Heat in Nevada, August 29, 2017

Area Forecast Discussion
National Weather Service Las Vegas NV
930 PM PDT Mon Aug 28 2017

.SYNOPSIS...A very hot weather pattern is expected across the Mojave
Desert Region much of this week as high pressure parks over southern
Nevada and surrounding states. Limited moisture circulating around
the area of high pressure will lead to isolated showers or
thunderstorms over the mountains each afternoon.
&&

.UPDATE...Still some very weak convection hanging on in central
Mohave County this evening but seeing a downward trend. Not
expecting to see any activity during the overnight period but
isolated thunderstorms look possible Tuesday afternoon in some
mountain areas. No updates needed this evening. -Harrison-

.PREV DISCUSSION...
245 PM PDT Mon Aug 28 2017

.SHORT TERM...through Thursday.

Temperatures this afternoon were running within 1-2 degrees of
Sunday's 21Z readings at most ASOS sites around the region. We will
likely tie the record of 110 set on this date in 1944 at McCarran
Airport. Also, convection around southern Nevada and northwest
Arizona has been a little more active, but clouds have been capped
around 25 Kft MSL due to a warm layer aloft and only light showers
or sprinkles are expected with most cells.

A slight change in the weather pattern will occur from Tuesday
afternoon into Wednesday leading to more thunderstorm development
over Inyo County and Esmeralda counties, but the rest of the region
will see little change in sensible weather. The cloud circulation in
satellite loops revealed that the center of the high was over
northeast Clark County this afternoon and it will hold its position
through Tuesday then be nudged over north central Arizona Wednesday
as a trough moves into the Pacific Northwest and brushes northern
California and northern Nevada. The cooling and increasing southwest-
northeast jet associated with the trough will enhance convection
over northern Inyo and Esmeralda counties late Tuesday into
Wednesday. The ridge will be suppressed somewhat Thursday as the
trough moves over the Northern Intermountain Region and this should
lead to slightly lower temperatures. The Excessive Heat Warning will
remain in effect through Wednesday evening.

.LONG TERM...Thursday Night through Sunday.

The main forecast challenges for the long term continues to be the
likely dissipation of excessive heat and introduction of monsoonal
moisture back into the region. Made only minor changes to ongoing
forecast.

For late-week, upper-level high pressure begins to weaken slightly
and wobble eastward as the wave breaks, sending energy over the
northern rockies. The ridge quickly rebuilds offshore and migrates
back over the region over the weekend and continues to amplify into
next week. Models still in decent agreement with eastern Pacific
activity developing. NHC currently tracking elongated trough
expected to develop further in the next few days and move
north/northwestward toward the southern tip of Baja. This looks to
be conducive to commencing a moisture surge into the area...however
high-amplitude ridge overhead looks to deflect much of that moisture
away from the area. Very low confidence in this pattern, as any
number of subtle changes will have large forecast impacts, such as
position of the high, depth of low-level moisture surge, etc.

In general, expecting cooling for the end of the week, with moisture
increasing south of I-40 for the weekend, with further increases
further north and west possible next week.
&&

.AVIATION...For McCarran...A light and variable wind, under 8
knots, will remain through the rest of the afternoon and will favor
an easterly direction. Between 03z-04z wind, a drainage wind will
setup and remain overnight. Showers and storms have favored higher
terrain in Clark and Mohave Counties today. This activity will
provide a small chance for outflow winds at the terminal through the
afternoon/early evening. Light, diurnal winds will set up again
Tuesday with slight chances for storms in the surrounding mountains
and in northwest Arizona. Few to scattered skies expected with cloud
bases between 15-20kft.

For the rest of southern Nevada, northwest Arizona and southeast
California...Thunderstorms have developed mainly in higher terrain
in northwest AZ and in southern NV. This activity will likely cease
by sunset with showers potentially lingering later into the evening
in southern Mohave County. As storms dissipate this evening, gusty
outflow winds will be possible, particularly for sites along the
Colorado River. Otherwise, winds will follow a flow pattern similar
to that observed the past few evenings.
&&

.CLIMATE...

Climate Records for Las Vegas

                 Forecast Max Temp       Daily Record Max Temp
August 29              109                    110 (1948)
August 30              108                    112 (1948)
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.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

Short Term...Adair
Long Term...Steele
Aviation...Boothe

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