Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Austin/San Antonio Texas
809 PM CDT sun Apr 20 2014

Update...
isolated thunderstorms and rain will be possible over western Val Verde County this
evening with light rain showers...sprinkles or drizzle possible
over much of the forecast area this evening. A weakening cell
entering Val Verde County should continue to weaken...but
additional thunderstorms will remain possible through the night
from the more unstable air aloft to the west. The rest of the
forecast remains on track for tonight.

The forecast for Monday afternoon through Monday night was tweaked
some to reflect closer alignment with the severe weather potential statement and Storm Prediction Center projections.
Several runs of the NAM model have shown a consistent pattern of
a possible cluster of strong to severe thunderstorms forming the
steep middle-level lapse rate region of north central Texas in the late
afternoon...then propagating S/SW into mainly The Hill Country
during the evening hours. This scenario is being replicated in the
later periods of many of the hi-res models. An 850 mb Theta-E axis
and the movement of a weak cold front will help steer this area of
instability... resulting in above average confidence. Thus despite
a low amount of coverage expected with these strong to severe
cells...will nudge probability of precipitation upward...especially in the evening hours
over the Edwards Plateau and Hill Country.

&&

Previous discussion... /issued 650 PM CDT sun Apr 20 2014/

Aviation...
ceilings will continue to vary widely across the region this evening
before ceiling bases begin to lower. Isolated-scattered rain showers/thunderstorms and rain remains
possible tonight...but areal coverage is too low to warrant
explicit mention of impacts at taf terminals. Conditions will
deteriorate overnight...with ceilings potentially falling to LIFR in
the near-daybreak hours. Patchy fog will also develop overnight...but
visibilities are mostly expected to remain MVFR or better. Southeast-southerly surface winds
of 5 to 10 kts overnight will increase to 10 to 15 kts during the
late morning hours on Monday. Low ceilings will remain across the region
until winds begin to increase and allow better mixing. VFR conditions
should return by 17-19z.

Previous discussion... /issued 335 PM CDT sun Apr 20 2014/

Short term (tonight through Monday night)...
a lot of clouds will remain across south central Texas through
Monday as deep southerly flow maintains saturated lower levels of
the atmosphere. There is a slight chance of rain tonight across
the eastern two-thirds of the area as an upper level trough over
the Texas Panhandle pushes to the east. Can't rule out an
isolated shower over parts of Val Verde County this evening as
storms over West Texas travel eastward through the period.
Rainfall amounts will generally be light or from a trace to a few
hundredths of an inch. Overnight lows are expected to be around
the lower 60s Hill Country to the middle 60s in the southern Rio
Grande plains.

Monday will start cloudy most areas with light rains and even
patchy fog across the coastal plains. Later in the day...several
upper level short-waves are forecast to move across central Texas
while a cold front pushes southward from North Texas. At the
surface...dewpoints are expected to reach the middle 60s with area
forecast soundings showing large instability numbers such as cape
of 2000-2500 j/kg and lifted index values of -4 to -8. We are
carrying low probability of precipitation for this event...however...any storms that does
develop has the potential to become strong to severe across The
Hill Country and Edwards Plateau from middle afternoon to about 9 PM
Monday. Looks like the activity will start with isolated storms
firing up ahead of the cold front by middle afternoon over the San
Angelo areas with storms getting better organized as they approach
The Hill Country late afternoon/early evening. Large hail and
damaging winds are he main hazards for this event. As the cold
front pushes across south central Texas late evening
Monday/overnight Tuesday...showers and storms will come to an end.

Long term (tuesday through sunday)...
a warming trend and fair weather conditions are expected for much
of the week. Highs will be ranging generally from the upper 80s
east of Highway 281 and around the lower 90s west. A series of
upper level short-waves are expected to move across the area late
Wednesday into Thursday for a slight chance of rain mainly along
and east of I-35 corridor. May see some showers and even a few
thunderstorms across the area the following weekend as another
upper level trough pushes across the Southern Plains.

&&

Preliminary point temps/pops...
Austin Camp Mabry 62 82 62 84 62 / 20 20 30 10 -
Austin Bergstrom international Airport 60 83 61 84 60 / 20 20 30 10 -
New Braunfels Muni Airport 60 83 61 85 60 / 20 20 30 10 -
Burnet Muni Airport 61 82 63 83 62 / 20 30 40 10 -
del Rio International Airport 65 86 66 89 67 / 20 10 20 10 -
Georgetown Muni Airport 62 82 63 83 63 / 20 20 40 10 -
Hondo Muni Airport 64 86 63 91 64 / 20 10 30 10 -
San Marcos Muni Airport 60 82 61 84 60 / 20 20 30 10 -
La Grange - Fayette regional 61 81 63 84 62 / 20 20 20 20 -
San Antonio International Airport 62 84 62 87 63 / 20 20 30 10 -
Stinson Muni Airport 63 86 63 89 62 / 20 10 20 10 -

&&

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

$$

Mesoscale/aviation...26
synoptic/grids...18
public service/data collection...33