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000
FXUS64 KSJT 270532
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1132 PM CST Thu Feb 26 2015

.AVIATION...
/06Z TAFS/

Ceilings are VFR (above 4000 ft) at the forecast terminals as of
530z and should remain so for most of the overnight period.
Widespread mid-level radar echoes are increasing across west TX in
advance of the next shortwave, which will bring snow to much of
the area during the day Friday. Snow is expected to develop at
KABI and KSJT as early as 10-11z. However, the column remains a
bit dry so it will take some top-down moistening before heavier
snow is observed. The greatest snow chances remain over the Big
Country between 12-18z. Visibilities will likely be reduced to 1/2
mile or so at KABI, but lighter snow farther south will limit
visibility reductions to 3-5 miles. Snow was not included in the
KJCT and KSOA TAFs.

By midday, the upper-levels begin to dry which could result in the
snow mixing with (or changing over to) freezing drizzle. The
intensity of this drizzle looks sufficient to cause minor
reductions in visibilities at times and should maintain MVFR
ceilings. However, isentropic ascent will increase markedly after
00z, resulting in widespread IFR/LIFR ceilings and drizzle or
freezing drizzle, occasionally mixed with snow/sleet.

Johnson

&&

.PREV DISCUSSION... /ISSUED 529 PM CST Thu Feb 26 2015/

AVIATION...
/00Z TAFS/

MVFR ceilings continue across much of the CWA this afternoon, with
cloud heights around 2000 ft. We should see a little improvement
during the evening hours, but conditions are expected to
deteriorate early Friday morning as the next shortwave affects
the region. Light snow will be possible by 12z from KSJT to KABI,
eventually moving into the KBBD area. This snow may reduce
visibilities to 1 mile or less at times, but the prevailing
visibility is currently forecast from 2 to 4 miles. MVFR and IFR
ceilings are expected to redevelop Friday morning, concomitant
with the arrival of the snow.

By midday, the upper-levels dry out, removing a large portion of
ice crystals from the column. The near surface layer is still as
cold as -10C, which should support some snow, but supercooled
liquid is expected to outweigh the ice crystals. This means snow
will become less likely, with the predominant precip type
expected to switch to freezing drizzle. IFR conditions will be
possible by afternoon, but are most likely after 00z.

PREV DISCUSSION... /ISSUED ISSUED BY NATIONAL WEATHER SERVICE
MIDLAND/ODESSA TX/

Short Term...

(Tonight and Friday)
.Accumulating snow likely across the Big Country on Friday...

Light snow continues across eastern portions of the Big Country
early this afternoon but will end within the next hour or so. The
Winter Weather Advisory that was in effect across the Big
Country was allowed to expire at 3 PM and will address potential
icy roads overnight with a Special Weather Statement. Tonight
will be cloudy and cold, with wind speeds subsiding to around 10 to
15 knots by early to mid evening. Lows tonight will range from
near 20 across northern counties, to the lower and middle 20s
elsewhere. Another embedded short wave will move across the area
on Friday, with the majority of the mid level ascent from this
feature affecting the Big Country. This is where the best
potential for accumulating snowfall will be as saturation occurs
within the dendritic growth zone. Latest models show a swath of
1 to 3 inches of accumulating snow generally north of Interstate
20 on Friday, with lighter amounts farther south. Snow should
begin across far western counties towards daybreak and overspread
the area during the morning hours. Far southern counties along
the I-10 corridor may see more of a light snow/sleet mix,
especially by afternoon. It will be cold on Friday, especially
across northern sections where snowfall and cloud cover will
hold temperatures in the mid and upper 20s all day. The cold
surface temperatures will allow roads across the Big Country to
become snow covered and slick. Given the high confidence for
accumulating snowfall, a Winter Weather Advisory will be issued
for the Big Country for Friday. Farther south, light accumulations
will be possible but should remain below advisory criteria.

LONG TERM...
(Friday night and Saturday)

There will be a chance of mainly freezing precipitation Friday
night and Saturday morning across much of West Central Texas. The
combination of weak mid level ascent and low level warm air
advection will lead to widespread light precipitation across the
area. The point forecast soundings indicate saturated low levels
and dry in the mid and upper troposphere. As a result, the
precipitation type will be freezing drizzle/light freezing rain
due to a warm layer developing a few thousand feet off the ground.
Also, light snow and sleet is still possible across the Big
Country Friday evening. A winter weather advisory may be needed
Friday night and Saturday morning for the Big Country, Concho
valley and Heartland. Ice accumulations of 1/10 of an inch will
possible along and north of Interstate 20. The main impact will be
hazardous travel conditions due to icy roadways. Temperatures will
remain cold, staying well below freezing Friday night across much
of the area, rising to around freezing by late Saturday morning.
The temperatures will be warm enough by Saturday afternoon, that
the precipitation should be mainly liquid. However, the Heartland
and eastern Big Country may still be cold enough for freezing
precipitation.

(Saturday night through Tuesday)
There will be a chance of showers and warmer temperatures late
this weekend through early next week. The combination of upper
level disturbances moving by and low level southerly flow will
bring a chance of showers and a few thunderstorms to the area.
Looks like rainfall amounts will be mainly light, with local
amounts 0.5 of an inch possible, especially across the eastern
half of the area. Also, a few thunderstorms will be possible
Tuesday, east of an Abilene to Junction line as a stronger upper
level trough and pacific cold front moves by. Temperatures will be
warmer with highs in the 50s and 60s Sunday and Monday, and
upper 60s to lower 70s by Tuesday. Lows will be in the 30s and
40s, with lower 50s along the I-10 corridor by Tuesday morning.

(Tuesday night through Thursday)
Looks like mainly a dry forecast for the middle of next week with
another shot of cooler air by Thursday. Highs will be in the 60s
Wednesday and in the upper 40s to lower 50s Friday as another cold
front moves through.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  19  28  24  39  39 /  20  80  40  40  30
San Angelo  23  30  27  48  45 /  20  40  30  30  20
Junction  25  35  29  48  44 /  10  20  30  30  30

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from 6 AM to 6 PM CST Friday FOR THE
FOLLOWING ZONES: Callahan...Fisher...Haskell...Jones...Nolan...
Shackelford...Taylor...Throckmorton.

&&

$$

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