Area Forecast Discussion
Issued by NWS San Angelo, TX

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FXUS64 KSJT 061837 AAB
AFDSJT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN ANGELO TX
137 PM CDT Wed May 6 2015

.UPDATE...
Increased POPs across the area this afternoon and evening.

&&

.DISCUSSION...

Severe weather threat is becoming more of a concern across the area
late this afternoon and evening, especially across the northern half
of the CWA.

Starting to see some good heating across central and northern
counties early this afternoon as stratus continues to
lift/scatter out. A moderately unstable airmass will develop
across the area this afternoon as mid/upper 60 dewpoints combine
with surface temps in the low/middle 80s to produce MLCAPES
between 2000-2500 J/KG and effective bulk shear of 35 to 40 KT.
Little if any convective inhibition exists across the area as
well, so storm initiation appears likely, especially along and
north of interstate 20 where less cloud cover exists. POPs were
increased this afternoon and evening areawide, with highest POPs
across northern counties. Large hail (some very large), damaging
winds and a few tornadoes will be possible. Updated zones have
been sent.

&&

.PREV DISCUSSION... /ISSUED 1223 PM CDT Wed May 6 2015/

AVIATION...
/18Z TAFS/

VFR conditions will prevail across the terminals this afternoon.
MVFR/IFR stratus will develop across the terminals later this
evening and overnight and persist through the morning hours on
Thursday.

Isolated to scattered strong/severe convection is expected to
develop across the area late this afternoon and evening. The most
favored area for thunderstorm development will be across KSJT and
especially the KABI terminal after 07/00Z. Confidence has
increased enough to include a TEMPO group for thunder at KABI this
forecast cycle. Will continue to monitor convective trends through
the afternoon/evening hours.

PREV DISCUSSION... /ISSUED 643 AM CDT Wed May 6 2015/

AVIATION...
/12Z TAFS/

Widespread MVFR stratus will rise to VFR or scatter out by Noon,
except for KSOA and KJCT along the I-10 corridor, where stratus
will likely persist into mid afternoon. MVFR stratus will return
this evening over West Central Texas. Isolated thunderstorms
possible this afternoon and evening, but coverage is too low to
include in terminal forecasts.

PREV DISCUSSION... /ISSUED 415 AM CDT Wed May 6 2015/

SHORT TERM...
(Today and Tonight)

Atmosphere will become moderately unstable again this afternoon
with GFS SB CAPES of 1800 to 2500 J/KG, with the potential for
severe thunderstorms. Shower and thunderstorm coverage, however,
will likely be isolated. The main mechanism for thunderstorms will
be diurnal heating. A few storms, however, may develop off a dry
line in the Trans Pecos and Permian Basin, and move into the
western Concho Valley and Big Country during the late afternoon
and evening. SPC day 1 outlook has slight risk of severe storms
along and north of I-20 with marginal potential to the south.

With less cloud coverage in the afternoon, highs will be in the
lower 80s today. Mild tonight with lows in the mid and upper 60s.

04

LONG TERM...
(Thursday through next Tuesday)

The active pattern with rain chances through most of the extended
forecast will continue.

Currently, we have one shortwave trough exiting the area to our
north, another shortwave moving into the California coast, and a
more pronounced low slowly drifting south into the Pacific
Northwest. With successive upper level lows reinforcing the trough
across the western U. S., we will remain under southwest flow.

With southwest flow aloft over the area, we will see periodic
shortwave impulses moving across west Texas. Timing of these
features is problematic, which greatly impacts rain chances across
the area. West central Texas will remain very moist as the dryline
will back up into far west Texas each night, and mix into or near
our western counties each afternoon. So, while the dryline will be
near our western border each day, without well-defined upper level
support to focus on, have kept slight chance to chance PoPs in the
forecast Thursday into Thursday night. Any severe threat for this
time period will be highly dependent on how much we can
destabilize each afternoon, and whether or not convection occurs.

Friday and Saturday, models agree that the large upper level low
will begin approaching the area. Although there may not be direct
influence from this low, there is more confidence in impact from
shortwave impulses rotating around the low in southwest flow
across our area. There is in turn more confidence in better
coverage of showers and thunderstorms from Friday night into
Saturday, especially for northern parts of the CWA as the better
energy associated with the wave will be to our north and
northwest. We will remain unstable during this time period,
combined with deep layer shear values between 35 and 50 knots,
there is a Slight Risk of severe thunderstorms both Friday and
Saturday. The main hazards will be large hail and damaging winds.

We should see a significant reduction in showers/storms Sunday
night into Monday as the last of this series of impulses moves
east, and we fall under zonal flow. However, a cold front will
move into the area by Monday which could serve as a focus for more
scattered showers and thunderstorms from Monday into Tuesday.

20

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  83  66  82  67  84 /  60  60  30  30  50
San Angelo  84  68  86  69  87 /  40  40  20  20  30
Junction  81  68  82  69  83 /  40  30  20  20  40

&&

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

$$

99/99




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