The weather is going to change and change dramatically starting late Friday with winds ahead of the artic front heralding in much colder air. The precipitation appears to be spotty initially but a number of the weather models are suggesting that the low will set up off of the northern California coast which would allow Pacific moisture to betapped into creating a possible major and prolonged snowstorm for the Lake Tahoe basin and the entire Sierra. Snow easily may fall to the hills around the Bay Area and definately should coat the Nevada valleys as well.

Keep you fingers crossed that the low does indeed setup off of the coast and taps the Pacific moisture but whatever happens it will be cold enough for at least 5-7 days for possible around the clock snowmaking with a bit of mother natures natural stuff thrown in for good measure.

Here is the weather synopsis for December 10:

Area forecast discussion
National Weather Service Reno Nevada
235 am PST Wednesday Dec 10 2008 

Short term... 

Quiet weather will continue through Thursday before significant
changes develop by Friday. A high pressure ridge will remain along
the West Coast today keeping Valley High temperatures a few degrees
above normal. Middle and upper slopes will remain warm as inversions
remain in place. A weak upper level disturbance will pass over the
area Thursday evening which will retrograde the ridge and bring some
cloud cover and slight cooling to the northern half of the County Warning Area. A few
light showers cannot be ruled out Thursday night over northern Nevada
associated with this disturbance...but the chance of measurable
precipitation is too low at this time to include in the forecast. 

A dramatic change will occur beginning on Friday. A strong cold
front will approach the area from the north on Friday. Strong
pressure and thermal gradients ahead of the front will bring breezy
conditions to the area by Friday afternoon with stronger winds
expected Friday night into Saturday morning...especially in the
Sierra and along Highway 395. This will break any inversions and
bring the warmest weather of the week to many areas over the southern
half of the area. Model soundings and cross sections also indicate a
critical layer developing near ridge top with very stable air above
the critical layer. This indicates impressive downslope wind
potential developing to the Lee of the mountains...especially Friday
night. Wind gusts during the day on Friday will likely approach
30-35 miles per hour especially north of Highway 50. By Friday night...winds in
excess of 50 miles per hour will likely develop in some lower elevations with
locally stronger winds. The main question is how widespread these
stronger winds will be. 700 mb winds increase to 50-60 kts by Friday
night which will likely cause winds along the Sierra ridges to peak
above 90 miles per hour. Therefore wind statements of some kind will be needed
in some areas for Friday night. Later shifts can analyze this
potential and issue statements as needed. 

Good frontogenesis will also develop along the front by Friday
evening over northern zones. Probability of precipitation were increased over the far north as a
moderate area of precipitation will likely be located right along
the front as stability decreases. Snow levels will drop quickly as
the front passes with a quick change from rain to snow expected.
Gmcguire 

Long term /Saturday through Tuesday/... 

Really no big changes in the synoptic pattern from the 00z model
solutions again. A large and cold trough will be over the west
most of the period with additional energy dropping south along the
Pacific coast. 

Arctic cold front will be pushing across the area Saturday bringing
a good chance for at least advisory level winds ahead of it. Front
looks drier today than yesterday. Expect a chance of rain ahead of
the front and snow behind it. Temperatures in the Sierra will be
below freezing for several days...and the Nevada valleys high may
struggle to reach 35-40 degrees Sunday through Tuesday. 

Model agreement is better Sunday through Tuesday with somewhat low
spread in the ensemble data. Only big concern is slightly
different speeds in the models on how fast the energy will drop
south. 00z GFS is a bit slower than the European model (ecmwf) which has the low
clearing the area late Tuesday night/early Wednesday. The GFS keeps
the low over the Sierra until Wednesday. Even most ensemble members
show a low or trough slowly moving south along the coast Sunday
through Tuesday. 

The biggest concern for this period is the moist onshore flow Sunday
through Tuesday...with favorable forcing and instability in the
model data. The pattern immediately brings the concern for a multi
day snow event in the Sierra. Have increased probability of precipitation Sunday and Monday
to likely in the Sierra due to the improved model agreement and
lower ensemble spreads. Snow ratios will be high...on the order of
20-30 to 1 for the Sierra peaks and 15 to 1 for areas down to 6000
feet including the Tahoe basin. So even quantitative precipitation forecast totals as low as 0.50
inches would bring significant powdery accumulations to the Sierra. 

Snow amounts may also be a concern for western Nevada Monday and
Tuesday. Based on the instability and lift in the 00z runs...snow
should easily push over the Sierra. 

Still several days to go until the event arrives so there could be
changes in the model solutions. For now they seem to be trending
toward a better chance for a winter storm.

Lake Tahoe Weather-Short Term

Quiet weather will continue through Thursday before a pattern change
takes place. High pressure will remain along the California coast through
Wednesday. A decent pressure gradient along the Sierra this morning
has produced ridge gusts up to 70 miles per hour over the Sierra in the Tahoe
basin and above 90 miles per hour in Mono County. These winds will decrease
during the morning…will still gust up to 50 miles per hour between sunrise
and midday before dropping off. Northeast surface winds over Lake
Tahoe will be 15-18 miles per hour with gusts 25-30 miles per hour early this morning
before diminishing after sunrise.

Temperatures will be slightly cooler in some valley areas of western Nevada
as strong inversions set up once again. Warm air aloft increases
today which will allow higher elevations to warm several degrees
from yesterday. High temperatures in western Nevada valleys will remain in
the middle 40s today…while highs in the Sierra will range from the
middle 40s to around 50.

A weak short wave will brush northern and eastern Nevada on Thursday which will
bring some cooling to northern areas of the County Warning Area as the ridge retrogrades
into the Pacific. Otherwise no significant weather is expected with
this feature. Gmcguire

Lake Tahoe Weather Long Term

Made a few adjustments to the forecast as timing confidence grows
for initial storm late this week. Really no big changes in the 00z
model solutions. Model agreement increasing along with decreasing
spread in the ensemble data fro Friday and Saturday. Ensemble spread
remains high for Sunday and into early next week where the forecast
is less confident.

GFS/European model (ecmwf) bring the front into the northern areas late Friday/early
Saturday and drive it into the southern areas Saturday afternoon.
Surface thermal and pressure gradients increase rapidly Friday
afternoon and Friday night ahead of the front. With highs forecast
to drop 20-30 degrees between Friday and Sunday…little doubt there
will be a good to significant wind event as the cold front blasts
across the area. 700 mb winds at 55-65 kts…with GFS soundings and
cross sections showing a favorable thermal profile that can produce
strong gusts along the Sierra front. Significantly increased wind
speeds to near Wind Advisory criteria /gusts 45 miles per hour/ for Friday
night…which may be on the low side for some locations.

On Saturday best chance for rain with an abrupt change to snow will
be along the front. Behind the front…cold moist and unstable air
will be in place so at least snow showers will remain possible into
early next week.

For Sunday and Monday…much uncertainty here as models have
different ideas on how additional moisture and energy will reach the
area. What seems certain at this time is temperatures will remain
below normal with possibility of a second system affecting the area.

00z GFS solution moves energy south along the Oregon and Washington
coasts. This would allow the system to direct Pacific moisture into
the Sierra and western Nevada Sunday through Tuesday. Certainly a
favorable pattern for significant snow accumulations.

The 00z European model (ecmwf) keeps the low onshore and thus has lower amounts of
moisture for Sunday and Monday. However…still enough to produce a
chance of snow all areas with the cold temperatures. So increased
snow chances to at least 30 percent all areas for Sunday and
Monday. The European model (ecmwf) flattens the flow Tuesday…but pushes the jet
directly over the Sierra…which also leans toward being favorable
for accumulating snow if it verifies.

Book your Lake Tahoe Vacation Rental Cabin, home or condo now!

Statement as of 3:10 PM PST on December 08, 2008

… Weather pattern change expected by this weekend…

A very cold North Pacific storm system is expected to push into
the region by this weekend… bringing an abrupt change to the mild
and dry weather we have been seeing since the Thanksgiving Holiday.

This cold system will bring strong winds to the area Friday and
Saturday. A significant cold front will sweep through our area
early Saturday morning. Temperatures are expected to plummet this
weekend with highs on Saturday and Sunday only in the 30s across
most of the lower valleys… highs in the teens and 20s in the
Sierra. Snow levels are expected to drop to all valley
floors… but the amount of moisture with this system remains
uncertain.

If you have travel plans for the weekend in the Sierra and western
Nevada… be prepared for winter driving conditions. Check our
website at www.Weather.Gov/Reno for updates on how these storms
may impact weekend travel.

It looks like we may actually have a pattern change to wet weather starting a week from Sunday. Read Accuweather blog from Ken Clark

The models have changed again and not in our favor if you want snow in the Lake Tahoe basin. It now appears that a massive high pressure ridge will be in place for at least the next week with no significant storms in sight. I have decided to write this entry with a total lack of optimism in the hopes that will change things back to a wet pattern! Ok, Ok I am superstitious but of that is what it takes to get some snow into the Lake Tahoe area so be it!

We should take all of this in stride however if last winter was any indication. Remember that we had no storms until the third week of December and even that was not a large storm. But, just after New Years we got whalloped with 6-9 feet of snow. That set us up for the rest of the winter which was stormy through February and then the storm door shut down again for March.

Many winters in the Sierra don’t really start until January so it is not too late to have a banner ski and snowboarding year.

Dana

Screenshot of December 17 GFS Model