Matt Makens

We tend to enjoy the model flip-flop that occurs when we look out past a few
days and see those storms on the horizon from days 5 to 14. You know the ones I
am talking about.

From hyped up headlines to snow-lovers tears, storms modeled beyond about day 5
are fun to watch but obviously over-published at times. With that in mind, I'm
going to publish information about a storm farther away than 5 days ;-)

Some of you commented on previous posts about the potential system for next
week, so let's see how it looks today. 

Side-by-Side of the GFS Ensembles from this morning's run to that of yesterday.

And the same but with Euro Ensembles.

In both cases we see discrepancies with consistency between the individual model
runs, and across both models. Although today's data is more consistent with a
strong trough barreling over the Great Basin in the middle of next week. Where
it ultimately tracks, and with what strength, could be rather 'interesting' for
Colorado and Denver. 

Two thoughts based on the modeling to date, not just the examples shown above.
Should we have two troughs move through as shown more so in yesterday's models,
there will be concerns over moisture availability for the second trough to work
with. By following quickly behind the first trough, moisture will be pushed too
far to our east. Second, I question the development of the second trough due to
energy, with a leading trough taking some of the potential vorticity with it to
the east there's less energy available for the second trough, theoretically.
That's an overgeneralization of the situation but I don't want to get into the
trenches today.

Notice how the most recent model runs are less excited about a first trough,
rather build up the second one. That's partly the dynamics at play I mentioned
and if this scenario continues to play out it'll mean larger impacts on Colorado
and the region.

I want to show you some data we use internally, these are precipitation
probablities run overnight and indicate the probability of receiving certain
threshholds of precipitation - not snow, total QPF. Here's one that ran on the
7th:

This one ran the next day:

That's an incredible change between the 15th and 16th's projections with just
one day's worth of data updates. 

This is part of the hype-drive of why I (we) continue to see cherry-picked
images of the robust outputs thrown on social media and yet I don't see the
weaker solutions posted as a follow up. I know why, I get it, but it is still
frustrating. 

Honestly, the solutions that remain possible are everything from a Northern
Plains blizzard, to our neck of the woods, to south of the state line; there's
an argument for those three placements. To be south of the city has support from
a rapidly tanking PNA which indicates that troughing for the western U.S. A
track right over us will be the path of least resistence with a baroclinic zone
stretching from Denver to Chicago. A northern track still remains a curiosity
for me... the long-anticipated stratospheric warming event is continually
delayed, and the AO is reacting to that delay. We can see that cold temperatures
originally progged for the Northern and Central Plains are much milder now as a
result. Without a strong northerly push and teleconnection support I feel as
though the current PNA may be overdone and the flow too progressive to allow
digging of the trough over the Four Corners. A northern Colorado or 1-80 Low may
be more probable, if indeed the weakening of the AO signal continues and if the
PNA should start to weaken. This northerly solution has the support of analogs
to the current GFS forecast (looking at past years with a similar current state
of the GFS and what ended up happening 8 days later). I know these are musings
of an overly fatigued meteorologist but they are all things that come to mind as
I think of next week's system. 

As of right now, I don't think yesterday's dual-trough scenario is all that
probable based on dynamics as I see them. I think today's solution is more
appropriate but the track will likely jump wildly over the coming days. Just me
chatting here, feel free to leave your thoughts below in the comments section.
It 'feels' like it won't track to slam Denver, but folks from Texas to Missouri
sure could be soggy, then deep snow for the Upper Midwest somewhere. 

Trying to take all data into consideration, here are the morning snowfall
probabilities. I just left the setting at 10:1 for the sake of this example.

Bottom line, we will continue to watch it with scientific interest, but aren't
about to talk about next week to our public users just yet. Thanks for following
along with us, Insiders!

It's there, then it's not: next week's snow for Colorado and Denver