Lake Tahoe Snow on the Way? Powder Days Ahead?
The Lake Tahoe area is on the cusp of what could be a game changing next few days of wet and stormy weather or another weather model wipe-out. I for one am in the middle on this one thinking Lake Tahoe will see high winds on Friday night ushering in a brief period of snow on Saturday. If, if, if the low slides down the California coast and parks just offshore the Sierras and Lake Tahoe could be in a for a multi-day snow event which potentially could lay down 2-3 feet of light champagne snow. If the low parks too far west then we might see a foot or so and if the low parks over land we might see under a foot! Keep you fingers crossed that the cold low can jettison enough moisture into the Sierras and Lake to give us a great start to the season and a very Merry Christmas!
The models into late next week are in perfect disagreement where the GFS brings another big storm to the Sierras and the European builds high pressure and clearing skies instead. The GFS has actually (so far) been much more consisitent with the upcoming weather event so I will dance with the one who brung me and go with another round of weather late next week. I must be going crazy!
Area forecast discussion
National Weather Service Reno Nevada
320 PM PST Thursday Dec 11 2008
..high winds possible Friday night and Saturday…
..Periods of snow this weekend into early next week…
Forecast on track for significant cold frontal passage Friday night
and Saturday morning and periods of snow into early next week.
Before the real action hits…we must fist deal with a weak system
moving through northern Nevada tonight and into the Great Basin
Friday morning. There is potential for light showers near the
Oregon border/northern Washoe County to Pershing County. Any precipitation
totals should be just a few hundredths at best.
The very strong cold front will drop out of the Pacific northwest Friday and is
expected to move into northern Nevada and northeastern California Friday
evening and through Mono/Mineral counties Saturday morning. Ahead of
the front…strong winds are anticipated and have upgraded the high
wind watches for Mono/Mineral and the Reno/cirrocumulus zones to warnings as
confidence is fairly high that wind warning criteria will be met.
Locally run mesoscale model shows a nice standing wave over Mono
County with winds of over 80 kts ducting down into the leeside
slopes of the Sierra. Standing wave signature is not as pronounced
further north into Reno…but with strong tropopause fold…impressive 700
winds and locally run wind program supporting high winds..have
upgraded the watch. Left the watch going for Lake Tahoe as strong
winds in the lower elevations are not as certain due to more precipitation
moving into the basin than previous thinking. Winds are still
expected to exceed 100 miles per hour over the ridges…but snowfall tends to
kill wind potential in the lower elevations. Have added wind
advisories to all other zones as gusts over 45 miles per hour are likely ahead
of the front…but jet set up and mountain wave activity isnt ideal
for widespread gusts meeting warning criteria.
The best chances of snowfall in the short term is expected Friday
night along and behind the front. Model solutions support 0.25-0.4″
of liquid over the higher terrain of the Tahoe basin. With the cold
temperatures…snow ratios would lead to up to 3 inches in the lower
elevations…including lake level…with as much as six or seven
inches above 7000 feet. Snow is also expected to accumulate in
Lassen and eastern Plumas counties and over the Surprise Valley of
California and into northern Washoe County. Have included 1 to 3
inches of snow for these areas. In western Nevada there will be hit
and miss snow showers but dont expect more than local accumulations
of up to an inch. Scattered to numerous convective snow showers will
continue Saturday and Saturday night due to good instability with
cold air aloft…but at this time accumulations will likely be less
than an inch in most places…with up to a several inches in favored
areas of the Sierra. Would be more snowfall if there was better
moisture and orographic lift into the Sierra.
The shock and awe of this system will be the sudden drop in
temperatures with most valley locations struggling to get out of the
30s Saturday with Sierra temperatures only peaking in the 20s. A
significant change compared to the mild winter season we have
experienced so far. Milne
Long term /Monday through Thursday/…
models are starting to diverge on the details in the long term
however all solutions continue to indicate active weather through
the period. The main uncertainties continue to be the track of the
low along the West Coast and the time duration that it lingers in a
favorable position to bring precipitation to the County Warning Area.
The Euro has slowed down the track of the low over the last 24 hours
which would be more favorable for a prolonger precipitation event. The
latest GFS runs have trended a little further offshore which would
mean a better overwater trajectory and moisture tap…however if it
tracks too far to the west the best dynamics and onshore flow would
be limited to the California coastline. A blend of these two
solutions matches well with the going forecast so there are no
significant changes with the expectation that models come back into
line over the next few runs.
On Monday the low will be positioned along the West Coast somewhere
from northern California to Washington with embedded shortwave energy and
strong jet dynamics over the Sierra. There is also decent isentropic
upglide ahead of the low however it appears to be rather shallow.
This will all lead to periods of moderate snowfall in the Sierra
with decreasing chances to the south and east toward central Nevada.
A cold and unstable airmass will bring snow to all elevations with
limited shadowing from the Sierra.
There appears to be a break in the upper forcing sometime Tuesday or
Wednesday but models can’t decide when. Either way…kept probability of precipitation above
climatology values as precipitation can’t be ruled out during this active period.
The GFS keeps wanting to dig another cold low down the West Coast by
Thursday while the Euro has a much weaker wave that drops into the
northern rockies. There are several GFS ensemble members that support the
West Coast low and just as many that have a ridge building into the
West Coast. With all the model uncertainty…there is currently
little confidence in the details beyond day 5 however the active
weather pattern should continue. Jordan