Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 292357
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
657 PM CDT Sun Mar 29 2015

.AVIATION...
/00Z TAFS/

A weak cold front currently near Abilene will move slowly south
across the area this evening. The front will weaken with time
and will likely not make it to the Junction terminal before
stalling. Winds will shift to the north behind the front but
gusty winds will be confined to mainly the KABI terminal for the
next couple of hours. VFR conditions will prevail for the most
part but could see some scattered to possible broken MVFR stratus
develop across the southern terminals early Monday morning.

&&

.PREV DISCUSSION... /ISSUED 350 PM CDT Sun Mar 29 2015/

SHORT TERM...
(Tonight and Monday)

A cold front has moved south into the north and northwest part of
our CWA (County Warning Area) this afternoon. This front will
continue to push south through this evening, and should reach a
Mertzon-San Angel-Coleman line between 7 PM and 8 PM. With the
front weakening, its forward progress will decrease tonight. The
front should stall near or just beyond the southeast and southern
border of our CWA by early Monday morning. The NAM low-level
moisture fields favor low cloud development across some of our
eastern and southern counties early Monday morning. At a minimum,
expect an increase in high cloud coverage overnight into Monday.
Overnight lows are expected to be in the lower to mid 50s.
Temperatures will be cooler Monday, with afternoon highs mostly in
the upper 70s to lower 80s.

19

LONG TERM...
(Monday night through next Sunday)

The main concerns with the long range forecast will be rain
chances Tuesday into Tuesday night, and a strong cold front at the
end of the week.

The upper level low currently west of the northern Baja Peninsula
will be moving into the Baja Peninsula by Monday night, and then
across northern Mexico on Tuesday. Models agree well that the low
will open up into a wave and weaken significantly as it approaches
our area. Monday night low level flow will back ahead of the low,
resulting in warmer overnight lows as additional moisture is
advected into the area. We may also see a few isolated
thunderstorms for the southeastern 2/3 of the area with the
moisture increase, and weak embedded shortwaves move across the
area ahead of the main trough. As synoptic lift from the main
trough moves in Tuesday and Tuesday night, rain chances increase,
and we have not made any significant changes to the inherited PoP
configuration with chance PoPs Tuesday for western areas, and then
Tuesday night generally for the eastern half of the area. With mid
level lapse rates from 7-9 degrees C/km, and 0-6km bulk shear
values from 25 to 35 knots, there will be the potential for some
of the thunderstorms to become organized and produce some hail
and/or strong wind gusts. We do not expect more than one or two
storms to approach severe levels, but it can`t be ruled out.

Zonal flow will follow the trough from Wednesday through the end
of the week. On Friday as a large trough strengthens over the
Great Lakes area, a strong cold front will move into the area.
850mb temperatures drop roughly 20 degrees Celsius from Friday to
Saturday over west central Texas behind the front according to the
GFS. Raw model data suggest temperatures may not even warm into
the 60s for Saturday. However, we will not go that cold. Models
also show weak shortwave energy moving across the area over the
top of the cold air mass in west/southwest flow, so will keep a
slight chance of precipitation in the forecast over the weekend as
well.

20

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  53  78  61  83  60 /   5   5  10  30  30
San Angelo  53  82  60  85  58 /   0   5  20  30  20
Junction  54  82  57  82  59 /   5  10  20  20  30

&&

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

$$

99/99/24





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