Area Forecast Discussion
Issued by NWS Las Vegas, NV

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909
FXUS65 KVEF 130508
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
908 PM PST Wed Feb 12 2025

.SYNOPSIS...The next major precipitation event is expected tonight
through Friday across the forecast area, including heavy snow above
7000 feet. Once this system exits to the east, warmer and drier
conditions return in time for the weekend.
&&

.UPDATE...Everything is on track tonight with winter storm warnings
going into effect at 10pm in the eastern Sierra and White Mountain
zones as well as the Spring Mountains and Sheep Range. Although it
may be after midnight before the snow begins in the higher
elevations of Clark County, but when it does start there will be
many hours where snow fall rates will be in the 2-3 inch per hour
range. The Flash Flood Watch for the Owens Valley also begins at 10
pm this evening with the highest probability of heavier rain during
the daylight hours on Thursday. No forecast updates planned this
evening.

.SHORT TERM...Tonight through Friday

All eyes are on the widespread atmospheric river precipitation event
tonight through Friday. Low pressure in the eastern Pacific Ocean
will move east towards the West Coast, leading to southwesterly flow
into southern California. Unlike previous events this season, this
setup is favorable for moisture advection far inland into the Mojave
Desert without being blocked by the Sierra Nevada. Precipitation
will spread across the area overnight, peaking tomorrow afternoon
and evening, then slowly decreasing on Friday. The two main concerns
with this system are snow and heavy rain.

Tomorrow morning, snow levels range from around 1000 feet in
northern Lincoln and Mohave counties to 2500-3000 feet in the Las
Vegas Valley, and from 4000 to 7000 feet in southeastern California.
Snowfall at this time should be light. Heavier snow is expected
later in the day, but snow levels will also rise as warmer air moves
in along with the moisture. By that point, snow levels of 6000 to
8000 feet can be expected. The Winter Storm Warning covers the
Eastern Sierra, White Mountains of California, Spring Mountains, and
Sheep Range from tonight through Friday. Heavy snow will lead to
hazardous to impassible road conditions. The NBM 4.2 and 5.0 seem to
be settling on snow amounts from 1 to 2 feet above 7000 feet in
elevation, and amounts closer to 3 feet towards the peak. Meanwhile,
2 to 4 feet of snow appears likely in the Sierra above 7000 feet
including Aspendell, with higher amounts towards the crest. Along
with snow, wind gusts of 50 to 60 mph are expected along with the
snow in the warned areas. Lighter snow amounts of a few inches to
one foot are expected in the southern Great Basin above 6000 feet
with minimal impact to population centers or roads.

The primary challenge at lower elevations will be rainfall. Decided
to lean more towards the HREF solution for rain because it captured
potential rain shadowing effects in the valleys better than the NBM.
The area of greatest concern is the Owens Valley, where a
combination of spillover moisture over the Sierra Crest and rain
falling over snowpack may lead to flash flooding. The Flash Flood
Watch remains in effect for Owens Valley late tonight through
Thursday night. Most likely rain totals in Bishop range from .1 to
.75 inch according to the HREF. Similar rain totals are likely for
Las Vegas, which if they pan out, would end the second longest
streak of days without measurable precipitation, currently sitting
at 213 days.

The system will begin to exit to the east on Friday. A tight
pressure gradient and increased winds aloft lead to gusty
southwesterly winds through San Bernardino County. The greatest
probabilities for advisory level winds are on high terrain rather
than in the valleys, but will continue to monitor trends to
determine if a headline becomes necessary.

.LONG TERM...Saturday through Tuesday.

Dry conditions return this weekend as our trough exits to the east.
In its wake, breezy north winds, especially in the lower Colorado
River Valley where gusts of 25+ mph are likely (70%). Don`t
anticipate winds to be strong enough to cause noteworthy impacts or
warrant headlines, but choppy conditions on the local lakes are
possible. Winds become light on Sunday as the pressure gradient
relaxes.

Our next system approaches from the NW on Monday, passing to our
east by Tuesday. Ensemble guidance depicts this shortwave as an
"inside slider", so main thing to watch for will be increased winds.
Latest NBM gives western San Bernardino County a 30-50% chance of
40+ mph gusts on Monday. On Tuesday, gusty north winds are expected
behind the trough, with a 50% chance of 40+ mph gusts in the lower
Colorado River Valley. Elsewhere, these probabilities range from 10-
40%. Given the NW trajectory of the system, precipitation chances
are very limited, with just 15-25% PoPs in our northeastern zones.
Anything that does fall will be light.

In terms of temperatures, we stay pretty close to normal values for
mid-February. Highs across most of the Mojave Desert are forecast to
be in the 60s or low 70s. Highs in the southern Great Basin in the
50s to low 60s.
&&

.AVIATION...For Harry Reid...For the 06Z Forecast Package...Nasty
weather is on tap for Thursday. Low clouds, with ceilings likely
below 5000 feet and possibly below 3000 feet, will invade the valley
tonight into early Thursday morning. Chances for rain will begin as
early as 7 AM, with snow also possible in the morning, before a
steady rain arrives by noon. Ceilings will drop below 3000 feet and
possibly as low as 1000 feet at times, with visibility also reduced
in rain and fog. Conditions will improve Thursday night, but there
will be a chance of showers Friday, primarily over the mountains.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 06Z Forecast Package...Very poor conditions are
expected Thursday, as MVFR to IFR ceilings and visibilities spread
over the region from southwest to northeast. Widespread rain and
mountain snow can be expected, along with terrain obscuration.
Conditions will improve from northwest to southeast Thursday evening
and night, but scattered showers and possibly a thunderstorm or two
are expected to develop Friday, primarily over the mountains.
&&

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

$$

UPDATE...Czyzyk
SHORT TERM...Meltzer
LONG TERM...Woods
AVIATION...Morgan

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