Area Forecast Discussion
Issued by NWS San Angelo, TX

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000
FXUS64 KSJT 051708
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1208 PM CDT Tue May 5 2015

.AVIATION...
/18Z TAFS/
Expect low end VFR ceilings(BKN030-040) this afternoon and evening
across West Central Texas. Looks like widespread stratus will
spread north across the area late tonight with MVFR ceilings
developing at the terminals after 06Z. Also, isolated to scattered
thunderstorms may develop along a dryline just to our west. A few
of these storms will probably move east and get close to the KABI
and KSJT terminals early this evening. However, confidence is not
high enough to add thunder to the terminals. The winds will be
south with gusts to 30 knots.

&&

.PREV DISCUSSION... /ISSUED 547 AM CDT Tue May 5 2015/

AVIATION...
/12Z TAFS/

MVFR STRATUS WILL PERSIST OVER MOST TERMINALS THE NEXT 24 HOURS.
SCATTERED LIGHT SHOWERS AND PERHAPS A THUNDERSTORM WILL BE
DEVELOPING AT KABI...KSJT AND POSSIBLY KBBD MID MORNING. HAD VCTS
AT KABI BY LATE MORNING. THUNDERSTORMS COVERAGE WILL BE LOWER
FARTHER SOUTH...SO ONLY HAVE VCSH ELSEWHERE.

PREV DISCUSSION... /ISSUED 338 AM CDT Tue May 5 2015/

SHORT TERM...
(Today and Tonight)

Upper shortwave in the 4 corners region will move northeast into
Colorado today, with best lift over the Big Country and northern
Concho Valley this morning and early afternoon. While this area
has the best chance of rain, the best potential for severe weather
will be in Crockett County and Western Concho Valley, east of a
Permian Basin/Trans Pecos dryline. GFS SB CAPES vary from 1500 to
2000 J/KG this afternoon (with higher values to the west) with 0-6
KM shear of 50 KTS over Crockett County. While severe
thunderstorms with large hail and damaging winds are possible, the
main threat may be heavy rainfall. Midland upper air precipitable
waters are about 200 percent of average. Some of the high
precipitable waters may move into western sections of the Concho
Valley and Big Country.

04

LONG TERM...
(Wednesday through next Monday)

The main theme in the long term portion of the forecast will
continue to be shower and thunderstorm chances.

Currently, we have an upper level low over Arizona that will be
moving off to the northeast over the next 24 hours or so. Behind
this low is another strong upper level that is moving southeast
into the Pacific Northwest coast. This second low will drop south
into southern California by Thursday afternoon/evening. This
second low will maintain our southwest flow aloft, which is likely
to result in passing weak ripples of energy moving across our area
between Wednesday and the end of the week.

This set up will maintain a good flow of moisture off the Gulf of
Mexico for our area. The dryline will be able to mix east into our
western counties during the afternoons, but probably not much
farther than that. While it`s hard to argue against having at
least some chance of precipitation in the forecast, Wednesday into
Thursday, it`s hard to latch onto a specific feature, other than
the dryline, that will serve to initiate widespread organized
convection for our area. However, with a moist and unstable air
mass in place, we could see isolated to scattered showers and
thunderstorms each afternoon, so have kept generally a slight
chance to chance in for the area for Wednesday and Thursday.

By the end of the week, as the next upper level low moves toward
the area, parts of west Texas should see another round of more
organized, widespread thunderstorm activity. However, the low is
expected to take a similar northern path as the current AZ low.
This would likely lead to the best chances for showers and
thunderstorms mainly off to our west through northwest as we saw
yesterday afternoon and last night. That said, will maintain
chance to likely PoPs Friday into Saturday morning for this next
low.

With surface based CAPE values generally between 1000 and 2000
J/kg and 0-6km bulk shear values 35-50 knots through the end of
the week, any thunderstorms that develop will have the potential
to strengthen to severe levels, with large hail and damaging winds
being the main hazards. In addition, precipitable water values
will be between 1 and 1.25 inches through the period, so heavy
rainfall, and local flooding will also be a concern, especially if
any training of activity develops over a particular area.

Models push a front into the area early next week, resulting in a
broad, stalled frontal zone over our area. Should this occur,
precipitation chances would continue. Have only gone with slight
chances for now as that is 6/7 days out at this time.

20

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene  74  65  83  65  82 /  50  60  30  40  40
San Angelo  76  66  83  67  87 /  40  40  30  20  20
Junction  77  66  82  67  84 /  30  30  30  20  20

&&

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

$$

21




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