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FXUS64 KEWX 051806 AAC
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
Issued by National Weather Service Brownsville TX
106 PM CDT Wed Jun 5 2024

...New AVIATION...

.UPDATE...
Issued at 1144 AM CDT Wed Jun 5 2024

With "cold" outflow having ripped through the Austin/San Antonio
metro as of 1130 AM, temperatures have dropped sharply (still in the
70s behind it). Traditionally, such outflows "work over" the
atmosphere and clean out the "yuck" for several hours following them.
Though partial sunshine will return and winds veer back around to
light southeast, temperatures will only recover back to the upper 80s
to lower 90s and heat index around 100 at best...so have cancelled
both the Heat Advisory and Warning east of Medina/Frio Counties. Will
need to keep an eye on these counties as well to see if the outflow
can power through...though expect it to begin waning as it heads
toward the Big Bend/Rio Grande Plains by early afternoon.

&&

.MESOSCALE UPDATE FOR THUNDERSTORM OUTFLOW
1144 AM CDT Wed Jun 5 2024

Outflow winds have been quite robust...and only a little shy of
severe levels as indicated by radar and surface obs. Austin gusted to
46 mph and San Antonio/International to 49 mph recently with other
gusts on the 30 to 40 mph range. The stronger convection is
moving into/off the southeast Texas coast so not expecting severe
thunderstorm warnings...but we`ll continue to issue special weather
statements to cover the stronger gusts until things quiet down in the
next hour or two.

&&

.SHORT TERM...
(Today through Thursday)
Issued at 253 AM CDT Wed Jun 5 2024

An MCS south of the Red River and a surface boundary extending west
into the Permian Basin will track to the south-southeast. The
showers and thunderstorms may move across eastern parts of our area
(mainly US 77 corridor) this morning, while the surface boundary
stalls somewhere near or across our area. This boundary will impact
the chances of convection, as well as, the extent of the dangerous
heat today into this evening.

As for the convection, moisture convergence near the boundary and
heating should generate showers and thunderstorms late this
afternoon. With upper level ridging beginning to build over our
area, areal coverage should be isolated to perhaps widely scattered.
Extreme CAPE up to 4,000 J/kg and steep mid level lapse rates of 8
to 9 C/km indicates a potential for a few strong to severe storms,
though shear and flow aloft will be weak. The threats are large hail
and damaging winds gusts. The showers and thunderstorms will
dissipate by late evening with loss of heating after sunset.

As far as the heat, expect continued dangerous temperatures and heat
indices south of the boundary. High temperatures in the upper 90s to
near 102 and heat indices of 108 to 112 are expected around the
greater San Antonio area. Although highs of 105 to 109 are expected
across the Rio Grande Plains, heat indices will be similar due to
mixing of dewpoints. Across both of those areas will issue a Heat
Advisory from Noon through 8 PM. High temperatures of 100 to 105 and
heat indices of 112 to 114 can be expected across Frio, Atascosa,
Karnes, and Wilson counties. Have issued an Excessive Heat Warning
for those areas. Temperatures and heat indices will be a bit lower
across the Hill Country into Central Texas and no heat products are
expected.

On Thursday, the upper level ridge becomes more centered over our
area. Due to subsidence underneath the ridge and some drying aloft,
no convection is expected. Some mixing with this drier air aloft
should allow for lower heat indices. However, our southwestern
counties may need a Heat Advisory due to the higher heat indices
there.

Heat Precautions: Never leave people and/or pets alone within a
closed car, stay hydrated with plenty of water, wear loose-fitting
and light colored clothing, and take frequent breaks within the
shade and air conditioning.

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 253 AM CDT Wed Jun 5 2024

The center of the mid-level ridge to our west over Northern Mexico
and the Desert Southwest shifts eastward over Texas from Friday into
the upcoming weekend. While the hot temperatures are expected to
maintain within this pattern, the ridge becoming more centered atop
of the region should help to squash any remaining rain/storm
chances, delay/limit the extent of the morning low stratus, and
promote more efficient atmospheric mixing during the afternoons.
This would likely yield to slightly lower afternoon dew points and
peak heat indices from Friday through this weekend in comparison
from yesterday`s observed values and today`s forecast values. While
nights remain quite warm, the overnight lows should also become a
little less oppressive as well.

The medium range guidance, including the ensemble means, continue
with a fairly consistent signal for a potential pattern change into
and through early next week. The mid-level ridge will gradually
start to buckle as a series of storm systems advance through the
northern plains into the Great Lakes region while additional weaker
shortwave disturbances advance through the central plains. Models
suggest that there could be enough oomph from the parent storm
systems for a front to possibly enter portions of Central Texas by
sometime around Monday. This front could provide enough forcing for
returning low to medium (20-30%) chances for rain and storms. The
front and/or any associated cold pool driven mesoscale features may
bring enough heat relief to where temperatures trend closer to or
even for a few locations perhaps below climatological average at
times between Monday and Wednesday of next week.

&&

.AVIATION...
(18Z TAFS)
Issued at 106 PM CDT Wed Jun 5 2024

Outflow that created gusty northeast winds across the Austin/San
Antonio metro has petered out and winds have veered to the
east/southeast at the terminals in this corridor. With atmosphere
stabilized not expecting any mentionable convection through the
afternoon...but do expect to see few-scattered cumulus to redevelop
by mid afternoon with mainly scattered cirrus above.

For this evening...some models (mainly GFS) hinting at possible quick
convection in the corridor but others are very limited...so despite
the remining 15-20 percent overall storm probabilities have left out
of the overnight TAF. That said...500 mb north/northwest flow with
embedded weak short waves is conducive...if atmosphere can recover by
late afternoon/early evening. Did not include any light haze/fog for
the 08Z-13Z window but something to consider, and did leave a period
of low VFR/high MVFR ceilings during this time as well.

As for Del Rio...the GFS hints at a potential interaction of the
outflow with possible Sierra Madre activity during the early to mid
evening but confidence is low in whether this can develop/move into
the area. For now, have left out but will need to keep an eye on as
well by late afternoon and early this evening.


&&

.CLIMATE...
Issued at 253 AM CDT Wed Jun 5 2024

         WED        THU        FRI
        06/05      06/06      06/07
------------------------------------------------
AUS   100/2018   103/2011   100/2022
ATT   101/2011   103/2022*  103/2022
SAT   102/2022   104/2022   104/2022
DRT   107/2022*  110/2022   108/1974

* TIED RECORD WITH MOST RECENT OCCURRENCE SHOWN

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              90  75  97  77 /  10  10   0   0
Austin Bergstrom Intl Airport  91  74  97  75 /  10  10   0   0
New Braunfels Muni Airport     91  75  99  75 /  10  20   0   0
Burnet Muni Airport            90  73  94  72 /  10  10   0   0
Del Rio Intl Airport          108  81 106  82 /  20  20  10   0
Georgetown Muni Airport        90  73  95  74 /  20  10   0   0
Hondo Muni Airport             93  75 101  75 /  10  20   0   0
San Marcos Muni Airport        90  73  97  74 /  10  10   0   0
La Grange - Fayette Regional   90  75  94  74 /  30  10   0   0
San Antonio Intl Airport       91  75  98  77 /  10  20   0   0
Stinson Muni Airport           91  76 100  76 /  10  20   0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for Dimmit-Kinney-
Maverick-Medina-Uvalde-Val Verde-Zavala.

Excessive Heat Warning until 8 PM CDT this evening for Frio.

&&

$$

Aviation Update..52/BSG