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Area forecast discussion
National Weather Service Austin/San Antonio Texas
1132 PM CST Mon Nov 11 2019

Update...
06z aviation forecast below.

&&

Aviation...
concerns through the overnight continue to be the ongoing wintry
mix. A mix of -ra/-fzra/-pl is ongoing through portions of The Hill
Country and central Texas. The precipitation will gradually shift
south through the night. There is a window through around 09z where
aus could see -fzra accumulating on metal and other elevated
surfaces. Farther south, -pl could mix in with the -ra at Sat/ssf
overnight, however little to no accumulation is expected.
The other story is the winds. North winds sustained 15-25kt with gusts
in some areas 25-35kt through the overnight. Winds speeds are
expected to gradually diminish during the day on Tuesday.

&&

Previous discussion... /issued 726 PM CST Mon Nov 11 2019/

Update...
temperatures came in colder behind the front than originally
anticipated. Significant drops in temperatures have now leveled out
slightly and an update was issued to reflect the change. Multiple
reports incoming of sleet in The Hill Country, and with lowered
temperatures, Llano and Burnet counties have been added to the Winter
Weather Advisory. As of right now, we are still closely monitoring
Williamson, Travis, and Hays counties as these are still several
degrees above freezing.

Previous discussion... /issued 406 PM CST Mon Nov 11 2019/

Short term (tonight through Tuesday night)...
a strong cold front continues to move southward this afternoon and as
of 3 PM was located generally along an Eagle Pass to Gonzales line. A
very sharp drop in temperature (as much as 10-15 degrees in 1 hour)
was noted behind the front along with very gusty north winds up to
45 miles per hour. Some light radar echoes are noted along and behind the cold
front, with only light rain being reported so far.

We will continue to see much colder air move in through the remainder
of the afternoon and evening hours across all of south central Texas.
The main concern for the evening and overnight hours will be where
the subfreezing temperatures near the surface align with the light
precipitation moving in from the west. At this time, it appears the
southern Edwards Plateau and portions of The Hill Country stand the
best chance for ice accumulations this evening and overnight. After
looking at forecast soundings, it appears the main wintry
precipitation type in these areas will initially be a mixture of rain
and freezing rain, with some sleet mixing in as the evening and
overnight hours progress. Accumulations should be favored for areas
along and north of a Comstock to Bandera to Johnson City line,
primarily on elevated roadways.

For the remainder of the region, the chance for accumulation of ice
is lower. However, we will need to monitor adjacent portions of the
I-35 corridor, mainly north of San Antonio, for the possibility of
some light ice accumulations. Again, the main impact would likely be
for some light glazing on elevated roadways, such as bridges and
overpasses. While temperatures should not have much trouble dropping
to freezing, it may be tough to get much accumulation on roadways
given light precipitation amounts, very Stout north winds and
continued dry air in the low-levels.

The chance for any wintry precipitation should end fairly quickly
from north to south Tuesday morning as drier air continues to move in
from the north and the precipitation shifts south of the region. High
temperatures will be well below normal on Tuesday with readings only
topping out in the upper 30s and 40s. Overnight lows Tuesday night
will drop into the 20s for areas along and east of a Rocksprings to
New Braunfels to near Pleasanton line. West of this area, an increase
in cloud cover should keep lows mainly in the lower to mid 30s.

Long term (wednesday through monday)...
a very cold start on Wednesday morning is expected with temperatures
likely at or below freezing for most areas, except possibly along
the Rio Grande. An increase in cloud cover from southwest to
northeast will limit afternoon sunshine, leading to high temperatures
in the upper 40s and 50s across the region. The northern edge of an
upper level low will approach the region Wednesday night. We will
hold off on the mention of any precipitation during the daytime
hours, but may need to monitor the Rio Grande for the possibility of
some brief light rain in the afternoon. As the upper low moves into
deep south Texas Wednesday night, we will mention a chance of light
rain across a good portion of south central Texas. The better chance
for rain should generally remain along and east of I-35 given higher
atmospheric moisture across this region. We do not expect any wintry
precipitation Wednesday night as thick cloud cover and return
southerly flow will keep overnight lows in the mid 30s to lower 40s.
Rain chances continue on Thursday as the upper low opens and moves
into the western Gulf of Mexico. Again, rain chances will be higher
for areas generally along and east of I-35. Another cold front will
move through during the daytime hours on Thursday. This front will
initially aid precipitation chances during the late morning and
afternoon hours. However, as dry air filters in behind the front in
the low-levels, and we see a more stable west/northwest flow aloft
move in, precipitation chances will end Thursday night.

Dry weather along with warmer temperatures are in store across all
areas on Friday with surface high pressure being the dominant weather
feature. High temperatures will be in the 60s for most areas, which
is still below climatological normals for mid November. As the
surface high moves east of the region Saturday, surface winds will
trend to a more southerly direction. The warming trend will continue
Saturday with highs in the 60s to near 70 along the Rio Grande. We
will keep the forecast dry during the daylight hours, but will
continue to mention a low chance for showers Saturday night as an
upper level trough approaches from the west. Rain chances will
increase on Sunday and with south to southeasterly flow in the low-
levels, we will see highs in the mid 60s to lower 70s. A Pacific cold
front will move through during the late afternoon and evening hours
and if the faster GFS verifies, we may need to adjust Sunday high
temperatures down a bit across the southern Edwards Plateau and
western Hill Country. We are not expecting any significant cooling
behind the Pacific front on Monday and may wind up with little change
as skies will clear behind the front and trough axis allowing for
more insolation.

Climate...
record low maximum temperatures and/or record low temperatures will be
possible Tuesday and Wednesday for parts of south central Texas. A
listing of these records are included below.

November 12
location record low (year) record low maximum (year)
Austin Bergstrom 26 (1980) 51 (2018)
Austin Camp Mabry 24 (1950) 41 (1907)
San Antonio 26 (1950) 45 (1907)
del Rio 31 (1932) 46 (1907)

November 13
location record low (year) record low maximum (year)
Austin Bergstrom 28 (2014) 42 (2014)
Austin Camp Mabry 27 (1911) 36 (1976)
San Antonio 28 (2018) 37 (1976)
del Rio 31 (1986) 40 (1986)

&&

Preliminary point temps/pops...
Austin Camp Mabry 29 45 27 53 40 / 60 - 0 - 30
Austin Bergstrom Intl Airport 30 45 25 53 38 / 60 - 0 - 30
New Braunfels Muni Airport 30 46 26 52 38 / 60 - 0 0 30
Burnet Muni Airport 25 44 24 52 38 / 60 - 0 - 20
del Rio Intl Airport 35 49 36 52 39 / 60 10 - 10 10
Georgetown Muni Airport 26 44 24 52 38 / 60 - 0 - 30
Hondo Muni Airport 33 50 30 52 39 / 60 10 0 - 20
San Marcos Muni Airport 30 46 25 53 38 / 60 - 0 - 30
La Grange - Fayette regional 30 45 25 52 40 / 60 - 0 0 30
San Antonio Intl Airport 32 47 30 51 41 / 60 10 0 - 30
Stinson Muni Airport 33 47 31 50 41 / 60 10 0 0 30

&&

Ewx watches/warnings/advisories...
Wind Advisory until 6 am CST Tuesday for Atascosa-Bandera-Bastrop-
Bexar-blanco-Burnet-Caldwell-Comal-De Witt-Dimmit-Edwards-Fayette-
frio-Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Kinney-
Lavaca-Lee-Llano-Maverick-Medina-real-Travis-Uvalde-Val Verde-
Williamson-Wilson-Zavala.

Winter Weather Advisory until 6 am CST Tuesday for Bandera-blanco-
Burnet-Edwards-Gillespie-Kendall-Kerr-Llano-real-Val Verde.

&&

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