Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Austin/San Antonio Texas
957 am CST Tuesday Mar 3 2015
Update...fog persists across The Hill Country and locations along
the I-35 corridor eastward. Some locations are still reporting
dense visibilities...and have decided to extend a good portion of
the dense fog advisory through noon.
Previous discussion... /issued 537 am CST Tuesday Mar 3 2015/
poor flying conditions will continue through this taf period with
either IFR or LIFR expected. All terminals were LIFR for most of
the night with del Rio lifting to IFR around 09z. The San Antonio
sites have now begun to bounce between IFR/LIFR as shower have
formed over the I-35 corridor. Expect improved IFR visby/ceilings with
the rain showers...with LIFR conditions between showers at Sat/ssf
through the morning hours.
Models show a slow improvement through the afternoon at the I-35
terminals with ceilings lifting to IFR and the fog dissipating. The
period of IFR will be short lived as ceilings lower again after sunset
and more fog is expected to develop. The I-35 terminals will
return to LIFR conditions between 03z and 06z and remain socked in
through the night. Rain chances increase during the day tomorrow
so have included prob30 groups at the end of the taf for the 30
hour tafs sites to reflect this. Winds would be light out of the south
by later today and remain southerly through tomorrow morning.
Del Rio is expected to see ceilings rise this afternoon with a few
breaks in the clouds possible. By 21z drt should be VFR for a few
hours under overcast skies. IFR ceilings return to drt by 06z.
Previous discussion... /issued 448 am CST Tuesday Mar 3 2015/
Short term (today through wednesday)...
areas of dense fog with patchy drizzle continued across much of
south central Texas early this morning due isentropic lift with
southerly winds just of above the persistent cool surface ridge.
Finally expect the long anticipated significant warm up today as
the surface trough along the coast weakens allowing for southerly
flow to spread across south central Texas. The dense fog will
persist through middle morning with some fog and drizzle lingering
into the afternoon. Isentropic lift decreases as southerly flow
takes hold allowing for some sun and the warmer temperatures. We
will still be below average with the coolest temperatures along
the I-35 corridor as surface ridge lingers there the longest due
to cool air banking up against the Escarpment. The lower level
jet strengthens tonight allowing some streamer showers to develop.
Another strong cold front...currently extending from the Dakotas
into northeast Colorado...will surge across central and south
central Texas during the afternoon. A favorable upper level jet
position...moisture convergence along the front and instability
indicate some thunderstorms are possible. An abrupt drop in
temperatures of 15 to 25 degrees is expected with the frontal
passage as strong cold advection spreads across our area.
Long term (wednesday night through monday)...
strong cold advection as surface high builds into our area will be
ongoing Wednesday night in the wake of the frontal passage. Upward
motion from favorable upper level jet position passing overhead
and middle level shortwave to our west will continue precipitation
chances. Forecast soundings show a freezing rain and sleet mix
developing over The Hill Country in the evening...transitioning to
a sleet and snow mix while spreading to remaining areas north of
Highway 90...including the I-35 corridor from San Antonio to the
northeast. Ice accumulations of less than one quarter inch may be
possible across The Hill Country. However...there is some model
uncertainty on amount of moisture that will be available as drying
will take place. A strong pressure gradient will generate windy
conditions. A Wind Advisory may be needed. Temperatures fall below
freezing across the northern areas by Thursday morning. Some rain
lingers Thursday afternoon into evening across the southeastern
areas as the jet moves off to the east while temperatures rise
above freezing all areas. A more widespread freeze is likely
Friday morning as clouds decrease due to continued drying and a
cold surface ridge over our area. The middle level shortwave reforms
into a low a little further west and then moves across southern
Texas this weekend. Moisture and upward motion increase leading to
slight chances of rain on Saturday into Sunday. Although...the
surface ridge persists this weekend into early next week...
temperatures will be above freezing and no winter precipitation
is currently expected. Some recovery in temperatures is expected
by early next week. However...they will remain below average.
Preliminary point temps/pops...
Austin Camp Mabry 64 60 67 30 39 / 20 20 70 70 20
Austin Bergstrom international Airport 64 60 67 30 38 / 20 20 70 70 20
New Braunfels Muni Airport 65 61 69 32 40 / 20 20 50 70 30
Burnet Muni Airport 63 57 60 27 37 / 20 30 70 60 20
del Rio International Airport 69 58 69 32 44 / 10 20 30 50 20
Georgetown Muni Airport 62 58 63 28 38 / 20 20 70 70 20
Hondo Muni Airport 65 59 71 33 41 / 20 20 40 70 30
San Marcos Muni Airport 65 60 68 31 39 / 20 20 60 70 30
La Grange - Fayette regional 69 63 70 33 40 / 20 20 70 60 30
San Antonio International Airport 63 61 71 32 40 / 20 20 50 70 30
Stinson Muni Airport 64 61 73 33 41 / 20 20 40 70 40
dense fog advisory until noon CST today for the following counties: