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

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393
FXUS64 KEWX 201501
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1001 AM CDT Sat Oct 20 2018

.UPDATE...
There is a band of rain showers stretched across our northern
counties and another area in the southeast. We have adjusted the POPs
for the next few hours to reflect this. We still expect rain chances
to shift to the west this afternoon and the rest of the forecast
looks good.

&&

.PREV DISCUSSION... /ISSUED 648 AM CDT Sat Oct 20 2018/

AVIATION...
MVFR ceilings early this morning are expected to lift to VFR between
16-18Z as a weak cold front/surface boundary slides across the South
Central Texas terminals, allowing for drier air to erode the lower
cloud bases. Have maintained VCSH mention for all terminals ahead of
the front. Area radars are showing some light showers drifting south
near AUS/SAT/SSF this morning and light rain lingering near DRT in
the vicinity of an upper level speed max. Dry conditions expected to
prevail behind the boundary with north winds increasing into the
10-15 knot range and persisting through the end of the period.

PREV DISCUSSION... /ISSUED 343 AM CDT Sat Oct 20 2018/

SHORT TERM (Today through Sunday)...
This weekend will see a brief break in the generally rainy pattern
that South Central Texas has seen through the last week. A boundary
will work south through the area through the day today bringing with
it a drier airmass. Along and ahead of the front a few showers are
possible Saturday morning, but other than lingering showers across
the Rio Grande Plains Saturday afternoon looks dry for most in South
Central Texas. Precipitable Water values will drop from the 1.5 to
2.0 inch moist airmass of the last several days down to PW values
less than an inch for Saturday night and Sunday. This will not only
mean a mostly dry Sunday, but a slightly cooler night tonight, day on
Sunday, and Sunday night. With the boundary around, and the closer
proximity to the large upper low across the SW U.S. showers will once
again be possible across the Rio Grande Plains, but the rest of South
Central Texas will see a dry and mostly cloudy day on Sunday.

LONG TERM (Sunday Night through Friday)...
With the drier airmass in place lows Sunday night will be about 5-10
degrees cooler than the lows Friday night, dropping to the low to mid
50s. Ahead of the next system afternoon highs on Monday will also be
cooler, around 60 degrees, about 20 degrees below seasonal normals.

The reprieve from the rain will be short lived as a disturbance
rotates through Texas in the southwesterly flow aloft. This
disturbance will tap into Pacific moisture, and allow for mid level
flow out of the southeast, pulling in Gulf moisture as well. This
means that the pesky phrase "heavy rain" will re-enter the forecast
for Monday. While widespread heavy rain is not expected at this
point, pockets of moderate to heavy rainfall are certainly possible
as the disturbance traverses central and south Texas Monday. Focus
for precipitation shifts eastward Monday night as the disturbance
exists, but with moisture back in place over Texas the rainy pattern
remains. Tuesday will be cloudy with isolated showers hanging around.

The next good chance for rain arrives Wednesday as the large upper
trough that has been sitting across the desert Southwest moves
eastward into the Central Plains. While the GFS trended slightly
drier, the ECMWF still shows a decent shot of rain for South Central
Texas during the day on Wednesday. Again, pockets of heavy rainfall
are not out of the question, but confidence in widespread heavy
rain is low at this time.

The forecast for the end of the week still remains uncertain as it is
highly dependent on Pacific Tropical Storm Vicente and a second yet-
to-form tropical system. Both global models show one or both of these
systems getting caught up in the upper level flow and pulled towards
Texas. The good news for the Hill Country and Edwards Plateau is
that there is now a fairly clear trend to keep the majority of the
rainfall across South Texas. This means that while rain chances
continue late into next week the heavier rainfall should be to the
south of the areas that have seen the most rain over the last 7 to 10
days.

Rainfall totals through Friday from the GFS and ECMWF show 2 to 4
inches, but again keep the heaviest rainfall along and south of the
I-10 corridor in areas that have generally been drier over the last 7
to 10 days compared to the Edwards Plateau and Hill Country. How much
rain and where the focus will be can still change through the next
few days as the models get a better handle on Wednesday`s trough and
the two Pacific tropical systems. Afternoon highs through the next
week will run about 10 degrees below seasonal normals in the mid 60s
to near 70, while overnight lows remain in the 50s only a few degrees
off where they should be this time of year.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              69  54  67  52  59 /  20  -    0  10  70
Austin Bergstrom Intl Airport  70  54  68  51  59 /  20  -    0  10  70
New Braunfels Muni Airport     71  56  68  52  59 /  30  10  -   10  70
Burnet Muni Airport            69  52  66  50  59 /  20  10   0  10  50
Del Rio Intl Airport           69  57  66  54  61 /  50  20  30  30  70
Georgetown Muni Airport        70  52  66  50  60 /  20  -    0   0  50
Hondo Muni Airport             71  58  69  54  61 /  30  10  10  20  70
San Marcos Muni Airport        71  55  68  52  59 /  30  10  -   10  70
La Grange - Fayette Regional   72  56  69  52  60 /  30  -    0   0  70
San Antonio Intl Airport       71  57  68  54  60 /  30  10  -   20  70
Stinson Muni Airport           72  59  69  55  60 /  30  10  10  20  70

&&

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

$$

Aviation...09
Short-Term/Long-Term...05
Public Service/Data Collection...YB



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