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

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FXUS64 KEWX 222352
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
652 PM CDT Fri Sep 22 2017

.AVIATION.../00Z_TAFS/
Very isolated showers and a thunderstorm is ongoing mainly south and
west of SSF/SAT and east of DRT. This activity should continue to
dissipate over the next hour more quickly than last evening, with
thunderstorms not expected as stability aloft is quite a bit stronger
above 10-12 kft than it was this time yesterday. Southeast 10-15 knot
winds with gusts to 20-25 knots should continue for a few more hours
before weakening later this evening into the overnight hours.

Model streamlines show onshore flow will be strongest at SAT/SSF and
DRT tonight, so MVFR ceilings should develop between 6-7Z at SAT/SSF
and 9Z at DRT, but they may hold off until after 9Z at AUS. IFR
ceilings may be possible along the I-35 corridor similar to the last
few nights, but confidence was too low to include them at this time.
Patchy fog will be possible at the I-35 TAF sites, particularly at
AUS where winds will be more calm and ceilings are less likely to
develop quickly due to the weaker onshore flow. All sites should
improve to VFR by 17Z with southeast 10-15 knot winds for the
afternoon. Convection will be possible at each site with the best
chances likely at SAT/SSF and west towards DRT, but coverage should
be very isolated so they have not been included in the forecast.



&&

.PREV DISCUSSION... /ISSUED 247 PM CDT Fri Sep 22 2017/

SHORT TERM (Tonight through Saturday Night)...
An inverted trough axis and onshore flow is allowing for a 20 to 40
percent coverage of showers and storms east of I-35 this afternoon.
Otherwise, temperatures are in the upper 80s to lower 90s with
southeast winds 10 to 15 mph. The shower and storm activity will
continue to push northwest aided by the propagation of outflow
boundaries. Moisture values drop off west of the I-35 corridor and
therefore the activity should dwindle to a 10 to 20 percent coverage
into the Hill Country. Average rainfall will be less than a half of
an inch, but some locations could be a bit more. Activity should be
dissipated by 9 PM as the atmosphere stabilizes with the loss of day
time heating. Lows tonight will bottom out in the upper 60s in the
Hill Country to the middle 70s in the southwest. Could see some
patchy fog once again across the eastern counties as the low-level
airmass remains moist there. The synoptic pattern will remain mostly
unchanged tomorrow and should see a similar coverage of showers and
storms with highs once again in the upper 80s to middle 90s.

LONG TERM (Sunday through Friday)...
For the start of the long-term forecast, a large trough axis will
encompass much of the western CONUS with a decent fetch of stronger
low-level winds across West Texas. Isolated showers and storms will
be possible for the eastern counties once again on Sunday, but some
additional showers and storms in West Texas within the low-level jet
should move into Val Verde County by Sunday night. The same can be
expected for Monday with the two zones of the western and eastern
counties having the higher PoPs with the I-35 corridor being slightly
less.

The rest of the extended forecast will be highly dependent on when a
cold front moves through the region and interacts with the trough to
the west. The GFS has it moving in around Friday while the ECMWF
moves it through by Wednesday morning. If the front were to move in
as early as the ECMWF is showing, high rain chances would be
warranted as strong lift moves over the frontal layer. The ECMWF
also shows some mesoscale influences and therefore has a risk of
heavier rainfall across the western counties for the Wednesday-Friday
time period. The GFS still has rain, but lesser amounts for the
totals until the front arrives on Friday. For now will show high
chance to likely PoPs in the Tuesday- Friday time period and will
refine these in the coming days as the forecast becomes more clear.
Nevertheless, a period of decent rain chances and below normal
temperatures appears likely sometime in the Day 5-10 period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              73  90  72  91  72 /  10  20  10  20  10
Austin Bergstrom Intl Airport  70  90  70  91  71 /  10  20  10  20  10
New Braunfels Muni Airport     71  90  71  90  71 /  10  20  10  30  10
Burnet Muni Airport            69  87  70  86  69 /  10  20  10  10  10
Del Rio Intl Airport           74  91  74  89  74 /  10  10  10  10  30
Georgetown Muni Airport        71  92  71  91  71 /  10  20  10  10  10
Hondo Muni Airport             74  94  73  96  74 /  20  10  10  20  10
San Marcos Muni Airport        71  91  70  92  71 /  10  20  10  20  10
La Grange - Fayette Regional   72  92  72  92  71 /  -   20  10  30  10
San Antonio Intl Airport       74  89  73  90  74 /  10  20  10  20  10
Stinson Muni Airport           74  90  74  90  74 /  10  20  10  20  10

&&

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

$$

Mesoscale/Aviation...LH
Synoptic/Grids...Runyen
Public Service/Data Collection...YB



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