Dense Fog in California, March 11 to 12, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
800 PM PST Thu Mar 11 2021

.SYNOPSIS...A large and slow moving storm system will continue to
affect our region and bring cool showery weather through Friday.
Scattered to numerous showers are possible each day with mainly
light snow accumulations in the higher terrain above 4000 feet. Dry
conditions return over the weekend with moderating temperatures.
Active weather will continue next week with precipitation and
gusty wind possible, but low confidence in details.
&&

.UPDATE...Will be brief this evening.

Quite the late afternoon here at the NWS office with strong core
dumping an impressive amount of graupel. Still some patches sticking
around our landscape rocks.

Decided to hoist a Winter Weather Advisory for elevations above 6000
feet for the mountains of Clark County and Lincoln County through
Friday afternoon. More rounds of snow coming with 4-8 inches of
additional accumulation for the Spring Mountains. 3-6 inches in
Lincoln County.

&&

.SHORT TERM...Tonight and Friday.

Scattered showers and isolated thunderstorms will continue through
this evening then diminish in coverage tonight. Hi-res models are
hinting at another area of enhanced precipitation tonight or Friday
morning, but very low confidence in this occuring. The main upper
level low should start weakening overnight, but extra lift from
numerous vort lobes rotating around the main low could allow for
enough convergence  and lift for this to occur. Based on model IR
satellite progs and ensemble probabilities for QPF/snow,there are two
areas where this could occur: northern Mohave through Clark County
or southern Lincoln into southern Nye county. Very low confidence in
the placement of this possible band (or if it will even develop), but
it could bring increased impacts including snow to 3000ft and higher
QPF. The other area of concern outside of any mesoscale processes
will be the higher terrain of western Esmeralda through northern
Inyo County as the flow turns more northeast and could result in
upslope enhancement. Increased precipitation chances and QPF in that
area overnight to capture this potential. Will need to update the
forecast as things unfold overnight, and people may want to check
the forecast and conditions before heading out in the morning, just
in case.

Outside of this potential enhanced area of precipitation, there
should be a decrease in precipitation coverage overnight with then
another uptick in activity much like today for Friday afternoon. The
center of the low will be shifted a bit more southeast on Friday
compared to today, so best chances for showers and isolate thunder
will be over eastern San Bernardino, Clark, Lincoln, and Mohave
counties. Similar condition are expected tomorrow, with a quick
couple inches of snow in  the higher terrain above 4000-5000ft and
light, quick moving rain showers. Continued to include a mention of
isolated thunder in areas under the coldest temperatures aloft.
Saturday through Wednesday.

.LONG TERM...Saturday through Wednesday

Cutoff low will continue to slowly move through the Four Corners
region Saturday. Moisture/instability wrapping back west around the
low will threaten far northeastern Mohave County with a slight
chance of showers. Elsewhere, conditions will be mostly sunny along
with northwest breezes generally 10-20 mph with gusts 25-30 mph.

Ensemble simulations remain consistent showing brief ridging on
Sunday before another trough progresses through the Great Basin
early next week. Main impact for the system will be a bout of
stronger southwest-west winds Monday. Models have diverged in
potential solutions with the main trough, with some models showing
the trough barreling through the region while others show a closed
low splitting off from the trough and sitting off the West Coast
instead. If the first solution pans out, increasing winds are likely
with the potential for 40+ MPH winds Monday or Monday night,
especially through San Bernardino into Mohave County. Will need to
watch trends and update as higher impacts are possible than the
current forecast conveys. Precipitation chances look low and light
in parts of Inyo County Sunday night/Monday and south central Nevada
and northern Mohave County Monday/Monday night. Temperatures will
peak Sunday before cooling several degrees Monday and Tuesday.
Temperatures warm on Wednesday under ridging.
&&

.AVIATION...For McCarran...Unsettled weather will remain through
Friday as a weather system continues to circulate through the
region. Winds will favor a southeasterly direction through much of
the afternoon today with gusts possible around 20 knots. Scattered
showers will be possible through Friday afternoon/evening in and
around the Las Vegas Valley. Potential for a few thunderstorms is
still possible, especially later this afternoon and again Friday
afternoon, but confidence is still too low on these developing in
the Las Vegas Valley to include them into the prevailing TAF. As
with shower and thunderstorm activity in and around the valley,
winds may become erratic and gusty at times. Winds will shift to
more of a northwesterly direction tonight, remaining less than 10
knots before becoming light and variable overnight into tomorrow
morning. Ceilings may get down to 4-5 Kft at times, but should
generally remain aoa 6-7 Kft.

For the rest of southern Nevada, northwest Arizona and southeast
California...Unsettled weather will remain through Friday as a
weather system continues to circulate through the region. Main
concern through the TAF period continues to be the scattered shower
and potential for thunderstorms across the region. As with shower
and thunderstorm activity, winds may become erratic and gusty at
times up to 40 knots. Besides, winds should favor a southerly
direction through this afternoon with possible occasional gusts to
around 20 knots. Winds will decrease and shift to a northerly
direction tonight and before becoming light and variable overnight
which will remain through tomorrow morning.
&&

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

UPDATE...Pierce

DISCUSSION...Nickerson
AVIATION...Kryston

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