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

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FXUS64 KEWX 182023
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
323 PM CDT Wed Oct 18 2017

.SHORT TERM (Tonight through Thursday Night)...
Very low pwat values will remain over South TX through this evening
as low level winds along the coast remains mainly alongshore through
late this afternoon. Surface to H850 winds should turn se this
evening as an upper level disturbance approaches out of Nrn Mexico,
but as shown in the CRP VAD winds, sfc to boundary layer flow
bringing Gulf moisture onshore will be slow to develop. Will expect a
late arrival of low clouds and possible fog with some areas along
I-35 not expected to see low level saturation until daybreak. Thus
the low level moisture could mix out quickly in the late morning over
the few central counties that see a low ceiling or patchy fog. By
Thursday afternoon, eastern counties will see rapidly deepening
moisture and perhaps enough instability contribution from the
approaching disturbance to generate some showers and perhaps an
Isolated storm or two. CAPE values should generally stay below 1800
J/KG.

With a slow trend on the returning southerly winds, the overnight
lows could end up being extra cool again in the protected valleys,
but not as dramatic as from those of this morning due to increasing
high clouds. Lowering diurnal ranges are expected for

&&

.LONG TERM (Friday through Wednesday)...
Upstream upper troughing is depicted as coming into the Southern
Plains states with a positive tilt which could make it more efficient
in generating rain chances in advance of the next significant front
expected Saturday night. Rain chances could thus be more independent
of diurnal trends by Friday and possibly even less dependent on the
moisture convergent axis that is forecast to stay mainly east of
Highway 281.

A deeper upstream trough replaces the relaxing upper level feature
during the day Saturday and could potentially create a brief dry-line
environment. Confidence is low on this period and will show PoPs
undercutting guidances Saturday into Saturday evening. Late Saturday
evening should show PoPs ramping up over the nw counties, with likely
PoPs along the front expected early Sunday morning. With all the
deterministic models showing good amplitude with the trough and a
similar timing, will also trim the timing to show reduced rain
chances from west to east during the day Sunday. A few strong storms
are possible overnight, but the late night timing of the front
should be a negating factor. Expected rainfall potential at this
point look to be mostly in the 1/4 to 1/2 inch range.

The sharpening of the trough could lead to some gusty winds to 30 mph
with the front, then a rapid decrease in wind and another chilly
overnight low for Monday morning. Surface high pressure keeps the
diurnal range high through Monday night, and another front reinforces
the cool and dry pattern on Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              59  82  65  81  70 /   0  20  20  30  30
Austin Bergstrom Intl Airport  55  81  65  81  69 /   0  20  20  40  20
New Braunfels Muni Airport     58  81  65  82  68 /   0  20  20  30  20
Burnet Muni Airport            55  79  64  79  67 /   0  10  20  30  30
Del Rio Intl Airport           59  79  66  82  68 /   0   0  20  10  -
Georgetown Muni Airport        56  80  64  80  68 /   0  10  20  40  30
Hondo Muni Airport             56  83  67  84  69 /   0  -   20  20  20
San Marcos Muni Airport        57  81  65  82  69 /   0  20  20  40  20
La Grange - Fayette Regional   59  84  66  83  69 /   0  20  20  40  20
San Antonio Intl Airport       59  81  67  82  70 /   0  10  20  20  20
Stinson Muni Airport           59  83  68  84  70 /   0  10  20  20  20

&&

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

$$

Mesoscale/Aviation...Runyen
Synoptic/Grids...Oaks
Public Service/Data Collection...Williams



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