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

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FXUS64 KEWX 170956
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
356 AM CST Sat Feb 17 2018

.SHORT TERM (Today through Sunday)...
Damp and cool weather will continue today into early Sunday as
shallow frontal inversion gradually erodes. Sfc dew points are slowly
recovering early this morning, and radar echoes are gradually
increasing to suggest areas of more light drizzle to reach the ground
by daybreak and some intermittent light showers.

A shortwave concentrating numerous showers over W-Central/N-Central
TX will eventually connect some weak synoptic lift into areas mainly
north of Hwy 71 later today, but the rains should still be mainly
isentropic due to secondary surge of high pressure along/east of
I-35. In any event, do not believe there will be many amounts topping
1/10 inch. A general easterly sfc wind should resume tonight and
preserve light isentropic lift and more trace to a few hundredths of
an inch type rains. The isentropic lift pattern weakens during the
day Sunday, but pooled moisture in seen in Pwat fields lifting north
during the day toward areas of weak shortwave activity moving
through the Big Bend area toward N-Central TX could lead to some
deeper layer convection generally north of the escarpment.

&&

.LONG TERM (Sunday Night through Friday)...
Cloudy and damp conditions continue through at least Wednesday.

By Sunday evening dewpoints approaching 60 degrees over the Hill
Country and continued unstable SWly flow aloft will possibly be
sufficient for a few thunderstorms over our northern counties. Model
qpfs show poor agreement which reflects the broad area of weak
instability and poor interrogation of smaller scale shortwaves
lifting out of the higher terrain to the SW. In general low end
chance PoPs will be expected Sunday night through Monday as the
surface to mid level pattern over Central TX changes little through
this period.

Late Monday night, a Pacific subtropical low that has helped funnel
abundant mid-level moisture into TX the past few days will be sheared
out and kicked east into TX by a new digging upper trough that
bottoms out over the AZ/NM border. This translates to enhanced qpf
and storm chances west of Hwy 281 by most of the ECM/GFS solutions.
In analyzing the 00z GFS, 50 knot winds at 850 mb setting up along
Hwy 281 could make for a favorable mcs environment given Pwat values
over 1.6 inches upstream from the higher qpf values to the west.
PoP values for 06Z to 12Z Tuesday could thus be under-forecast,
especially along I-35 & around San Antonio. The deterministic GFS/ECM
solutions have been pretty consistent in depicting an mcs type of
environment as a cold front drops into S-Central TX early Wednesday.
The timing of the front is still handled by both models in terms of
run-to-run consistency, so a vague threat for heavy rain Tuesday into
early Wednesday remains the primary concern and for areas along/east
of the Hwy 281 corridor.

One trend that appears to be coming into shape is a drier picture in
the wake of the storm complex and front Wednesday, especially in the
GFS runs. Flow aloft remains SWly, so do not want to completely rule
out the wetter ECM forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              62  52  70  62  77 /  40  30  30  30  30
Austin Bergstrom Intl Airport  62  52  70  62  77 /  40  30  30  30  30
New Braunfels Muni Airport     64  52  72  61  78 /  40  30  30  20  30
Burnet Muni Airport            61  50  68  60  75 /  40  30  30  30  30
Del Rio Intl Airport           76  58  72  61  81 /  20  30  40  10  10
Georgetown Muni Airport        60  49  69  62  76 /  50  30  30  30  30
Hondo Muni Airport             70  56  74  62  81 /  40  30  40  20  20
San Marcos Muni Airport        64  52  71  61  77 /  40  30  30  30  30
La Grange - Fayette Regional   65  54  73  63  77 /  40  30  30  20  30
San Antonio Intl Airport       66  54  72  62  79 /  40  30  40  20  30
Stinson Muni Airport           68  55  74  63  80 /  40  30  30  20  20

&&

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

$$

Mesoscale/Aviation...Allen
Synoptic/Grids...Oaks


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