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000
FXUS64 KSJT 171103 CCA
AFDSJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN ANGELO TX
602 AM CDT MON MAR 17 2014

.AVIATION...
/12Z TAFS/

VFR conditions will occur today and tonight across West Central
Texas. Skies will be generally clear with only some patchy
high clouds traversing the area. Light winds this morning will
become south-southwest and increase this afternoon. For tonight,
south-southwest winds will continue, and will become gusty at
KABI and KSJT. Overnight gusts over 30 KT at KABI, and over 25 KT
at San Angelo, are possible. With a southwesterly low-level jet
developing tonight, low-level wind shear will be possible at KJCT
and KSOA, where surface wind speeds should remain under 10 KT.

19

&&

.PREV DISCUSSION... /ISSUED 403 AM CDT MON MAR 17 2014/

SHORT TERM...
(Today and Tonight)

A shortwave upper trough over the Pacific Northwest will dive
southeast across the central Rockies tonight, emerging into the
central High Plains by early Tuesday morning. This will induce
surface troughing in the lee of the Rockies. Light winds across our
area this morning will become south-southwest and increase this
afternoon with increased surface pressure gradient. After a cold
start to the day, temperatures will rebound into the upper 60s to
lower 70s for highs this afternoon, with ample sunshine. With mostly
clear skies tonight, low temperatures across our area are expected
to be 10-20 degrees warmer than the previous night, as south-
southwest winds continue. The mildest readings will be across the
Big Country and Concho Valley (including the Abilene, Sweetwater,
San Angelo and Sterling City areas), where winds will be gusty
overnight.

19

LONG TERM...
(Tuesday through Sunday)

A strong shortwave trough will move quickly across the Central
Plains on Tuesday. The attendant surface cyclone will break away
from the central High Plains Monday night, moving swiftly east,
dragging a cold front south in the Lone Star State on Tuesday. There
are some model differences regarding the timing of this front with
the NAM/GEM being the faster solutions and the GFS/ECMWF delaying
the cooler air until later in the day. As stated yesterday, with the
upper trough lifting east-northeast across the Central Plains and
the lack of significant thermal gradient, I have trended slower. I
expect temperatures in the low to mid 80s across West Central TX on
Tuesday afternoon. West to northwest winds will increase to around
15 mph (could be stronger if the GFS verifies where deep,
unidirectional flow sets up midday), shifting to the north in the
afternoon. There is very little moisture for this front to work with
(precipitable water near 0.25") so PoPs remain nil.

Temps will be slightly below climatology on Wednesday. Highs are
expected to reside generally in the mid/upper 60s with east winds
around 10 mph. Overnight temps will be near climo Thursday morning
with low/mid 40s anticipated areawide. Strong quasi-zonal flow aloft
will develop on Thursday, with strong pressure falls in the lee of
the Rockies. This will increase southerly winds to 10-20 mph by
Thursday afternoon and will help push highs back into the 70s. A
strong low-level jet, moisture advection, and increasing cloud cover
will keep overnight lows in the 50s for most areas Thursday night.
Conditions Friday look similar to what is expected for tomorrow,
with gusty southwest winds developing ahead of a cold front, pushing
temperatures into the 80s across most of the area. I expect any
precip during this time to remain to the east of the CWA. However,
some of the models are indicating that there could be just enough
moisture return to support some convection along the boundary over
the eastern counties.

PoPs were removed on Saturday.  It appears that moisture will be
pushed off to the south and east and the shortwave advertised
yesterday seems to have fizzled out. However, both the ECMWF and GFS
are in agreement with a weak system affecting the area on Sunday.
Thus, slight chance PoPs were moved to Sunday and continued into
Monday. As we move into the early part of next week, the models are
showing a bit of a pattern change, transitioning to a classic split
flow pattern with a strong subtropical jet streaming across northern
Mexico and a strong ridge building up the West Coast ahead of a Gulf
of Alaska low. This pattern would suggest winter still has a ways to
go for folks in the eastern half of the CONUS but we`ll be more apt
to be on the edge of any cold snaps. Regardless, this could improve
our rain chances next week (not saying much) as southern stream
shortwaves move along the subtropical jet.

Johnson

FIRE WEATHER...
The main concerns for elevated fire weather conditions are on
Tuesday and Friday of this week.

Somewhat elevated fire weather conditions are expected to develop
this afternoon across western sections of West Central Texas, to the
west of a Throckmorton, to Abilene, to San Angelo, to Ozona line.
Across this area, relative humidity values will drop below 20
percent during the afternoon, with south-southwest winds increasing
to 10-15 mph.

On Tuesday, elevated fire weather conditions are expected to develop
by late morning and continue through the afternoon, primarily across
the area north of a Brownwood to Eden to Mertzon line and into
northwest Crockett County. Gusty southwest winds will veer to
west-northwest, followed later in the afternoon by a shift to
north-northwest winds with the passage of a cold front. Relative
humidity values will rapidly drop below 20 percent, with minimum
values of 8-12 percent by late afternoon.

On Friday afternoon, elevated fire weather conditions will be
possible across the area west of a line from Merkel to San Angelo to
Mertzon. Across this area, southwest to west winds 10-15 mph will be
combined with relative humidity values falling to and below 20
percent.

19

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  70  50  77  37  65 /   0   0   0   0   0
San Angelo  72  48  82  39  68 /   0   0   0   0   0
Junction  69  40  84  42  71 /   0   0   0   0   5

&&

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

$$