Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 032244

Area Forecast Discussion
National Weather Service Reno NV
244 PM PST Wed Mar 3 2021


Mild temperatures will rise to well above average Friday. Breezy
winds Thursday afternoon will increase Friday. Except for a few
snow showers this evening in Mono County, dry conditions will
prevail through Friday evening. Cooler temperatures and chances
for mountain snow and valley rain and snow return Saturday with a
more active winter weather pattern possible for much of next week.



The main change to the short term forecast was to increase winds
Friday and Friday night.

Low pressure is moving ashore over southern California this
afternoon. It is mostly just a mid and high cloud maker for
northeast CA, the Sierra, and western NV; however, as it scoots
over southeast CA and southern NV this evening there remains a
lower-end chance for some very light snow over western Mono
County and in the White Mountains. Given the HRRR now shows
nothing east of the crest and slightly less than half of EPS
members show any snow at all in southern Mono County, chances
mostly remain at less than 50%. In any case, little impact is
expected as trans-Sierra passes are closed and Hwy 395 is unlikely
to see more than a brief snow shower here and there (and then only
south of Mono Lake).

Thursday and Friday, south flow increases over the Sierra and
western NV in between a ridge axis over the eastern Great Basin
and a trough approaching the West Coast. These increased winds
and less overall cloud cover will improve mixing and push
temperatures up into the upper 50s to upper 60s across most lower
elevations with 50s for Sierra valleys. Friday looks to be the
warmer and windier day. Wind speeds don`t look overly strong
into Friday evening with gusts mainly 25-35 mph with Sierra ridge
gusts 60-80 mph. However, a burst of winds could accompany the
trough passage later Friday night.

As for precipitation, the system for late Friday night and
Saturday remains a fast-mover. Thus, snowfall amounts in the
Sierra and parts of northeast CA look to be limited; however,
snowfall rates could briefly ramp up near the trough passage
Saturday morning for some travel concerns. More on that below.

.LONG TERM...Saturday into next week...

*Main Message: Colder and wetter pattern change likely beginning
this weekend and extending into next week.

Changes made this forecast cycle:

*Increased POPs for Friday night-Saturday system as well as
throughout next week mainly for northeast California, the Sierra,
and extreme portions of western Nevada.

*Decreased high temperatures for next week.

Confidence continues to increase in a colder and wetter pattern
change across much of the western United States through much of next
week, starting out with an appetizer system for Friday night into
Saturday. Following the gusty winds on Friday, moisture moves into
the region for Friday night. The overall progression of this storm
remains quick according to the recent model guidance with peak
precipitation intensity from midnight Saturday through Saturday

While most of the precipitation will likely fall as snow during this
time in the Sierra, elevations around and below 5000 ft in Lassen
and Plumas counties could see a rain to rain-snow mix first before
snow levels drop to all valley floors by Saturday morning as the
shortwave trough`s front sweeps through. Even though the ensembles
as well as the deterministic GFS and ECMWF show the system pushing
through the region rather quickly, the trough looks to be dynamic
becoming more negatively-titled as it treks over the Sierra and
western Nevada. If the strength of the shortwave does indeed
materialize, then this would provide sufficient forcing enough to
see some intense snowfall rates for a short period of time in the
Sierra. This would include the Tahoe Basin and the Sierra passes.
Because of the more southerly flow, most of western Nevada is
expected to be shadowed out for the majority of this storm. As of
now, best chances for some light rain-snow mix to snow showers
for these locations would be Saturday morning, coinciding with the
trough`s frontal passage.

Here are the current NBM snow probabilities across the region:

Susanville: 10% chance for >1"

Truckee: 15% chance for >3", 45% chance for >2"

South Lake Tahoe: 25% chance for >3", 50% chance for >2"

Sierra Foothills: 25% chance for >1"

Reno-Carson City: 40% chance for a coating

Mammoth Lakes: 15% chance for >2"

The areas most likely to be impacted will be the Sierra passes where
3-6 inches of snow is possible. Expect hazardous travel during this

After a brief break on Sunday, most, if not all forecast guidance
points to a general trough setting up over the West for most of next
week. At this time, no significant atmospheric river type systems are
expected; however, the pattern overall looks to favor a 3-4 day
period of waves containing modest moisture with the potential for
a few inches of liquid equivalent moisture across the Sierra during
this period. The GEFS, EPS, and the Day 3-7 WPC Clusters all show
this potential outcome which has increased our confidence in not
only precipitation chances but also colder temperatures across the
region. Winds do not look too impressive at this time due to the
core of the upper-level jet remaining towards the south of the
forecast area for next week. To sum up, anticipate high and low
temperatures 4-8 degrees below average, periods of precipitation,
breezy to gusty southwest winds, and Sierra travel impacts from
Monday through next Thursday. -LaGuardia



VFR conditions will prevail through Friday. The only possible
exception is in Mono County west of Highway 395 into this evening
where terrain obscuration with isolated to scattered -SHSN are
possible. For KMMH, it is likely to remain VFR although brief
-SHSN are possible.

South winds will begin to increase in higher elevations Thursday
and Friday, with some of these winds mixing to the terminals.
The main effect would mainly be increased turbulence, although
the potential for LLWS may increase Friday night/early Saturday
with a fast moving trough passage. -Snyder/MJD


.REV Watches/Warnings/Advisories...




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