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

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FXUS64 KEWX 300025 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
725 PM CDT Thu Apr 29 2021

.UPDATE...

Have made adjustments to the short term forecast given the latest
observational trends and model guidance. Raised PoPs overnight for
the coastal plains and across much of the CWA on Friday as models
have become more bullish on convection firing across the region as
the frontal boundary currently located to the south-southeast of
the CWA tires to back into southern portions of our area. With the
closed upper level low situated to the west, we also remain in a
favorable location for added lift. Additionally, we went ahead and
raised the QPF values, matching with the latest update from WPC.
Generally, 1 to 2 inches of rain are expected through Friday night
with localized higher amounts within the heaviest and strongest
convection. Portions of the coastal plains have been placed in a
marginal to slight risk for excessive rainfall overnight. A slight
risk of excessive rainfall holds across portions of the coastal
plains from 12Z Friday through 12Z Saturday while much of the area
will be a marginal. A marginal risk for severe weather also will
remain possible for tomorrow along portions of the Rio Grande and
coastal plains. Given considerable cloudiness and increase in the
rainfall potential, have lowered highs slightly tomorrow.

&&

.AVIATION...00Z TAF Package

For the I-35 TAF sites...IFR/MVFR ceilings primarily prevail with
brief instances of LIFR conditions possible at times. With rain,
generally light, increasing in areal coverage through tonight and
maintaining through much of the period, expect for visibility
restrictions as well at times. The thunderstorm potential is to
increase as well, especially from overnight into Friday, and will
elect to include vicinity thunderstorms, after 04Z for KAUS and
after 09Z/10Z at KSAT and KSSF.

For KDRT...VFR conditions continue into tonight before ceilings
become MVFR into the overnight and for Friday. Shower activity
becomes possible, mainly after daybreak and will remain in the
forecast through the rest of the TAF period. In addition to the
showers, an isolated thunderstorm could be possible but elect
to leave out of this TAF package for now.

&&

.PREV DISCUSSION... /ISSUED 206 PM CDT Thu Apr 29 2021/

SHORT TERM (Tonight through Friday Night)...

A cold front that was hung up northwest of the San Antonio and
Austin metro areas is finally easing its way across those areas
while portions of the front farther south have reached the lower
Texas Coast. An upper level low is dropping south into the Mexican
State of Chihuahua. The cold front will stall near the Texas Coastal
Plains tonight into Friday while the upper level low remains over
Chihuahua. These two features will continue to provide the upward
forcing of an unseasonably moist airmass (PWs around 150 percent of
normal at 1.1 to 1.5 inches) to generate showers. The highest POPs
for tonight into Friday due the strongest upward forcing will focus
along the frontal zone near the Coastal Plains, as well as an area
of greater divergence aloft over Central Texas, the Hill Country,
and the Edwards Plateau. There could be pockets of locally heavy
rains due to the unseasonably moist airmass and possible training of
cells. Elevated instability will allow for isolated to widely
scattered thunderstorms. A few strong to perhaps severe storms are
possible due to modest shear and mid level lapse rates. As the upper
level low begins to move toward the Big Bend, the front moves back
to the west across South Central Texas Friday night. Upward forcing
strengthens leading to more widespread rains, with the unseasonable
airmass allowing for heavier rains. Increased instability may allow
for a few more stronger to perhaps severe storms, as well.

LONG TERM (Saturday through Thursday)...

The upper level low pressure system moving across northeastern
Mexico is forecast to push northeast into the middle Mississippi
Valley by Sunday. At the surface, a low pressure system developing
across the Coastal Plains moves inland and pushes a warm front into
the southern counties by Saturday. This scenario has the potential to
bring scattered to numerous showers and thunderstorms across most
locations. Some thunderstorms across the eastern half of the areas
including Austin and San Antonio metros could become severe with
large hail and damaging winds as main weather threats. Also, the
Weather Prediction Center Day 3 Excessive Rainfall Outlook puts the
entire area under a marginal risk of rainfall exceeding flash flood
guidance. Rainfall amounts could range from one to two inches with
isolated higher amounts. We will have more details on this on future
forecast packages as models come to better consensus.

Dry weather conditions are expected Saturday evening across the Rio
Grande and then pushing to the east and rest of South Central Texas
during the overnight into Sunday morning. There may be a few
lingering showers or isolated storms across the far east on Sunday
morning, but overall, Sunday should be dry with partly cloudy to
mostly sunny skies out west. Highs ranging from the lower to mid 80s
across the Hill Country and Interstate 35 to upper 90s across the
southwest counties.

The warming trend continues on Monday with highs in the upper 80s
and lower 90s most locations to near 100 across the southwest.

The next chance for rain comes on Tuesday as an upper level short
wave moves across the Four Corners region and then across central
Texas. A cold front ahead of the upper level short wave is forecast
to move over the area and cool temperatures just a bit on Wednesday
and Thursday with mostly sunny skies expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              67  73  65  75  63 /  50  80  70  70  60
Austin Bergstrom Intl Airport  67  74  64  76  63 /  50  80  70  70  60
New Braunfels Muni Airport     67  76  65  77  63 /  50  80  70  70  50
Burnet Muni Airport            63  70  62  73  60 /  50  70  70  70  50
Del Rio Intl Airport           64  77  64  78  62 /  20  50  70  60  20
Georgetown Muni Airport        65  73  63  74  63 /  60  80  70  70  60
Hondo Muni Airport             64  78  64  77  61 /  30  70  70  70  30
San Marcos Muni Airport        66  75  64  75  63 /  50  80  70  70  50
La Grange - Fayette Regional   70  77  67  77  66 /  60  80  60  70  60
San Antonio Intl Airport       66  76  66  75  63 /  40  80  70  70  40
Stinson Muni Airport           68  78  67  77  64 /  40  80  70  70  40

&&

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

$$

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


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