Area Forecast Discussion
Issued by NWS San Angelo, TX

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000
FXUS64 KSJT 251126
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
526 AM CST THU DEC 25 2014

.AVIATION...
/12Z TAFS/

South winds will increase to 20-25 kts today at KABI/KSJT, gusting
to 35 kts. Slightly weaker winds 15-20 kts (gusting to 25 kts) are
anticipated at the other forecast terminals. This warrant an Airport
Weather Warning for KABI this afternoon. Winds will decrease to
generally 12 kts or less at KJCT, KSOA, and KBBD after 00z, but
are forecast to remain gusty overnight at KABI and KSJT. VFR
conditions will prevail across the majority of West Central TX
through the next 24 hours. However, low stratus is expected to
move into the KJCT area after 09z.

Johnson

&&

.PREV DISCUSSION... /ISSUED 452 AM CST THU DEC 25 2014/

SHORT TERM...
(Today and tonight)

Analysis of the 00z raob data indicates shortwave ridging aloft
over the Southern Plains. The departing trough axis has cleared
the Lone Star State but another well defined shortwave trough is
currently digging southeast across the Great Basin. Strong
westerlies in advance of this system are resulting in rapid lee
cyclogenesis over the High Plains, with surface pressure falls
exceeding 1 mb/hr centered on the OK Panhandle. Southerly winds
are responding by increasing in the favored areas for gusty
nocturnal winds. Sweetwater and San Angelo are reporting sustained
winds near 15 mph, but light winds continue in the sheltered areas
of the northwest Hill Country. Temperatures are in the 20s in the
river valleys, but have increased to near 40 degrees where gusty
winds have developed.

Lee cyclogenesis will continue today, with winds at 850 mb progged
to reach 40 kts by early afternoon. We are seeing high clouds
increasing from the west, but vertical mixing should be deep
enough to bring some of these stronger winds to the surface.
Sustained winds will be in the 20-30 mph range, gusting over 35
mph at times. Winds are marginal for a wind advisory, but given
the fact that it is a major holiday, an advisory will be issued.
Model 850 mb temperatures of 10-12C should support max
temperatures in the 60s this afternoon. Statistical guidance has
shown a cold bias in these scenarios, so forecast max temperatures
are 2-3 degrees warmer than the 00z GFS/NAM MOS products.
Southerly winds will continue through the overnight hours,
remaining gusty at times. Overnight lows will generally be in the
low to mid 40s across the CWA and low clouds will be possible by
sunrise over the northwest Hill Country from Junction to San Saba.

LONG TERM...
(Friday through Monday)

Looks like warm temperatures Friday and then a cold front due in
this weekend, with colder temperatures Saturday through Monday.
A slight chance of rain Friday and Saturday. The medium range
models indicate another strong upper level trough currently diving
into the southwest U.S. will lift northeast across the Southern
and Central Plains Friday. At the surface, a lee trough to our
west will keep southerly winds going and help warm temperatures
into the mid and upper 60s. A cold front will move through West
Central Texas late Friday night and Saturday morning as the upper
level trough passes by. It will be much cooler this weekend with
highs in the 40s to lower 50s. Lows Sunday morning will be back
down in the upper 20s to lower 30s. Temperatures will rebound a
few degrees Monday with highs in the 50s. A few showers will be
possible Friday and Saturday due to weak upper level forcing. In
addition this system does not have a lot of moisture to work with.

(Monday night through Thursday)

Much colder temperatures are likely by next Tuesday and Thursday
across West Central Texas. Also, there is the possibility of some
light wintry precipitation. The medium range models are indicating
major amplification at 500 MB pattern along the west coast with an
upper ridge. At the surface an arctic cold airmass(1045+ MB surface
high) will drop south out of western Canada into the central and
western U.S. by early next week. The cold front will probably move
across our area Monday night into Tuesday morning. The GFS model
was indicating a shallow cold airmass and 850 MB temperatures
staying above 0 deg C through out much of the event, and the ECMWF
model indicating 850 MB temperatures below zero. The CMC model is
the coldest at 850 MB across our area by 144 hours with readings
well below 0 Deg C. The bottom line, is much colder temperatures,
with highs in the 30s and lows in the upper teens to mid 20s.
There is the possibility of some light wintry precipitation
Tuesday night through Wednesday night due to weak upper level
disturbances moving across the arctic airmass. The BUFKIT
soundings support mainly freezing rain. However, the cold air
should be deep enough for light snow mixed with a little sleet,
mainly across the eastern 2/3 of the area.

FIRE WEATHER...
Temperatures will be 5 to 10 degrees above normal this afternoon
with minimum relative humidity values between 20 and 30 percent.
Southerly 20 foot winds will increase to 20-25 mph by midday,
gusting to near 35 mph at times. Despite the recent wetting rain,
generally dormant vegetation will yield elevated fire weather
conditions this afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  64  46  66  36  43 /   0   0   5  20  20
San Angelo  65  44  69  40  47 /   0   0   5  20  20
Junction  63  44  69  43  51 /   0   0   5  20  20

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY from 10 AM this morning to 6 PM CST this evening
FOR THE FOLLOWING ZONES: Brown...Callahan...Coleman...Fisher...
Haskell...Jones...Nolan...Runnels...Shackelford...Taylor...
Throckmorton.

&&

$$

Aviation: 25
Short-term: 25
Long-term: 21



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