late this morning/early afternoon across the
San Antonio area to bring lower vsbys for a short period of time if
showers do occur.

&&

.PREV DISCUSSION... /ISSUED 650 PM CDT Mon Oct 19 2020/

AVIATION...
With the front hanging to our north keeping South Central Texas in
the moist southerly flow airmass, the typical overnight pattern of
VFR until around 06z, then a mix of MVFR/IFR through the morning
hours, mixing out around 18z is expected for tonight into Tuesday AM.
While the greatest chance for IFR cigs will be at the I-35 Terminals
(AUS/SAT/SSF), IFR could extend all the way westward to DRT for a few
hours. Winds, which have been gusty this afternoon, will gradually
decrease overnight and be south-southeasterly at or less than 10
knots for the overnight and Tuesday morning periods.

PREV DISCUSSION... /ISSUED 222 PM CDT Mon Oct 19 2020/

SHORT TERM (Tonight through Tuesday Night)...
Current satellite and obs show that the shallow cold front has
stalled along our northern CWA and is beginning it`s retreat
northward, having made it through portions of Burnet, Llano, and
Williamson counties. This leaves the rest of the region under
southeast flow, above normal temperatures, and elevated dewpoints.
This persistent flow will bring back a low stratus deck overnight
with possible patches of fog over the interior Hill Country.
Weakness in the ridge aloft along the Coastal Bend will allow for a
chance at some isolated shower activity for the Coastal Plains and
extending into the southern extent of the I-35 corridor. Chances for
rain should keep widespread fog development at bay. Temperatures
overnight will also be moderated by the elevated moisture with
overnight lows expected 10+ degrees above normal for this time of
year.

Frontal boundary to our north will dissipate and mostly clear skies
will give way to another warm and humid October day on Tuesday.
Expect another warm night Tuesday night with a return of low clouds
and possibly fog. Weather pattern remains unchanged through the rest
of the short term with broad troughing over the CONUS and
subtropical ridges over the Atlantic and Pacific basins with a
weakness in the ridging aloft over South Texas.

LONG TERM (Wednesday through Monday)...
The weakness in the ridging aloft drifting to the east combined with
a moist southerly lower level jet may produce very patchy early
morning drizzle along the Escarpment and an afternoon shower or two
near the Coastal Plains on Wednesday into Thursday. Well above normal
temperatures continue.

An upper level shortwave rotating through the broad troughing over
the CONUS will bring a cold front across our area midday into evening
on Friday. Cannot rule out a shower or two along the front due to
weak moisture convergence. With a frontal passage later in the day,
above normal temperatures continue.

Upper level ridging briefly builds into southern Texas as the front
retreats north this weekend. Slightly below normal temperatures on
Saturday warm to slightly above normal on Sunday.

Ridging eases off to the south as the broad troughing deepens. This
brings a much stronger cold front across our area on Monday. Deeper
moisture and an unstable airmass may allow for isolated showers and
thunderstorms. The ECMWF has a morning frontal passage with
temperatures dropping during the day from early morning highs while
the GFS has a late afternoon into next Monday night frontal passage
with one more day of warm temperatures. For now, will go with the
blended guidance until a model consensus develops. The airmass behind
this front will be the coldest thus far in this fall season. Model
temperatures in the GFS indicate a possible freeze in parts of the
Hill Country for next Wednesday morning (October 28th).

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              87  70  86  67  86 /  10   0  -    0  -
Austin Bergstrom Intl Airport  88  69  86  67  87 /  10   0  -    0  10
New Braunfels Muni Airport     90  70  89  69  89 /  10  -   10   0  10
Burnet Muni Airport            86  67  84  66  85 /  10   0  -    0   0
Del Rio Intl Airport           90  70  89  70  91 /  -   -    0   0   0
Georgetown Muni Airport        87  68  86  66  86 /  10   0  -    0   0
Hondo Muni Airport             90  67  89  67  90 /  -   -   -    0  10
San Marcos Muni Airport        88  68  87  67  87 /  10   0  10   0  10
La Grange - Fayette Regional   89  70  88  68  87 /  10   0  10  -   10
San Antonio Intl Airport       88  70  87  69  88 /  10  -   10   0  10
Stinson Muni Airport           89  69  87  69  88 /  10  -   10  -   10

&&

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

$$

Short-Term/Aviation...17
Long-Term...Platt


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