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

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422
FXUS64 KEWX 220008
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
708 PM CDT Sun Apr 21 2019

.AVIATION... /00Z TAFS/

With a large low latitude storm system approaching from the west,
will use a blend of persistence to offset the climo influnced MOS
guesses for the onset and mix-out of low clouds. Model forecasts have
not handled the nocturnal low level wind trends well and may
continue to handle the winds poorly tonight. Despite locally dense
fog developing for about 3 hours this morning at AUS, am hesitant to
lower any vsbys to even mvfr at this time. Winds were well decoupled
early this morning and this could be the signal for how low cigs and
vsbys get should they drop to below 8 knots tonight. However, would
expect to see less decoupling and an overall wind increase with the
upstream storm system getting slightly closer and farther south. As
was noted on VAD winds from this morning, a return of surface winds
below 8 knots may mean some low level wind shear issues could
develop. Will allow for more ifr cigs overnight into early Monday
and extend the I-35 period of mfr cigs for midday Monday due to the
build-up of low level moisture.

&&

.PREV DISCUSSION... /ISSUED 256 PM CDT Sun Apr 21 2019/

SHORT TERM (Tonight through Monday Night)...
Breezy and gusty conditions are forecast to continue through this
evening. Winds decrease a bit tonight into Monday morning while
averaging 8 to 12 MPH through the period. Low level moisture will be
increasing tonight continuing through Monday with cloudy skies
forecast to prevail for the rest of the short term period.

With moisture increasing overnight, lows will be warmer than
previous couple of mornings with lower 60s across the Hill Country
and mid to upper 60s over the rest of the area.

Cloudy skies are forecast to prevail for most of the day on Monday
with highs in the upper 70s across most locations to mid 80s along
the Rio Grande. Another surge of breezy southerly winds is
anticipated for Monday afternoon with speeds of 10 to 15 MPH with
gusts up to 25 MPH.

Moisture deepens Monday night into Tuesday morning according to area
forecast soundings mainly along the I-35 corridor/escarpment area,
and kept intact the patchy fog and drizzle forecast area mentioned
in previous forecast package.

LONG TERM (Tuesday through Sunday)...
An upper low level system is forecast to push southeast across the
southwest CONUS into northern Mexico on Tuesday. This system is
forecast to slowly push to the east and across central Texas by
Wednesday afternoon/evening. At lower level, a cold front is forecast
to push from central Texas into the Hill Country on Wednesday
morning. In the mean time, increased moisture is anticipated to
spread across most of south central Texas through the period.

With all these features in place come chances for rain beginning out
west across the Edwards Plateau/Hill Country on Tuesday night and
then spreading to the southeast overnight/Wednesday morning. Some
storms may become strong to severe as they come out from the Mexican
mountains. Also, these storms could produce locally heavy rain as
precipitable water values are forecast to be near the two standard
deviation.

As the upper low level system tracks to the east on Wednesday, the
cold front will slowly push across south central Texas. Latest model
guidance bring a surface low out of Mexico and put it across the area
to add a degree of difficulty to this particular forecast period.
Weather models do agree on the potential for severe weather across
south central Texas on Wednesday and then transitioning into a heavy
rain event. The severe weather risk area covers the eastern two-
thirds of south central Texas with possibly large hail and damaging
wind gusts as main threats. Can`t ruled out isolated tornadoes as mid
level wind shear ranges from 50 to 55 knots per area forecast
soundings. Storm rainfall totals forecast ranges from 2 to 3 inches
across the northern part of south central Texas with lesser amounts
elsewhere. Can`t ruled out isolated higher amounts up to 4 inches.

Showers and thunderstorms will come to an end from west to east as
the upper level system moves to east Texas and the frontal passage
pushes across the Coastal Plains Wednesday night into Thursday.

Rest of the week into the weekend looks good with a warm up trend in
store through the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              65  79  66  78  65 /   0  -   10  30  50
Austin Bergstrom Intl Airport  64  79  66  78  64 /   0  -   10  30  50
New Braunfels Muni Airport     64  79  66  79  64 /   0  -   10  30  50
Burnet Muni Airport            63  77  64  75  63 /   0  -   10  40  70
Del Rio Intl Airport           65  82  67  83  65 /   0  -   10  30  70
Georgetown Muni Airport        65  79  66  77  63 /   0  -   10  30  60
Hondo Muni Airport             64  83  66  81  65 /   0  -   10  30  50
San Marcos Muni Airport        64  79  66  78  64 /   0  -   10  30  50
La Grange - Fayette Regional   65  80  67  79  65 /   0  -   -   20  40
San Antonio Intl Airport       65  80  67  78  66 /   0  -   10  30  50
Stinson Muni Airport           65  80  67  79  66 /   0  -   10  30  50

&&

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

$$

Aviation...Oaks
Short-Term/Long-Term...04
Public Service/Data Collection...33



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