262
FXUS64 KSJT 131145
AFDSJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
645 AM CDT TUE AUG 13 2013
.DISCUSSION...
look for VFR conditions to dominate West Central Texas today, before
another cold front moves into the Big Country and brings the
possibility for thunderstorms across that area tonight. Please see
aviation below for details.
.AVIATION...
We've been writing about another weak cold front moving into West
Central Texas for several days now. So, I'm sure you're not
surprised the cold front looks likely to move into the Big Country
around sunset this evening. By sunrise Wednesday morning, I'm
looking for the front to be somewhere near a Sterling City to
Brownwood line. Not only will this front bring a surface wind shift,
it will also bring the possibility for thunderstorms. in addition,
the NAM is indicating the front will bring MVFR ceilings to the Big
Country as well. For now, I didn't want to include any MVFR
ceilings, mainly because the timing is in the last 6 hours of this
forecast cycle. What's more, the MAV-based guidance doesn't indicate
any MVFR ceilings with the front. So, I only included prevailing
scattered at 3,500 feet above ground level in the Abilene terminal
beginning at 06Z tonight. Surface winds tonight, south of the front,
will be light and variable around 6 knots or less.
Huber
.SHORT TERM...
Today and Tonight
Hot today and another cold front tonight with possible rain.
Well here we are only about 24 hours from the appearance of this
cold front we've been anticipating now for many days. The latest
surface analysis indicates this front lies nearly east to west
across northern Oklahoma. North of the front in Kansas, some
locations are reporting rain, with temperatures in the 65 to 70
range. The NAM and GFS still do not agree very well on the timing of
this front; the NAM is still faster by 6 to 8 hours. So, after
coordination with WFO Lubbock and WFO Norman, I decided to go with a
NAM-based timing solution for my surface wind grids. This solution
brings the leading edge of the front, or wind-shift line, into our
northern Concho Valley and northern Heartland counties by 12Z
Wednesday. The best rain chances for the next 24 hours still look to
be Tuesday night, mainly after midnight across the Big Country.
That's when the front should be moving into our Big Country area.
Meanwhile, highs today will again be a category or two above
seasonal normals, with lots of sunshine and some compressional
warming. Lows tonight close to MOS guidance and near persistence
look reasonable.
Huber
.LONG TERM...
Wednesday through Monday
The main focus through the long term will be rain chances through
the second half of the week as a weak cold front affects the area.
By Wednesday, the pattern shift from mainly ridging over our area to
northwest flow will be underway, with a cold front moving into the
area. Model differences have been maintained between the NAM and
GFS, with the NAM bringing the front through faster (as well as the
ECMWF). With the pattern shifting to northwest flow over our area,
and ongoing convection expected along the Red River valley Tuesday
night helping to push the cold front through the area Wednesday,
providing a good focus for thunderstorm activity Wednesday afternoon
into Wednesday night. As a trough deepens across the Mississippi
River valley through the second half of the week, northwest flow
will continue to establish itself across our area. This will result
in higher confidence in at least a slight chance for shower or
thunderstorm activity through the end of the week, especially for
our northern counties. Especially considering easterly, moist
upslope flow into higher terrain behind the front through the end of
the week as well. Therefore, we will continue to keep at least a
slight chance for showers and thunderstorms through the end of the
work week. Will not change too much as far temperatures are
concerned. These may need to be lowered if there is ample cloud
cover and rainfall, but there may also be enough sun each day to
warm temperatures well into the 90s even behind the front.
Beyond the end of the week, southerly low level flow and a more
typical summer pattern will return with generally drier and warmer
conditions.
&&
.PRELIMINARY POINT TEMPS/POPS...
ABILENE 99 72 91 70 91 / 5 20 40 30 30
SAN ANGELO 100 72 96 71 97 / 5 10 20 20 20
JUNCTION 99 72 99 72 98 / 5 10 10 10 10
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
Huber/20