424
FXUS65 KVEF 161713
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1013 AM PDT Tue Jul 16 2024

.SYNOPSIS...Storm coverage will become more isolated today with
fairly weak storms anticipated mainly across Northwest Arizona
through Wednesday. Storm chances will gradually build back
westward Thursday through the weekend as the Four Corners high
migrates west. Temperatures will also heat up ad climb well above
normal over the weekend.

&&

.UPDATE...Satellite imagery is showing mainly clear skies across
much of the area this morning with some scattered clouds over
parts of northern Mohave County, northern Inyo County, and
southern Nevada.

We are expecting less thunderstorm coverage today with convection
primarily tied to the higher terrain. Both the HREF and HRRR have
storms firing over the Spring Mountains, Sheep Range, and along
mountain ranges south of Las Vegas as well as the higher terrain
of Mohave and Lincoln counties later this morning, continuing
through the afternoon before ending a few hours prior to sunset.
One difference noted between the two models output is slightly
greater storm coverage in the later runs of the HRRR that include
storms developing across more of the southern Great Basin and also
in the western half of San Bernardino County including Highway 62
east of the Twentynine Palms area.

Expect another 5 degree above normal temperature day across the
region today. In Las Vegas, the high temperature is forecast to
be 110 degrees which, if reached, will be day 2 of the next 110+
streak that is currently forecast to continue into at least, early
next week. The previous streak of 11 consecutive days of 110 or
higher this summer occurred from July 3 through July 13. With this
past Sunday being the one-off for temps below 110, Las Vegas has
had high temperatures of 110 degrees or hotter for 12 of the 15
days so far in July. Add in the 7 days in June when temperatures
rose to 110 or hotter, the total number of days at or above 110
so far this year - sits at 19, as of yesterday. This is just 10
days shy of the record annual total of 29 set back in 1940.

The record number of July mornings with low temperatures of 90
degrees or warmer in Las Vegas sits at 8 - set last year. With a
low temperature of 90 degrees this morning, the current streak of
July days sits at 6. Our forecast calls for a low temperature of
90 degrees or warmer in Las Vegas for each morning over the next
7 days. This means we could tie the record as early as Thursday
morning and break it as early as Friday morning, if the current
forecast verifies.

&&

.PREV DISCUSSION...1250 AM PDT Tue Jul 16 2024...

.SHORT TERM...through Wednesday.

A few very light showers persist this evening across southern
Mohave County associated with mid level moisture trapped within
the Four Corners High circulation. Convection today will trend
more sparse owing to some drier mid-level air working in from the
west and the presence of a subsidence inversion near 500mb
developing over the area. This warm layer will still permit some
afternoon cumulus build ups over the higher terrain, but will
likely stifle most updrafts outside of northwest Arizona where
somewhat deeper moisture exists. Meanwhile, warm temperatures will
prevail with somewhat greater surface heating than past days
expected thanks to reduced convective coverage.

.LONG TERM...Thursday through next Tuesday.

The high pressure ridge will continue to retrograde back to the
west, amplifying as it goes. As this ridge moves back towards us, we
will see the upper-level flow become more southerly, allowing for
additional moisture to creep into the area. As such, we see
precipitation chances increase across the eastern portions of our
forecast area on Thursday and Friday. By the weekend, both the
GEFS and ECMWF ensemble means are in good agreement that the ridge
will be centered over where Nevada, Utah, and Arizona meet (i.e.,
directly overhead). With the ridge moving back overhead and
settling above us, we will see temperatures increase a little each
day as we head into the weekend. By Saturday we will see the
reintroduction of Major HeatRisk in the lower elevations,
accompanied by patchy Extreme HeatRisk in places. Major and
Extreme HeatRisk will become more expansive on Sunday as the ridge
remains positioned overhead. These hotter than normal
temperatures will continue to help fuel afternoon convection as
moisture remains trapped under the ridge. With the moisture
around, overnight lows will remain elevated and conditions may
feel more humid than our typical heat events.

Forecast confidence decreases as we head into next week due to
uncertainty in the location of the ridge and potential for
monsoonal influences to impact the area.

&&

.AVIATION...For Harry Reid...Winds will largely favor typical
diurnal trends today, with variable or northeast winds this morning,
then becoming southerly during the afternoon.  Speeds through the
afternoon should generally remain less than 10kts, although
occasional gusts to 15kts are possible once the winds turn to the
south.  Southwest winds will develop by sunset with speeds of 10 to
12kts possible through 07Z before decreasing.  Isolated areas of
convection are possible over the higher terrain surrounding the
valley this afternoon.  While no storms are expected to impact the
terminal area directly, outflow winds from nearby storms can not be
ruled out during the late afternoon or early evening.  VFR
conditions will prevail with only a FEW clouds AOA 12kft AGL
forecast.

For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated thunderstorms are again possible today, but
most of the activity should be confined to the higher terrain of
southern Nevada and northwest Arizona.  Any of the storms will be
capable of producing lightning, brief periods of heavy rainfall,
CIGs less than 8kft that could obscure areas of higher terrain, and
sudden gusty outflow winds.  Away from storms, south-to-west winds
8kts to 12kts with occasional gusts to 15kts, along with VFR
conditions with only a FEW clouds AOA 12kft to 15kft AGL are
expected at the regional TAF sites. The threat of isolated
thunderstorms continues on Wednesday, mainly across northwest
Arizona.

&&

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

&&

$$

UPDATE...Salmen

SHORT TERM...Outler
LONG TERM...Stessman
AVIATION...Planz

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