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

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FXUS64 KEWX 231124
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
524 AM CST Fri Feb 23 2018

.UPDATE...
12Z Aviation forecast below.

&&

.AVIATION...
At 11Z a complex of TSRAs was located over the SAT area. This complex
will lift northeast through the morning, exiting the SAT/SSF
terminals around 13Z. Can`t rule out TSRAs near AUS, but lightning
coverage that far north has been isolated so for the time being will
just mention SHRAs at AUS TAF through 14Z. As the complex moves away
consensus guidance suggests LIFR ceilings and visibilities in its
wake across much of the region, including SAT/SSF/AUS. Exception may
be at DRT where ceilings remain IFR and visibilities MVFR to VFR.
Ceilings and visibilities at SAT/SSF/AUS should improve 20Z-22Z to
IFR to MVFR as winds this afternoon become southeast. LIFR conditions
are expected to re-develop later tonight.

&&

.PREV DISCUSSION... /ISSUED 403 AM CST Fri Feb 23 2018/

SHORT TERM (Today through Saturday)...
The persistent southwest flow regime at the H5 level continues to
keep PoP chances rather high throughout the short term. Already this
morning we have seen one impulse exit to the northeast while yet
another impulse approaches from the southwest. These various subtle
shortwaves are tapping into areas of elevated instability and
relatively high PWATs and resulting in thunderstorms with some
moderate to heavy rain potential. 6-7 degree lapse rates in the -10
to -30 level are helping to produce frequent lightning activity in
these convective cells as well. Upwind propagation vectors of around
20 kts should keep this morning`s complex moving fairly quickly to
the north and east and as they do, move into a less favorable shear
and CAPE environment, thus expect these cells to become a bit more
disorganized in once they move east of the I-35 corridor.

Similar to yesterday, as this morning`s complex moves off, we will
likely get a bit of a break from rainfall this afternoon and evening
before the next piece of energy comes across by early tomorrow
morning and another round of showers and thunderstorms re-develops.
So far, this morning`s rainfall has been focused along the I-35
corridor and should shift eastward, which has largely missed out on
the more significant rainfall over the last several days, thus
believe the CWA will be able to take the rainfall. Do believe between
a half inch to an inch and a half of rain will be possible
associated with this morning`s convective complex in and around the
San Antonio area but then generally below a quarter inch will is
expected after 18Z today.

Still expecting a frontal passage Saturday which should finally dry
things out for the area beginning Saturday afternoon. Dewpoints
behind the front are progged to drop into the 20s and northwest winds
spread into the area. May even see the sun Saturday afternoon, which
will be a welcome sight after several days of overcast skies.

LONG TERM (Saturday Night through Thursday)...
The trough that has been responsible for our prolonged southwest flow
set up will finally move off Saturday night and into Sunday morning.
The region will enjoy at least a couple days of warmer/dryer
conditions before another trough replaces the previous one over the
Rockies. PoP chances return to the forecast Tuesday as the 850 mb
front surges north and southerly low level flow returns. Isentropic
upglide will bring back low clouds and probably drizzle or light rain
to the area Tuesday, then the focus will be on how the trough
progresses from Wednesday on.

While the Canadian model shows a stubborn closed low slowly
traversing the US/Mexico border, both the GFS and ECMWF progressively
bring the trough across the Texas Panhandle with a slight negative
tilt. This will increase storm chances in the northwest zones
Wednesday as another cold front moves through the CWA from the west,
but if the speed of these models continues, then this should clear
out quickly by Wednesday night and Thursday morning leaving the
latter half of the week relatively dry.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              66  60  74  46  67 /  90  40  60  10  20
Austin Bergstrom Intl Airport  68  61  75  45  66 /  90  40  60  10  30
New Braunfels Muni Airport     69  61  76  47  66 /  70  40  50  10  20
Burnet Muni Airport            62  57  72  42  67 /  70  40  70  -   10
Del Rio Intl Airport           66  57  76  45  73 /  30  30  -    0   0
Georgetown Muni Airport        64  59  72  42  67 /  90  40  70  10  20
Hondo Muni Airport             67  61  77  45  70 /  50  40  30  10  10
San Marcos Muni Airport        68  62  75  46  65 /  90  40  50  10  30
La Grange - Fayette Regional   71  64  75  49  64 /  80  30  60  20  40
San Antonio Intl Airport       69  62  76  48  68 /  60  40  40  10  20
Stinson Muni Airport           70  63  77  49  68 /  50  40  30  10  20

&&

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

&&

$$

Mesoscale/Aviation...Runyen
Synoptic/Grids...TB3



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