San Antonio, Texas 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

354
FXUS64 KEWX 221154
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
554 AM CST Sun Dec 22 2024

...New AVIATION...

.SHORT TERM...
(Today through Monday)
Issued at 141 AM CST Sun Dec 22 2024

Key Messages...

- Warmer weather Sunday and Monday with increasing humidity.

- A slight chance of light rain or sprinkles near the escarpment
tonight/Monday morning.

Low clouds are returning over the area today in a piecemeal fashion,
with southerly H850 winds giving the 5000 foot layer saturation
first and the mostly east surface winds being slower to saturate the
lowest levels. A few pockets of lower ceilings below 2000 feet are
forming along the western escarpment from Uvalde to north San
Antonio, but with dewpoints still in the 30s and 40s to suggest the
moistening arriving at the boundary layer level. Meanwhile areas
east of I-35 may have to wait until late this morning for lower cigs
and possibly not until early this evening. The coverage of ceilings
above this level should be more continuous and even the skies over
our far eastern counties should encounter a few periods where skies
are mostly cloudy. The cloud impacts should hold max temps below 70
degrees along and NW of Del Rio to San Antonio to Taylor. Even the
areas that should see more sunshine will probably be capped in the
70-75 degree range.

Light showers have been a signal by the NAM and some of the high res
models for tonight into early Monday mainly over the western
escarpment. Measurable rains can not be ruled out, but the highest
amounts should be only around 5 hundredths of an inch. Some patchy
fog may also form in the areas where these low rain chances are
expected. South winds in the moist layer are expected to ramp up
tonight which should combine with the cloudiness to hold min
temperatures up to well above December normals. The high mins and
southerly winds will also contribute to a daytime warming trend to
bring most areas into the 70s despite the continued abundance of
clouds.

&&

.LONG TERM...
(Monday night through Saturday)
Issued at 141 AM CST Sun Dec 22 2024

Key Messages...

-Way above normal temperatures throughout the period

-Multiple albeit weak systems will impact mostly eastern areas of our
 CWA

Temperatures starting Monday night will be running way above normal
due to the return of southerly winds pumping in moisture and clouds
due to onshore flow. Our overnight lows will range anywhere from the
upper 50s to lower 60s. While highs will range from lower to middle
70s each day which is 10-15 degrees above climatological averages
for this time of year(lower 60s). With the warm temperatures also
comes the increase in humidity values so it could feel a big muggy
the next few days before drier air moves in on Saturday.

Speaking of moisture, we seem to be turning the corner when it comes
to systems impacting mainly our eastern areas with 3 systems waiting
in the wings for us. The first system as has been previously
advertised in prior discussions looks to impact our area mainly on
Christmas Eve as a cold front pushes through our area. Global models
continue to back off on moisture overspreading the area. Additionally
when looking at the chances for strong thunderstorms with this
system, instability values for MUCAPE look to max out at around 700
j/kg when storms initiate. Thus while there is some instability the
moisture looks to already have moved past our area and off to the
east thus reducing the forcing needed to produce stronger storms.
Looking at the Hi-Res models, particularly the FV3 and the NAM, they
both show very little in the way of convective precipitation.
Additionally while looking at recent model guidance all 3 of our
reliable models have trended down in not only precip amounts but also
chances of precip for this storm system so have capped pops at
20-30% for most areas north of San Antonio with the exception being
our extreme northeastern counties with pops generally around 40-45%.

The next storm system, #2 is set to arrive sometime Thursday
afternoon into Thursday evening and looks to swing through our area
via a closed low pressure system in northern Texas moving northeast
into Missouri. As it does so Global models paint a cold front
extending from the low back into South-Central Texas with a warm
front moving through the area earlier in the day. This setup looks a
little bit more promising especially with the triple Low setup and
as such the Global models seem to agree with both the GFS and Euro
being consistent in timing but inconsistent in strength. The GFS
once again is leaning towards lighter precip amounts compared to the
bullish amounts the Euro is spitting out. Decided to go with a blend
between the two as the previous couple runs show some level of
consistency with forcing and enough moisture noted along with fairly
good levels of vorticity showing up. Feel there is certainly a
better chance that we could see more moisture out of this system then
the previous one. However, as we have seen recently its best not to
get our hopes up as amounts tend to trend down as higher Hi-Res model
guidance comes in and as we get closer to the event.

Lastly, our third system looks to arrive sometime Friday night into
Saturday morning with chances for more showers and storms as a cold
front looks to slice through our area. As with the previous systems
the western part of our CWA looks to completely miss out on any
precip while our eastern areas look to receive repeated rounds of
showers and storms.

&&

.AVIATION...
(12Z TAFS)
Issued at 527 AM CST Sun Dec 22 2024

Scattered mostly MVFR cigs are forming over much of the higher
terrain along and north of Del Rio to San Antonio with a brief spell
of IFR cigs forecast for DRT later this morning. SAT/SSF should see
most of the day in MVFR cigs but AUS may only see a brief period as
drier air could still mix in from the SE since a dry NE surface wind
continues over SE TX. Onshore winds should be more uniform by this
evening, and AUS will likely get closer to falling near the same time
as SAT/SSF into MVFR to IFR. The NAM model has performed slightly
better than the GFS in the lower level moisture return, so will keep
with the IFR prevailing in the final hours of the TAF periods. Some
light showers could form tonight between DRT and SAT, but low model
QPF values would suggest not much of an impact on the respective
airports.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              67  54  75  60 /   0  20  10  10
Austin Bergstrom Intl Airport  68  55  76  61 /   0  20  10  10
New Braunfels Muni Airport     69  55  77  60 /   0  20  10   0
Burnet Muni Airport            64  54  72  59 /   0  10  10  10
Del Rio Intl Airport           69  59  76  58 /  10  20  10   0
Georgetown Muni Airport        66  54  74  60 /   0  10  10  10
Hondo Muni Airport             67  57  75  60 /  10  20  20   0
San Marcos Muni Airport        68  54  76  60 /   0  20  10   0
La Grange - Fayette Regional   69  52  76  59 /   0  10  10   0
San Antonio Intl Airport       68  58  75  62 /   0  20  20   0
Stinson Muni Airport           70  58  77  62 /   0  10  10   0

&&

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

$$

Short-Term...18
Long-Term...CJM
Aviation...18