435
FXUS65 KVEF 121135
AFDVEF

Area Forecast Discussion National Weather Service Las Vegas NV 435
AM PDT Wed Mar 12 2025

.SYNOPSIS...A potent upper level system will impact the region
today through Friday with the highest and most widespread impacts
expected Thursday. Widespread mountain snowfall, gusty winds, and
light rain are expected at times. Calmer weather will resume over
the weekend, but gusty winds and shower chances return early next
week. Temperatures will be well below normal today through Friday,
with high temperatures Thursday and Friday running up to 15 degrees
normal for this time of the year. Temperatures will slowly warm this
weekend with near normal temperatures returning by Sunday.
&&

.SHORT TERM...Through Friday.

Continuing to fine tune details and impacts with the incoming upper
level trough today through Friday.

Confidence in the precipitation chances through this afternoon is
low. Brief ridging this morning will give way to height falls as the
trough approaches from the west. There is some moisture available
left over from the system that tracked to the south yesterday. PWATs
will range from 0.6 inches south of I-40 in San Bernardino and
southern Mohave counties, to around 0.3 inches in Lincoln, Nye, and
Esmeralda counties. This is about 125%-150% of normal for this time
of year, but it`s overall rather dry. Meanwhile, heights will fall
this afternoon, but they will be weak height falls and forcing in
general will be weak. These things combined would not support much
in the way of precipitation chances through the afternoon. However,
some hi-res models are insistent that isolated to scattered showers
will develop in the Southern Great Basin. The flow does increase out
of the south to southwest, which would be favorable for
upsloping...and thats where hi-res models that show precipitation
this afternoon have the highest precipitation chances. Other hi-res
models keeps much of the area precipitation-free until after 3PM PT.
Not sure if the amount of moisture and upper level support will be
enough to get precipitation to blossom as widespread as some of the
models are suggesting, but it`s not out of the question either.
Decreased precipitation chances through the morning to keep the area
dry before the flow increases and height fall moves in, but left
precipitation chances this afternoon as is from the previous
forecast. Will make adjustments as needed to reflect ongoing trends
and mesoanalysis. Anything that is able to develop today will be
light as NBM (which is one of the more robust models for
precipitation develop this afternoon) shows less than a 20% chance
for precipitation amounts over 0.10 inches for this afternoon.

The rest of the forecast seems to be on track. Precipitation will
overspread the region tonight as moisture and forcing increases with
the trough shifts into Southern California. The highest risk for
precipitation impacts will be Thursday morning into the early
afternoon as the best forcing with a punchy vort-max rounding the
trough axis as it moves through the region. Snow levels will drop
Thursday from around 6000ft in the early morning to around 4000ft by
the afternoon as colder air filters in with the trough overhead and
the flow turns north. Precipitation chances will linger Thursday
night and Friday, though impacts on Friday may be lower than
Thursday as the flow turns northwest on the back side of the trough
and drier air pushes into the region. High probabilities for over a
foot of snow accumulations on the Spring Mountains and in the
Sierra. Snow will likely fall through Westgard Pass in the White
Mountains. Lighter amounts are expected in the Southern Great Basin-
though one note about the Winter Weather Advisory in the Southern
Great Basin- pockets of higher impacts are possible. Over the
region, the advisory captures the most widespread expected impact
level. But in a few locations like Lida Summit, US-93 just north of
Pioche, and the higher elevations on RT-319 between Caliente and
Cedar City, UT- there are indications that higher snow accumulations
and moderate winter impacts are possible. In general, anyone driving
through the Southern Great Basin Thursday should be prepared for
rapidly changing conditions as road elevations increase and decrease
quickly in spots. You may quickly drive into snow with elevation
changes. Elsewhere further south when there are no winter headlines
in effect- same word of caution for I-15 through Mountain Pass, CA
and I-40 east of Kingman where an inch or two of snow could fall
which doesn`t sound like much but given the sudden change in road
conditions- it could be hazardous. Did not make any changes to the
winter headlines as timing and larger scale impact expectations have
not changed.

Winds will be the other impact of concern. South to southwest winds
this afternoon as the pressure gradient increases with the incoming
system. Widespread gusts 25-35 MPH are expected by late afternoon.
The highest chance for wind impacts with gusts over 40 MPH over a
period of time long enough for impacts to develop is in Inyo County
where the Wind Advisory and Winter Storm Warning with strong wind
wording goes into effect. Some ensembles show increasing
probabilities for wind gusts over 40 MPH in parts of Esmeralda and
central Nye counties, however it would not pick up until just before
sunset based on low level wind profiles. Probabilities diminish in
the evening through that area as we lose mixing. Did not expand the
Wind Advisory north into Esmeralda and central Nye as the short time
frame could limit wind impacts. Tonight and Thursday, winds will
increase from west to east as the trough moves through. On Thursday-
widespread wind impacts are expected. Wind advisories or mention of
wind impacts in the winter products blanket most locations on
Thursday, no changes have been made to wind headlines on Thursday as
widespread gusts 35-45 MPH are expected. Winds will turn north
through Thursday night into Friday and wind speeds will diminish as
the trough pulls away from the area. The best chance for lingering
wind impacts Thursday night will be in the Western Mojave Desert and
Yucca Valley...and continuing impacts are possible into Friday but
will assess the need to extend the Wind Advisory for that area as we
get closer to Friday.

Temperatures today will be near to slightly below normal before a
drop in temperatures is expected Thursday. Colder temperatures will
continue into Friday High temperatures on Thursday and Friday will
run 10-15 degrees or more below normal.

.LONG TERM...Saturday through early next week.

The progressive pattern will continue this weekend in the wake of
the departing trough, as flow aloft transitions northwesterly and
ridging develops over the western CONUS Saturday and Sunday.
Ensemble guidance and cluster analyses are in good agreement
regarding the evolution of the upper pattern, with the
aforementioned ridging and associated increasing thicknesses
allowing for a gradual warming trend that will see temperatures
rebound back into the 40s and 50s in the mountains and 60s and 70s
across lower elevations. The ridge will also keep any precipitation
at bay, and keep winds on the light side areawide, making for a
pleasant weekend, especially for those who may have outdoor plans.
Heading into next week, ensembles indicate the next trough to impact
the region will move ashore over the California Coast early Monday
morning, bringing increased cloud cover and the next chance for
precipitation to portions of the area. However, while guidance has
been consistent with the timing of this next trough, it has been
shown to dampen somewhat and trended drier without an accompanying
pronounced IVT plume. Overall, the best rain chances look to be
favored over western and northern portions of the area Monday and
Tuesday, though trends with this system will bear watching. For now,
have maintained the NBM solution with rain chances around 30-50% for
the aforementioned areas early next week, and a cooldown expected on
Tuesday as the trough translates east of the area.
&&

.AVIATION...For Harry Reid...For the 12Z Forecast Package...Light
winds this morning are expected to go southerly by late morning,
with gusts of around 25 knots possible through the afternoon and
evening. Clouds based around 6000 feet are expected to develop and
increase in coverage during the morning, going broken at times
through the afternoon. Clouds and winds should both decrease a bit
overnight, followed by increasing clouds as low as 3000 feet
Thursday morning, with a rainy day likely.

For the rest of southern Nevada, northwest Arizona and southeast
California...For the 12Z Forecast Package...A cloud deck around 8000
feet MSL southeast of Interstate 15 is expected to persist through
the day and even expand into the southern Great Basin. This will
cause obscuration of higher terrain. These clouds should scatter out
in the evening. Southerly winds will also increase today, with gusts
as high as 40 to 60 knots over the mountains, leading to moderate to
severe turbulence. Meanwhile, low ceilings and precipitation chances
will reach the Sierra crest in the afternoon and expand across the
entire region by Thursday morning, leading to a messy day over most
of the area until skies clear from west to east Thursday night.
&&

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

&&

$$

SHORT TERM...Nickerson
LONG TERM...Phillipson
AVIATION...Morgan

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