312
FXUS64 KEWX 172332
AFDEWX
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
532 PM CST Fri Jan 17 2025
...New AVIATION...
.SHORT TERM...
(Tonight through Saturday night)
Issued at 209 PM CST Fri Jan 17 2025
Key Messages...
- Cold front arrives tonight bringing cooler temperatures for
Saturday.
- Widespread hard freeze is expected Saturday night over the Hill
Country with temperatures falling into the 20s.
A weak upper level shortwave has managed to squeeze out some showers
across the region this afternoon. Little to no accumulation is
expected from this, as we`ve mainly noted trace amounts at locations
that have observed rain. This disturbance has also been a bit more
expansive with regard to cloud cover than earlier guidance had
indicated, so we`ve opted to lower highs today for most locations.
It will still be FAR warmer than we are going to see temperatures
for at least the next week, so enjoy those 60s.
Our long-advertised cold front is currently situated over the
northern Texas Panhandle. This front will make rapid progress
southward this afternoon and evening, arriving in the Hill Country
and Southern Edwards Plateau between midnight and 3am and moving
through the remainder of South Central Texas by 9am Saturday. Highs
will likely be reached in the morning over the Hill Country and
northern I-35 Corridor with locations south and west warming into
the 60s and perhaps lower 70s over the southern Rio Grande Plains.
The really cold push of air arrives as an arctic front and secondary
push of air arrives Saturday night with temperatures plummeting into
the 20s and 30s. The short term forecast is dry but the long term is
a different story. For more on that, scroll below.
&&
.LONG TERM...
(Sunday through Friday)
Issued at 209 PM CST Fri Jan 17 2025
Key Messages:
-Hazardous cold occurring early to midweek with very high confidence
(80-100%) in hard freezes each night from Sunday night through
Wednesday Morning.
-Be prepared to protect People, Pets, Plants, and Pipes from the
cold weather.
-Increasing chances for winter precipitation from Monday evening
through Tuesday morning but low confidence on total accumulation
amounts. At least minor travel impacts expected.
-Warming up Wednesday, but monitoring another system towards late
week.
The arctic air will be in place as the period starts on Sunday
morning with area temperatures ranging from the mid 20s across the
Hill Country to the upper 20s and low 30s elsewhere across South-
Central Texas. Factoring in breezy northerly flow with winds around
15 to 25 mph, and higher gusts, wind chills will range anywhere from
10-15 degrees across the Hill Country to 15-25 degrees elsewhere.
This may necessitate a Cold Weather Advisory for a portion of the
region. Mostly sunny conditions are then expected through the rest
of the day on Sunday, allowing for temperatures to climb into the
40s for most locations, and around 50 along the Rio Grande. A
widespread hard freeze is expected Sunday night through Monday
morning, with lows in the teens across the Hill Country and low to
mid 20s for most other locations. While wind speeds will weaken
slightly Sunday night into Monday morning, Cold Weather Advisories
and possibly an Extreme Cold Warning could be needed as wind chill
values range from the single digits to the teens.
In addition to the very cold temperatures, MLK JR Day should start
off with mostly sunny skies but the cloud cover steadily increases
in response to the approaching weather system, which we`ll go into
more detail about down below. This cloud cover and increasing
moisture will help to cap afternoon highs in the 30s/lower 40s on
Monday.
While differences are still noted within the latest medium range
guidance, the solutions have narrowed regarding the 500 mb pattern
with the amplification of the shortwave diving south-southeastward
from the Pacific Northwest and the location/strength of the coastal
low/trough off South Texas. The GFS and the GEFS members over the
past 18 to 24 hours have trended toward a slower, more amplified,
and colder/wetter solution than the past runs. While the GFS/GEFS is
still running a tad warmer compared to the ECMWF/EPS and especially
the CMC/GEPS, it`s certainly much closer than what prior runs of the
GFS/GEFS had indicated.
This continued trend has necessitated a farther nudge upwards into
the medium chance (40-60%) category for precipitation from the I-35
corridor eastward into the coastal plains. If the recent model
trends continue to hold, then PoPs will likely need to be increased
even more.
Initially, around and soon after the onset of this event, a mixed
precipitation type event may take place near and south of the I-10
and US HWY 90 corridor Monday evening, with modeled sounding
profiles, indicating a weak warm nose aloft. North of this region,
the precipitation should mainly be snow. Forecast soundings show the
column cooling with time across southern areas overnight and through
Tuesday morning with the predominate precipitation type changing to
snow. The precipitation chances are expected to decrease by Tuesday
afternoon across the region as the base of the trough swings through
and then moves east of the area.
While both snow and ice accumulation is looking possible across
portions of the region (30-50% from I-35 eastward for at least half
an inch of snow), it remains difficult to pin down the total amounts
this far out. Additionally, the snow to liquid ratios and shapes
could also become quite tricky, especially as there is the concern
for a very dry layer at least initially, at the more favorable
dendrite growth zone. Again, like the previous discussion had
pointed out, the deterministic runs of the GFS and ECMWF total snow
is on the higher end of it`s ensembles. In addition, more
fluctuations in the models are likely, which is why we are showing a
gradual increase upward in PoPs rather than a larger jump. It should
also be stressed to exercise extreme caution when viewing snow or
freezing rain accumulations from any one model or certain apps this
far out. Probabilistic guidance from the Winter Storm Severity Index
continues to show a modest increase in probabilities for minor to
moderate impacts across portions of the region.
Some clearing does look to take place from west to east Tuesday
afternoon, but it might be too late for central and eastern areas to
have a big impact on temperatures, especially if there is any snow
on the ground. We have held high temperatures in the mid to upper
30s for central and eastern areas Tuesday afternoon and low 40s
immediately along the Rio Grande.
Monday night into Tuesday morning and again Tuesday night into
Wednesday morning will continue with hazardous cold weather with
Cold Weather Advisories or even possibly Extreme Cold Warnings in
effect as the overnight lows fall into the teens and 20s with colder
wind chills ranging from the single digits to the teens.
Southerly flow finally resumes during the day on Wednesday, with
highs rebounding into the mid 40s to near 50 degrees along the Rio
Grande. There is very low confidence in Thursday and Friday`s
forecast, as there remains considerable timing differences on the
next upper level trough, associated cold front, and a coastal low.
The deterministic GFS and CMC guidance is leaning dry but the
GEFS/GEPS ensemble mean does have some light QPF in our eastern most
areas. The 12Z ECMWF run came in rather wet but the EPS mean remains
on the lighter side. We will keep precipitation chances in the
slight chance (20%) range. We`ll have to again monitor the surface
temperatures closely but we`ll get to those details as we get closer
in time.
&&
.AVIATION...
(00Z TAFS)
Issued at 522 PM CST Fri Jan 17 2025
The main story for this forecast period will be the strong FROPA
expected tonight. Model guidance and forecast soundings indicate some
rare LLWS developing around or shortly before midnight and
continuing for a few hours before subsiding after 9-12Z. Winds are
expected to shift to the west or west-northwest late this evening and
then northerly after sunrise on Saturday. Up to 40-50 kts of wind
shear look likely at about 2000 ft at AUS, SAT, and DRT, generally
out of the west or west-northwest. Once the front moves through wind
shear is expected to subside. However, northerly winds will remain
and become quite gusty at all sites. The timing of these gusty winds
is expected to start around 16Z for all sites except KDRT where the
front is expected to move through slightly earlier with gusty winds
expected around 13Z. Expect VFR ceilings to continue throughout the
forecast period for all sites.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 45 56 29 42 / 0 0 0 0
Austin Bergstrom Intl Airport 45 57 29 42 / 0 0 0 0
New Braunfels Muni Airport 46 61 31 44 / 10 0 0 0
Burnet Muni Airport 41 54 27 40 / 0 0 0 0
Del Rio Intl Airport 49 68 34 47 / 0 0 0 0
Georgetown Muni Airport 42 54 27 39 / 0 0 0 0
Hondo Muni Airport 46 65 31 47 / 10 0 0 0
San Marcos Muni Airport 44 59 29 42 / 10 0 0 0
La Grange - Fayette Regional 46 57 29 42 / 0 0 0 0
San Antonio Intl Airport 48 62 32 44 / 10 0 0 0
Stinson Muni Airport 49 63 33 46 / 10 0 0 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term...MMM
Long-Term...Brady
Aviation...CJM
No recent Short Term Forecast (NOW) has been issued for NWS Austin/San Antonio CWA (EWX).
No recent Special Weather Statement (SPS) has been issued for NWS Austin/San Antonio CWA (EWX).
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