Excessive Heat in Nevada, June 19 to 21, 2016

Area Forecast Discussion
National Weather Service Las Vegas NV
930 AM PDT SUN JUN 19 2016

.SYNOPSIS...High pressure will build over the Four Corners region
through early this week, leading to dry and very hot conditions
across the area. Many record highs and record warm lows will be in
jeopardy Sunday through Wednesday. Some moisture is expected to move
into the region leading to a slight chance of precipitation for the
high terrain Wednesday and Thursday.
&&

.UPDATE...Warming up on this Father's Day with temperatures as much
as 3 to 9 degrees warmer at 9 am as compared to Saturday. Ridge
progged to expand further westward over Nevada and California making
Monday and Tuesday the hottest days. Excessive Heat Warning goes
into affect at 10 am this morning and continues through Wednesday.
No update necessary.
&&

.PREV DISCUSSION...206 AM PDT SUN JUN 19 2016
.SHORT TERM...through Tuesday night.

WV imagery is currently showing the separation of a vorticity
maximum in the Pacific Northwest. One piece will rapidly progress
eastward across the US/Canada border on Sunday as the remaining piece
meanders just west of the Washington coast before an upstream upper
low from the Gulf of Alaska kicks it eastward early this week. As
the Pacific Northwest vort lobe waits for the upstream kicker, it
will generate downstream ridging in the Intermountain West, allowing
for an upper high in northern Mexico and the adjacent southern
Rockies to shift slowly northward and westward. As this occurs,
substantial warming will commence in our area today and last through
much of the new work week. Temperatures will climb 5-10 degrees
above Saturday's values today and will increase another 3-8 degrees
on Monday as 600+ dam 500-mb ridge anchors itself in the Four
Corners region. With the approaching high, the surface pressure
gradient will relax, and surface winds will be noticeably lighter
today and Monday compared to the past week.

The forecast gets a little more complex Monday night and Tuesday, as
several operational and higher-resolution models bring an increase
in upper and midlevel moisture northward from northwest Mexico on
the western periphery of the upper ridge. This coincides with the
eastward push of the aforementioned vort lobe off the Pacific
Northwest coast. Though low-level moisture will be scant, rendering
any chance of precipitation on Tuesday virtually nil, the clouds may
reduce maximum temperatures somewhat (and keep lows somewhat warmer
Monday and Tuesday nights). The effect would be small, but
potentially enough to keep some sites from reaching records. Bumped
up sky cover grids during this period given the improved model
agreement, but was more hesitant to lower max temps Tuesday at this
point. Something to keep an eye on, though.

.LONG TERM...Wednesday through Saturday.

Hot weather will continue through the extended as a broad
subtropical ridge remains across the southern US. This means
regional temperatures will remain 5 to 10 degrees above normal
through the weekend. Only fly in the ointment will be some low grade
monsoon moisture which may begin to edge into the region midweek
onward. Convection chances look pretty limited as most of the
moisture is mid and high level, but it may result in occasional
bouts of cloud cover which will suppress high temperatures a few
degrees. We will need to keep an eye on the pattern beyond this
weekend as ECMWF has some early indications of deeper monsoon
moisture entering into the Southwest, but its still rather early in
the season, so we will have to wait and see.
&&

.AVIATION...For McCarran...VFR through the period. Mostly light and
variable winds with some preference to a northeast or east direction
in the late morning and early afternoon. Winds will switch to west
or southwest near sunset but should generally remain below 10 kts.
Hot temperatures are expected through the upcoming week, leading to
potential high density altitude concerns.

For the rest of southern Nevada...northwest Arizona...and southeast
California...VFR conditions through the period, though there may be
some visibility reductions at times in Inyo/San Bernardino counties
from upstream smoke. Light, mostly terrain-driven flow is expected
through the period.
&&

.CLIMATE...Excessive heat is expected early next week. Here is some
climatological perspective for various locations in the area. Below
are three tables. The first table lists the current forecast highs
between June 20th and 22nd. The second is a list of daily high
temperature records between June 20th and 22nd. The third table
lists all-time June high temperature records. Both the records
tables indicate the dates/years in which the records were set.
Though not shown, several record warm low temperatures are also in
jeopardy on these days.

Forecast Highs       6/20         6/21        6/22
-------------------------------------------------------

Las Vegas             113          113         110
Laughlin              121          116         115
Death Valley          123          123         122
Barstow-Daggett       114          112         111
Needles               122          117         116
Kingman               111          107         106

Daily Records        6/20         6/21        6/22
-------------------------------------------------------

Las Vegas          113/2015      111/1954    115/1954
Laughlin           117/1989      117/1990    118/1990
Death Valley       125/1961      125/1961    124/1961
Barstow-Daggett    114/2015*     115/1961    113/1954
Needles            118/1961      117/2008    120/1968
Kingman            105/2015*     106/2008    105/2005
-------------------------------------------------------
* 114 at Barstow-Daggett set in 2015 and 1961; 105 at Kingman set in
  2015 and 2008

Monthly Records for June
------------------------------------------------------
Las Vegas          117/2013 (6/30)
Laughlin           125/1994 (6/29)
Death Valley       129/2013 (6/30)
Barstow-Daggett    118/1994 (6/30)
Needles            123/2013 (6/29)
Kingman            112/2013 (6/29)

&&

.FIRE WEATHER...Very hot conditions will develop across the
southern Great Basin and Mojave Desert through Wednesday.
Fuels will continue to dry out during this time. However, wind
speeds are not expected to reach critical fire weather thresholds. A
slight chance of thunderstorms exists for the high terrain on
Wednesday and Thursday, with some potential for a lightning start
or two, particularly given the very dry low levels expected.
&&

Update...Pierce

Short Term/Aviation/Fire Weather...Shafer
Long Term...Outler
Climate...Shafer/Lericos

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