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000
FXUS65 KVEF 071700
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1000 AM PDT Wed Jun 7 2023

.SYNOPSIS...A large closed low pressure system will slowly
move across southeastern California and southern Nevada today and
Thursday, which will produce scattered showers and isolated
thunderstorms. Another system will follow a similar track late this
weekend into early next week resulting in a prolonged period of well-
below normal temperatures and unsettled weather.
&&


.UPDATE...As mentioned in the short term forecast discussion, a
closed area of low pressure will move east-northeastward through our
forecast area today. A rain band pushed through Inyo and San
Bernardino counties this morning. This band will continue to push
through Clark and southern Nye counties over the next couple of
hours. In general, rain observed with this band has been light.
National Park Service in Death Valley observed 0.08" this morning,
which has been the highest total so far. Through the afternoon, the
center of the low will move into Inyo County, resulting in
convective activity across Inyo, Esmeralda, southern Nye, and
western Clark counties. Death Valley National Park will be of
particular concern today due to their vulnerability to flash
flooding and their proximity to the center of the low. Surface-based
CAPE values will range from 100-250 J/kg according to the HREF,
though all-day cloud cover could prohibit much in the way of surface
heating. That said, forecast HRRR soundings show upward of 1 inch of
PWAT in Death Valley. Coupled with dynamic forcing and orographic
lift, thunderstorm activity in the Coso and Panamint ranges could
put down between 0.50 and 1.00 inches of rain. In addition to flash
flooding, inverted-V soundings in adjacent areas could result in
gusty winds in excess of 40 mph from the direction of stronger
cells. In southern Inyo County, DCAPE values could approach 1000
J/kg once the convective temperature has been met, so thunderstorm-
related wind gusts at or above 50 mph cannot be ruled out. No
changes made to the forecast this morning, as it looks to be in good
shape.
&&


.PREVIOUS DISCUSSION...229 AM PDT Wed Jun 7 2023/


.SHORT TERM...Today and Thursday.

Satellite loops early this morning showed an energetic looking
closed low churning over southeastern California. The HREF tracks it
slowly across Inyo/northern San Bernardino counties today then over
southern Nevada tonight and Thursday. Considerable cloud cover was
evident with the core of the system and this will limit surface
heating over Inyo/northern San Bernardino counties today. However
dynamic forcing and cold pool instability near the circulation
center were sufficient to generate and keep nocturnal thunderstorms
going early this morning north of Bakersfield. This will lead to
concerns for thunderstorm development later this morning through the
afternoon over southern Inyo County...especially Death Valley
National Park which is so prone to flash flooding. While most
showers should be light to moderate, the HREF has been indicating
75th-90th percentile 6 hr QPF values of 0.5"-1.0" this afternoon
over the Coso and Panamint ranges, so localized heavy rain and flash
flooding will be a minor risk today for these areas. Snow levels
around 9500 feet over Inyo County will also support the potential
for accumulating snow in the high Sierra and possibly the mountain
peaks in Death Valley such as Telescope Peak. Amounts will generally
be less than 2", but convective bursts cloud produce locally higher
amounts.

Scattered showers and isolated thunderstorms will also develop over
northern San Bernardino, southern Nye and western Clark counties
with generally 20-40 percent probabilities of measurable rain...50-
60 percent in the Spring Mountains. However, more limited moisture
will result in the primary threat for these areas to be brief
convective wind gusts over 40 mph...with localized gusts potential
over 50 mph. High temperatures will be 4-8 degrees lower than
Tuesday across most of the forecast area due to the height falls,
cloud cover and weather associated with the closed low.

The low center will slowly weaken and lift toward the northeast
tonight and Thursday, which will bring showers and isolated
thunderstorms over central and northern Lincoln County along with
isolated storms over the southern Sierra and parts of Esmeralda and
central Nye counties. Elsewhere, a subsident regime in the wake of
the lift low should keep the weather dry and temperatures will climb
3-5 degrees...but highs will still only be in the upper 80s to
lower 90s across most of the Mojave Desert zones.

.LONG TERM...Friday through next Wednesday

A building ridge over the Intermountain West should allow for some
warming over the forecast area toward the end of the week. However,
these highs will still be several degrees below normal. This pattern
should keep thunderstorm activity at bay as well. A low pressure
system drops south along the Pacific Coast on Saturday, reaching the
forecast area by Sunday. Moisture advection from the Pacific Ocean
and dynamic lift from this system gives the area its next chance for
thunderstorms. The highest PoPs are over mountains and higher
terrain where orographic lift will enhance storm development.
Forecast soundings feature high based inverted-V profiles, a sign
that strong outflows may be a challenge with these storms. Will iron
out the details with coming forecast packages.
&&


.AVIATION...For Harry Reid...Light winds favoring a southwesterly
direction early this morning will increase and turn to the southeast
by late morning. Model guidance continues to show a shift in wind
direction to the south-southwest after 20Z and gusts increasing to
around 20kts. VCSH has been included in the TAF after 21Z, with most
shower activity confined to the higher terrain west of the field.
While TS has not been included in this package, it cannot be ruled
out, and if stronger cells do form, outflow winds with westerly
components may affect the field during the late afternoon or early
evening. The gustiness should end after sunset, and winds less than
10kts are likely overnight into Thursday morning. VFR cigs will
prevail with SCT-BKN skies AOA 10kft expected through the TAF
period.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered showers and a few embedded thunderstorms are
likely across the western Mojave Desert, Sierra, and higher
elevations of southern Nevada today, with KDAG and KBIH the most
likely sites to see direct impacts. South to southwest winds gusting
over 20kts are also expected at most sites, with KEED and KIFP
experiencing the highest winds. Winds will diminish by late evening,
with all sites seeing winds fall to below 10kts. Outside of areas of
precipitation, VEF cigs will prevail with SCT-BKN skies AOA 10kft
through the TAF period.
&&


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


UPDATE...Varian
SHORT TERM...Adair
LONG TERM...Meltzer
AVIATION...Planz

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