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Area forecast discussion 
National Weather Service Austin/San Antonio Texas
916 am CDT Thursday Aug 21 2014

Update...heat advisory issued for southeast counties for this
afternoon and early evening. The most likely locations to see
105-110 degree heat index is along and south of a La Grange to
Gonzales to Floresville line. North of this line to the I-35
corridor 103-105 degree heat index expected. With the exception of
The Hill Country...most locations across south-central Texas
remained near or above 80 degrees for lows this morning...compounding
heat exhaustion potential. Minor tweaks up in actual temperature forecast
also made based on highs from yesterday...starting temperatures for
today...and ridge building towards the area.

Also...and elevated fire danger is possible this afternoon and
evening along the Rio Grande...where min relative humidity values dip to around
25 percent and gusty winds occur.

Jr

&&

Previous discussion... /issued 626 am CDT Thursday Aug 21 2014/

Aviation...
the I-35 taf sites have been alternating between VFR and MVFR this
morning due to patchy stratus across south central Texas. Expect
the status to stick around through 15z causing periods of MVFR
ceilings along the I-35 terminals. Del Rio could also see periods of MVFR
ceilings...similar to the last two mornings...so have continued to
carry the tempo group from 13 to 15z. VFR conditions this
afternoon under partly cloudy to mostly sunny skies. Stratus will
once again develop tonight...building over the I-35 terminals
between 07z/08z and at drt around 11z Friday morning then burning
off by 16z.

Winds will continue to be strong and gusty today out of the south
(aus/Sat/ssf) and southeast (drt). The highest wind speeds are
expected to be this afternoon when we could see sustained winds
between 10-15 knots and gusts as high as 25 knots. Winds weaken to
around 10 knots tonight.

Previous discussion... /issued 342 am CDT Thursday Aug 21 2014/

Short term (today through friday)...
a couple of weak showers continue from storms that moved into the
western zones late this evening. These should continue to weaken
as they progress north over the next few hours. Otherwise...today
will be hot and dry for much of south central Texas. Cant
completely rule out a stray shower this afternoon but moisture
levels are too low to warrant any mention of activity in the
official forecast at this time. Precipitable water values remain around 1.5
inches or less on Friday and will keep the forecast dry. The
drying of the atmosphere is in response to a building high moving
in from the east. The subsequent subsidence is therefore drying
out the atmosphere and ending rain chances for the area. Low-level
thermal profiles are not expected to change too much and high
temperatures should be persistent...around the middle 90s to near
100 degrees.

Long term (friday night through wednesday)...
the upper high is forecast to weaken and lift north by Sunday.
This is in response to a low pressure system moving into the
northern plains. This should allow moisture values to slowly
increase again with afternoon shower and thunderstorm activity
returning to the forecast on Wednesday. The return of precipitation could
be a bit sooner than that depending on the rate of the moisture
return...but opted to leave the forecast dry until Wednesday for
now. Just beyond the current package...the GFS is forecasting a
fairly progressive trough moving through the plains Thursday which
would send a frontal boundary into Texas Thursday/Friday bringing
rain chances for much of the forecast area. The European model (ecmwf) is much
slower with its handling of the upper trough and keeps high
pressure persistent over the Southern Plains. The more progressive
pattern of the the operational GFS is supported by most of the
gfsensemble members as well as the Canadian so it does bear
watching.

&&

Preliminary point temps/pops...
Austin Camp Mabry 101 78 99 75 99 / - - 0 0 -
Austin Bergstrom international Airport 101 76 99 73 98 / - - 0 0 -
New Braunfels Muni Airport 102 75 100 72 99 / - - 0 0 -
Burnet Muni Airport 98 75 96 73 96 / - - 0 0 -
del Rio International Airport 98 78 98 75 97 / 10 0 0 0 -
Georgetown Muni Airport 99 79 97 74 96 / - - 0 0 -
Hondo Muni Airport 99 75 98 72 97 / - 0 0 0 -
San Marcos Muni Airport 100 77 99 73 97 / - - 0 0 -
La Grange - Fayette regional 102 79 99 76 99 / - - - - 10
San Antonio International Airport 100 80 99 76 98 / - - 0 0 -
Stinson Muni Airport 102 78 100 75 99 / - - 0 0 -

&&

Ewx watches/warnings/advisories...
heat advisory from 1 PM this afternoon to 7 PM CDT this evening for
the following counties: Delaware Witt...Fayette...Gonzales...Karnes...
Lavaca...Wilson.

&&

$$

Mesoscale/aviation...07
synoptic/grids...76
public service/data collection...33

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