Scientific Forecaster Discussion
fxus64 kewx 212340
Area forecast discussion
National Weather Service Austin/San Antonio Texas
540 PM CST sun Jan 21 2018
at kaus, MVFR cigs and rain showers in the vcnty will continue through 03z,
then scattered MVFR level clouds through 07z. At ksat/kssf, scattered MVFR level
clouds will linger through 06z. Otherwise, VFR flying conditions
will prevail tonight through Monday evening. Southerly winds 7 to 12
kts with gusts up to 20 kts ahead of the dryline, then winds shift to
northwesterly with passage of the dryline this evening into
overnight, increasing to 10 to 18 kts with gusts to 26 kts with
passage of a cold front overnight into early Monday.
Previous discussion... /issued 311 PM CST sun Jan 21 2018/
Short term (tonight through Monday night)...
Pacific cold front and associated storm system is making a slow
arrival into western portions of the forecast area this afternoon as
shower activity is becoming better congregated along a pre-frontal
trough/dryline feature over central Texas. A few storms are forecast in
the late afternoon mainly north at east of Austin Metro with 1000
j/kg CAPES, moderate low level shear and better thunderstorm
focusing mechanisms expected to stay just outside of the forecast
area to the N/NE. Would not be surprised to see a small hail report
over Williamson/Lee counties, but most of the afternoon/early
activity should remain as showers. Farther west some breezy and dry
conditions could briefly flare of fire weather concerns, but mainly
over sparsely populated areas of western Val Verde County, where
neighboring counties have a red flag warning in effect. Winds along
I-10 in the sjt forecast area remain well-behaved, so do not expect
to see any surprise strong winds for the first period.
The cold front should become more visible on the map this evening as
the strong mixing from the dynamic upper low to the north relaxes. By
sunset, the focus for light showers and patchy drizzle should shift
east of I-35, and no significant rains are expected in the area after
midnight. Moderate northwest winds will clear out the moisture by daybreak
and create breezy and dry conditions that might favor the spread of
fires over mainly near and west of I-35 where humidities will drop
the most. Residual ground moisture east of Highway 281 could minimize
the threat for fires, but persistent moderate winds could dry out
fine cured fuels by late afternoon.
Cool and dry air with light winds could lead to some light freezes
north of Highway 90, but obviously this Pacific front is bringing
modified air in from the west.
Long term (tuesday through sunday)...
a flat zonal pattern aloft brings a seasonal and dry weather
forecast for Tuesday through Thursday with winds mainly Continental
easterlies as broad surface ridging settles over the lower
Mississippi Valley through Wednesday. Southerly winds pick up a bit
on Thursday to lead to bring clouds and moisture back into all of the
south central Texas by Thursday night. Rain chances increase Friday
as another fairly deep upper trough approaches. This upper trough
begins as one similar in strength to the one currently passing
through TX, with thunderstorm chances possibly grazing parts of
central Texas and our western counties remaining dry.
Preliminary point temps/pops...
Austin Camp Mabry 46 66 38 65 37 / 20 0 0 0 0
Austin Bergstrom Intl Airport 46 66 36 64 34 / 30 0 0 0 0
New Braunfels Muni Airport 45 67 36 65 35 / 20 0 0 0 0
Burnet Muni Airport 41 63 33 62 33 / 10 0 0 0 0
del Rio Intl Airport 41 66 36 66 37 / 0 0 0 0 0
Georgetown Muni Airport 43 64 34 63 33 / 20 0 0 0 0
Hondo Muni Airport 41 69 34 66 33 / 0 0 0 0 0
San Marcos Muni Airport 46 66 36 66 35 / 20 0 0 0 0
La Grange - Fayette regional 47 66 36 65 36 / 50 0 0 0 0
San Antonio Intl Airport 46 68 38 66 37 / 10 0 0 0 0
Stinson Muni Airport 45 68 38 66 38 / 10 0 0 0 0