Area Forecast Discussion
Issued by NWS San Angelo, TX

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000
FXUS64 KSJT 202357
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
557 PM CST Thu Nov 20 2014

.AVIATION...
/00Z TAFS/
The moisture return will continue tonight, bringing MVFR CIGS back
into the area at all sites before 6 AM local time Friday morning.
MVFR ceilings could be moving into the KJCT/KSOA sites as early as
midnight tonight, then spread quickly north across KBBD/KSJT by
09Z or earlier. At times, CIGS may dip down into the IFR category,
and this was already reflected well in the previous set of TAFs,
so we held on to the mention of sub-1000 foot ceilings from the
early through mid morning hours. Would expect these to be more
prevalent at KJCT/KSOA/KBBD where moisture is richer, but will
also keep the TEMPO groups for these low ceilings at KSJT and
KABI. Expect to see ceilings slowly lift tomorrow, possibly rising
into the VFR category after 18Z. Winds will continue to be
southerly at around 10 knots or less. 20

&&

.PREV DISCUSSION... /ISSUED 320 PM CST THU NOV 20 2014/

LONG TERM...
(Tonight and Friday)

All the action starts Friday Night, so this short term portion of
the discussion will be pretty brief.

Low level moisture has certainly increased across West Central Texas
this afternoon, although much deeper moisture is still to the south.
Dewpoints in the low to mid 60s are lurking across South Central
Texas and the Rio Grande Valley. Some of this moisture will surge
northward again tonight, and low clouds and stratus will be much
more prevalent than we saw earlier today. This will also keep
overnight low quite a bit warmer as well, with lows from the mid 40s
to mid 50s across the area. The stratus will mix out a little on
Friday, but temperatures will still likely be a few degrees cooler
than what we are seeing this afternoon. Deepest moisture will remain
across the eastern areas on Friday, east of a Brownwood to Junction
line, and could see a stray warm advection shower or storm.

Otherwise, all eyes on the potent storm system coming ashore across
the Pacific Northwest this afternoon and its dive to the southeast
towards the Southern Plains.

07

LONG TERM...
(Friday night through Saturday night)

The primary concern for Friday evening and Saturday will be the
widespread rain chances. An upper level low will dig south into
northern Mexico and move east across the Permian Basin Friday into
Saturday. The jet stream wrapping around this low will bring upper
level support to West Central Texas. Meanwhile, return flow from the
gulf has introduced higher dew points, with values Saturday between
50-60 degrees.

The primary lift will begin across the Big Country sometime after
00Z on Friday. The lift is expected to expand southwest across the
remainder of the forecast area. Increased pops across the area to
reflect better confidence in the imminent rainfall on Saturday. The
upper level low is expected to close off and slow its eastward
progression. This will allow the lift to linger a while longer along
our eastern most border. For this reason, slight chance pops were
introduced early Saturday night mainly east of a line from Mason,
to Brady, to Haskell.

PWATs are forecast to be between 0.75-1 inch for the majority of the
forecast area, thus some areas could see periods of heavy rainfall.
Precipitation will be more widespread than scattered/discreet cells.
This will likely prevent a severe weather outbreak, though hail and
high winds will be possible on Saturday.

JMD

(Sunday through Thursday)

The upper low will open into a trough and lift northeast out of our
area by early Sunday. Fairly strong, gusty west-northwest winds
could occur late Sunday morning through early Sunday afternoon, with
tightened surface pressure and lower to mid-level height gradients
across our area. This to occur as the aforementioned upper trough
lifts northeast out of Texas, and an upper trough deepens over the
north-central CONUS. Winds aloft are progged to become well-aligned
up through 850 to 700 mb, favoring downward momentum transport. The
only negative factor (to some extent) may be increasing high cloud
coverage as an upper level jet develops across the southern Rockies
into Texas. With the combination of stronger winds, warm and dry
conditions, increased fire weather concerns will be possible Sunday.
This may be mitigated by wet ground surface conditions, however, if
rainfall amounts and coverage are extensive on Saturday.

With the evolution of the upper trough over the central third of the
CONUS, dry surface cold front will push south across west central
Texas Sunday night, with highs on Monday about 10-15 degrees cooler
than Sunday.

The 12Z GFS and ECMWF have increasing differences in the middle to
late part of next week with the forecast evolution of the upper
level pattern across much of the CONUS. But both models show a
quiet, dry setup for our Tuesday and Wednesday. The ECMWF brings a
strong cold front south across west central Texas on Thanksgiving.

19

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  50  69  58  65  49 /  10  10  80  90  10
San Angelo  51  71  58  69  49 /  10  10  60  80  10
Junction  54  71  61  69  49 /  10  20  50  80  10

&&

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

$$





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