Area Forecast Discussion
Issued by NWS San Angelo, TX

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000
FXUS64 KSJT 271202
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
602 AM CST Fri Feb 27 2015

.AVIATION...
/12Z TAFS/

Near LIFR to MVFR conditions have begun to affect area terminals
early this morning due to light snow affecting parts of the area.
KABI has been as low as 3/4 of a mile in light snow already this
morning, and will likely see additional reductions to visibility
this morning. By early afternoon, expect the snow to be moving
east of the area. However, the low levels will continue to
moisten, resulting in lowering CIGS, and the development of light
drizzle or freezing drizzle later this afternoon and tonight, as
well as BR causing visibilities to be reduced to 3SM to 5SM at
times. Will carry IFR conditions through the overnight hours, as
conditions will not be able to improve until temperatures can warm
on Saturday. 20

&&

.PREV DISCUSSION... /ISSUED 451 AM CST Fri Feb 27 2015/

SHORT TERM...
(Today and Tonight)

A band of light snow was moving through the Concho Valley at 3 AM
this morning, and will continue moving north into the Big Country
early this morning. Light snowfall amounts of a dusting to around
a half inch are possible with this snow as it moves through. This
snow is associated with synoptic scale lift moving into the area
ahead of a shortwave trough moving east/southeast through northern
New Mexico early this morning. As this shortwave continues to move
to the east or east/southeast today, additional light snow is
expected to overspread most of the area. The most persistent
snowfall is expected generally across the Big Country through
early afternoon today. Total new snowfall across the Big Country
is expected to be between 1 and 3 inches, with isolated higher
amounts in some locations, especially in Haskell and Throckmorton
counties. So, the current advisory is in good shape. The only
change to the advisory may be to start it with the issuance of the
morning zones as opposed to 6 AM.

Although we are already getting light snow in the Concho Valley,
the most likely areas of significant accumulations are still
expected across the Big Country. However, if snow persists across
the Concho Valley, will not rule out the expansion to the south
into the Concho Valley area to address additional accumulations.

By midday, the snow is expected to move off to the east as the
shortwave continues eastward, with only light additional snowfall
during the afternoon hours. Temperatures will struggle to reach
freezing north of an Ozona to Mason line today.

Through the overnight hours, we are still looking at the potential
for additional very light patchy precipitation across the area due
to isentropic lift over the top of the cold surface air mass.
Thinking has not changed with respect to precipitation type
overnight a well. Due to saturation in only the low levels,
freezing drizzle or light freezing rain are expected to be the
predominant precipitation type. Although, light snow or sleet may
mix in at times. The precipitation is expected to be so light
tonight that accumulations will be very minimal if they occur.

20

LONG TERM...
(Saturday through Thursday)

As isentropic lift continues, will have a chance of light
precipitation on Saturday. Forecast soundings show a decreasing
sub-freezing layer just above the surface with an increasing warm
nose above the sub-freezing layer. The soundings also show
saturation below 800-850mb with drier air above. Temperatures
will slowly climb through the day with southeast surface winds,
and by late afternoon are expected to range from the mid 30s
across our far northern counties, to the mid to upper 40s along
the I-10 corridor. With these indications, expect mostly drizzle
and freezing drizzle. The area along/north of I-20 (Big Country)
will have the longest duration of freezing drizzle, possibly into
early afternoon before temperatures climb above freezing.

Have a chance for showers Saturday night and Sunday, with warm
air advection and possibility of a weak embedded shortwave entering
the area. Temperatures are only expected to drop a few degrees or
remain nearly steady Saturday night. Highs Sunday should range from
the mid 50s north to mid 60s south across west central Texas. May
have some decrease in cloud cover across our western and southwestern
counties during the afternoon.

A weak cold front is progged to move south into our area Sunday night,
and stall on Monday. With increasing moisture and some instability,
will have a chance for showers and a few thunderstorms, especially
Monday.

By early next week, an upper trough is progged to develop into
the southwestern part of the U.S., with southwest flow aloft ahead
of it and embedded shortwaves entering our area. The aforementioned
front is progged to lift north as a warm front Monday night, and a
Pacific front or surface trough may move east into our area Tuesday
night. This setup keeps the 20-40 PoPs going for showers/isolated
thunderstorms.

An upper trough entering the north-central U.S. will send a
stronger cold front south across our area late Tuesday night or
Wednesday morning. The 00Z GFS and ECMWF differ on how soon the
southwest U.S. upper trough will lift out across Texas, Wednesday
evening vs. Thursday morning. By that time, limited moisture
should preclude any chances for precipitation in our area.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  26  24  38  36  59 /  80  50  40  30  20
San Angelo  30  27  45  42  65 /  60  40  30  20  10
Junction  35  29  46  43  65 /  20  30  30  30  20

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 6 PM CST this evening FOR THE
FOLLOWING ZONES: Callahan...Fisher...Haskell...Jones...Nolan...
Shackelford...Taylor...Throckmorton.

&&

$$





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