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

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FXUS64 KEWX 241153

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
653 AM CDT Sat Mar 24 2018

MVFR ceilings around 1200-1800 feet continue to hold at all sites
this morning, with models continuing to trend away from much lower
ceilings. The latest aircraft sounding at AUS shows a very moist
profile below these ceilings, so they may briefly lower to IFR.
However, IFR ceilings should not last very long so we have left them
out of the current TAF and will handle with amendments as needed.
Ceilings will lift to VFR around 17-19Z at all sites with southerly
winds a bit weaker than yesterday closer to 10 knots. MVFR ceilings
should return later this evening at all sites, with IFR and possibly
LIFR conditions possible overnight. Unlike last night where this
seemed unreasonable, weak winds combined with a moist surface and
boundary layer should allow for at least patchy if not widespread fog
that could potentially cause LIFR conditions this time tomorrow.


.PREV DISCUSSION... /ISSUED 405 AM CDT Sat Mar 24 2018/

SHORT TERM (Today through Sunday)...

No major weather highlights over the weekend as humid and above
normal temperatures persist with clouds lingering through most of the

Synoptic pattern reflects a progressive surface low pressure system
near MO while a strong subtropical Bermuda high off the coast off
intercoastal FL is creating a tight pressure gradient over TX that is
causing gusty south winds and ample moisture influx. Despite winds,
kept light drizzle and mist chances in the official forecast from
early this morning to near late morning due to low boundary layer
resultant dewpoint depressions. Clouds will linger throughout the day
despite temperatures reaching into the upper 70s/low 80s. A repeat
of overcast skies is expected Sunday morning while H5 southwest flow
over the SW/Mexico strengthens ahead of a western CONUS trough
digging south along the coast. Embedded impulses providing dynamic
lift will shift across west/central TX within a developing jetstreak
exit region.

The best coincidence of lift and instability Sunday afternoon will
be across the Edwards Plateau and into north-central Texas. There
remains some questions to marginal storm development as the capping
inversion could impair thunderstorm development or updraft vigor for
south-central Texas. GFS suggests a weaker cap while the NAM and
ECMWF indicate higher inhibition. Have kept thunder wording limited
in coverage and percentage to adjacent Hill Country and southern
Edwards Plateau areas for tomorrow afternoon.

LONG TERM (Monday through Friday)...

Weather highlights continue to focus on the moderate to high
confidence in widespread wetting rains and thunderstorms Tuesday and
Wednesday of next week. Main hazard during this window will be
pockets of heavy rainfall along with some strong storms with gusty
winds and lightning. Given the latest dry conditions and higher then
normal soil infiltration capacity, flash flooding is not expected at
this time.

Starting off on Monday, the H5 pattern will feature a progressive
trough over the four corners region with stronger mid- and upper-
level winds overspreading much of Texas. A few strong thunderstorms
could form across north-central Texas but again this area looks to
remain too capped for much development Monday afternoon. Will need to
watch late Monday night into Tuesday morning for thunderstorm
development however as an 850MB low-level jet feeds into an elevated
frontal axis along the higher terrain. Pressure falls will begin
Tuesday morning and with implied divergence aloft increasing, shower
activity should begin to blossom over the Hill Country and much of
central Texas. An elevated front will also help provide a focus of
moisture convergence over the region into Tuesday afternoon.
Overnight Tuesday into Wednesday appears to be the prime window for
the heaviest rain potential as a reinforcing surface front from the
north provides greater vertical motion alignment underneath the
right-entrance region of an H3 jetstreak with PWATs 1.4-1.7". The
front and overall system should be progressive enough not to support
training storms as low-level flow does not appear to be parallel to
the frontal axis. The risk of heavy rainfall will end behind the
front through mid-day Wednesday.

The base of the trough axis should finally swing through Texas by
early Thursday and help bring in cooler and drier air from the
northwest. Expect near normal temperatures late week and into next
weekend with dry conditions.


Austin Camp Mabry              84  66  87  68  85 /  10  10  10  20  10
Austin Bergstrom Intl Airport  84  66  87  68  85 /  10  10  10  20  10
New Braunfels Muni Airport     84  65  88  68  85 /  10  10  10  20  10
Burnet Muni Airport            85  65  87  66  84 /  10  -   20  20  10
Del Rio Intl Airport           88  66  91  67  90 /  -   -   -   20  20
Georgetown Muni Airport        85  66  88  68  84 /  10  10  10  20  10
Hondo Muni Airport             85  66  92  67  88 /  10  10  -   20  10
San Marcos Muni Airport        84  66  88  68  85 /  10  10  10  20  10
La Grange - Fayette Regional   83  68  86  69  85 /  10  10  10  20  10
San Antonio Intl Airport       84  65  88  68  85 /  10  10  10  20  10
Stinson Muni Airport           85  66  89  69  87 /  10  10  10  20  10




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