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[Printable]
974
FXUS64 KSJT 200848
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
347 AM CDT SAT SEP 20 2014

.SHORT TERM...
(Today and tonight)

A quick glance at the water vapor loop suggests that the upper-level
anticyclone is building over northern Mexico with a general easterly
flow over West TX. Mid-level winds are a bit more nebulous, with the
remnants of Odile becoming very difficult to discern. A band of
showers developed across the Concho Valley early this morning,
running from Colorado City, to Robert Lee, to Miles. However,
organization was poor and this activity continues to weaken. Farther
west, activity has been more persistent. Based on radar trends, it
appears that there may be an MCV from earlier convection near
Midland. That would make sense given the precipitation trends on
it`s eastern flank. This feature will weaken as it moves slowly
east, but will continue to interact with a very moist environment.

This morning, the models (including the hi-res runs) focus the
precipitation over the northern half of the CWA. However, by midday,
we should see sufficient heating in the southern half of the
forecast area for scattered diurnal convection to develop. Even with
temperatures only warming into the mid 80s, BUFR soundings in the
San Angelo area show no cap with SBCAPE values near 1500 J/kg. It
still appears that showers will be the predominant weather type, but
thunderstorms are still possible. Precipitable water values remain
between 1.8" and 2.0" across West Central TX, which is approximately
2 standard deviations above normal (or in the 95th percentile). The
melting level will be around 15,000 ft AGL, supportive of efficient
warm rain processes. Thus, the threat for locally heavy rainfall
will continue. That said, the heaviest rainfall has been rather
localized over the past few days, and should remain as such, so no
Flash Flood Watch will be issued at this time.

Convection is expected to shift back to the west this evening, with
the best rain chances being west of an Abilene to San Angelo line.
PoPs for tonight are tapered from 60% in the west to 30% in the
east. The heavy rainfall threat will continue, but is expected to
shift west in line with the better organized convection. Slightly
drier air is forecast to work into the area tonight with overnight
lows mainly in the upper 60s.

Johnson

.LONG TERM...
(Sunday through Friday)

Drier air in the mid level works in from the northeast Sunday.
There is still enough moisture to bring isolated to scattered
showers and thunderstorms, however, with the best chance of rain
west of a Sweetwater...San Angelo...Sonora line. A few areas of
locally heavy rainfall are possible west of the line, where the
NAM and GFS indicated precipitable water above 1.5 inches.
Unfortunately a weak cold front, previously in the computer
models, and possible focus for heavy rainfall in West Central
Texas, is not present Sunday.

The GFS and the EC models indicated isolated afternoon convection
next week, as moisture at and below 700 MB remains, along with
weak ridging aloft. Maintained the slight chance of showers and
thunderstorms Monday, but left out the rest of the work week
given low probability of occurrence.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  84  69  86  68  86 /  60  40  20  10  20
San Angelo  83  69  86  67  87 /  60  40  30   5  20
Junction  85  71  87  68  89 /  50  40  20  10  20

&&

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

$$

25/04








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