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

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FXUS64 KEWX 201923

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
223 PM CDT Sun Jun 20 2021

.SHORT TERM (Tonight through Monday Night)...
Doing a quick check of the afternoon satellite and radar partly to
mostly cloudy exist this afternoon across South Central Texas thanks
to a smattering of low level cumulus and higher level cirrus clouds.
This may help moderate temperatures slightly in areas that see more
cloud cover, with temperatures already warming to the Century mark
at the mostly sunny Del Rio as of 2pm. Satellite has shown a few
isolated showers across the Coastal Plains that have snuck into
DeWitt and Lavaca Counties at times. These southeastern Coastal
Plains counties have the best chance of seeing additional isolated
showers and maybe a rumble of thunder or two through the rest of the
afternoon and evening. This shower activity is thanks to the weak
upper low that based on water vapor and model data is now being
absorbed into the mid-level flow across east Texas.

With increased surface flow off the Gulf of Mexico tonight should be
another typical moist summer night with overnight low clouds forming
for most areas by daybreak. Monday will be another partly cloudy day
with the cloud cover playing a key role in the afternoon
temperatures. Combined with increasing temperatures and dew points
areas that stay more cloud free like parts of the Rio Grande Plains,
Edwards Plateau, and Coastal Plains will see heat index values climb
into the 105 to 111 range, being highest along the Rio Grande Plains
and Winter garden regions. Due to this parts of the area will almost
certainly need a Heat Advisory. With questions still about cloud
cover will lead the product issuance to later shifts. During the day
on Monday a few isolated showers and storms are possible, mainly
across the Coastal Plains and areas of east Texas.

Precipitation chances will increase late in the day on Monday into
the overnight hours as a VERY late season cold front moves through
the area. The global models have now come in line with the high
resolution models and bring the front through some time between 00z
(7pm) and 06z (1am) Monday evening and early Tuesday morning. With
the earlier timing the ample moisture ahead of the front the Storm
Prediction Center has introduced a Marginal Risk (Level 1 out of 5)
for much of the area (excluding the Coastal Plains). Model soundings
do show ample CAPE, but fairly limited shear for tomorrow evening.
Think that a few strong to severe storms could fire thanks to the
added lift from the front, and the front arriving shortly after the
peak heating of the day does add credence to this. Another note is
that the NAM and GFS still hint at the development of a meso-low
along the Rio Grande or over Mexico as the front passes to the
south. With precipitable water values between 1.5 and 2 inches some
locally heavy downpours could also be possible. With the progressive
nature of the front and the recent dry spell this would most likely
be some beneficial rainfall and much of a flooding threat other than
typical minor impacts.


.LONG TERM (Tuesday through Sunday)...
The frontal boundary will stall near our southern border Tuesday.
There will be a chance for showers and thunderstorms across the
southern half of our CWA with the best chances over the southeastern
counties. The front will also "cool" us off a bit. Highs Tuesday will
be about 10 degrees lower than Monday. The low level flow will
quickly turn back around to southeasterly Tuesday night and Wednesday
pushing the front back north as a warm front. There will be a slight
chance for showers over the southeast, but rain is not likely
anywhere. The southeasterly flow will bring warmer air back to the
region and temperatures will increase through the end of the week.
The upper level ridge will build back to the east through the middle
of the week. Next weekend an upper level trough will push down
through the Central Plains pushing the ridge to the east. This may
produce enough lift around the southwestern edge of the ridge to
generate convection over our CWA.


Austin Camp Mabry              78  96  70  85  73 /  -   10  70  20   0
Austin Bergstrom Intl Airport  78  96  69  85  72 /  -   10  70  20   0
New Braunfels Muni Airport     77  96  72  88  74 /  -   -   60  20   0
Burnet Muni Airport            76  94  67  83  71 /   0  20  70  -    0
Del Rio Intl Airport           79 104  74  92  77 /   0  -   60  20  -
Georgetown Muni Airport        78  95  68  83  71 /   0  20  80  10   0
Hondo Muni Airport             78  98  73  89  74 /  -   -   50  20   0
San Marcos Muni Airport        77  95  71  87  73 /  -   10  60  20   0
La Grange - Fayette Regional   78  94  74  88  75 /  10  20  70  30  -
San Antonio Intl Airport       79  97  72  88  74 /  -   -   60  20   0
Stinson Muni Airport           79  99  74  90  76 /   0  -   50  20   0




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