Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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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.


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




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