520
FXUS64 KEWX 120815
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
315 AM CDT Mon May 12 2025

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.SHORT TERM...
(Today through Tuesday)
Issued at 303 AM CDT Mon May 12 2025

Key Message:

- Much warmer today; record heat expected Tuesday.

Early morning observations show temperatures range from the lower
50s to the mid 60s along with a wide range of dew point temperatures
in the lower 30s to upper 50s. Skies are clear and with light winds,
morning low temperatures will likely bottom out in the upper 40s to
upper 50s.

Temperatures will trend upward today given plenty of insolation and
dry air in the lower levels. The warmest readings will be out west
along the Rio Grande with upper 90s to near 100 in the forecast.
Farther east, highs will be in the upper 80s to mid 90s. While these
temperatures will be above climatological normals, no records are
expected to be broken today. This will change on Tuesday as the low-
level thermal ridge amplifies from west to east across the region.
While it will be hot across all areas, the southwest to westerly
winds in the lower levels will tend to keep the warmest readings
generally along and west of the I-35 corridor. Based on current
forecast temperatures, a Heat Advisory will likely be needed for
these areas. We have noticed some differences in the MOS guidance
with regards to temperatures and will continue to monitor and adjust
the forecast as needed. Regardless, this early season heat wave is
on the way and residents are urged to prepare for heat-related
impacts beginning Tuesday.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 303 AM CDT Mon May 12 2025

Key Message:

- Daily and monthly high temperature records are at risk Wednesday and
  Thursday.

- Moderate to Major risk of heat-related impacts continue through the
  week.

- Now is the time to ensure you have access to effective cooling. Additional
  safety information and resources can be found at the following
  websites: www.heat.gov and www.weather.gov/safety/heat

The potentially historic heat wave commencing Tuesday is expected to
continue through midweek. While Wednesday is forecast to produce the
hottest temperatures during this stretch, increasing moisture and
overnight temperatures throughout the week will result in a Moderate
to Major risk of heat-related impacts persisting into the weekend.

Wednesday remains on track to be the hottest day of the week, and
both dynamical and dynamical-statistical guidance has held steady in
depicting exceptionally high temperatures for this time of year,
though we continue to note some discrepancies in the two forms of
model guidance. The ingredients for a near-record to record-breaking
day for heat remain in the picture... the core of a highly anomalous
850mb thermal ridge (which could be the warmest low-level thermal
ridge ever recorded for this time of year based on NAEFS and ENS
ensemble outputs), southerly surface flow, and low-level isentropic
descent along a dry line all overlapping in South Central Texas.
While the hottest ambient temperatures will likely be over the Rio
Grande Plains and northern Hill Country on the dry side of the dry
line, additional moisture on the moist eastern side of the dry line
will likely make apparent temperatures along the I-35 corridor and
Coastal Plains comparably hot. Southwesterly flow developing from
about 500mb upwards should help to bring some Pacific moisture aloft
and facilitate cirrus or cirrostratus cloud cover, which could
mitigate some heating. While the precise value of high temperatures
will be sensitive to this cloud cover, in all likelihood those clouds
will be too thin and too high up to forestall significant warming.
Current forecast highs for Wednesday range from around 100 over the
Coastal Plains to around 103 to 105 along the I-35 corridor. The
lower elevations of the Rio Grande Plains and localized parts of the
Hill Country, subjected to descending air west of the dry line, are
currently forecast to see highs from about 105 to 110.

On Thursday, shortwave troughing over the central Plains causes the
thermal ridge over our area to shift east and become more diffuse,
with the increased troughing providing more opportunity for cloud
cover. Ambient temperatures should drop slightly, but it should
still be a very hot day with highs around 100 to 105. Reinforced
troughing towards the end of the week and through the weekend will
help to whittle down the thermal ridge further, resulting in
temperatures ticking down slightly, with forecast highs moreso in
the upper 90s to around 100 rather than hovering near 105.
Unfortunately, the increase in troughing is accompanied by a zonal
extension of the subtropical jet over North Texas. This increases
onshore southerly flow and causes more moisture to stream into our
area, leading to a gradual climb in dew points. Thus, heat indices
comparable to Wednesday`s highs are forecast to continue through the
weekend. Overnight temperatures are also expected to increase
through the week in the 70s due to this added moisture, providing
diminishing respite from the day`s heat. In fact, low temperatures
towards the weekend may also challenge daily record high minimum
temperatures for some sites.

Concerning rain chances, most of the long-range forecast remains
dry. However, the southwesterly flow aloft generated by western
CONUS troughing could open the door for a few high terrain storms
that could cross into our area this weekend, mainly from Mexico.
We`ll also need to watch for isolated chances for afternoon/evening
activity along the dry line as the strengthened troughing brings a
pathway for disturbances to temporarily enhance lift on that
boundary. Wind patterns aloft are slightly more conducive for that
from Friday onwards, though it will be difficult task to overcome
elevated stable air. Thus, rain chances remain low, with periodic 10
to 20 percent PoPs over the southern Edwards Plateau, Hill Country,
and northern I-35 corridor from Friday into the weekend during the
early evenings with some potential for thunder if showers do
materialize.

&&

.AVIATION...
(06Z TAFS)
Issued at 1233 AM CDT Mon May 12 2025

VFR conditions are expected at area TAF sites through the current
forecast period. Light and variable or light north winds continue
through the overnight into Monday morning, with winds eventually
becoming east to southeast.

&&

.FIRE WEATHER...
Issued at 303 AM CDT Mon May 12 2025

Elevated to locally near critical fire weather conditions are
possible each afternoon through the week mainly along and west of
the I-35 corridor, including the Edwards Plateau and Rio Grande.
Monday marks a transitional day between the slightly cooler weather
of the past weekend and a summer-like fire weather pattern
developing midweek. Light winds this afternoon generally below 8 mph
sustained at 20 ft are forecast with minimum RH values of 10 to 20
percent along and west of the I-35 corridor.

A drying and warming trend ramps up through Wednesday, resulting in
lower RH values closer to 10 percent over the Rio Grande Plains and
southern Edwards Plateau with temperatures above 100F throughout
South Central Texas. Southerly flow is forecast each afternoon along
and east of I-35 with 10 to 15 mph winds. Areas west of I-35 may see
a mix of 5 to 10 mph westerly to southerly winds due to daily
advances of the dry line. Temperatures tick down a few degrees after
Wednesday and moisture increases slightly, resulting in an increase
in daily minimum RH values for most areas. However, afternoon RH
values near 15 to 20 percent may continue along the Rio Grande and
southern Edwards Plateau through the weekend. The dry and potentially
record-setting warmth throughout the week could lead to more active
fire weather conditions going forward as fuels dry.

&&

.CLIMATE...
Issued at 255 AM CDT Sun May 11 2025

RECORD MAX TEMPERATURES TUESDAY THROUGH SATURDAY
(* TIED RECORD WITH MOST RECENT OCCURRENCE SHOWN)

         TUE       WED       THU       FRI       SAT
        05/13     05/14     05/15     05/16     05/17
------------------------------------------------------
AUS    94/1967*  96/2003   96/2003   97/2018*  97/2018
ATT    98/1925   97/2022   98/1925   99/2022*  99/2022
SAT    98/2009*  97/2022*  98/2022   97/2022* 100/2022
DRT   104/1995  103/2003  102/2022  107/2013  105/2013

RECORD MAX TEMPERATURES FOR MAY
-------------------------------
AUS   102 ... set on 05/07/1998
ATT   104 ... set on 05/24/1924
SAT   104 ... set on 05/31/2004
DRT   112 ... set on 05/26/2024

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              92  65 103  74 /   0   0   0   0
Austin Bergstrom Intl Airport  90  62 102  72 /   0   0   0   0
New Braunfels Muni Airport     93  63 103  71 /   0   0   0   0
Burnet Muni Airport            89  65 102  72 /   0   0   0   0
Del Rio Intl Airport           98  68 108  75 /   0   0   0   0
Georgetown Muni Airport        88  64 102  73 /   0   0   0   0
Hondo Muni Airport             93  62 106  68 /   0   0   0   0
San Marcos Muni Airport        91  62 102  70 /   0   0   0   0
La Grange - Fayette Regional   88  64  98  71 /   0   0   0   0
San Antonio Intl Airport       93  66 104  73 /   0   0   0   0
Stinson Muni Airport           95  65 105  72 /   0   0   0   0

&&

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

$$

Short-Term...Platt
Long-Term...Tran
Aviation...Platt