Area Forecast Discussion
Issued by NWS Midland/Odessa, TX

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421
FXUS64 KMAF 200533
AFDMAF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX
1233 AM CDT Wed Aug 20 2014

.DISCUSSION...

See Aviation Discussion below.

&&

.AVIATION...

KMAF radar shows the LLJ in full swing tonight, w/~30kt return
flow right off the deck. Expect return flow to continue next 24
hours. Forecast soundings develop a widespread cu field by late
morning, w/bases 5-6 kft agl. Convection will be possible west and
south aagain today, on the periphery of the upper ridge. For now,
we`ll only include it at KFST, w/MVFR visibilities due to heavy precip.

&&

.PREV DISCUSSION... /ISSUED 831 PM CDT Tue Aug 19 2014/

UPDATE...
Dropping rain chances east and increasing chances west of the Davis
Mountains.

DISCUSSION...
Convection across much of southwest Texas and New Mexico appears
to be winding down for the evening. Additional convection is
entering west Texas from northern Mexico. NAM model hints that
shortwave may be aiding in continuing development of convection
over this area. With precipitable water values near 1.50", heavy
rainfall is possible from the Rio Grande to the Davis Mountains
overnight.

PREV DISCUSSION... /ISSUED 618 PM CDT Tue Aug 19 2014/

DISCUSSION...
See aviation discussion below.

AVIATION...
Storms are slowly decreasing, but there are still some focus areas
and for now will leave in a TEMPO TSRA at FST til 02z. SE winds
around 10kts thru the night are expected. Late in the period TSRA
will again be possible at CNM/FST/INK. PEQ seems the most favored
of the three and will include a PROB30 late Wed PM.

PREV DISCUSSION... /ISSUED 318 PM CDT Tue Aug 19 2014/

UPDATE...
Added isolated thunderstorms this afternoon and evening over
northern portion of the forecast area.

DISCUSSION...

Well-developed cumulus apparent on visibility satellite imagery
over southeast New Mexico and the northern parts of the Permian
Basin. Radar indicating thunderstorms have initiated within this
cumulus field. Would expect continued development of at least
isolated thunderstorms through the afternoon with further
development occurring on intersecting boundaries.

PREV DISCUSSION... /ISSUED 215 PM CDT Tue Aug 19 2014/

DISCUSSION...

The shear axis which gave the Permian Basin scattered thunderstorms
yesterday is still over west central Texas, but weaker than a day
ago.  Also, the atmosphere is fairly stable where rainfall occurred
yesterday, so scattered thunderstorms look unlikely this afternoon
and evening in these areas.  However, subtropical moisture is
prevalent over the higher terrain, and along with a shortwave trough
over Chihuahua, if not along the Rio Grande River, scattered
thunderstorms are expected to develop over the Davis and Glass
Mountains, along with the Marfa Plateau, Stockton Plateau and
Lower Trans Pecos.  The main threat from these storms will be
heavy rainfall and localized flash flooding.

An ua trough will dig further south along the California coast by
Wednesday, while an ua ridge remains entrenched over the
southeastern ConUS.  The forecast area will remain between these
synoptic scale features the next few days until the mentioned ua
trough ejects northeastward over the central Rockies.  Southerly
flow aloft over the region during this time will direct subtropical
mid and upper level moisture over the area, which along with
periodic shortwave troughs, result in thunderstorms chances
continuing into next weekend.  The western half of the forecast area
will have the best chance for thunderstorms, but some models are
indicating thunderstorm activity developing east of a semi permanent
surface trough, that is, over the Permian Basin.  Not quite sold on
the further east solution considering differences in how strong the
ua ridge will be over eastern reaches of the CWA, not to mention
differences amongst models in the timing of the ua trough ejecting.

The potential exists for heavy rainfall and flash flooding over
the higher terrain through the rest of the week considering PWats
will be 1.5 to 2 inches for much of this time.  Will not carry
PoPs quite high enough to warrant a Flash Flood Watch, which would
likely be issued for locations west of a Hobbs to Alpine to Big
Bend line, but subsequent shifts may come up with the agreement
necessary to do so.  Will mention in the Hazardous Weather Outlook
for now.  Temperatures will be at or slightly above normal through
the week, except over western reaches of the forecast area where
clouds and precipitation will tend to temper readings.

&&

.MAF WATCHES/WARNINGS/ADVISORIES...
NM...NONE.
TX...NONE.

&&

$$

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