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

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FXUS64 KEWX 221628
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1028 AM CST Sun Jan 22 2017

.UPDATE...
Very strong W-NW winds of 20-30 mph are occurring across most of
South Central Texas and these winds are expected to increase slightly
over the next few hours to 25-35 mph while gradually veering to the
northwest. Winds at 925 mb are between 45-55 knots as expected based
on aircraft sounding and VAD wind profiles from radars, but EWX did
show slightly stronger winds at 13Z. The strongest winds should occur
over the next few hours through early afternoon as models continue
to indicate winds will increase as these stronger winds aloft mix
down more efficiently while the surface pressure gradient and
associated isallobaric component to the flow increases. Winds will
most likely be strongest along the Balcones Escarpment where there
will be an additional downsloping component to the flow, particularly
from San Antonio to Georgetown. These areas are the most likely ones
to see sustained winds approaching 35 mph with gusts approaching 50
mph through early afternoon with perhaps a few gusts as high as 55
mph. The pressure gradient is still expected to begin relaxing by
mid-afternoon to help winds begin to decrease, with winds generally
falling below 15-20 mph by early evening as the atmosphere also
begins to decouple. Therefore, the expiration time of 6 PM for the
Wind Advisory currently looks good, with counties out west likely
possibly falling below criteria a few hours early.

The grids and associated products have been updated to include the
slight increase in wind speeds, along with increasing temperatures a
few degrees based on 850-925 mb temperatures being a bit higher than
forecast suggesting advection is a bit slower and weaker. Dew points
have been adjusted based on observations as well, with minimum
relative humidity values as low as 12-15 percent over Dimmit and
Maverick Counties to 30 percent over our easternmost counties. The
Red Flag Warning remains in effect until 6 PM for all of South
Central Texas based on these low relative humidity values combined
with strong winds and moderate to extreme fire danger forecast by TFS.
The areas of greatest fire weather concerns for today are still
along and west of a line from Fredericksburg to San Marcos to Cuero
where very high to extreme forecast fire danger and 10-hour fuel
moisture values are forecast to be below the 10th percentile.



&&

.PREV DISCUSSION... /ISSUED 523 AM CST Sun Jan 22 2017/

AVIATION DISCUSSION...FOR 12Z TAF PERIOD...
Winds will be the only aviation concern this period as sustained
west-northwest winds of 20-30 kts with gust potential as high as 40+
kts exists for the I-35 terminals. KDRT will also be windy but should
peak in the upper 30 kt range being farther from the strongest
pressure gradient.

Time frame for the highest wind gust potential looks to be late
morning into the early afternoon, roughly 16Z to 20Z and have noted
this in prevailing lines for KAUS/KSAT/KSSF. Wind direction should
slowly shift from west to northwest (280-310 degrees) over the course
of the day. Thus, all north/south oriented runways should be impacted
by significant crosswinds. Winds will subside beginning 20-21Z and
by nightfall should calm to below 10kts at all sites.

PREV DISCUSSION... /ISSUED 433 AM CST Sun Jan 22 2017/

SHORT TERM (Today through Monday)...
The main concern in the short term portion of the forecast will
continue to the be the gusty west to northwest winds today along with
fire weather concerns. Gusty west winds are already in place across
the region and given a tight pressure gradient and some afternoon
mixing, the gusty conditions will continue. Winds should peak from
mid-morning into the early afternoon with sustained west to
northwest winds of 25 to 35 mph with gusts near 45 mph. A Wind
Advisory will remain in effect until 6 PM across all of south central
Texas. Around sunset, the lower levels will decouple and wind gusts
will subside. On Monday, dry weather is expected along with southwest
winds in the 10-15 mph range. Given dry air in place and plenty of
sunshine, we expect afternoon highs in the 70s.

LONG TERM (Monday Night through Saturday)...
The weather pattern will remain conducive for dry conditions and
above normal temperatures through midweek as zonal flow aloft remains
intact. Temperatures should peak on Tuesday with some cooling
expected on Wednesday behind a Pacific cold front. Temperatures
remain steady on Thursday and Friday and should cool down below
normal on Saturday as a cold front moves in. We will mention a low
chance for rain Friday night and Saturday as the front moves across
the region. Otherwise, dry weather is in store for south central
Texas this week.

FIRE WEATHER...
Dry and windy weather along with moderate to high fire danger across
the region will result in critical fire weather conditions across all
of south central Texas today. A Red Flag Warning is in effect for all
areas until 6 PM today. Minimum afternoon humidities will range from
near 15 percent along the Rio Grande to near 30 percent in the
coastal plains. The dry and windy conditions along with cured fine
fuels will result in rapid fire growth and spread today. Fast moving
grass fires are likely with any fire starts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              71  45  73  51  79 /   0   0   0   0   0
Austin Bergstrom Intl Airport  71  43  73  48  79 /   0   0   0   0   0
New Braunfels Muni Airport     72  43  74  48  79 /   0   0   0   0   0
Burnet Muni Airport            67  41  74  49  77 /  -    0   0   0   0
Del Rio Intl Airport           71  42  77  48  79 /   0   0   0   0   0
Georgetown Muni Airport        67  42  72  50  77 /  -    0   0   0   0
Hondo Muni Airport             74  41  76  46  81 /   0   0   0   0   0
San Marcos Muni Airport        72  43  73  48  79 /   0   0   0   0   0
La Grange - Fayette Regional   71  44  70  51  79 /   0   0   0   0   0
San Antonio Intl Airport       72  44  75  50  80 /   0   0   0   0   0
Stinson Muni Airport           75  44  75  49  80 /   0   0   0   0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM CST this evening for the following
counties: Atascosa...Bandera...Bastrop...Bexar...Blanco...Burnet...
Caldwell...Comal...De Witt...Dimmit...Edwards...Fayette...Frio...
Gillespie...Gonzales...Guadalupe...Hays...Karnes...Kendall...Kerr...
Kinney...Lavaca...Lee...Llano...Maverick...Medina...Real...Travis...
Uvalde...Val Verde...Williamson...Wilson...Zavala.

&&

$$

Mesoscale/Aviation...Allen
Synoptic/Grids...LH
Public Service/Data Collection...Williams


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