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

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551
FXUS64 KEWX 211138
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
638 AM CDT Sat Oct 21 2017

.AVIATION...
IFR CIGs have developed in the San Antonio area while AUS and DRT are
MVFR. We expect CIGs to drop to IFR at AUS and DRT within the next
hour or two. CIGs should rise to VFR by early afternoon. A cold front
will move through the region overnight into Sunday morning. The front
will bring thunderstorms during the overnight hours which will reduce
conditions to MVFR for a couple of hours. Behind the front winds will
become northerly at 10 to 15 kts with gusts up to 25 kts.

&&

.PREV DISCUSSION... /ISSUED 353 AM CDT Sat Oct 21 2017/

SHORT TERM (Today through Sunday)...
A mid and upper level trough over the Four Corners region moves
across the Rockies today to the High Plains this evening. Surface low
pressure deepens maintaining a moist southerly lower level flow over
our area. Could see a few patches of light fog and drizzle this
morning, however chances are too low to mention. A streamer shower
band may set up along the Highway 77 corridor and have slight chance
POPs there today. Otherwise, airmass is too capped over our area.
Above normal temperatures are expected today.

The mid and upper level trough moves out across the Central/Southern
Plains tonight and Sunday. A dryline drifting east this evening may
generate showers and thunderstorms over the Edwards Plateau into the
Hill Country this evening and have low chance POPs there. As the
trough moves further out into the Plains, a cold front surges across
our area late tonight into Sunday morning. Models are in very good
agreement with only a 3 hour difference from fastest to slowest.
Expect it to enter the Hill Country in the predawn hours, cross the
I-35/Highway 90 Escarpment around or a little after sunrise, then
exit to the Coastal Plains by late morning. A line of showers and
thunderstorms is expected along the front. Moderate CAPE and shear
may allow a few of the storms to become strong to marginally severe
with strong wind gusts and hail the main threats. Due to the speed
of the front, only a brief heavy downpour is anticipated with the
stronger storms. In the wake of the front, a tight pressure gradient
brings breezy to gusty winds as surface high pressure builds into
our area along with much drier air allowing skies to clear.
Temperatures will drop in the morning after the frontal passage and
then recover to near normal in the afternoon with ample sunshine.

LONG TERM (Sunday Night through Friday)...
Surface high pressure settles into our area Sunday night into Monday
with decreasing winds. An upper level trough dropping southeast out
of the Canadian Rockies merges with the Plains trough by Tuesday with
the result an upper level ridge along the West Coast and a long wave
trough along and east of the Mississippi Valley. The Canadian trough
also sends another cold front across our area Monday night with a
reinforcing surge of high pressure bringing another round of breezy
to gusty winds on Tuesday. No rain is expected as no moisture return
is expected. The pattern aloft will continue through the remainder of
the week, although model disagreements develop by late week into next
weekend. The GFS has been consistent with the passage of an upper
level shortwave trough and cold front for next Friday, while the
ECMWF now shows the trough moving across the southern Plains next
Saturday night with the frontal passage late next Saturday. For now,
will favor the GFS due to its consistency and have kept POPs out of
the forecast. The ECMWF model brings POPs next Saturday. Temperatures
will average below normal the entire week with well below normal lows
mid week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              86  66  78  51  81 /  10  80  50   0   0
Austin Bergstrom Intl Airport  87  66  78  49  81 /  10  80  50   0   0
New Braunfels Muni Airport     88  67  79  50  81 /  10  80  50   0   0
Burnet Muni Airport            84  60  75  48  80 /  10  90  20   0   0
Del Rio Intl Airport           85  63  82  52  83 /  -   40  -    0   0
Georgetown Muni Airport        86  63  76  49  80 /  10  90  30   0   0
Hondo Muni Airport             88  66  82  48  84 /  -   70  30   0   0
San Marcos Muni Airport        87  67  78  49  82 /  10  80  50   0   0
La Grange - Fayette Regional   87  68  78  50  79 /  20  60  70   0   0
San Antonio Intl Airport       88  67  81  51  82 /  -   70  40   0   0
Stinson Muni Airport           90  69  81  52  82 /  -   60  50   0   0

&&

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

$$

Mesoscale/Aviation...05
Synoptic/Grids...04



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