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

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FXUS64 KEWX 262033
AFDEWX

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

.SHORT TERM (Tonight through Wednesday Night)...
As suspected, models were too weak with generating enough convection
along the I-35 corridor, and overemphasized rainfall totals over the
western counties. There were a few areas that appeared to receive
6-8 inches in the past 24 hours, mainly over the Rio Grande Plains to
the NW of Cotulla. Flooding has been mostly limited thus far due to
the dry soils and the steady and moderate rain over most areas and
more intermittent character of the heavier rains.

Tonight, the model consensus retraces higher rainfall amounts
westward in response to the way the cold front leaks southward over
eastern counties and hangs up over the Rio Grande. An mcv is lifting
north out of the Laredo area and is set to drop a potential 2 to 4
inches over the rain soaked soils of the Rio Grande Plains. Higher
res models target a new round of more robust convection to fire
closer to DRT and push east into the Hill Country in the late night
to daybreak hours Wednesday. If these trends play out, the continued
pressure over the convective focal points will likely result in
another robust round of intermittent convection over the Hwy 281/I-35
corridors with 1-3 inches possible on top of 1-2 inches that
occurred today. The watch area continues to anticipate isolated storm
totals around 10 inches, but with only isolated totals around 8
inches between this afternoon and when we suspect the event to end
Thursday afternoon. This means we continue to expect 4-6 inches as
widespread storm totals over the current watch area. Should we need
to expand the watch closer to I-35, the amount totals may be less,
say 3-5, but equally capable to produce flash flooding given the
terrain and urban influences.

Rain chances for Wednesday night should continue to retract westward
according to the consensus QPF, but the trends are backing off the
more dire stationary complex scenarios depicted in some of the
Monday model runs. Again isolated 5+ amounts may concentrate over
isolated areas where mcv activity exists in the late night hours, but
this should be the final period for the heavy rain threats on this
scale.

&&

.LONG TERM (Thursday through Tuesday)...
Conditions should gradually improve during the day Thursday
assuming the qpf retraction of higher amounts to the Mexican border
occurs. River flooding will become the more significant concern by
this time and rain chances will slowly decrease into Saturday with
the higher daily rains mainly below 1/2 inch. Temperature trends
should be flat through Saturday with abundant moisture and cloud
cover continuing; afterwards look for decreasing clouds Sunday into
Tuesday with mostly east winds and temps near normals.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              72  85  71  84  68 /  60  40  40  30  40
Austin Bergstrom Intl Airport  72  85  71  85  68 /  50  40  30  30  40
New Braunfels Muni Airport     72  84  71  85  69 /  50  60  40  40  30
Burnet Muni Airport            70  81  68  80  64 /  60  40  40  40  50
Del Rio Intl Airport           72  82  70  83  68 /  90  90  80  70  60
Georgetown Muni Airport        71  84  70  83  66 /  60  30  30  40  50
Hondo Muni Airport             73  86  71  87  68 /  80  80  50  50  40
San Marcos Muni Airport        71  85  71  85  68 /  50  50  40  30  40
La Grange - Fayette Regional   73  88  73  88  70 /  30  30  20  30  20
San Antonio Intl Airport       72  84  72  85  70 /  60  70  40  40  40
Stinson Muni Airport           73  84  72  85  71 /  60  70  40  40  30

&&

.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...Allen
Synoptic/Grids...Oaks
Public Service/Data Collection...Williams



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