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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KEWX 171705
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1105 AM CST Sun Dec 17 2017

.AVIATION...
LIFR/IFR conditions continue this morning and should continue to hold
on for most of the afternoon with only a brief period of VFR possible
late this afternoon before LIFR returns this evening. Visibilities
tonight could go below 1/2 a mile across all terminals, but will
just mention 1sm for now. The 00z TAF package may need to lower that
further. Conditions will once again be slow to improve tomorrow as
well with LIFR/IFR continuing for much of the day.

&&

PREV DISCUSSION... /ISSUED 412 AM CST Sun Dec 17 2017/

SHORT TERM (Today through Monday)...
Surface observations early this morning indicate gradually lowering
ceilings and visibilities across the western half of the CWA.
Consensus short term guidance indicates dense fog gradually
developing first near and south of U.S 90 and west of I-35 now
through 12Z and expanding northeast through the Hill Country and I-35
corridor 12Z-14Z. Areas of dense fog have been added into the
forecast and there is a good likelihood a Dense Fog Advisory will be
issued later as trends become clear on where the dense fog forms.
Otherwise, after the morning low stratus and fog lift we will see
high abundant high clouds streaming into the area from the southwest
this afternoon and evening. Highs today in low to mid 60s (possibly
upper 50s for those locations that take longer for low clouds to lift
and where cirrus is thicker).

Tonight, isentropic upglide will increase after midnight in response
to the next upstream upper level low approaching. Models are in good
agreement with isolated showers developing overnight and Monday
morning across the eastern 2/3rds of the CWA. The focus Monday
afternoon should shift primarily into far eastern areas of the CWA as
an initial shortwave lifts northeast. Can`t rule out some isolated
thunder Monday afternoon across this region.

LONG TERM (Monday Night through Saturday)...
The aforementioned upper level low will elongate and move into the
Panhandle and Far West Texas Monday night and the into West Central
Texas Tuesday. Strong forcing will overspread northern areas of the
Rio Grande as well as the western Hill Country overnight Monday
night and into central and eastern areas of the CWA during the day
on Tuesday and initially elevated showers and storms are expected to
develop west to east. Steep elevated lapse rates and deep layer
shear values of 50-60 kts across the western half of the CWA could
potentially yield some stronger storms and a small hail threat late
Monday night into Tuesday morning. As the storms move east of I-35
Tuesday afternoon there is the potential for them to become surface
based ahead of a developing front. MLCAPE values around 1000 j/kg
and deer layer shear values of 40-50 kts will be sufficient to
produce a risk for strong to possibly severe storms, mainly near and
east of U.S. 77 Tuesday afternoon. SPC currently clips the far eastern
CWA in a Marginal risk for severe storms in the Day 3 outlook.

Dry air will quickly filter into western areas of the CWA Tuesday
afternoon and the eastern CWA Tuesday evening. Warmer and dry
conditions are then forecast Wednesday and Thursday.

A strong cold front is forecast to move through the area early
Friday. Models have trended more progressive with the upper level
pattern and most GFS ensemble members no longer cut off an upper
level low west of the area over the weekend. In fact, deterministic
runs of the 00Z ECMWF, GFS, and Canadian are now mainly dry over the
CWA behind the front Friday night and Saturday. I have maintained a
low 20 PoP to account for uncertainty but removed any mention of
Wintry Precip Friday night and Saturday at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              64  50  62  58  68 /   0  20  40  60  70
Austin Bergstrom Intl Airport  62  50  63  58  69 /   0  20  40  60  70
New Braunfels Muni Airport     63  51  64  59  70 /   0  20  40  60  70
Burnet Muni Airport            64  48  60  54  64 /   0  10  40  50  70
Del Rio Intl Airport           58  47  63  53  71 /   0  10  10  30  10
Georgetown Muni Airport        62  49  61  56  66 /   0  10  40  50  70
Hondo Muni Airport             62  49  65  58  72 /   0  20  20  50  60
San Marcos Muni Airport        62  50  64  59  70 /   0  20  40  60  70
La Grange - Fayette Regional   64  53  66  62  74 /   0  20  40  70  70
San Antonio Intl Airport       64  52  64  60  72 /   0  20  30  60  70
Stinson Muni Airport           62  52  65  61  73 /   0  20  30  60  60

&&

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

$$

Mesoscale/Aviation...Hampshire
Synoptic/Grids...17
Public Service/Data Collection...Williams


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.