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

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FXUS64 KEWX 231729

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1129 AM CST Mon Nov 23 2020


Late this morning, cigs have begun to scatter out at SAT/SSF, but
will take another 1-3 hours at AUS and DRT before VFR conditions
return. Overnight, southerly winds will pump more moisture back into
the region and conditions will deteriorate with IFR cigs likely at
all sites. SAT could briefly brush LIFR, and will also have the best
potential for fog overnight although it`s unlikely to become dense.
Isolated shower activity will be possible along the I-35 corridor
late tonight through Tuesday morning and have introduced VCSH.
Southerly flow will strengthen during the day Tuesday and cigs may
hold on into the early afternoon at the I-35 sites.


PREV DISCUSSION... /ISSUED 350 AM CST Mon Nov 23 2020/

SHORT TERM (Today through Tuesday)...
Yesterday`s front that moved through much of the region has since
dissipated and left South-Central Texas under northeasterly flow at
the surface. Cooler temperatures and drier air have been also
filtered in with an overcast layer of low stratus developing
overnight due to continued southerly flow just off of the surface.
Forecast soundings show much of the boundary layer remaining saturated
with the exception of the lowest few hundred feet. High resolution
models indicate chances for light rain to drizzle for the western
half of the CWA this morning and already seeing some light returns
on radar as of this writing.

Fairly quiet short term period with afternoon temperatures near
normal today and pleasantly drier dewpoints than the previous
several days. This near seasonal weather will be short-lived as
shortwave ridging takes hold and southeasterly surface winds return.
As Gulf moisture is advected back over the region Monday night, we
will see a return of low stratus and potentially some fog
development near the San Antonio metro and portions of the Hill
Country Monday night. A quick warm up for Tuesday with highs back
well above normal with upper 70s to mid 80s across the board.

LONG TERM (Tuesday Night through Sunday)...
An upper level trough moves across the Plains Tuesday night and the
Middle Mississippi Valley into the Great Lakes on Wednesday. This
drags a dryline into Rio Grande Plains and Edwards Plateau Tuesday
evening, then a cold front overtakes the dryline and moves across all
of South Central Texas Tuesday night into Wednesday morning. There is
sufficient moisture convergence and forcing for a slight chance of
showers east of a Killeen to Bastrop to LaGrange line Tuesday night
into early Wednesday morning. Isolated thunderstorms are possible
due to weak instability and mid level lapse rates. Cooler, though
still above normal temperatures are expected Wednesday as a surface
high drifts across our area.

An upper level trough drops south over the Great Basin on Thursday to
the Four Corners region where it closes off Thursday evening while
another trough moves across the Northern Plains into the Great Lakes
dragging a stronger cold front south across the Central and Southern
Plains. Moisture increases on Thursday with a brief warming trend as
southerly flow returns.

Models continue their lack of consistency and consensus for Firday
through the weekend. The following are the solutions of the latest
(23/00Z) model runs.

The GFS brings the front through all of our area by Friday evening
due to the Plains to Great Lakes trough being deeper than shown by
the other models. This generates showers and thunderstorms along and
ahead of the front Friday into Friday evening with little or no rain
Friday night. Then, a slower closed low/trough moves over Texas
Sunday bringing overrunning showers and a few thunderstorms Saturday
through Sunday midday. Much colder temperatures are indicated by the
GFS due to clouds, rain, and cold advection across all areas late
Friday through Sunday.

The ECMWF/GEM are few hours slower bringing the front into the Hill
Country late afternoon into evening. Stall it generally along the
I-35 corridor Friday night into Saturday morning before finally
moving it through by Saturday evening as the closed low moves across
the Plains. The showers and a few thunderstorms end Saturday night
as a mid level dry slot moves over our area. A potentially large
range of temperatures is shown on Friday and Saturday with much
cooler temperatures across all area on Sunday.

Due to the lack of consistency and consensus will continue to take a
blend of the guidance. Will maintain showers and thunderstorms for
Thursday night through Sunday morning due to upward forcing of a
moist airmass along weak instability and mid level lapse rates. This
solution brings chances of wetting rains to much of our area to
possibly take a little edge off the drought conditions. Much cooler
temperatures are expected later Friday through Sunday due to clouds,
rain, and cold advection.


Austin Camp Mabry              69  59  79  58  72 /   0  20  20  30   0
Austin Bergstrom Intl Airport  71  59  80  58  73 /   0  20  20  30   0
New Braunfels Muni Airport     72  62  83  61  76 /   0  20  20  10   0
Burnet Muni Airport            65  59  78  52  70 /   0  20  20  30   0
Del Rio Intl Airport           74  63  85  55  78 /  10  -   -    0   0
Georgetown Muni Airport        67  57  78  53  70 /   0  20  20  30   0
Hondo Muni Airport             74  60  83  57  79 /  10  20  20  -    0
San Marcos Muni Airport        71  59  81  59  74 /   0  20  20  20   0
La Grange - Fayette Regional   73  60  82  63  74 /   0  10  20  20   0
San Antonio Intl Airport       71  62  81  61  76 /   0  20  20  10   0
Stinson Muni Airport           73  62  82  61  77 /   0  20  20  -    0




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