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

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FXUS64 KEWX 210601 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
101 AM CDT Wed Oct 21 2020

.UPDATE...
Please see the 06Z aviation forecast discussion below.

&&

.AVIATION...
Low cloud development is noted on satellite imagery early this
morning, with fairly stout southeasterly flow in place from the
surface up to roughly 4k MSL according to area VWP products. Low
clouds will initially come in low-end MVFR for the I-35 sites and
upstream obs show some IFR cigs are already in place. With this in
mind, we have opted to add a mention of TEMPO groups between 10-14Z
for IFR cigs along I-35. Similar to trends over the last several
days, improving conditions will take shape after 15Z, with all areas
likely to head back into VFR territory between 17-18Z. We could also
see an isolated shower or two this morning, but any rain will be
brief and have opted to keep out of the forecast for now. Out west at
DRT, low clouds will develop this morning, resulting in MVFR cigs.
The current forecast brings MVFR cigs in around 11Z, but if current
trends continue, we may need to start cigs a little earlier.
Improvement back to VFR will take shape after 17Z as southeast winds
become gusty.


&&

.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  68  86  69  86 /  10  10  10   0  10
Austin Bergstrom Intl Airport  88  66  86  68  87 /  10  10  10   0  10
New Braunfels Muni Airport     90  69  89  70  89 /  10  10  10   0  -
Burnet Muni Airport            86  67  85  67  81 /   0   0  -    0  10
Del Rio Intl Airport           90  69  90  68  90 /  -    0   0   0  -
Georgetown Muni Airport        87  66  86  68  85 /  10   0  -    0  10
Hondo Muni Airport             90  67  90  67  90 /  10  10  -    0  -
San Marcos Muni Airport        88  67  87  68  87 /  10  10  10   0  -
La Grange - Fayette Regional   89  68  88  70  87 /  -   10  10   0  -
San Antonio Intl Airport       88  69  87  70  87 /  10  10  10   0  -
Stinson Muni Airport           88  69  88  69  88 /  10  10  -    0  -

&&

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

$$

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



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