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

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FXUS64 KEWX 281152
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
652 AM CDT Tue Mar 28 2017

.AVIATION... /12Z TAFS/

IFR cigs will blanket the escarpment TAF sites through 15Z. DRT
should see a brief lowering into ifr cigs by 13z. by 16Z cigs should
be lifting as surface winds begin to gust over 20 kts. No convective
impacts are expected at the taf locations before 04Z, but a few
morning sprinkles with 6SM or better vsbys are being reported over
Nrn Hill Country AWOS sites. A squall line is expected by mesoscale
models to materialize near DRT by around 04Z and threaten the metro
TAF sites by 08Z or 09Z. Improvements are forecast again by 11Z or 12Z
Wednesday.

&&

.PREV DISCUSSION... /ISSUED 324 AM CDT Tue Mar 28 2017/

SHORT TERM (Today through Wednesday)...
Early this morning a warm front extended from West Central Texas
through East Texas and an upper level low was digging through
Arizona. Through the morning hours isolated showers may occur beneath
the cap as moisture streams north. Storms may initiate mid to late
afternoon across the far northwest Hill Country and farther north
through West Central Texas up into the Red River in the low level
theta-e ridge and near the dry line advancing east.

The main opportunity for storms farther south across the CWA will
come tonight into Wednesday morning as the Pacific front and upper
level low advance east. Models are in relatively good agreement with
convective initiation along the Pacific front sometime in the
00Z-03Z time frame from West Texas down into Val Verde County.
Initially the storms may begin in a discrete mode. With steep mid
level lapse rates with the approach of the upper trough MUCAPE values
of nearly 3000 j/kg and deep layer shear of over 50 kts are forecast
across far western areas of the CWA with a highly diffluent flow
aloft. This should yield initially a large hail threat. The storms
may organize into a line of storms through the western Hill Country
03Z-06Z as a 40-50 kt low level jet develops overnight and low level
moisture flux convergence increases. The line eventually is forecast
to reach the I-35 corridor overnight into early Wednesday morning. A
damaging straight-line wind and hail threat will be the primary
risks as the line organizes and moves east. A lesser, but non-zero,
threat for isolated tornadoes will occur as well. There are some
suggestions by some of the hi-resolution models that the line of
storms could weaken early Wednesday morning as it moves east of I-35
through the eastern CWA.

Due to the speed of the system the heavy rainfall potential appears
to be minimal, with generally 1/2 to 1 1/2 inches of rainfall
possible across northern areas and 1/4 to 1 inch across southern
areas. SPC has expanded the Slight Risk farther into the CWA for
tonight. Have included mention of severe in the forecast along and
west of I-35/I-37 for tonight and held off for now east of this
corridor for Wednesday morning.

Drier conditions and clearing will take place across the central and
western CWA Wednesday afternoon. Wind speeds across Val Verde and
Edwards counties may become breezy and gusty along with low RH
values occuring. This could lead to an elevated to critical fire
weather day Wednesday afternoon across this area, dependent on how
widespread the rainfall is tonight and impacts on fuel moisture.

LONG TERM (Wednesday Night through Monday)...
A secondary surge/front will move through the CWA Wednesday night. A
few showers may be possible across the far southeastern CWA overnight
as the front encounters pool of moisture. Breezy and slightly cooler
during the day on Thursday. South Central Texas will be in between
systems on Friday, with clear skies and a cool start to the morning
but highs rebounding back into the mid 80s to low 90s with dry air in
place.

Moisture return will take place Saturday ahead of the next upper
level low. Showers and storms appear likely with this system,
favoring western areas Saturday night and central and eastern areas
Sunday. Am siding slightly toward the more progressive ECMWF solution
with lower POPs and drier conditions for Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              84  66  85  56  78 /  20  90  50  10   0
Austin Bergstrom Intl Airport  85  67  84  55  78 /  20  90  60  10   0
New Braunfels Muni Airport     85  65  85  55  79 /  20  90  50  10   0
Burnet Muni Airport            80  58  81  51  74 /  30  90  40  10   0
Del Rio Intl Airport           86  57  84  56  82 /  20  60   0   0   0
Georgetown Muni Airport        83  64  84  55  75 /  20  90  50  10   0
Hondo Muni Airport             84  62  87  53  82 /  20  90  20  10   0
San Marcos Muni Airport        85  66  85  54  79 /  20  90  50  10   0
La Grange - Fayette Regional   85  69  82  59  77 /  10  60  80  20  -
San Antonio Intl Airport       84  65  86  55  80 /  20  90  40  10   0
Stinson Muni Airport           85  67  86  56  81 /  20  90  40  10   0

&&

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

$$

Mesoscale/Aviation...Oaks
Synoptic/Grids...Runyen


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