Christmas Blizzard 12/20 - 12/28

[Minny_Weather]

SREF plumes are actually pretty split on making my main ptype snow for the first low.

 

[hawkstwelve]

12z Euro with another big shift to cooler conditions for Christmas.

 

Unfortunately, it's also maintaining the freezing rain threat. Sure hope we can avoid this!

[Minny_Weather]

Euro is definitely way farther east with the system. throwing a curveball for many and knocking on LNK's doorstep

00Z

 

12Z (most recent run)

[hawkstwelve]

24 minutes ago, Minny_Weather said:

SREF plumes are actually pretty split on making my main ptype snow for the first low.

 

Thanks for reminding me of these. The EMC GEFS plumes are trending in the right direction for FSD. The 06z run had the highest percentage of p-type being snow of any run so far and luckily, it shows freezing rain chances at being under 10%. I wish the EPS had a similar graph so we could compare it to it's own ensemble suite but I haven't found one like this yet.

[hawkstwelve]

12z EPS is the best run so far for many spots outside of W NE/SD. Big jump eastward with the snowfall totals.

 

[Hawkeye]

Models still can't agree about the initial wave of rain Friday.  The trend is back south, possibly missing Cedar Rapids completely.  The GFS and a few other models still get a couple tenths up here.

[Black Hole]

Model round up for down this way. Snow in the air starting to look like a reasonable bet. Marginal temps and daytime timing should keep accumulation at bay. 

[hawkstwelve]

12z EPS probabilities of receiving 1+ inch and 3+ inches of snowfall. Pretty big increase across the board. In fact, Sioux Falls now has a higher chance of receiving 3+ inches on the 12z run than the 00z run showed of us receiving 1+ inch.

[Clinton]

1 hour ago, Minny_Weather said:

Euro is definitely way farther east with the system. throwing a curveball for many and knocking on LNK's doorstep

00Z

 

12Z (most recent run)

Wow the Euro even wraps some snow around for me.  Temperature trends are getting colder.

[Clinton]

The Euro showing 3 to 4 inch rainfall amounts for mby.  I will need to look but that will likely break some records for December. 

[MIKEKC]

I know, its the ICON!!!  BUT.....other data runs are getting close to this. 

There is a trend for an upper level low to form and this run is showing Christmas evening for KC. We're in it!! The ole comma head, those can get interesting. Trended colder on this model too. 

[Minny_Weather]

2 minutes ago, MIKEKC said:

I know, its the ICON!!!  BUT.....other data runs are getting close to this. 

There is a trend for an upper level low to form and this run is showing Christmas evening for KC. We're in it!! The ole comma head, those can get interesting. Trended colder on this model too. 

ICON isn't as trash as some people want to claim it is. It's won a couple of storms before.

[MIKEKC]

GFS in on the ULL and colder solution.....WHO gets the Christmas Miracle.

[Jayhawker85]

49 minutes ago, MIKEKC said:

I know, its the ICON!!!  BUT.....other data runs are getting close to this. 

There is a trend for an upper level low to form and this run is showing Christmas evening for KC. We're in it!! The ole comma head, those can get interesting. Trended colder on this model too. 

I thought the 540 line was the rain/snow threshold? That’s showing it’s in central ks?

[Black Hole]

24 minutes ago, Jayhawker85 said:

I thought the 540 line was the rain/snow threshold? That’s showing it’s in central ks?

540 is the statistical point where there is a 50% chance of rain and 50% of snow. It often is where the switchover occurs if there is lots of cold air coming in or you have steady and heavy precip but often is not if there is limited low level cold. In those cases the upper levels are colder than "needed" but the lower levels are too warm. Hope that helps. 

I've seen snow at up to 546 thickness when it came with thunderstorms. 

[Black Hole]

I should probably add to my previous comment that model inconsistencies aside, if there was a place where a switchover could occur with relatively warmer temperatures it would be in that northwest portion of the wraparound. Quite often the winds go nearly calm aloft allowing for the diabatic cooling to cool most of the lower atmosphere to 32-34F. Then as soon as the snow stops the temp will jump to 40F. 

[CentralNebWeather]

NWS blend. 

[hawkstwelve]

00z GFS looking much closer to the Euro solution now with the handling of the second (third?) low. Omaha is now in play for Christmas snow.

CMC is now off on it's own.

[jcwxguy]

Wow

[Clinton]

Canadian further east.

[bud2380]

This storm may have some twists and turns yet. So far the one thing that hasn’t changed is widespread heavy rain. And I am keeping my fingers crossed that stays. 

[Hawkeye]

The 00z UK moved the heavy rain into western Iowa and eastern Nebraska, and Cedar Rapids gets stuck in a dry hole.  This run doesn't even drop any rain in CR until Monday night.  Every model is still a little different.  There are a lot of pieces of energy spinning around, making it difficult to pin down the details.

[gabel23]

Looks like we have thermo, precip and precip type situation going on. I like the fact that the nam in its early stage is taking on a euro/gfs approach. Let’s hope the euro had it right all along. 

[gabel23]

12 minutes ago, Hawkeye said:

The 00z UK moved the heavy rain into western Iowa and eastern Nebraska, and Cedar Rapids gets stuck in a dry hole.  This run doesn't even drop any rain in CR until Monday night.  Every model is still a little different.  There are a lot of pieces of energy spinning around, making it difficult to pin down the details.

Looks like the current gfs and today’s euro. 

[hawkstwelve]

00z CMC ensembles with a big time jump in probabilities of 1+ inches. Even 3+ inch chances ain't half bad now. More closely aligns with the new GFS/Euro pairing than it does with its own 00z OP run. 24-hour precip ending Tuesday evening shows a decent area of wraparound precip with that second low. Also another shift to cooler temps over a large area on Christmas Day. 

Might we be starting to see at least a little bit of consensus among the models? 

[hawkstwelve]

00z Euro literally jumps right over Sioux Falls with the 10+ inch totals and we end up with 3. I'd still happily take it! Sioux City to Omaha gets buried on another run. 

This is looking very similar to the 00Z GFS. 

[gabel23]

Looks like euro is holding true. I’m loving the trends tonight… The only problem is what happens to the area of low pressure? Looks like trends are slowing down and the euro has occlusion occurring over Iowa; that would bode well for heavy snow to the northwest. Gfs, cmc, and nam are also starting to show that as of tonight…

[Grizzcoat]

ULL's like this one are notoriously hard to forecast. Which is why I have no clue that NWS DMX posted this map just on Wednesday. Way too much time to STILL go on this. Something tells me there might be just a little bit of bias involved. Now I have pic saved on here and if the NWS eats Crow ( deletes the pic) - got this to show them :O)

[Minny_Weather]

Someone is going to cash in on this one. I don't think it'll be me, but someone will be happy at the end of all this. 

It would be nice to get the ground covered here, but I think I might need to wait until at least January.

[Grizzcoat]

I got good vibes on parts of IA getting at least accumulating snow on this one. Definitely seeing colder / eastern trends with much of guidance. 

Latest AFD from DMX -

Still watching for the potential for wintry precip types Tue-Wed.
GEFS/ECENS probs for accumulating snowfall have increased over at
least the western half of the state, although with temps progged
to hover around 0C in the lowest few KM above the surface it is
difficult to make any confident assessments on ptype at the
moment. Forecast continues to mention mostly rain but does have
some periods of wintry mix included. This will need to be
monitored over the coming days.

[Grizzcoat]

Decent snows now on 06Z GFS into C.IA...............

Twin Cities also seeing good snows this run......... 

[Minny_Weather]

3 minutes ago, Grizzcoat said:

Decent snows now on 06Z GFS into C.IA...............

Twin Cities also seeing good snows this run......... 

Mankato gets seriously slammed

[Grizzcoat]

Still snowing at this hour for many areas that have received appreciable accumulations-

[Grizzcoat]

MPX's moring AFD-

An upper level low is forecast to
develop on the heels of the initial surface low passage, which will
act as a secondary mechanism for continued rain chances through the
middle of next week. Grand Ensemble QPF output has increased,
illustrating the potential for area storm totals in the 1-1.25"
range. Indications are that most of the precipitation will fall as
rain from Sunday-Tuesday, however the arrival of colder air/wintry
precipitation to the northwest of the upper level low is plausible,
as this idea is a common theme within upper-level lows this time of
the year. A fair amount of uncertainty in where/when a transition to
a wintry p-type exists at this time, so we will have to keep
reevaluating this potential over the coming days.

[hawkstwelve]

A couple interesting tidbits from FSD's AFD. They aren't willing to bite yet on any significant snowfall here but they're noticing the same trends we are with models starting to converge on a solution. 

The big story in the forecast remains the potential for the first widespread and substancial precipitation the region has seen in quite some time. This risk will be due to a series of troughs just now beginning to enter the Pacific Northwest and a secondary trough moving into southern California. Sampling of these systems while over the Pacific has likely been poor, leading to quite a bit of model fluctuation. However with both of these troughs and the coinciding jet streaks now onshore, the hope is for better sampling and resolution in model guidance with today`s model runs.

The forecast becomes much more uncertain from late Sunday night through Wednesday, as there is a great deal of uncertainty on the eventual evolution of a trough that slows and deepens over the Central Plains Monday into Tuesday. The ECMWF remains deeper and further northwest than the GFS, but both model camps have shown some progression towards a common solution. We see the same signals in ensemble guidance though there seems to be much more consensus in the ECMWF ensemble than the GFS ensemble (higher and more concentrated probabilities versus lower and more broad brushed).

[hawkstwelve]

06z ICON is looking pretty similar to the GFS/ECMWF. 

[Minny_Weather]

6 minutes ago, hawkstwelve said:

06z ICON is looking pretty similar to the GFS/ECMWF. 

Probably the best run for me yet.

Which is still only about 3", but it's still the best lol

[Minny_Weather]

Worth noting that we probably shouldn't be taking any of the euro's operational runs too seriously right now. EPS is still all over the place.

[hawkstwelve]

Speaking of the EPS, here's a comparison between the low locations on the 06z EPS and GEFS. 

[Black Hole]

5 minutes ago, hawkstwelve said:

Speaking of the EPS, here's a comparison between the low locations on the 06z EPS and GEFS. 

Classic underdispersion there with very little overlap between model systems but both of them pretty confident.