Excessive Heat in California, June 27 to 28, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
1034 AM PDT Sun Jun 27 2021

.SYNOPSIS...Warming trend is underway as above normal
temperatures expected through Monday. Monsoonal moisture returns to
the area midweek bringing chances of showers and thunderstorms.
&&

.UPDATE...
Another hot and dry day is in store for today. Max temps will top
out well above normal at a degree or two higher than yesterday.
Excessive Heat Warning remains in effect today and tomorrow for the
lower elevations west of Las Vegas in Nevada and into portions of
southeast California. Otherwise, clear skies and light,
northeasterly breezes can be expected.

&&
.SHORT TERM...through Monday Night

Features we are monitoring in the short term are the anomalously
strong high center positioned over the Pacific Northwest and British
Columbia as well as a trough over low pressure over the central and
southern Rocky Mountain states.

The ridge axis does extend south from the Pac NW through western
Nevada and California which will bring a bout of well above normal
temperatures through Monday. Pockets of high to very high HeatRisk
remain mostly concentrated within our California area of Inyo and
western San Bernardino County, as well as southern Nye County.
Made no adjustment to our existing Excessive Heat Warning.

Eye's then turn to our east as model simulations still indicate
initial increase in moisture that is pooled over New Mexico will be
on the move west across Arizona Monday night into Tuesday. Forecast
soundings show mid levels of the atmosphere moistening while lower
levels remain dry, especially over the southern Sierra. Any storms
that develop over the Sierra Monday into Tuesday have the potential
to produce dry lightning. Regarding the Fire Weather Watch, will
allow day shift to collaborate with surrounding office's on this
mornings fire call.

.LONG TERM...Tuesday through Saturday.

Expansive PacNW ridge will induce an easterly flow across the
Southwest for much of next week. Meanwhile, an inverted trough will
slowly progress westward Tue-Thu out of the Four Corners region and
add some additional moisture and lift to the overall flow pattern.
While this isn't the typical 'Four Corners High' monsoon set up, it
is one that promises above normal precipitable water filtering into
the region along with periods of enhanced dynamic forcing. Another
fly in the ointment is any potential enhancement of low level
moisture from Hurricane Enrique which is currently tracking
northward off the Mexican coastline.  All in all, lots of potential
shower and storm chances next week but also a lot of uncertainty in
the details. For now, the NBM generated 20-30% chance daily PoPs
nearly area wide look to be a fair bet. Meanwhile, with the
increased cloud cover and higher dewpoints around, temperatures will
hover closer to seasonal normals.
&&

.FIRE WEATHER...Thunderstorm activity along the Sierra Crest on
Monday afternoon and Tuesday afternoon has prompted the issuance of
a Fire Weather Watch for dry lightning. The excessive heat combined
with very dangerous fuel conditions factored into this decision.
Wildfires are already ongoing and it is feared more lightning
activity may bring about dangerous wildfire growth to the area early
this week. Later in the week more moisture works it way in from the
east which will somewhat diminish the threat of dry lightning.
Nonetheless, fire danger is likely to remain high through the week.
&&

.AVIATION...For McCarran...Winds are expected to be light and
variable early this morning, but will gradually turn northeast after
15z with speeds increasing to around 10 kts with occasional gusts
approaching 20 kts, especially after 18z. Northeast winds will
gradually diminish after sunset and eventually shift to the
southwest during the evening hours. Heat will be increasing each day
through the early part of the week which may affect air operations.
No thunderstorm activity is expected until at least Tuesday at the
earliest.

For the rest of southern Nevada, northwest Arizona and southeast
California...Northeast winds will be seen over much of the area this
afternoon with speeds generally remaining under 10 kts. However,
there will be a few gusts especially across Clark, Lincoln, and
Mohave Counties where gusts may approach 20 kts this afternoon. VFR
conditions will be the predominate condition. There will be some
thunderstorm activity over the Sierra Crest beginning on Monday
afternoon. Midweek, thunderstorm activity will again pick up across
the area as Monsoon moisture returns.
&&

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

SHORT TERM...Pierce
FIRE WEATHER...Lericos
LONG TERM...Outler
AVIATION...Gorelow
UPDATE...Guillet

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