288
FXUS65 KVEF 192007
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
107 PM PDT Thu Sep 19 2024

.SYNOPSIS...An area of low pressure will slowly move south along
the California coast today before turning inland and moving across
the southern Great Basin tomorrow. This will keep temperatures
several degrees below normal through Friday as well as bringing
the threat of precipitation to the region. Drier and warmer
conditions will return over the weekend and continue into next
week as a high-pressure ridge builds over the western US.

&&

.SHORT TERM...through Saturday.

Current infrared and water vapor satellite imagery show a cut-off
low pressure system churning off the coast of central California.
This system will continue to dig south and east, moving through our
forecast area tomorrow. Showers and thunderstorms will be possible
in the crest of the Eastern Sierra this afternoon and evening as
this system continues to push south. While the Sierra-Nevada are
expected to intercept the majority of the moisture, there is around
a 25% chance the White Mountains and the northern portion of the
Owens Valley will see showers and thunderstorms from the meager
moisture that manages to spill over the Sierra. Snow levels in the
Eastern Sierra will be around 9,500 feet or higher with 1 to 3
inches of snow accumulation possible along the ridgeline.

Precipitation chances will increase across the Mojave Desert and
southern Great Basin tomorrow as this low pressure system tracks
inland and through our forecast area. The better dynamics and
instability associated with this trough will result in increased
convective potential, meaning that thunderstorms will be possible
tomorrow. Heavy rain and lightning will be the primary threats with
any thunderstorms that develop. Small hail and graupel will also be
possible with thunderstorms tomorrow, but will not pose the same
threat as the heavy rain and lightning. Unlike typical monsoonal
convection, convection tomorrow will continue into the evening and
the overnight hours as the low continues to track east. The far
eastern portions of our forecast area will see a 20 to 30% chance of
precipitation early on Saturday morning as this low exits the region.

Outside of these morning precipitation chances in the eastern
portions of our forecast area, weather on Saturday will be dry and
mild as we find ourselves under dry northerly flow aloft with rising
500 mb heights. These rising heights will allow for temperatures to
warm up a few degrees from Friday into Saturday. However,
temperatures will still be slightly below normal.

.LONG TERM...Sunday through next Thursday.

Dry weather and warming temperatures will continue into early next
week as an upper-level ridge establishes itself over the Western US.
Forecast uncertainty increases around Tuesday/Wednesday as a cut-off
low is forecast to drop down the leeward side of this ridge. The
uncertainty arises from interensemble discrepancies regarding where
the leeward side of the ridge will be located relative to our
forecast area and how far southwest this low will dig into the
southwestern US. Should this system slide down the leeward side of
the ridge and eject right into the Central Plains as some models
indicate, we will see the early week warming trend continue. If this
low ends up in the Four Corners region as a few models show, we
would be looking at temperatures cooling a few degrees during this
time. However, it is worth noting that the latter solution is in the
minority with only 23 of the 100 ensemble members that make up the
Canadian, GFS, and ECMWF ensembles showing a solution similar to it.


&&

.AVIATION...For Harry Reid...East to southeast wind direction this
afternoon into the early evening hours. Sustained speeds 8-12 knots,
there is about a 50% probability for an occasional gust to between
14-17 kts. Winds will shift back to a westerly direction overnight
with speeds 8 kts or less. East to southeast wind direction will be
favored again Friday afternoon into early evening. However, there
will be isolated showers and thunderstorms developing over the
higher terrain tomorrow afternoon and evening. Any impacts in the
valley may hold off until late tomorrow afternoon and evening when
there is about a 30% probability for wind gusts greater than 30 kts.
There will be some periods Friday with ceilings down to 8 kts in
the valley.

For the rest of southern Nevada, northwest Arizona and southeast
California...An area of low pressure will slowly move east across
southern California tomorrow, and through northwest Arizona Friday
night. Highest probability for showers and thunderstorms will be
under the low center in San Bernardino County Friday afternoon and
early evening, then southern Nevada and northwest Arizona Friday
night. Ceilings will range between 6-8 kft AGL at times with
localized mountain obscurations. Aside from the gusty wind potential
associated with any showers and thunderstorms Friday, surface winds
will generally be from an east to southeast direction in northwest
Arizona and southern Nevada. While, surface winds at KBIH will be
from the north.

&&

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

&&

$$

DISCUSSION...Stessman
AVIATION...Pierce

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