Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 301729
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1229 PM CDT THU OCT 30 2014

.AVIATION...
/18Z TAFS/

A cold front will approach KABI around 21z, KSJT just after 00z, and
the southern sites during the late evening hours, resulting north
winds of 5 to 10 knots. Isolated to scattered showers and
thunderstorms will be possible late this afternoon and evening, and
this is covered with VCTS groups. Most convection should be south of
the area shortly after 06z. In addition, stratus development may
result in MVFR ceilings, at mainly KSOA, KBBD and KJCT. A return to
VFR conditions is forecast by mid morning early to mid morning
Friday.

&&

.PREV DISCUSSION... /ISSUED 651 AM CDT THU OCT 30 2014/

AVIATION...
/12Z TAFS/

Plan for VFR conditions to dominate for the next 24 hours. Stratus
and patchy fog didn`t develop this morning, as the previous
terminals indicated. However, IR imagery and METAR data indicate
patchy stratus with a MVFR ceiling is just south and southeast of
our southern terminals. So, watch for amendments.

PREV DISCUSSION... /ISSUED 457 AM CDT THU OCT 30 2014/

SHORT TERM...
(Today and Tonight)

Another cold front will push south across West Central Texas during
the next 24 hours and bring cooler temperatures along with the
possibility for rain. The front will likely begin pushing into our
northern Big Country counties around mid afternoon, and it should be
south of our counties by sunrise Friday morning. Although lift along
and near the front will be marginal, slight chance PoPs looks
reasonable given other model indicators. Otherwise, afternoon highs
today will be warmer than usual, for this time of year, mainly in
the upper 70s to around 80. Lows tonight, closer to seasonal
averages look good, given timing of the cold front.

Huber

LONG TERM...
(Friday through Wednesday)

The main concern in the extended forecast continues to be with the
potential for much needed rainfall early next week. Also have a
potential for scattered frost across some of our northern and
eastern counties late Friday night/early Saturday morning.

By sunrise Friday, the cold front and associated rain chances will
be south of our area. Expect the back edge of cloud cover to be
across our southern counties, with skies clearing during the
morning. Temperatures will be cooler on Friday, with afternoon highs
expected to range from the mid to upper 60s across our northern
counties, to the lower 70s in the south.

Fairly strong surface high will move from the northern Plains Friday
morning to the mid-Mississippi Valley by Saturday morning, with a
ridge extension south into Texas. Strong radiational cooling is
expected Friday night, and the 00Z GFS and NAM are trending colder
with the overnight lows. Light east winds are expected for much of
the night, with the longest duration of light winds across the
eastern third of our area. With clear skies and drier air,
temperatures are expected to drop into the mid 30s to lower 40s for
overnight lows, with the coldest readings in the low-lying areas of
our northern and eastern counties. NAM MOS guidance is colder than
the GFS MOS with the lows, and at this time going with a compromise
blend. Given the forecast minimum temperatures and temperature/
dewpoint depressions, scattered frost will be possible in some of
our northern and eastern counties early Saturday morning.

Return flow will develop Saturday and continue on Sunday with gusty
south winds on Sunday. Expect to have a reduced diurnal range in
temperatures Sunday through Monday, with increased moisture and
cloud cover. A strong upper level trough will move east across the
western U.S. on Saturday. The northern part of the trough will be
more progressive and move across the northern Plains on Monday.
The southern portion will become detached as it enters the
southwestern U.S. The 00Z GFS maintains more of an open wave with
this part of the trough, and moves it slowly east across New
Mexico on Tuesday. The ECMWF develops a closed low over Arizona,
and then takes the low south-southeast into Mexico before lifting
northeast toward Texas later in the week.

Both models continue to show south-southwest flow developing
aloft over Texas, and both show moisture from an eastern Pacific
tropical system getting pulled northeast across Mexico and into
Texas. With the slow approach of a cold front from the north.
Despite some differences between the GFS and ECMWF, the setup in
both models favors a concentration of showers and thunderstorms
along the front, with additional convection ahead of the front
generated by embedded disturbances aloft entering the area. Strong
lift and anomalously high precipitable water values favor a
potential for heavy rainfall. We have slight chance PoPs for the
northwestern part of our area Sunday night, with expanding and
increasing PoPs Monday and Monday night. The highest chance and
coverage of showers/thunderstorms is expected to be Tuesday into
Tuesday night, though some timing uncertainties remain. The cold
front is progged to move slowly south across our area during that
time.

With the timing uncertainty, we have lingering PoPs into Wednesday.
With the eventual departure of the system, clearing skies are
expected with cooler temperatures. Leaning toward the more
progressive GFS at this time, but PoPs may need to be carried a day
longer if models trend to a closed low solution.

19

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  47  67  38  67  52 /  30   5   0   0   5
San Angelo  52  71  39  71  53 /  30  10   5   0   5
Junction  54  72  38  70  52 /  40  10   5   0   5

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

Daniels




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