Q&A: Sunday Storm

So, anyone have any suggestions for a new hobby?  This one is killing me.

I'm going to try to anticipate and answer your questions about the Sunday/Sunday night storm.  Here we go...

Q: How much snow we gonna get?

A: Wow, you skipped right past the foreplay and went right in...

Q: Blah blah blah. What do the models say?

A: Here's the graphic:

Q: Why are they all different?

A: If they were all the same, we'd only have one model and a bunch of models would be out of a job. Like Melania.

The models are starting to agree on a couple of things:

• A later-arriving, slower-moving storm.  Slower pace means snow could pile up where it does fall, and in those spots, have a greater impact on Monday morning commute.
• A more compact precipitation field.  Oddly, the storm tracks on most of these models are very favorable for heavier snows in southern Wisconsin, but the snow gradients are really tight.

Q: Wait, your prediction isn't on there. Chicken?

A:  It's at the bottom of the post. 

Q:  Okay, which model should we trust?

A:  The correct one.  Alternatively, NAM.

Q:  What could still change?

A:  High pressure to the southeast could kick our storm farther northwest, or the track could flatten out and go completely zonal, or equatorial sea surface temperatures could suddenly cool, or a negative North Atlantic Oscillation could...

Q:  You lost me.

A:  No worries, I don't even understand negative NAO.

But seriously, the slightest movement to the north in the storm track, or a wider precipitation field, will make a big difference.

Q:  Exactly when will snow start and end in my backyard?

A:  I have no idea where your backyard is.  Ask me on Facebook.

Q:  Will schools be closed Monday?

A:  Probably not in Dane County.  Possibly southern Green.  More likely to the east and southeast. 

Also, wasn't that Melania joke funny?

Q:  Seriously, how much snow?

A:  Okay, here's the completed chart.

 
Q:  Shit!

A:  Disclaimer: still subject to change, snow lovers.  30 miles could turn this forecast upside down.

Q:  So, where should I go if I really want to see a shit-ton of snow?

A:  Elgin, Illinois would be a good bet.  No I-Pass?  Try Lake Geneva.
 
Q:  Will it be windy and cold too?

A:  First windy, then cold. 

Q:  Cool. When's the next storm after that?

A:  In December.

I'll be the first to let you know if anything changes!!

Sunday Snow Update: Models Align and Go Big

Either the weather models are really onto something, or they all went out and got shitfaced together last night.

Regardless, now would be a really good time to assess your Sunday travel plans.  More on that in a bit.

We're 3 days out from what will likely be our first significant snowstorm of the season.  This is when we expect to start seeing some model consistency, and the first runs of the day are giving us exactly that.  Track and intensity will still come into sharper focus the closer we get, but models now are at least similar in their interpretations of this event.

Here's how NWS is currently assessing the path of the low.  I mentioned in my post yesterday that the "ideal" track for heavy snow in southern Wisconsin is through central Illinois and into lower Michigan.  The NWS path cone gives us that.

(Click any image to embiggen it)

Here's an animation of the Euro's track:

And Euro snow totals:

GFS totals:

GFS-FV3 has consistently been really big with totals:

And the GDPS (Canadian):

Meanwhile, Accuweather is at 5.1" and the Weather Channel ranging 6-10".  Accuweather, for reasons even Accuweather can't explain, is frequently 2-4 degrees warmer than every other forecast on the planet.  And 2-4 degrees would make a huge difference with a storm like this.

All of these totals will change as track and intensity becomes clearer.  But this level of model agreement is enlightening 72 hours out.

My expectation is that by Noon Friday, NWS out of Milwaukee will have issued a Winter Storm Watch for our area.  That watch could come even earlier because of holiday weekend travel impacts.  Also tomorrow, we'll start to see the short-range high resolution models, which will be helpful in assessing storm track.

If you are traveling home on Sunday, and home is in the southern half of Wisconsin, I'd suggest getting home by 2pm or so.  In the meantime, fill up your gas can and test your snowblower.  And be sure to tease your kids with the possibility of school closings Monday morning.

One more note.  We haven't discussed wind yet.  I would expect a fair amount of wind out of this storm (from the northeast), making travel even more treacherous.  White-out conditions aren't out of the question.

Feel free to share if you have friends or family traveling Sunday.  Have a great Thanksgiving.  I'm around to answer any questions.

~Scott

Significant Snow Possible Sunday/Monday

Normally, I'd wait another 24-48 hours before posting about a storm that's a good 4 days away, but (1) I know a lot of folks will be traveling Sunday as they wrap up Thanksgiving weekend, and (2) there has been some model consistency on this storm for the last couple of days, which increases confidence.

Here's the quick take, and then we'll get into some detail:

• There will be a storm in our part of the country late this weekend;
• Current thinking on timing is late Sunday/Monday;
• It will bring rain to some, snow to others, and a rain-to-snow changeover for others;
• Because of the path of the storm, there should be abundant moisture, which could result in heavy (6"-plus) snowfall for some;
• Timing, storm track and accumulations will come into better focus sometime on Friday.

The two main mid-range weather models, GFS and Euro, have been literally alternating their interpretations of this storm.  The GFS model runs every 6 hours; the Euro every 12 hours.  During one run, GFS will show heavy snow in Wisconsin and Euro will show rain...then in the next run, GFS goes light snow and Euro goes heavy.  Since Monday, they've vacillated between 0" and 20" (GFS FV3) of snow in our general area.  This is pretty normal at this range.

Here's the set-up:

Low pressure comes on shore in the northwest early Friday.  You see it on the surface map west of Oregon:

In the middle of the country, a separate system will bring us rain Friday night and Saturday morning.

The second system moves southeast toward Utah and Colorado 24 hours later:

 

After dipping into the southern plains (and grabbing significant moisture from the Gulf), the low starts to head northeast, and is centered in Missouri Sunday morning:

 These tracks will wobble and change as we get closer to the actual event.  There are three key variables I'm watching that will greatly impact the type of precipitation we get, and how heavy it is:

1. How far south will the low get before it tracks northeast?  If it gets into northern Texas, it can pick up significant Gulf moisture. 
2. How much cold gets wrapped to the southeast with the passage of the first low on Saturday? This will help determine our precipitation type, and the timing of a rain-to-snow changeover on Sunday.
3. Where will the low track once it starts heading northeast?  If you scroll back up to the Sunday morning surface map, you can see high pressure in North Carolina.  This ridge, if it sets up, could serve as a "block" for our low, sending it slightly west and bringing us mostly rain.  Remember that a low cannot "move" a high; the high always wins when it comes to steering.  But if that high pressure is weak, or sets up father south or east, that allows the low to track through central Illinois and into lower Michigan, which would be the "ideal" storm track if you're hoping for heavy snow.  

Storm track is vital because the heaviest snow will fall the northwest and west of the low, as its counter-clockwise circulation pulls cold air in behind it.  The low position shown below (0z GFS-FV3 model; showing 7pm Sunday) is ideal for heavy snow in southern Wisconsin.  So it's no wonder that this is the model that's currently throwing down 20" in Janesville.

As we get closer to the weekend, shorter-range mesoscale models will come into play, so we'll be able to see how NAM, WRF and the Canadian model are interpreting track and intensity.  It's at that point that the National Weather Service will determine if we have enough confidence and model consistency to issue a Winter Storm Watch.

I'll be updating this storm throughout the weekend, and will probably have predictions for you on Friday afternoon.

In the meantime, let me know if you have any questions!

~Scott

Dueling Models and Our First Snow

GFS and the Euro just can't play nicely together.  Our two main weather models are fighting again, and if you're a fan of winter, you're rooting for the Euro to win.  If you don't, you're pulling for GFS.

If you've been keeping up with Rippeology, you know that my forecasts have favored the potential for early season snow and cold as we wait patiently for El Nino to set up.  In my Winter Outlook on October 14th, I discussed early season snow pack in Canada, and how that might impact our November.  In last week's post (pertaining to the current November 3-10 period), I showed you how cold and slow-moving systems could set us up for snow in the near future.

Those predictions look like they may verify.  It's snowing in northern Wisconsin this morning; some spots will see 3-5" by late afternoon.  And looking ahead 7-10 days, it's quite possible (likely even) that southern Wisconsin could see its first accumulating snow.

Before we discuss that, let's take a quick look at the short term:

• Today's rain will amount to over an inch in spots and be accompanied by some fog.
• Another system will quickly replace today's low. Look for rain to redevelop again Monday night as low pressure deepens to our southeast. 
• For election day on Tuesday, that low will also create a fair amount of wind. Here's noon Tuesday wind as that low quickly scoots north of the Hudson Valley.  Be prepared for blustery conditions as you head out to vote.

(Remember you can click on any image to enlarge).

 

Once we get through Tuesday, things start to get interesting.  Reinforcing shots of Canadian air will bring us our coldest temperatures of the season.  But this is where the GFS and Euro models start to throw down different solutions.

Take a look at 6:00 Friday evening.  Note where GFS puts low pressure, off the east coast:

 

 Now look where the Euro puts the low:

 

As a result of the closer proximity of the low (remember, winds rotate counter-clockwise around a low), here's how the Euro sees surface temps at 6am Saturday morning...

And how GFS sees it...

So, the models disagree by 8 degrees in Madison.  But that 8 degrees makes a difference.  If the Euro is right, the cold pocket settles long enough to sustain snow.  If GFS is right, temps easily rebound to more seasonal levels and snow becomes less likely.

Watch how the Euro spills cold air into our area over the next 10 days...

With that cold air in place, Euro sees two chances for snow: 1) a slight chance Thursday night into early Friday, and 2) a better chance next Sunday night into Monday.  Again, GFS disagrees.

Here's 10-day total snowfall from GFS...

And from the Euro...

So, which model should we believe when they can't both be right (but could both be wrong)?  The Euro tends to do better in mid-range, and seems to handle winter storm tracks better.  But we're in a transitional window right now, fall to winter.  And seasonal transitions are really hard to call because temperature is SO important.  That's why that 8 degree difference caught my eye.

I still favor snow for south-central Wisconsin over the next 10 days.  How much remains to be seen.  But rest assured I'll be watching it closely and keeping you posted!

~Scott