396
FXUS65 KVEF 121646
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
946 AM PDT Fri Jul 12 2024

.SYNOPSIS...One more day of near record heat before temperatures
begin to moderate with the arrival of some monsoonal moisture over
the weekend. A few thunderstorms will develop across northwest
Arizona and far southern Nevada this afternoon and evening with a
risk of very strong wind gusts. More widespread thunderstorm
development is expected over the weekend. Storm coverage will
trend more isolated next week as drier air works in from the
west.

&&

.UPDATE...For most of the area, heat will once again the main story
today as highs threaten daily records at several climate sites.
However, for portions of northwest Arizona, thunderstorms and strong
outflow winds may steal the spotlight. Latest HREF continues to show
a strong signal for outflow winds this afternoon/evening, mainly for
central Mohave County. Severe winds (gusts of 58+ mph) will be
possible with any storm in this area, and outflow winds will likely
propagate well ahead of the convection. Folks on the area lakes
should remain weather-aware today and be prepared to get off the
lake quickly. Convective coverage ramps up tomorrow and Sunday as
better moisture moves in. Strong outflow winds and dry lightning are
expected to be the primary hazards, but cannot rule out isolated
flash flooding in Mohave County and the Lower Colorado River Valley
where PWATs are higher. A gradual decrease in monsoonal activity is
anticipated next week as drier air tries to move in from the west.

&&

.SHORT TERM...through Sunday.

Much anticipated relief from the long-duration heatwave is on the
horizon, but we have one more day of record or near record highs
left today. Afternoon highs this afternoon should peak near, or
very slightly below values observed Thursday. There is some added
cloud cover around today which will help initialize that cooling
trend, but the low levels remain quite dry and heights remain
quite high, so it won`t be cooling much. The more dramatic cooling
will hold of for Saturday when temperatures drop 2-4 degrees
areawide. Heat Risk, which as been predominantly high or extreme
for most of the region the past week, drops to moderate almost
everywhere with the exception of the Las Vegas Valley footprint,
where elevated overnight lows keep the risk a little higher.
Nonetheless, with with a fairly noticable drop in temperatures
Saturday and the likelihood of convection around, no changes have
been made to the current head headlines, and the expectation is
to expire them as scheduled Friday evening. Even more noticable
cooling is expected for Sunday, though temperatures will still
remain several degrees above normal.

While the high pressure ridge responsible for the heat begins to
slide eastward today, the flow aloft will become more easterly,
opening the door for increasing monsoonal moisture over Arizona to
work north and westward. The western edge of this deeper moisture
will creep westward today, allowing fairly robust storms to
develop across the Coconino Plateau and drift westward into Mohave
County during the afternoon and evening hours. The HREF and
several successive runs of the HRRR continue to advertise a strong
wind component with these storms, and insist on an organized
outflow boundary propagating westward in the evening across
Mohave County and into the Colorado River Valley, and eventually
Las Vegas Valley by around sunset. This isn`t surprising with
DCAPE values of 1500-2000 j/kg spread across the the region, and a
similar environment yesterday produced a measured 77 mph
thunderstorm wind gust in Kingman. HREF probabilities for 30 knot
wind gusts (~35 mph) reach around 50 percent in the Las Vegas
Valley this evening, while peaking above 90 percent across central
and eastern Mohave Counties. Similarly, a 50 percent probability
is suggested for wind gusts of 50 knot (58 mph) for central and
eastern Mohave county, with chances of wind reaching that
magnitude decreasing on approach to Las Vegas. These strong winds
may strike suddenly and arrive well ahead of any lightning or
audible thunder, so stay weather aware across the Lakes this
afternoon and evening.

Moisture will increase further Saturday and Sunday with the flow
aloft becoming more southeasterly. Precipitable water values will
climb to 1-1.25 inches along the I-15 corridor, and reach near
1.5 inches near Lake Havasu. This represents a fairly typical
monsoonal environment with a risk of storms producing a least
localized flash flooding potential as well as strong winds, and
dangerous lightning. Drier air focused further west across the
Sierra and Owens Valley, along with swifter northerly storm
motion, will favor the potential for dry lightning and fresh fire
starts.

.LONG TERM...Monday through Thursday.

Monsoonal moisture from the weekend will linger to start the work
week, but a slight southwesterly component in the winds aloft will
gradually push the moisture eastward through mid-week. As a result,
PoPs of 20+ percent, which exist on the high terrain from the Spring
Mountains and points east on Monday, become confined to eastern
Lincoln and Mohave Counties Tuesday - Thursday. Main concerns with
most storms will be gusty outflow winds and dry lightning, though
convection in Mohave County and the Lower Colorado River Valley will
have the potential to produce isolated flash flooding due to the
greater PWAT values. Latest WPC ERO gives paints this area with
marginal risk of excessive rain (at least 5% chance of occurring) on
Monday.

For areas along and west of I-15, temperatures remain above normal,
though not expecting the blistering heat we`ve seen this week. Highs
across the Mojave Desert are forecast to be in the 100-115 range,
with lows in the 80s across our lower deserts and 60s/70s in our
northern locations. Combined, this should yield widespread Moderate
HeatRisk through the week.

&&

.AVIATION...For Harry Reid...Southwesterly winds under 10 knots
become variable in the early morning hours. Later in the morning,
winds remain light but shift to the east. Thunderstorm activity is
expected around the region in the afternoon and evening. Although
storms should remain outside the vicinity of the terminal, gusty
outflow winds are expected to reach the terminal. Confidence is
greatest in a push of southeasterly winds in the late afternoon and
evening originating from convection over northwest Arizona. There is
a 30 percent chance of peak gusts reaching 35 knots. Outflows from
the northwest and southwest also cannot be ruled out, but should be
short lived if they occur. Convection and outflow boundaries should
slow down overnight with variable winds resuming in the early
morning hours. Temperatures rise above 100 degrees by 17Z and fall
to less than 100 degrees by 08Z.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds follow a diurnal pattern this morning at most
locations. Thunderstorm activity picks up in the afternoon and
evening, with the greatest chances in Mohave County and Clark
County. Although confidence is low in thunderstorm development in
the vicinity of any terminal, gusty outflow winds may reach
terminals in the Las Vegas Valley and Colorado River Valley. These
winds will probably come from the east to southeast as the greatest
chances for thunderstorms are over high terrain in Mohave County.
However, outflows from other directions are possible depending on
exactly where storms form. At KBIH, gusty westerly winds may reach
the terminal in the late afternoon due to convection over the
Sierra. Thunderstorm activity and accompanying outflow winds taper
off overnight. Outflow winds are unlikely at KDAG and winds should
remain diurnal throughout the forecast period.

&&

.FIRE WEATHER...One more day of intense and record breaking heat
before temperatures begin to moderate and increasing monsoonal
moisture works into the region. A few thunderstorms will develop
this afternoon and evening across Northwest Arizona and the
eastern Mojave Desert with a risk of very strong and erratic wind
gusts. Thunderstorms will increase in coverage across much of the
region Saturday and Sunday, with dry thunderstorms remaining a
concern across western Inyo County where a Red Flag Warning remains
in effect for the Sierra and Owens Valley.

&&

.CLIMATE...Numerous climate locations have a forecast high
temperature and/or forecast warm low temperature within 3 degrees of
the daily record.

The table below shows the daily record maximum temperature and the
year the record was last set. An asterisk (*) denotes which records
are in jeopardy (within 3 degrees of the forecast).

MAX   FRI, JUL 12
  RECORD (Yr)

Las Vegas     114(2003)*
Bishop        108(2020)*
Needles       124(1925)
Daggett       115(2021)*
Kingman       111(2020)*
Desert Rock   112(2021)*
Death Valley  130(1913)

The table below shows the daily record warm minimum temperature
and the year the record was last set. An asterisk (*) denotes
which records are in jeopardy (within 3 degrees of the
forecast).

WARM MIN      FRIDAY, JUL 12
              RECORD (Yr)

Las Vegas     94(2020)*
Bishop        69(1990)*
Needles       96(2021)
Daggett       87(2012)*
Kingman       80(2021)*
Desert Rock   83(2023)*
Death Valley  107(2012)


&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures. The potential exists of strong wind gusts today across
parts of the area, and reports of dust, high wind speeds, or wind
damage are encouraged.

&&

$$

UPDATE...Woods
SHORT TERM...Outler
LONG TERM...Woods
FIRE WEATHER...Outler
AVIATION...Meltzer

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