Had a rough morning.  Woke up in a lot of pain and spent most of the day in bed.  Picked up a stomach virus I think.  I'll spare you the lovely details of my morning.  I'm back at the computer this evening as my wife is handing me drinks to nurse me back to health.

I'm glad it came when we have a break from the storms!  We did see some snow fall yesterday afternoon.  I had a forecast out for a coating up to 2 inches on the mountains.  Most saw that with one exception.  Heavier precip sat just along and North of the North shore of the lake.  So those ski resorts to the North side are were reporting 3-4 inches of fresh snow up top this morning.  We've been on a good trend lately of beating the forecast.

The next storm is winding up off the coast and will be pushing moisture into Northern CA by Monday night.

Not much change to the forecast for the upcoming week.  It's still a complicated storm and the forecast models are not in agreement on timing and details still.  But the overall forecast of 1-2 feet on the mountains by Thursday morning and 1-2 more by Saturday morning is still the forecast, that I have had out for several days now.  Let's do a brief summary of the model differences by day.

Tuesday:

There is good forecast model agreement through Tuesday night.  After more sun Monday and highs back into the 40's on the mountains and 50's at lake level, we should wake up to light rain/snow showers Tuesday morning.  At first we have a flow out of the South ahead of the cold front.  So good shadowing of the precip East of the crest.  We have seen this many times before when the Southerly winds are the wrong direction to push the precip over the mountains.  We can have heavy snowfall West of the basin along the crest while it's not doing hardly anything across the Tahoe basin.

Here is a look at the European precip forecast map through Tuesday as an example.  You can see up to an inch of liquid on the West slopes of the Sierra, but barely any precip making it into the basin, especially the East side.

So that's what we expect for Tuesday.  It will be in the 40's at lake level with snow levels sitting around 8,000 feet through the day.  We could be seeing moderate wet snowfall above that along the crest, and mainly light rain showers in the Tahoe basin. 

Then the cold front pushes through during the evening bringing heavier snowfall and dropping snow levels below lake level.  The timing on the snow level drop versus the speed of the precip is always tough, but above 7000 feet expecting mostly snow with this heavier band, and snow to lake level overnight Tuesday night.  We could see 4-9 inches of snow on the mountains on the East side of the lake by Wednesday morning, and 10-18 inches on the West side.

Wednesday:

Here is where the forecast models start to diverge.  The last few days the European model showed a 2nd wave of heavier snowfall moving in Wednesday into Wednesday night, and the GFS had a break on Wednesday.  Today they have flipped with the GFS now showing a 2nd wave and the European model showing a break by Wednesday night into Thursday.  Where the European model shows a high end of 1.9 inches of liquid near the crest, the GFS now shows up to 3.5 inches!

The 18z run on of the GFS today was the 2nd run in a row showing this wetter scenario.  I'm not sure what the buy into with the models flip-flopping less than 3 days out from this 2nd wave.  All I can do for now is to use the average of the two like usual, and tell you to lean towards the low end to be safe for now.  We could see an additional 4-12 inches of snow on the mountains by Thursday morning. Here is the the 48 hour forecast.

Again, I'm staying with the low end.  So overall my forecast hasn't changed the last few days.  I'm still watching for 1-2 feet of snow on the mountains above 7,000 feet in total by the Thursday morning reports.  It's really not a lot of snow for 48 hours.  It's only an average of a quarter to half an inch of snow per hour.  As a comparison the last storm we averaged around 1 inch per hour over the 3 day period.

Thursday:

The GFS is faster to bring in the 3rd round of heavier precip during the day Thursday as the main area of low pressure approaches the coast.  The European model has a break Thursday and then brings in heavier precip Thursday night.  The GFS is also wetter in total.  The main difference would be higher snow ratios if the snow fell at night versus during the day.  Taking the model average we could see an additional 9-17 inches of snow by Friday morning.

Friday:

The GFS is winding things down as the low spins down the coast and then inland over Central CA.  The European model drops the low further South before turning inland.  Thursday-Friday is mainly timing differences with the GFS bringing the moisture with the low in Thursday into Thursday night, and the Euro Thursday night into Friday.  Friday night the storm should wind down with maybe some scattered snow showers.  Taking the model average we could see an additional 5-9 inches on the mountains by Saturday morning.

As you can see, this is a complicated forecast.  After the cold front drops snow levels Tuesday evening we don't have to worry about the snow level forecast.  Just have to worry about the timing and track of the subsequent waves of precip Wed-Fri.  If there is no 2nd wave Wednesday and we see a break, and then the low moves down the coast further West away from us and into Southern CA, then we could see below the low end of the forecast.  If we get a 2nd wave Wednesday and the low tracks over us Thursday-Friday, then we could see the high end or even higher at some mountains.

Look at the crazy 12z GFS with a heavy band of precip Thursday into Friday bumping liquid totals over 6 inches near the crest.

It backed off again on the 18z run, but it still has over 5 inches of liquid in total along the crest by Saturday morning.  The European model tops out around 4 inches.  The Canadian model is showing around 4 inches, and the ensemble mean runs 3.0 - 3.5 inches.

Again, lean towards the lower end of the forecast for now.  We saw 2-4 inches of liquid the last storm, but 20:1 ratios on average which created 40-80 inches of snow.  This time we should average closer to 10-12:1 on the mountains.  Here is the updated 4 day snowfall forecast by next Saturday.  Please don't redistribute without my disclaimer that we are leaning towards the low end of the forecast, and that this is a complicated storm with many moving pieces that aren't certain.

The last storm had these same issues with a cold front, subsequent waves of moisture, and the track of the main low.  We got hit just right with all of them and the forecast for 3-5 feet ended up being 4-7 feet by the end.  For this storm I have had a forecast for several days now of 2-4 feet.  We could see only 1-3 or if everything comes together just right again we could see more than 2-4 feet.  All we can do is watch as each piece moves in.

Aside:

I noticed something interesting on the 18z GFS precip forecast this afternoon.  Not sure if it's a sign or I'm just delirious from being sick?  I was thinking maybe I could try to sell it on Ebay for 28k like that girl did with the Virgin Mary grilled cheese.

Long-Range:

The trough still looks like it is going to settle in over the West Coast through the week of the 19th.  That should allow more storms to drop down from the North Pacific and bring us some more snow.  

There are some signs showing that we could finally ridge up the week of the 26th.  Hopefully we get a lot more snow by then.  We need another 6 feet or so to break into "Miracle March" territory.

Stay tuned, stay healthy...BA

It's ON!!!

Call me crazy, but on March 17, 2018, I am going to "Feel the Thrill of the Chill" by taking a quick dip in the chilly waters of Lake Tahoe to raise money for Special Olympics. This is my fifth year supporting a great organization. But I can’t do it alone. I need your help, are you with me?

https://specialolympics.donordrive.com/index.cfm?fuseaction=donorDrive.participant&participantID=8972

Trying to get at least one donation from each of the 50 states.  I'll give a shout out on here when I get a new state!  Thank you to Pennsylvania for joining the list today!

Thank you,

Richard