Hey, thanks for joining
us here on 9 News Plus.
I'm meteorologist Chris Bianchi.
So you may have heard about the
amount of snow and rain that we've
seen in California and in some cases,
record levels of snow and
rain out in California.
It's been driven by something
you probably heard of something
called an atmospheric river.
So I'm going to explain what that is,
why California has seen so much rain,
snow and also for us here in Colorado.
How that's impacted our weather
because it's had some pretty
substantial impacts on our weather.
And by the way, this week, here,
this week of March the 14th,
we're gonna have some pretty
substantial impacts from that
atmospheric river set up as well.
So let's start things off though,
by taking a look at what we've seen
in California so far this winter,
and boy oh boy, this is just stunning.
664 inches in soda springs, CA.
By the way,
that does not include the March 14th,
March 15th Storm system,
which is likely to bring another couple of.
Feet of snow to a lot of these areas,
so some areas here almost for
sure gonna end up with 700 inches
worth of seasonal snowfall.
Put that in perspective,
what you're looking at here,
this is between about 50 to
60 feet worth of sniffle.
I want to repeat that Mammoth Mountain
600 inches of snow that is equivalent
to 50 feet worth of snowfall.
So to springs,
it's about 56 feet worth of snowfall.
So this is just again an
enormous amount of snow.
And yes, in the Sierra Nevada,
we can get these big systems,
we can get these big storm seasons.
We're likely going to end up.
In fact in some cases we've already
ended up with our highest snow totals
on record in some of these areas.
So just stunning by the way,
the southern Sierra Nevada mountains,
they're high snowpack to date on record.
So again,
this is record level stuff for us now.
It's not just snow,
it's also rain.
How about this in San Francisco
since October.
The first almost more than two
feet worth of rainfall and that
is more than 10 inches above the
season to date average force and.
The San Francisco area,
so just again enormous amount of
water that has just come on down,
it's all as a result of an atmospheric river.
Again,
this is a term you've probably
heard of quite a few times.
In fact you can see it.
This is as of March 14th,
you can see the atmospheric river in action.
So what it is,
it's a narrow ribbon of a just
a big plume of moisture.
It's basically again a river
about 30,000 feet up in the air.
It's about the level where
jet planes fly and where.
Where the jet stream is where you
get just this narrow plume about
two to 300 miles wide of really
just bountiful moisture that just
streams into areas and has numerous impacts.
So let's get in a bit more detail
about an atmospheric river, right?
So you get it at this point.
It's a narrow plume of a lot of water
that streams into the western US,
especially this time of year.
So there it is.
I just showed it to you on satellite.
It was very evident and
notice where it dips down.
It dips into Hawaii,
so sometimes this is referred
to as the Pineapple Express.
If you've ever been to Hawaii,
probably don't have to tell you it's warm,
it's muggy.
So when you're taking moisture
from Hawaii and you're taking
it on up into California and
taking deep tropical moisture,
another weather 1 on one as that
warmer air can hold more moisture.
So when you're going South with this,
you're at accessing areas that
have more water available to them.
And you're taking it into areas
that don't have typically as
much water available to them.
So again, a Pineapple Express,
atmospheric River,
Yukon area,
little pressure that sets on
up off the California coast,
it takes all that water and it streams
it and to southern parts of California
and central parts of the state as well.
So I kind of mentioned this
a short while ago,
atmospheric rivers often between about,
well 250 to 375 miles wide and that
means that that moisture is pretty
concentrated in a small space.
And so some places,
like Northern California, Oregon,
Washington may not even see any rain or
snow from an atmospheric river set up,
while Southern Central California's
get pounded with all of this water.
But specifically,
and by the way,
the amount of water that's within
one of these atmospheric rivers,
it's more than it's between 8
to 15 times more water than the
flow of the Mississippi River,
which is the largest river system in the
United States and one of the top five.
Largest river systems in the entire world.
So at this point,
hopefully you understand a couple of things.
One,
atmospheric rivers have a ton of
water within them because they
access the central Pacific Ocean,
which has a lot of tropical
and humid air available to it,
and they're fairly narrow in
terms of their scope.
Now for the Sierra Nevada specifically,
I was just mentioning, right,
how there's about 50 to 60 feet
worth of snowfall that's falling,
almost all of it from these
atmospheric rivers.
So this is how it works for
an atmospheric river.
The best analogy for an atmospheric river,
this one I use all the time.
Think about taking a wet sponge and
then just squeezing out all that water.
That's what basically mountains
do with these atmospheric rivers.
So you get all that moisture that's
just being streamed into these mountains.
And by the way,
remember,
the Sierra Nevada can go up as
high as 14 to 15,
almost 15,000 feet in elevation.
So you get this,
you've got the Pacific Ocean,
right? It's flat.
And then next thing, boom.
You've got these mountains and it forces
the air to rapidly rise and condense.
And what that does is it
produces a ton of snow. So again,
what I was mentioning with the sponge,
that's what these mountains do
with these atmospheric rivers,
they just take every last bit of moisture
out and it's very sudden rise because again,
when you go from Hawaii to the Sierra Nevada,
there's nothing to stop that that rise.
So this air rapidly rises,
it condenses into all that snow,
and the result is what I
was just showing you.
600 plus inches worth of snowfall
and that just thinks the upslope
from these atmospheric river events.
Now back here at home in Colorado,
we felt some of that notice here on
the snowpack map here across Colorado.
How the Arkansas,
the S Platte,
yeah they've had decent snow seasons,
but notice how the San Juans and
the Gunnison River basins are
doing way better than basically
everybody else across the state.
The Gussin and the San Juans are
often usually getting a lot of their
moisture from their these atmospheric rivers.
Set up.
So an old,
kind of very basic 101 of Colorado weather
forecasting is if it's raining in LA,
it's probably gonna snow in the
San Juans a day or two later.
And that's kind of what we're looking at.
In fact, this is as of March 14th.
I know some of you may watch this later,
but this is as of March 14th, 2023.
Notice LA how it's raining and by the way,
just dumping rain once again for us
in the southern parts of California.
Sierra getting pounded with more
feet of snowfall.
Well, guess where all that water's going?
Yeah,
into Colorado as we get into
your Wednesday and your Thursday.
It's an atmospheric river setup,
which means again,
the San Juans and the Gunnison River
basins will probably get the most
snow at this upcoming storm system.
And there you go,
winter storm warnings up for the
mountains of southwestern Colorado.
We're up to two feet where the snowfall
will come down in those areas,
but then notice a little further
east and N we're only talking
about maybe 6 to 14 inches worth of
snowfall as you get further east and
away from that atmospheric river.
And then for us here in Denver.
Well, we're on the Lee side of the mountains,
which means we get downsloping with
the opposite of the upslope winds,
which I was mentioning with that
sponge analogy.
Yeah,
we get the other side of things
where it's basically adding a hot
up bunch of hot air to a sponge.
You basically just dry things on out
and we get maybe a few snow showers
on your Thursday and that is pretty much it.
But it's kind of recap things when
we're talking about an atmospheric
river in California,
a those atmospheric rivers can oscillate.
They can sometimes impact
the Pacific Northwest.
Seattle, Portland, OR often feel those,
but this season it has been relentless
for central and Southern California
where we've had an atmospheric river
again and again and again and again,
and that has pounded that part of
the state with these narrow 2 to 400
mile wide bands of intense moisture.
And then into the mountains
you get that upslope flow,
you force the air rapidly rise,
it condenses, it,
squeezes out every last drop of moisture
and results in just feet upon feet.
Worth of snowfall and that's why we've
seen the season we have out there in
California and it has been one to remember.
And here in Colorado we're
certainly feeling some of the
impacts from that as well.
So hopefully that answers your
questions about atmospheric rivers,
how they work and why they've
led to quite the season for
friends out in California.