Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Austin/San Antonio Texas
543 PM CST Wednesday Dec 17 2014
moisture continues to stream north across the region this evening.
Light drizzle/rain is expected overnight and fog has begun to form
and will prevail across the region by 06z. MVFR ceilings will become
IFR between 03z east and 07z west. Should begin to see slow
improvement in ceilings and visibilities between 15z-17z with VFR conditions
returning 18z-20z. Could see a few rain showers at any time on Thursday.
With the timing and location issues that exist will not include
in the forecast at this time. For the 30 hour terminals
(kaus/ksat) have included rain showers/thunderstorms and rain after 19/01z due to increasing
coverage across the region and back down to MVFR conditions.
Previous discussion... /issued 341 PM CST Wednesday Dec 17 2014/
Short term (tonight through Thursday night)...
late afternoon radar imagery shows a line of showers and
thunderstorms along and east of I-35 north of San Marcos. This line
of convection is gradually decreasing...but we still expect
additional activity to develop this afternoon and evening. We/ll
continue to mention thunderstorms through this evening as some
elevated instability is still present. We should see a gradual
decrease in showers after midnight for areas west of I-35... with
scattered showers continuing east of I-35. Patchy fog will likely
develop across most of the region tonight...especially over the
western Hill Country and southern Edwards Plateau. The sref and
hi-res nmm and arw show better potential for fog development and
lower visibilities across the mentioned region. Fog will continue
into Thursday morning...then begin to dissipate in the afternoon.
Rain chances will continue on Thursday for areas along and east of
I-35 as an upper level shortwave trough moves into northern Mexico.
Beginning Thursday night...the pattern becomes more active across
south central Texas as a surface low develops over deep south Texas.
This will set up a low-level baroclinic zone roughly along a Laredo
to Victoria line. We can expect an increase in low-level moisture
Thursday night as the upper level shortwave trough over Mexico moves
in from the west. Large scale forcing for ascent arrives late
Thursday night and showers and thunderstorms will become more
widespread after midnight. We/ll continue to mention the possibility
of locally heavy rainfall for areas generally along and east of
I-35. Can/T completely rule out a strong storm or two across the
region as well. Given the elevated (not rooted in the boundary
layer) nature of these storms...hail will be the primary concern.
Long term (friday through wednesday)...
showers and storms will be ongoing across much of the region Friday
morning. The southern edge of an upper level trough will move east
of the region throughout the day and this will bring a decrease in
precipitation chances. We/ll continue to mention a good chance for
rain across most areas Friday morning...then show a decrease in rain
chances during the afternoon. Event rainfall totals are expected to
remain in the 1 to 2 inch range for areas east of Highway 281. We
could see some isolated totals up to 3 inches east of I-35 as this
area will remain in closer proximitiy to the moist axis along the
coast. A dry forecast is in store Friday night as northerly winds
bring drier air to the region. Dry and cool conditions continue this
weekend with continued northerly flow in the low-levels. We do
expect another upper level trough to move into Texas on Sunday. At
this time...we Don/T expect any precipitation with this trough as
moisture will be lacking. Later shifts may need to monitor the
coastal plains for light shower activity on Monday...but confidence
is too low to warrant a mention in the forecast at this time.
Temperatures briefly rebound to near normal on Monday before a
cold front moves through on Tuesday. Dry and cool conditions are
expected on Wednesday.
Preliminary point temps/pops...
Austin Camp Mabry 52 68 54 59 45 / 40 20 80 60 10
Austin Bergstrom international Airport 51 68 54 59 45 / 40 20 80 60 10
New Braunfels Muni Airport 55 69 57 62 44 / 40 20 80 60 10
Burnet Muni Airport 48 67 51 57 40 / 40 10 70 50 10
del Rio International Airport 49 67 54 65 43 / - - 60 20 10
Georgetown Muni Airport 49 67 51 56 44 / 50 20 80 60 10
Hondo Muni Airport 53 70 56 64 41 / 20 20 80 40 10
San Marcos Muni Airport 53 68 55 60 45 / 40 20 80 60 10
La Grange - Fayette regional 56 69 57 62 48 / 50 40 90 70 10
San Antonio International Airport 55 69 58 63 46 / 30 20 80 60 10
Stinson Muni Airport 56 69 58 64 45 / 30 20 80 60 10
public service/data collection...32