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Area forecast discussion...updated 
National Weather Service Austin/San Antonio Texas
626 am CDT sun Sep 21 2014

Aviation...
middle level clouds across the I-35 corridor have not allowed for low
clouds to form this morning. Expect to see a broken deck 050-070
through 14z-15z then scattering out. Kdrt does have MVFR ceilings
and expect this to continue through 17z-18z then becoming VFR.
Eastern sites only have isolated chances for convection today.
Best chances would be in the 17z-23z period. Kdrt will have
scattered convection so have included vicinity in the taf through
17z. Will continue to see convection through 00z but timing is
uncertain so have left out mention at this time. East/southeast winds will
increase to 5 to 10 knots after 14z. Winds at kdrt will be
easterly after 02z at speeds of 5-8 knots. The I-35 terminals will
see light and variable winds after 02z-04z. For the 30 hour sites
kaus/ksat will see a north/NE wind at 7-10 knots after 14z Monday as a
weak boundary moves into the region.

&&

Previous discussion... /issued 337 am CDT sun Sep 21 2014/

Short term (today through monday)...
dry air continues to filter into the area from the east...although
precipitable water still remains around 1.75 inches in the east and a little over
2 inches in the west. An upper level anticyclone continues to
develop over northern Mexico...and will pull down remnant moist
air from Odile across the Rio Grande plains and western Edwards
Plateau this afternoon and evening. Thus...the trend of stepping
down the coverage and intensity of convection will continue
today...with a gradient of probability of precipitation from unmentioned 10 percent in the
northeast to 30 percent on the Rio Grande plains. In addition...
the threat for locally heavy rainfall has ended. Most locations in
our area will remain dry today and those receiving rain should
average 1/4 inch or less.

A weak front will arrive on our northeastern border counties by
midday Monday...and all models indicate precipitable water converging and pooling
ahead of the boundary. There should be weak to moderate
instability and little or no cap...so we expect scattered showers
and thunderstorms along the front. The areas with the best chances
for rain will be along and east of I-35.

Long term (monday night through saturday)...
we retained probability of precipitation for Monday evening as the front drifts southward
through our area. After that...the latest models are trending
drier than previous runs...thus we decided to remove probability of precipitation for Tuesday
through Thursday. The dry atmosphere will allow for cool and
pleasant mornings with lows in the 60s at many locations...and
warm afternoons with temperatures a few degrees either side of 90.
Low and middle-level winds should return to a more southeasterly
direction by Friday...and with a cut-off low developing over
Texas...we brought back probability of precipitation Friday afternoon and evening for the
coastal plains.

The medium range models have the cut-off low featured somewhere
near Texas...but the evolutions range from one centered more on
our area (gfs) to one centered more on the Sabine River (ecmwf).
The sensible weather will be greatly impacted by placement...with
areas east of the center likely in an uncapped...tropical
environment...while areas to the west of the center relatively
dry. We decided to go with a dry forecast closer to the European model (ecmwf) at
this time.

&&

Preliminary point temps/pops...
Austin Camp Mabry 91 70 89 68 85 / 10 10 20 20 10
Austin Bergstrom international Airport 91 68 89 67 85 / 10 10 20 20 10
New Braunfels Muni Airport 92 69 92 69 89 / 10 10 20 20 10
Burnet Muni Airport 90 69 88 66 86 / 10 10 20 20 10
del Rio International Airport 90 71 90 70 87 / 30 30 20 20 10
Georgetown Muni Airport 91 70 89 66 86 / 10 10 20 20 10
Hondo Muni Airport 92 69 93 70 91 / 20 10 20 20 10
San Marcos Muni Airport 90 69 90 69 86 / 10 10 20 20 10
La Grange - Fayette regional 92 71 91 71 87 / 10 10 20 20 10
San Antonio International Airport 91 71 93 71 89 / 20 10 20 20 10
Stinson Muni Airport 92 71 93 71 89 / 20 10 20 20 10

&&

Ewx watches/warnings/advisories...
none.
&&

$$

Mesoscale/aviation...10
synoptic/grids...26

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