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afdewx

Area forecast discussion
National Weather Service Austin/San Antonio Texas
1252 am CDT Mon Jul 23 2018

Update...
see below for the 06z aviation discussion...

&&

Aviation...
VFR conditions should prevail for the entire taf period at all
terminals. Guidance suggests the possibility of MVFR conditions east
of Interstate 35, but aus/Sat/ssf should remain clear of morning
stratus and any patchy fog this morning. The only terminal that has a
slight chance of some brief MVFR conditions would be ssf, but this
remains unlikely. Winds will be out of the south/southeast for the
entire forecast period, with wind speeds a bit less today compared to
previous days (sustained winds in the 8 to 10 knot range by Monday
afternoon).

&&

Previous discussion... /issued 310 PM CDT sun Jul 22 2018/

Short term (tonight through Monday night)...
late morning surface winds will mostly from the southwest leading the
less cloud cover and temps warming faster than yesterday by about 2
or 3 degrees. This should lead to todays highs being more consistent
with those of Friday after a many temps trended down a degree or two
Saturday. Dry air seen from composite layer precipitable water
satellite product early this afternoon should send temps soaring over
the northern Hill Country and another 108 degree day is expected at
Llano. The sharper anticyclonic rotation over northwest Texas/SW OK is drifting
SW and will be over our northern County Warning Area border for Monday, yielding
possibly the hottest day of the year and possible new records for all
4 climate stations as shown below. 850 mb temps will approach 30
celsius over the northern Hill County and raw model data suggests
that a few areas could reach the 110 mark. While the forecast highs
for tomorrow should exceed those of today, no new threat areas were
identified for possible upgrades in the npw product for excessive
heat warning and heat advisory. Mid level moisture begins to increase
over central Texas Monday evening, but under the sharpest part of the
anticyclonic flow in the mid levels, very little convective activity
is developed by cams models in the County Warning Area with only some brief
activity suggested over north central Texas. Will need to watch closely
as the 36 hour hrrr shows pwat values reach around 1.75 toward 00z
around Llano. Areas near the northern border of the County Warning Area could need to
watch for strong outflow winds early Monday evening.

Long term (tuesday through sunday)...
mid level moisture continues to spill south across Texas and a better
chance for elevated convection is suggested for Tuesday. The early
morning arrival of this pattern could work out good for the area with
the lower convective temps possibly developing a less severe looking
inverted-v profile. Still afternoon temps near Highway 281/I-35
corridors could approach 100 degrees which could support strong
downdrafts. Areas west of 281 could see the stronger storm downdrafts
Tuesday. With a weakening front moving with this bubble of mid level
moisture chances are, the outflows will occur once, and then
stabilize the area in its wake. This means that while convection
could impact most of the area with wind, the chance of precip is more
likely to be isolated. Remnant convection could develop in the
convergent low level winds mainly south of I-10 Wednesday before
upper stability regains control.

With little moisture expected from convection, am shifting extended
period high temps for thurs-Sat to be more of a true split between
the hotter ecm and the "cooler" GFS guidances. Further shifts toward
the hotter ecm may be needed should the frontal wind shifts and
thunderstorm outflows turn out weaker than projected. Another
weakness in the ridge over North Texas could bring about additional
slight chance pops next Sunday.

Climate...

Record daily high temperatures vs. Forecasted highs

7/22 7/23
sun Monday
--------------------------
rec/forecast rec/forecast
aus 102/103 103/106
att 104/104 104/107
drt 105/105 105/109
Sat 102/102 103/103
--------------------------

&&

Preliminary point temps/pops...
Austin Camp Mabry 107 79 99 78 100 / 0 10 20 20 -
Austin Bergstrom Intl Airport 106 78 99 76 100 / 0 10 20 20 -
New Braunfels Muni Airport 105 77 100 76 99 / 0 - 20 20 10
Burnet Muni Airport 107 78 99 76 99 / 0 10 20 20 -
del Rio Intl Airport 109 81 107 80 103 / 0 0 10 20 20
Georgetown Muni Airport 108 77 99 76 99 / 0 20 20 20 -
Hondo Muni Airport 107 75 103 76 101 / 0 0 20 20 10
San Marcos Muni Airport 105 77 99 76 99 / 0 10 20 20 10
La Grange - Fayette regional 104 78 97 77 99 / 0 10 20 20 10
San Antonio Intl Airport 103 79 99 77 99 / 0 0 20 20 10
Stinson Muni Airport 106 78 102 78 100 / 0 0 20 20 10

&&

Ewx watches/warnings/advisories...
heat advisory until 7 PM CDT this evening for Atascosa-Bandera-
Bexar-blanco-Caldwell-Comal-De Witt-Edwards-Fayette-frio-Gillespie-
Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Medina-real-
Uvalde-Wilson.

Excessive heat warning until 7 PM CDT this evening for Bastrop-
Burnet-Lee-Llano-Travis-Williamson.

&&

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