Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 252348 AAA
AFDSJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN ANGELO TX
548 PM CST THU DEC 25 2014

.AVIATION...
/00Z TAFS/

South winds are decreasing across the area early this evening.
Winds will continue out of the south tonight and Friday, and
will still be gusty at times. The higher speeds and gusts will be
at KABI, where occasional gusts of 20-25 kt are expected.
Considerable high cloud coverage will remain across the area. Some
low cloud development with MVFR bases/ceilings is expected early
Friday morning at KJCT, KBBD and KSOA. Also carrying a scattered
low cloud layer at KSJT. Low clouds should break up around mid-
morning Friday.

19

&&

.PREV DISCUSSION... /ISSUED 345 PM CST THU DEC 25 2014/

SHORT TERM...
(Tonight and Friday)

Upper low will be centered over the four corners area by tomorrow
morning with the forecast area continuing under a southwest flow
aloft. Most of the northern CWA will continue under a wind
advisory for the remainder of the afternoon with south to
southwest winds abating this evening and into tomorrow. Morning
lows tomorrow will be in the mid 40s with some low clouds building
into the forecast area from the south. 850mb temperatures this
afternoon of 8C - 10C will warm another 4C degrees by tomorrow
translating to warmer afternoon highs tomorrow in the mid to upper
60s under partly to mostly sunny skies.

15

LONG TERM...
(Friday night through New Years Day)

A fairly active week of weather is ahead for the area.

Have kept the mention of a slight chance for showers in Friday
night into Saturday as a cold front moves through the area, and a
shortwave trough approaches from the west. Any precipitation that
does fall with this initial system will be very light. If the cold
front can come through earlier enough, and cool temperatures down
enough, it is not out of the question for areas mainly west of a
Sweetwater to Haskell line to see a little snow mixed in with the
rain Friday night into Saturday morning. However, no accumulations
are expected. Have moved precipitation eastward quickly on Saturday
as the event should be mainly over by Noon.

An arctic cold front will move into the area Monday night,
setting the area up for a cold few days next week. Along with the
cold weather, there will be the potential for a light wintry mix
of precipitation for at least the northern half of the area from
Tuesday night through New Years Day. Tuesday into Tuesday night,
GFS soundings show temperatures from the surface through 750mb
below freezing, with the coldest forecast temperatures near -6
Celsius for the northern 2/3 of the CWA. Above this cold near
surface layer is a 10 to 15 thousand foot dry layer. These
soundings suggest the potential for light freezing rain or drizzle
Tuesday/Tuesday night. While this precipitation is expected to be
very light (only a few hundredths liquid equivalent), it only
takes a very small amount of any kind of frozen precipitation to
create hazardous road conditions in this area. However, mesoscale
details associated with a system 5 to 7 days out cannot be
reasonably forecast, so have gone with a gradient of precipitation
type with light snow possible for northern/western areas, a mix of
rain/freezing rain for central areas, and mainly liquid for
southern areas. However, areas along the I-10 corridor could also
see some light freezing rain/drizzle next Tuesday night into
Wednesday morning. Highs Tuesday and Wednesday are currently
forecast to be in the 30s, but we could be even colder, as models
often underestimate how cold these arctic air masses are,
especially if we have cloudy skies and light precipitation.

Both the GFS and ECMWF show an upper level closed low getting
organized to the west of the area during the second half of the
week. This would normally result in south to southeasterly flow in
the lower levels, with associated warming and increasing low level
moisture, and additional chances for precipitation. So, have kept
slight chances of precipitation going through New Years Day with
liquid precip advancing northward.

20

FIRE WEATHER...
Elevated fire weather conditions will improve this evening as
southerly 20 foot winds decrease to 10-15 mph. Temperatures will
be 5 to 10 degrees above normal tomorrow but minimum relative
humidity values will increase to over 30 percent. Through the
beginning of next week 20 foot winds should remain below 15 mph
and minimum relative humidities will remain above 30 percent.

15

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  45  65  34  43  28 /   0   5  20  20  10
San Angelo  44  69  36  47  30 /   0   5  20  20  10
Junction  44  69  41  51  34 /   0   5  10  20  20

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY until 6 PM CST this evening FOR THE FOLLOWING
ZONES: Brown...Callahan...Coke...Coleman...Concho...Fisher...
Haskell...Irion...Jones...Nolan...Runnels...Shackelford...
Sterling...Taylor...Throckmorton...Tom Green.

&&

$$








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