Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 290552 AAA
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1055 PM PDT THU JUL 28 2016

.SYNOPSIS...Dangerously hot conditions are expected to continue
through Friday with isolated afternoon mountain thunderstorm
activity. Cooler temperatures and more widespread thunderstorm
activity is expected over the weekend and next week as monsoon
moisture returns to the area.
&&

.UPDATE...Boosted cloud cover and raised PoPs into the slight chance
category for much of the region overnight. Activity continues to
linger across southern Clark county and additional showers are
breaking out across Death Valley and Lincoln county. Outflow
boundary interactions and very warm surface temperatures beneath a
midlevel cloud deck will allow for weak convection to persist. Added
cloud cover will also keep overnight lows quite warm across the
area.

-Outler-

&&


.PREV DISCUSSION...207 PM PDT THU JUL 28 2016
.SHORT TERM...through Sunday night.

This morning, satellite imagery showed a large thunderstorm complex
rolling westward across the Gulf of California and the Baja
Peninsula. A deep moisture pool now resides over this region and
available for any disturbance to tap and bring north towards our
area. Such a feature has been forecast by the models for several
days and remains the feature of interest for the upcoming weekend.

But first, today and Friday. Temperatures at 1 PM were running
similar or slightly warmer than yesterday in areas that have been
cloud free. Areas that had debris cloudiness for much of the day
thus far, including Las Vegas, were running several degrees behind
yesterday through the morning hours but have since recovered as
cloud cover decreases. Las Vegas now looks on track to reach and
potentially exceed the record for the day. An Excessive Heat Warning
continues for today and Friday. Since around 11 AM, isolated
thunderstorms have been forming over the higher terrain of Clark,
central Nye, Lincoln and northern Mohave counties. The HRRR
forecasts this trend continuing through the afternoon with the
potential for stronger outflow winds. Later this afternoon, storms
are forecast to develop over the Sierra and then roll off into the
Owens Valley, White Mountains and into Esmeralda county. Isolated
storms should last through the evening hours then dissipate
overnight. Similar atmospheric conditions exist for Friday however
with no resolved lifting mechanism, terrain driven convection is
likely but possibly less coverage. Temperature wise, lows will begin
Friday morning quite warm and afternoon highs will remain very hot.

Now back to the weekend forecast. An easterly wave is forecast to
bring the deeper moisture currently over Baja and the Gulf of
California northward over the weekend. The wave axis tilts in a
southwest to northeast direction as it pushes north but is still
forecast to be over central Baja Saturday. Although high pressure is
weakening by Saturday, it may limit the northward reach of the
moisture. As the wave accelerates northward Saturday night, moisture
is forecast to surge ahead of it potentially setting the stage for a
very active day Sunday. High pressure off the southern California
coast Sunday may act against the western extent of storm formation
with development more isolated. over the western CWA, especially if
the GFS verifies. In fact, convection would be limited west of line
from Caliente to Daggett. The Sunday temperature forecast shows
there are model differences however and this lowers confidence
somewhat. The GFS temp forecast for Sunday is near normal while the
ECMWF is 6-8 degrees below normal. Stay tuned.

.LONG TERM...Monday through Thursday.

This period was not changed and the following was parsed from the
previous long term discussion.

Meanwhile...a persistent dry westerly flow is forecast across the
southern Sierra into south central Nevada Monday through the middle
of next week in the base of a mean Pacific Northwest trough. This
will keep moisture confined primarily to eastern San Bernardino
county...southern Nevada and northwest Arizona after Monday.

Temperatures will lower through the weekend with the moisture
increase and remain in the 100-105 degree range across most of the
Mojave Desert region through next week.
&&

.AVIATION...For McCarran...Isolated storms in the higher terrain
surrounding the valley will generate outflows that may affect the
terminal at times this afternoon and this evening and possibly again
tomorrow afternoon. Although a storm affecting the terminal is
unlikely, this cannot be ruled out. Otherwise, light/diurnally-
driven winds expected the next 24 hours. Chances for storms increase
this weekend.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Isolated storms will affect the high terrain in much of
the area through early this evening, with outflows producing
gusty/erratic winds potentially impacting the terminals, especially
KVGT, KHND, and KBIH. Chances return again tomorrow. Otherwise,
light/diurnally-driven winds expected through the period.
Increasing chances for storms across the area this weekend.
&&

.FIRE WEATHER...Very hot conditions expected areawide again on
Friday before a return to more typical mid-summer heat resumes.
Isolated thunderstorms will be possible over the mountainous terrain
Friday, and some storms may produce several lightning strikes but
limited rainfall especially across southern Nevada. Increasing
monsoon moisture will result in expanding thunderstorm coverage over
the weekend and wetter storms. Winds will be fairly light aside from
some afternoon breezes and thunderstorm outflow.
&&

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

$$

Update...Pierce

Short Term...Salmen
Long Term...Adair
Aviation...Shafer

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