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

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FXUS64 KEWX 260827
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
327 AM CDT Tue Sep 26 2017

.SHORT TERM (Today through Wednesday)...
A large area of rain with embedded thunderstorms continues mainly
across areas west of Highway 281. Heavier convection developed
yesterday evening across the southwest CWA and has since moved to the
southeast following the best instability axis. The HRRR has had a
decent handle on the precip overnight and shows it lingering into the
late morning hours with a slow eastward progression continuing.
Think this trend from the model seems decent and will follow this
closely in the near-term, showing high PoPs across the south in the
morning hours with increasing PoPs out west this afternoon.

Little has changed regarding the synoptic setup versus yesterday
with the base of the deep trough remaining over the southwest CONUS
with southwest flow aloft in place across South-Central Texas.
Southeast flow from the surface up to 700 mb is aiding in the lift as
isentropic upglide and this will ensure continued chances of periods
of showers and thunderstorms beyond this morning for the remainder
of the short-term forecast. The highest PoPs will remain across the
western CWA in the best region of this low-level lift and any
responses from perturbations within the southwest flow. For the most
part, think the heavy rainfall chances will be limited in the short-
term without the presence of a surface boundary and significant
upper forcing. Will have to watch for the development of any MCVs
that would aide in the rainfall production. Think there could be some
advisories or an occasional Flash Flood Warning needed in the short-
term, but not expecting wide-spread flooding. High temperatures will
be in the 80s to near 90 degrees with a low tonight in the lower 70s
across much of the area.


&&

.LONG TERM (Wednesday Night through Monday)...
On Wednesday night, the cold front currently in northern Oklahoma and
the Texas Panhandle will be approaching our northern counties and
will move move into the area by Thursday afternoon. This boundary
with the similar synoptic setup should allow for an uptick in the
intensity of rainfall across our western counties as it serves as a
focus for continued shower and storm development. The ECMWF is
showing this quite well with a QPF bullseye across the western
counties on Thursday. The overall threat of Flash Flooding should be
highest then, especially if we do get several rounds of rain over the
next couple of days which will help saturate the top soil and allow
for sufficient runoff for flash flooding. Additional storm total
rainfall amounts through Thursday will be 4-6 inches across the
western counties with isolated totals up to 10 inches. Lesser amounts
can be expected for the remainder of the CWA.

Once the front pushes through the area by the evening hours on
Thursday, the threat for heavy rainfall will diminish. Will end PoPs
Saturday night with lingering low chances of rain behind the cold
front on Friday. Temperatures behind the front will be much cooler
with highs this weekend in the 80s and lows in the 50s/60s. The GFS
shows a weak disturbance bringing rain to the area on Monday, but the
ECMWF does not show this. Will forecast a 20 PoP for the much of the
area for now.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              88  72  87  71  87 /  60  40  40  30  40
Austin Bergstrom Intl Airport  88  71  87  71  88 /  50  40  30  30  30
New Braunfels Muni Airport     87  72  88  71  88 /  70  40  40  40  40
Burnet Muni Airport            83  69  82  68  81 /  60  50  50  40  40
Del Rio Intl Airport           84  72  83  70  84 /  90  90  80  70  60
Georgetown Muni Airport        87  71  86  70  85 /  60  40  40  40  30
Hondo Muni Airport             88  72  89  71  89 /  90  70  70  60  40
San Marcos Muni Airport        88  71  87  71  88 /  60  40  40  30  40
La Grange - Fayette Regional   90  72  90  73  90 /  40  20  20  20  20
San Antonio Intl Airport       86  73  87  72  87 /  80  50  50  40  40
Stinson Muni Airport           86  73  87  72  88 /  80  50  50  40  40

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening for the following
counties: Bandera...Dimmit...Edwards...Frio...Kerr...Kinney...
Maverick...Medina...Real...Uvalde...Val Verde...Zavala.

&&

$$

Mesoscale/Aviation...05
Synoptic/Grids...Hampshire


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