Dust Storm in Arizona, July 26 to 27, 2018

Area Forecast Discussion
National Weather Service Las Vegas NV
133 PM PDT Thu Jul 26 2018

.SYNOPSIS...Dangerous heat is will continue through at least
Saturday. Thunderstorms will become more limited through the week
as the main area of high pressure moves overhead.
&&

.SHORT TERM...Through Saturday Night.

Scattered showers and thunderstorms are expected to continue through
the evening. Flooding is possible with these storms if they
backbuild or train, however PWATs are on the low side so threat for
flash flooding is low. Gusty winds will be the main threat as
sounding from this morning show a dry, inverted-V type sounding.
Mesoanalysis shows moderately strong DCAPE as well, and with any
virga (which has been noted on numerous area webcams), gusty to
strong winds are possible from these storms. Hi-res model wind
fields show multiple outflows over the southern Great Basin and into
southern Nevada. Storms should linger through the first part of the
night. While CIN does increase, CAPE will remain on the high side
through midnight. If any outflows remain over the area, could see
isolated to scattered storms continue through the first half of the
night. After that, it will quiet down quickly.

Going forward, thunderstorm chances decrease the next few days, with
only isolated chances expected in the higher terrain by Saturday.
The bigger concern for Friday and Saturday will be the heat. High
temperatures will remain at the current levels or drop back only a
degree or so through the first half of the weekend. With adjustments
made to high and low temperatures based on new model guidance, heat
risk continues to be in the dangerous zones. Based on this, extended
the heat products through Saturday.
&&

.LONG TERM...Sunday through Wednesday.

High pressure is forecast to remain anchored over the Southwest with
weak disturbances rotating around the high each day. With little
change in moisture, it will continue to feel sticky, but just a
little less oppressive than what we are currently experiencing. All
guidance drops temperatures Sunday through mid week to around 3 or 4
degrees above normal. Confidence is low that we will actually see
temperatures drop this much given models forecasting little change
in the positioning and strength of the high. In fact, the trend for
this ongoing heat wave has been for guidance temperatures to come in
warmer on day 4 as the influence of climatology decreases. This is
beginning to appear with the MEXMOS guidance raising Sunday (day 4)
temperatures and this time, even Monday (day 5) temperatures. It's
worth noting, the European mos, which has been the warmest (and more
superior) MOS guidance for this heat event is now cooler by day 4
than the GFS MOS.

Since moisture is forecast to change little in the extended, any
embedded feature in the flow could act as a lifting mechanism for
developing thunderstorms each day.
&&

.CLIMATE...Near record temperatures are expected through Friday. The
table below shows the record highs and the year recorded for
McCarran (Las Vegas), Death Valley, Needles, Barstow/Daggett, Bishop
and Kingman.

                    RECORD HIGH TEMPERATURES (YEAR)
                    ---------------------
                    THU(7/26)   FRI(7/27)
LOCATION            ---------------------

McCarran        |   116(1943)   115(2016)
Death Valley    |   127(1933)   127(1933)
Needles         |   118(1959)   119(2016)
Barstow/Daggett |   114(1995)   115(1995)
Bishop          |   108(1975)   108(2016)
Kingman         |   108(1934)   108(1934)
&&
&&

.AVIATION...For McCarran...Outside of thunderstorm influences, winds
will be light and follow diurnal trends. Storms are possible around
the airspace, but may remain over the higher terrain. Bigger issue would
be outflows as the weather setup is favorable for long distance
outflows. Will need to monitor and update if needed as confidence is
low on which direction and when outflows may effect the valley.
Currently have mention of showers, but storms are possible as well,
especially if any outflows move to or through Las Vegas.
Precipitation chances quiet down over night, and should be more
limited for Friday. Hot temperatures will continue through at least
the weekend.

For the rest of southern Nevada, northwest Arizona and southeast
California...Beyond thunderstorm influences, generally tranquil
weather is expected with winds less than 15 knots and variable cloud
amounts with bases above 12 kft. Best chances for thunderstorm
activity will be over high terrain of the Sierra and southern Nevada
through the evening. Thunderstorm chances will be more limited on
Friday.
&&

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

SHORT TERM/AVIATION...Wolf
LONG TERM....Salmen
CLIMATE...Boothe

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