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

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FXUS64 KEWX 202340
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
640 PM CDT Tue Oct 20 2020

.AVIATION...
A SCT to BKN cloud deck has formed across parts of the I-35 corridor
in South Central Texas this evening. Skies though remain VFR with
southeasterly winds generally a few knots either side of 10 knots.
Winds will decrease overnight with another round of MVFR stratus
building into AUS/SAT/SSF by 07z. This will remain until about 17z
Wednesday morning. Clouds will mix out with a VFR afternoon expected
Wednesday, with winds remaining out of the south around 10 knots. At
DRT, the window for MVFR should be small - 11z to 17z - and winds
should be gusty out west tomorrow afternoon.

&&

.PREV DISCUSSION... /ISSUED 211 PM CDT Tue Oct 20 2020/

SHORT TERM (Today through Wednesday Night)...

A moist southerly lower level flow continues across our area while a
weak mid level impulse moves overhead. Expect a repeat of the low
clouds overnight into Wednesday morning across all areas, as well
as, streamer showers late tonight into Wednesday morning across the
Hill Country and Escarpment areas due to the low level jet and the
impulse. Rainfall amounts will only be a few hundredths of an inch.
Heating will mix the low clouds and showers out by midday Wednesday.
Chances of showers will be less late Wednesday night due to some
drying and have left mention out of forecast, however cannot rule
out a few spotty showers. Temperatures remain several degrees above
normal due to a lower level thermal ridge.

LONG TERM (Thursday through Monday Night)...

Warm, humid conditions will continue Thursday and Friday, with highs
in the 80s to lower 90s thanks to persistent southeasterly flow off
the gulf. There could be a few isolated showers Thursday afternoon,
primarily across the Coastal Plains. But the main story for the long
term is two cold fronts in the forecast as we head through the
weekend into early next week.

The first will be relatively benign, reaching the area later in the
day on Friday and bringing temperatures back down to near or just
below normal for Saturday. Can`t rule out isolated post-frontal
showers for the Hill Country and Edwards Plateau, but chances are
too low to even include mention in the forecast at this time.
Southerly flow will quickly return and bring us right back into the
warmth and humidity for Sunday.

All eyes are on the potential for a strong cold front early-middle
part of next week with medium range models indicating a chance for
our first true push of arctic air to reach south central TX. This
front could also bring chances for much needed rainfall by Tuesday,
potentially the first rain in well over a month for some locations.
Emphasis on COULD, because it`s no guarantee. There remains some
disagreement in just how progressive the deep upper trough is as it
traverses the CONUS. Today`s 12Z runs have trended much further to
the west with the upper level pattern, which would mean a later
FROPA, potentially as late as Wednesday if the upper low cuts off as
the EC/CMC are now indicating. This solution could even lead to the
front stalling out like the last one just did yesterday. The
potential is there for overnight lows as cold as the mid- upper 30s
for portions of the Hill Country Tuesday and/or Wednesday morning,
and although I did lower the post- frontal temps from the NBM
initialization a couple of degrees that was perhaps a mistake given
model trends and the wrench thrown into the forecast by the 12Z
ECMWF. The spread of potential max/min Ts is easily around 30 degrees
for the early part of next week based on what the front eventually
does. Given it`s a La Nina year, wouldn`t be surprised at all if it
just never quite makes it here, but time will tell.

PREV DISCUSSION... /ISSUED 1234 PM CDT Tue Oct 20 2020/

AVIATION...
/18Z TAFS/
VFR flying conditions prevail this afternoon into evening. MVFR CIGs
return overnight, around 21/06Z at the I-35 sites, then around 10Z
at KDRT. There could be brief lowering to IFR in -SHRA, however,
PROBs are too to mention. Clouds mix to VFR late Wednesday morning to
midday. S to SE winds 5 to 10 KTs prevail at the I-35 sites with a
few gusts to 20 KTs this afternoon into evening. SE winds 9 to 15 KTs
prevail at KDRT with a few gusts to 25 KTs this afternoon into
evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              87  69  87  68  86 /  10  10  10  10  10
Austin Bergstrom Intl Airport  88  69  88  66  86 /  10  10  10  10  10
New Braunfels Muni Airport     90  70  90  69  89 /  10  10  10  10  10
Burnet Muni Airport            86  67  86  67  85 /  10  -    0   0  -
Del Rio Intl Airport           90  69  90  69  90 /   0  -   -    0   0
Georgetown Muni Airport        87  68  87  66  86 /  10  10  10   0  -
Hondo Muni Airport             90  67  90  67  90 /  10  10  10  10  -
San Marcos Muni Airport        88  68  88  67  87 /  20  10  10  10  10
La Grange - Fayette Regional   89  70  89  68  88 /   0   0  -   10  10
San Antonio Intl Airport       88  70  88  69  87 /  20  10  10  10  10
Stinson Muni Airport           89  70  88  69  88 /  10  10  10  10  -

&&

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

$$

Short-Term/Aviation...Treadway
Long-Term...05



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