Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 280955
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
355 AM CST Sun Dec 28 2014

.SHORT TERM...
(Today and Tonight)

The upper trough over northern Mexico and southern New Mexico is
moving east. Light mixed precipitation has developed across our
southern counties, in an area of lift ahead of the approaching
trough. The precipitation is patchy across Crockett and Schleicher
Counties, and is becoming a little more widespread across Sutton and
Kimble Counties. From radar indications, precipitation is most
likely a mix of sleet and rain across sutton into Kimble Counties,
and light snow/flurries possibly mixed with a little sleet in
Crockett County. This precipitation will continue early this
morning, then should taper off by mid-morning as the upper trough
axis shifts east into the area. With some wet bulb cooling and
surface temperatures dropping to near freezing, we are closely
monitoring radar and observation trends with the precipitation. At
this time, only minor if any accumulation of sleet and snow is
expected, with a possibility of localized slick spots developing on
some bridges and overpasses.

Cloud cover will decrease, beginning from the northwest by late this
morning, and continuing east across our area this afternoon.
Temperatures will recover into the upper 40s to lower 50s for highs
this afternoon. With mostly clear skies tonight, low temperatures
will be dependent on wind speeds. Appears that the low-lying areas
and river valleys of our eastern and southern counties will have the
colder lows in the mid to upper 20s. Lows are expected to be mostly
in the lower 30s elsewhere.

.LONG TERM...
(Monday through Sunday)

Main focus continues to be the potential for wintry precipitation
this week

Initial arctic air mass moves into the northern sections of West
Central Texas as early as late Monday afternoon, and then continues
to push southward across the remainder of the area Monday Night.
Center of the surface high will continue to settle southward,
reaching the Red River Valley by Wednesday Night. This will make
for a very cold mid week as the colder air deepens. Aloft, a
deepening upper level trough will eventually close off and begin
to slowly work its way towards Texas.

At first, the system will be far enough west of the area, that we
will be only looking at fairly weak isentropic lift for Tuesday
and Wednesday. This will first saturate the lower levels and
produce widespread cloud cover which will limit diurnal spreads,
and then eventually start to produce a little light precipitation.
Model soundings show the only real moisture to work with will be
in the lower levels, and probably not cold enough to produce snow.
Drizzle/freezing drizzle/light freezing rain most likely. Amounts
should be light, but doesn`t take much to produce some real
headaches.

Both the GFS and the ECMWF show a more potent shortwave rounding
the base of the upper low and approaching for Thursday and
Thursday night. This will tend to shift winds above the surface
back to the south and southeast, bring better moisture into the
area, and combine with the better life to produce much better
precipitation chances. Models show the surface high shifting east
and allowing slightly warmer temperatures to move back into the
area just in time and limit the potential for significant icing.
Problem is, this will need to be very closely watched, with the
shallow cold air masses sometimes very slow to shift east,
especially when cloud cover prevents much mixing. Soundings
suggest that should it would take much cooling of the column to
produce much bigger concerns. For right now, have stayed on the
cool side of guidance, but still just warm enough. But will want
to watch for what could be a somewhat lower probability but much
bigger impact event on Thursday into Friday.


&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  49  33  57  27  35 /   5   0   0   5  10
San Angelo  52  31  62  30  38 /   5   0   0   5  10
Junction  51  27  62  33  42 /  10   0   0   5  10

&&

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

$$

19/07





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