Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
FXUS64 KEWX 281139
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
539 AM CST Tue Feb 28 2017
Low clouds and fog have conditions at area airports MVFR/IFR and this
will continue to the case through the morning. Conditions will
improve to VFR between about 18Z and 20Z and remain that way through
the end of the period in San Antonio and Del Rio. AUS will drop back
to MVFR for a few hours overnight. A cold front will move through the
region early Wednesday morning and turn winds to the north-northwest.
.PREV DISCUSSION... /ISSUED 406 AM CST Tue Feb 28 2017/
SHORT TERM (Today through Wednesday)...
Low clouds and winds in the 5-10 mph range are leading to a warm and
muggy night across South-Central Texas. Temperatures are in the
upper 60s and lower 70s and these values should not drop much further
before sunrise. With the moisture and warmer temperatures,
visibility values are beginning to drop into the 1-3 mile range
across some locations. Current forecast is handling this well with
the mention of patchy fog. Overall, the chances for dense fog are
not too high given the wind speeds, but will continue to monitor
trends through the night for any possible updates.
Models have come in drier today as it looks like the CAP will hold
in addition to drier air in the mid-levels. Therefore, have removed
the mention of precip from the forecast. The strength of the CAP is
being aided by strong southwesterly flow in the lower levels of the
atmosphere. While this will decrease the chances of rain for today
these winds will increase daytime temperatures. Highs today will
return into the 80s across much of the area and will actually be a
bit warmer than yesterday. Could even see some lower 90s across the
southwestern portion of the CWA.
A mid-level trough axis currently located across the western CONUS
will move east today/tonight before moving through the Central
Plains by tomorrow morning. This will send a cold front south into
the CWA after midnight tonight, with the front exiting the area
shortly after sunrise. With the expected surface forcing from the
synoptic boundary, a few isolated showers or thunderstorms will be
possible along or near the boundary. CAPE values will generally be
less than 1500 J/kg but with high shear values, can`t rule out a
stray strong storm. However, given that the overall expected coverage
of activity is expected to be low, will not mention anything in the
HWO at this time.
For tomorrow behind the front, temperatures will be in the 60s and
70s with breezy northerly winds around 10-20 MPH. Afternoon humidity
values will drop below 20 percent for areas west of Highway 281 and
this should allow for elevated to near critical fire weather
conditions to develop for this area. Will highlight this threat in
the graphicast, HWO, and Fire Weather Forecast.
LONG TERM (Wednesday Night through Monday)...
Highs Thursday should be in the 60s areawide for a near picture-
perfect day with partly cloudy skies and lighter winds. The forecast
had been calling for a chance of rain Friday night into Monday as an
upper trough moves near the region behind the frontal boundary.
Latest 00z model guidance digs the trough more to the south on
Thursday which will slow down the eventual eastward progression to
the system. Therefore, have lowered PoPs in the Friday night and
Saturday time frame with only 30s on Sunday as the system finally
nears the region.
With the later arrival, the best lift will coincide with southerly
flow at the surface on Sunday. While upward motions are still
expected in the mid-levels with vorticity advection ahead of the
upper low, we will not have any low-level lift to help aide in precip
production. If the system would have moved through earlier, in that
Friday night and Saturday window, east/northeast winds in the lower
levels of the atmosphere and increasing southerly flow ahead of the
trough in the mid-levels would have led to increasing isentropic lift
and thus, higher rain chances. Low rain chances will continue into
Monday as southerly flow increases, but overall coverage is not
expected to be too high. Temperatures Sunday and Monday will be back
in the 80s for much of the area.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 85 61 70 44 67 / 10 20 - 0 0
Austin Bergstrom Intl Airport 86 61 71 43 67 / 10 20 - 0 0
New Braunfels Muni Airport 86 62 73 43 67 / 10 10 - 0 0
Burnet Muni Airport 81 55 66 38 64 / 10 20 0 0 0
Del Rio Intl Airport 89 55 77 45 69 / 10 0 0 0 0
Georgetown Muni Airport 82 58 67 40 65 / 10 20 - 0 0
Hondo Muni Airport 87 59 78 42 69 / 10 10 - 0 0
San Marcos Muni Airport 86 61 73 43 67 / 10 20 10 0 0
La Grange - Fayette Regional 86 65 73 43 67 / 10 20 10 0 0
San Antonio Intl Airport 86 62 75 45 67 / 10 10 - 0 0
Stinson Muni Airport 87 63 76 47 67 / 10 10 - 0 0