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

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001
FXUS64 KEWX 172357
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
557 PM CST Fri Nov 17 2017

.UPDATE...
Please see the 00Z aviation forecast discussion below.

&&

.AVIATION...
VFR skies will continue until late evening when low clouds and low
end MVFR cigs will move into the I-35 corridor between 04-07Z. Cigs
will continue to lower and fog will develop early Saturday morning,
bringing conditions into LIFR and IFR. Some improvement is
anticipated beginning mid-morning as winds turn westerly in advance
of a strong cold front. Rapid improvement to VFR is expected between
17-18Z as drier air and gusty north winds follow behind the front.
Expect continued gusty north winds for the remainder of Saturday
afternoon. At DRT, VFR will continue until roughly 18/08Z when fog
will develop. Conditions should drop quickly around 10Z in fog and
low cigs with LIFR expected as winds go light in advance of the
front. We expect a rapid return to VFR around 16Z behind the front.
Gusty NNW winds are also in store behind the front through tomorrow
afternoon at DRT.

&&

.PREV DISCUSSION... /ISSUED 301 PM CST Fri Nov 17 2017/

SHORT TERM (Today through Saturday)...

Main weather highlight will be a cold front passage Saturday morning
to early afternoon through the entire region. While no rain is
expected with the frontal passage, surface winds from the north will
be elevated in the 20 to 30 mph range. Gusts could reach upwards of
35 mph at times. The dry air and elevated winds will pose a near-
critical fire weather concern Saturday afternoon.

An airmass boundary between warm, moist and cooler, drier air
currently exists across north Texas. A stronger mid- and low- level
trough currently over the southern Rocky Mountains will shift across
the southern plains overnight and through the day Saturday. This
system will increase northwest flow greatly early Saturday morning
and usher in the drier, cooler airmass to South-Central Texas.
Temperatures Saturday will start warm with the humid airmass in place
initially. Limited deep moisture and lack of dynamics will negate
rain chances with the frontal passage. Clouds will clear quickly
behind the front for full sun as dry air shifts in over the region.
The full sun, dry air, and strong boundary layer mixing will allow
for a decent surface warm-up before the greater cool down occurring
Sunday morning.

A strong pressure gradient will be present with the frontal passage
as high pressure quickly develops across north Texas. Have increased
forecast wind speeds over guidance values given the likely strong BL
mixing of 30 to 35 mph winds down to the surface at times. These
conditions will border on wind advisory criteria. Will hold off for
now on the wind advisory but have issued a special weather statement
for the high winds. A wind advisory may be needed if observed winds
are expected to be higher by another 5 mph. Winds will calm through
the evening hours.

LONG TERM (Sunday through Thursday)...

Dry and cool conditions are expected for the second half of the
weekend and into the first part of next week. Next chance of rain
will be Tuesday afternoon ahead of another weak cold frontal passage
mid-week. A quiet and pleasant Thanksgiving is expected with near
average temperatures in the upper 60s.

PWATs will drop below 0.25" by Sunday as surface dewpoints fall into
the low 30s and the upper 20s. Much cooler temperatures are expected
Sunday morning with mid to upper 30s in the Hill Country and the 40s
most all other locations. The coldest morning will be Monday morning
as temperatures will approach the mid 30s to low 30s in the Hill
Country and the upper 30s for KAUS to low 40s for KSAT as north winds
persist.

Low-level wind flow will switch to the east and then south by late
Monday into Tuesday, allowing for the first hints of moisture return.
Dewpoints should recover back into the 50s and low 60s by Tuesday
afternoon and lead to some weak instability developing with a weak
cap in place. At this same time, a positively tilted trough will
sweep across the region. There remains some question to the amount
and quality of the moisture return to support greater shower or
thunderstorm development possibilities Tuesday afternoon. Latest GFS
has backed off previous runs of QPF generation and this is more in
line with the ECMWF with the best chances confined to the coastal
plains in the deeper moisture environment. Additional model runs are
needed to further refine the convective chances during Tuesday
afternoon. Drier air will filter into the region behind the trough
passage Wednesday and Thursday with pleasant and quiet conditions
expected for the late Holiday week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              68  81  44  63  42 /  -   -    0   0   0
Austin Bergstrom Intl Airport  67  82  43  64  38 /  -   -    0   0   0
New Braunfels Muni Airport     64  83  43  64  39 /  -   -    0   0   0
Burnet Muni Airport            65  73  39  61  38 /  -    0   0   0   0
Del Rio Intl Airport           58  80  43  65  42 /   0   0   0   0   0
Georgetown Muni Airport        67  77  41  63  39 /  -   -    0   0   0
Hondo Muni Airport             62  85  41  67  39 /   0   0   0   0   0
San Marcos Muni Airport        66  83  43  64  39 /  -   -    0   0   0
La Grange - Fayette Regional   69  82  43  64  40 /  -   10   0   0   0
San Antonio Intl Airport       66  83  45  64  41 /  -   -    0   0   0
Stinson Muni Airport           65  84  45  65  41 /  -   -    0   0   0

&&

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

$$

Mesoscale/Aviation...24
Synoptic/Grids...17
Public Service/Data Collection...YB



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