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

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FXUS64 KEWX 270555
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1255 AM CDT Tue Jun 27 2017

.UPDATE...
See below for the 06z aviation discussion...

&&

.AVIATION...
Light rain showers are ongoing presently across the eastern Hill
Country and extending into the Balcones Escarpment and the Interstate
35 corridor. These will impact the I-35 TAF sites of SAT/SSF/AUS from
now until likely 7z-8z. Impacts should be fairly minimal as rainrates
are generally on the order of 0.1-0.2 inches per hour (and
decreasing) and lightning is non-existent. CIGs may alternate
between VFR and MVFR as some heavier pockets of showers impact the
TAF sites. Convection is currently ongoing near DRT but the more
intense showers and thunderstorms appear to likely avoid DRT just to
the west, so have included VCTS in the TAF for the 6z to 7z time
period. Shower activity should diminish by around 8z for all TAF
sites. Otherwise, CIGs are anticipated to lower to MVFR for the San
Antonio sites by around 7z before returning to VFR around 19z Tuesday
afternoon. At AUS, CIGs are expected to lower to MVFR by 14z before
returning to VFR by 17z Tuesday afternoon. VFR should prevail for the
entire forecast period at DRT. Isolated shower activity returns
Tuesday afternoon for the Interstate 35 TAF sites. Winds will remain
generally out of the east from 5-10 knots.

&&

.PREV DISCUSSION... /ISSUED 750 PM CDT Mon Jun 26 2017/

UPDATE...
Numerous outflow boundaries continue to produce scattered showers and
thunderstorms over South Central Texas, particularly along the I-35
corridor between San Marcos and New Braunfels and in the Edwards
Plateau and western Hill Country. A more organized area of convection
centered in Mason County associated with a weak MCV is beginning to
move into the western Hill Country as well. We are not expecting a
real organized low-level jet to develop tonight, but new convection
that develops should be able to produce brief heavy downpours of 1-2
inches with locally higher amounts falling within about an hour.
Thermodynamic profiles support this as well given a fairly moist
adiabatic lapse rate up to about 20,000 feet with a weak stable layer
limiting much deeper convective growth. Thus, most of this activity
will be in the form of showers with isolated thunderstorms, allowing
for very efficient warm rain processes. We are not expecting a
widespread flash flood threat, but some nuisance low-water type
crossing advisory-level flooding is expected and an isolated flash
flood warning cannot be ruled out over locally saturated areas where
outflow boundaries merge. Thus, we have increased POPS to 50-60
percent along and west of I-35 and north of Highway 90, quickly
tapering POPs off further south and east.

Shower and thunderstorm activity should decrease after Midnight ,
leaving mostly dissipating stratiform rain over the region. Thus, we
have decreased POPs to 20-30 percent over most of the region after
Midnight with only very isolated thunderstorms (if any) expected.
This relative lull in activity due to stabilization from this
evening`s convection should limit much development prior to Noon
tomorrow except in the Coastal Plains where the atmosphere should not
be as worked over as convective chances are quite a bit lower there
tonight. Thus, POPs have been decreased and thunderstorms removed
from the forecast tomorrow morning everywhere except the Coastal
Plains, with the rest of the forecast left alone as scattered showers
and thunderstorms should develop across most of the region tomorrow
afternoon as the atmosphere destabilizes with numerous outflow
boundaries serving as a focus for convection.


&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              90  72  91  74  93 /  40  10  20  -   30
Austin Bergstrom Intl Airport  90  71  91  74  93 /  40  10  20  -   30
New Braunfels Muni Airport     90  71  90  73  93 /  40  10  30  -   30
Burnet Muni Airport            88  70  89  72  92 /  40  10  10  -   10
Del Rio Intl Airport           91  72  95  75  98 /  30  10  10  -   10
Georgetown Muni Airport        89  70  90  73  92 /  40  10  20  -   20
Hondo Muni Airport             90  70  92  73  95 /  40  10  20  -   10
San Marcos Muni Airport        90  71  90  74  92 /  40  10  20  -   30
La Grange - Fayette Regional   89  72  90  75  91 /  50  20  40  20  40
San Antonio Intl Airport       89  72  91  74  94 /  40  10  20  -   20
Stinson Muni Airport           90  73  91  74  94 /  40  10  20  -   30

&&

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

$$

Mesoscale/Aviation...Williams
Synoptic/Grids...05



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