Area Forecast Discussion
Issued by NWS Las Vegas, NV

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639
FXUS65 KVEF 242137
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
237 PM PDT Sat Aug 24 2019

.SYNOPSIS...Weather concerns will shift from afternoon breezes
over the weekend to excessive heat early to mid-week next week.
Moisture may begin increasing once again towards the end of the
week.
&&

.DISCUSSION...Despite weak surges of low-level moisture and modest
surface-based instability, conditions are calm, mostly clear skies
and relatively light winds.

Ridging has started to build in overhead this afternoon. This has
warmed temperatures aloft, capping instability along the Colorado
River. These warm, capping temperatures are expected to strengthen
as the ridge expands further southeastward over the next couple of
days. Under ridge influence, temperatures at the surface will
increase a few degrees each day through Tuesday, approaching near
record temps across the Mojave Desert by Tuesday afternoon. Due to
uncertainty in the near-surface moisture, held off on hoisting any
heat headlines for now. Outside of extreme heat concerns, the
forecast remains benign in terms of convective activity and winds.

By midweek the forecast becomes slightly more complex. Extended
ensemble guidance remains fairly consistent with previous runs,
resolving a moisture surge in response to a tropical disturbance
south of Baja California in the Wednesday/Thursday timeframe. With
an increase in moisture, chances for thunderstorms across portions
of the Mojave Desert will start to increase while temperatures would
cool. However, a similar surge was also noted during the developing
stage of tropical storm Ivo, which did not materialize.

Forecast uncertainty increases further after Wednesday due to low
confidence in the position of subtropical ridge. Ensembles indicate
it may wobble westward and eventually overhead. Under this scenario,
another spike in temperatures is likely -- possibly to dangerous
levels -- along with suppressed convective activity.
&&

.FIRE WEATHER...Dry and hot conditions along with periods of breezy
winds, especially across the southern Great Basin are expected
through the rest of the weekend. Winds will be calm early this week
as temperatures increase. Critical to near critical humidity with
poor overnight recovery (less than 35%) is expected through at least
Tuesday. Moisture may increase later this week, resulting in
increasing thunderstorms chances across the Mojave Desert,
especially over higher terrain.
&&

.AVIATION...For McCarran...East winds up to 8 kts may hang around
through 22z this afternoon before shifting more to the south and
southwest with speeds around 10-15 kts. Wind speeds will gradually
diminish overnight and remain generally light Sunday morning. Winds
may once again turn east to southeast with speeds around 8-10 kts
after 16z and gradually turn more southerly in the afternoon. No
operationally significant clouds expected.

For the rest of southern Nevada, northwest Arizona and southeast
California...Most areas across the region will see south to
southwest winds 10-18 kts into this evening before winds diminish
overnight. Winds across the western Mojave Desert are expected to
remain light easterly this afternoon before gradually shifting to
the west after sunset. Little change in winds are expected on
Sunday. No operationally significant clouds expected.
&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

$$

DISCUSSION/FIRE WEATHER...Boothe
AVIATION..................Gorelow

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