Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 281808
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1208 PM CST Sat Feb 28 2015

.AVIATION...
/18Z TAFS/

Look for very challenging flight weather to continue for the next
24 hours. The forecast for all terminals includes a slight
improvement into MVFR categories for this afternoon. However,
confidence is not very high regarding that possibility. Light
freezing drizzle will return this evening to all terminals.

Huber

&&

.PREV DISCUSSION... /ISSUED 1054 AM CST Sat Feb 28 2015/

UPDATE...
To extend the Winter Weather Advisory...

DISCUSSION...
As previously discussed, temperatures remain below freezing across
West Central Texas with continued reports of light freezing
drizzle and icy roadways. The Winter Weather Advisory was extended
until 6 PM for all of West Central Texas. The southern counties,
including the Interstate 10 corridor, may get above freezing by
mid afternoon, but given the uncertainty the advisory was
extended to include all counties. Some counties may need to be
canceled early, depending on trends this afternoon. Temperatures
and weather grids were tweaked to match current trends.

PREV DISCUSSION... /ISSUED 1013 AM CST Sat Feb 28 2015/

UPDATE...
To lower temperatures this afternoon...

DISCUSSION...
The Arctic airmass that has been affecting West Central Texas the
last couple of days remains entrenched across the area. Models
tend to not handle these shallow airmasses well, and tend to erode
the airmass prematurely. This seems to be the case today, with
most areas remaining overcast through the day. It is still
possible that we see a few breaks in the cloud cover across mainly
Crockett County this afternoon, but confidence is not high.
Temperatures this afternoon were trended down by a few degrees,
but will continue to monitor as these temperatures may need to be
tweaked down a bit farther. Given the lowered temperatures,
freezing drizzle was continued farther south and east, into the
afternoon hours. Some adjustments to the current Winter Weather
Advisory may be needed but will make a final decision in the next
hour or so.

PREV DISCUSSION... /ISSUED 624 AM CST Sat Feb 28 2015/

AVIATION...
/12Z TAFS/

IFR to LIFR conditions will continue through the morning hours
across the area. We should see a slight improvement in conditions
by early afternoon with CIGS lifting to near 1000 feet with a
decrease in the amount of drizzle and fog. By tonight, as
temperatures cool, IFR to LIFR conditions will likely set back in
after 00Z with very low CIGS and lowered VSBYs redeveloping
across the area. 20

PREV DISCUSSION... /ISSUED 451 AM CST Sat Feb 28 2015/

SHORT TERM...
(Today and Tonight)

The wintry weather will continue through today...

Freezing drizzle continues to affect the entire area this morning,
with additional light ice accumulations, and travel conditions
continuing to degrade. Have lowered highs to near freezing across
the Big Country area today, and cooled highs across most of the
rest of the area. The cold air mass at the surface, coupled with
the accumulated ice, and cloudy conditions today argues for cooler
highs. With WAA over the top of the saturated low levels, light
freezing drizzle will continue through the morning hours across
the entire area. We should see a change-over to plain drizzle for
areas mainly south of a Sweetwater to Brownwood line as
temperatures here will finally climb above freezing. With
temperatures struggling to warm above freezing across the Big
Country, expect any light precipitation to continue to be in
either a freezing or frozen form. To keep the wording simpler,
have gone with what we believe will be the predominant drizzle or
freezing drizzle for the forecast. With additional very light
accumulations possible for the Big Country area this afternoon,
have extended the Winter Weather Advisory through 6 PM tomorrow
for the 8 Big Country counties as well as Coleman and Brown
counties.

Overnight, winds are expected to veer to a more southeasterly
direction. This should help to start erode the cold surface air
mass a little better area-wide. Temperatures in the Big Country
will be either steady or very slowly rising through the night, but
have kept the precipitation there largely freezing for now. The
rest of the area should continue to see liquid precipitation if
any occurs. However, the saturated layer of air will continue to
thin out overnight, making precipitation of any kind less likely.
Have not extended the Winter Weather Advisory through Sunday
morning as it is possible that temperatures will rise through the
overnight hours, and we could see improving conditions across the
Big Country.

20

LONG TERM...
(Sunday through Friday)

A challenging forecast with temperatures Sunday and Monday, with
large (10-20 degree) differences between the warmer GFS and
colder NAM MOS. At this time, leaning toward a solution in
between. Surface winds should be southeast to south during the
day Sunday, ahead of an approaching cold front from the north.
Should also have some decrease in cloud cover by afternoon across
the west and southwest part of our area. The backdoor type cold
front will move through west central Texas Sunday evening into
Sunday night. Highs Monday are expected to be several degrees
lower than Sunday across the northern half of our area, and only a
few degrees cooler in our southern counties. Cloud cover is
expected to be widespread on Monday, with isolated to scattered
rain showers possible in a warm air advection pattern.

An upper trough is progged to evolve over the southwestern U.S.
early next week, with several disturbances out ahead of it
entering Texas in southwest flow aloft. With mid-level ascent and
increasing depth of moisture across our area, will have a chance
of showers with a few thunderstorms Monday night and Tuesday, with
sufficient destabilization of the airmass. Tuesday looks to be the
warmest day of this forecast when highs should be in the 70s, with
winds veering to the southwest and a decrease in cloud cover from
the west.

A fairly strong cold front is progged to push south across west
central Texas Tuesday night or Wednesday morning. The main upper
trough over the southwestern U.S. is progged to shear out into
Texas Wednesday afternoon/evening, becoming absorbed into a trough
digging southeast into the Plains states. Carrying mainly chance PoP
for showers/isolated thunderstorms Tuesday night, followed by a
lingering low PoP for the eastern half of our area on Wednesday.

In the wake of the frontal passage, colder temperatures are
expected Wednesday and Thursday, as a strong surface high drops
south and southeast across the Plains and into the Mississippi
Valley. Dry weather is expected Thursday and Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  31  30  54  36  47 /  50  30  20  20  40
San Angelo  33  33  62  41  56 /  40  20  10  20  30
Junction  36  36  63  44  62 /  40  30  20  20  30

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 6 PM CST this evening FOR THE
FOLLOWING ZONES: Brown...Callahan...Coke...Coleman...Concho...
Crockett...Fisher...Haskell...Irion...Jones...Kimble...Mason...
McCulloch...Menard...Nolan...Runnels...San Saba...Schleicher...
Shackelford...Sterling...Sutton...Taylor...Throckmorton...Tom
Green.

&&

$$






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