493
FXUS65 KVEF 121940
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1240 PM PDT Fri Jul 12 2024

.SYNOPSIS...One last day of excessive heat today as the pattern
begins to shift towards a monsoonal one. Expecting a first taste
this afternoon with strong thunderstorm outflow winds probable in
Mohave County and on the area lakes. Temperatures cool slightly this
weekend as storms become more numerous. Rain chances become more
isolated next week as drier air filters in from the west.

&&

.SHORT TERM...through the weekend.

The day is finally here! The final day of this excessive, extreme,
historic (insert your favorite descriptor) heatwave is upon us.
Highs today will once again threaten daily records at several
climate sites, but some relief is on the way. Monsoonal moisture
and more widespread convection/clouds tomorrow will bring
temperatures down sufficiently to allow the heat headlines to
expire. That being said, it is still going to be hot, with
temperatures remaining above normal through the weekend. Now,
let`s talk about storms.

The 500mb high that has long been positioned just to our west or
practically overhead is finally beginning to move to the Four
Corners area. Positioned just to our north today, there isn`t much
southerly component in the flow aloft, thus moisture remains rather
meager today. However, there will be just enough to spark
thunderstorms in eastern Mohave County this afternoon, with slightly
greater coverage than we saw yesterday. Like yesterday, the very dry
low-levels will make strong outflow winds the primary hazard with
any convection. Latest HREF shows 750-1000 J/kg of surface-based
CAPE atop 2000+ J/kg of DCAPE, suggesting an environment rather
favorable for strong thunderstorm outflow. And indeed, the CAMs have
latched on to this potential, with the HREF showing 30-60% chances
of 40+ mph wind gusts over central Mohave County and all the way to
the I-15 corridor in southern Nevada. What the outflow does when it
gets to the Las Vegas Valley is more uncertain. Some guidance has it
kicking off additional storms on the terrain surrounding the valley,
while others do not. This will be something to watch in subsequent
model runs and as the actual convection evolves this afternoon.
Should storms fire in the Las Vegas vicinity, strong winds will be
possible in the valley. In terms of rainfall, not expecting much.
HREF ensemble max 3-hr QPF tops out at ~0.5" on some of the high
terrain in Mohave County, but the ensemble mean remains less than
0.1".

Southeasterly winds aloft within the high`s anticyclonic flow will
usher in better moisture tomorrow and Sunday as it shifts east.
Latest EPS mean PWAT has values of 0.75"+ across much of the area,
with the 1.00"-1.50" values largely confined to the southern half of
the CWA. This moisture combined with slight cooling aloft will yield
CAPE values of 250-1000 J/kg for most of the area. Despite the
increase in moisture, low levels will remain relatively dry as temps
stay above normal. 12z HRRR soundings show DCAPE of 1500-2200 J/kg
from Bishop to Needles, suggesting strong outflow winds will
continue to be the primary hazard. Any flash flood potential is
confined to eastern Mohave County where WPC maintains a marginal
risk for excessive rainfall this weekend. In the Sierra and Owens
Valley, the combination of dry low levels, cured fuels, and
scattered thunderstorms will yield high fire danger this weekend.
Due to this threat, a Red Flag Warning is in effect for the area
Saturday and Sunday.

.LONG TERM...Monday through Thursday.

Monsoonal moisture from the weekend will linger to start the work
week, but a slight westerly 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...For Harry Reid...Light east winds will become southeast
this afternoon. 15-20KT gusts are possible with the southeast winds,
especially after 21Z. There is a low chance for convection to impact
the terminals directly today with a 20% probability for thunderstorms
between 01Z to 05Z. However, watching the potential for strong
outflow winds from distance thunderstorms to push through this
evening. If these winds were to reach the terminals, it would be
between 01Z-04Z, likely as an east or southeast wind. Gusts over
35KT are possible with these winds.

After 06Z, a quiet night with dry conditions and light diurnal winds
tonight through Saturday morning are expected. Convection will
develop again Saturday afternoon after 20Z in and around the
terminals with chances for thunderstorm at the terminal higher
Saturday compared to today, around 40%-50%. Any thunderstorms could
bring lightning, brief rain, and sudden gusty winds. Will need to
watch the potential for more gusty outflow winds Saturday afternoon
from distant thunderstorms in the late afternoon and evening, which
are possible but confidence is too low for outflows at the terminal
to include them in the current TAF package. Outside of convective
influence, expecting breezy south to southwest winds Saturday
afternoon with a moderate (40%-50%) chance for gusts over 20KT.
Occasional SCT clouds around 15fkt-20kft are expected through the
TAF period.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered thunderstorms will develop this afternoon in
western Arizona and southern Clark County. The highest risk for
thunderstorms will be in Mohave County as well as the Spring
Mountains and the terrain in far southern Clark County. Any
thunderstorms may produce lightning, brief rain, CIGs to 10kft, and
sudden gusty winds. Watching for an outflow to move out of northern
Mohave County this evening through southern Nevada, potentially
making it as far as Death Valley. There is a 40%-60% risk for sudden
gusty winds over 35KT through MOhave County and the northern
Colorado River Valley between 00Z-03Z, with lower chances around 20%-
30% in the southern Colorado River Valley, southern Clark County,
and southeast Inyo County. COnvection and the threat for sudden
gusty winds will dissipate after 04Z and a dry night with diurnal
wind trends is expected tonight.

Outside of the potential convection- winds today will favor the
south to southeast wind speed around 10KT and occasional gusts up to
20KT this afternoon. At KBIH, gusty west winds are possible after
21Z. Winds will become light and diurnal overnight and continue
through Saturday morning. More widespread scattered thunderstorms
are possible Saturday afternoon across much of the region, which
could bring additional gusty outflow winds and lightning to the
area.

&&

.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.

&&

$$

DISCUSSION...Woods
AVIATION...Nickerson

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