Chris's Corner - The Winter Break is About to End

The pieces of the complex puzzle appear to be falling into place for a return of winter weather to the heart of the Bistate area. The potential for a fairly widespread moderate snow event...high end advisory or warning level event is on the table. While there may be some brief mixing early on in the event as evaporative cooling takes over...the bulk of the precipitation should fall as snow for the vast majority of viewing area as it stands right now. The other time for potential mixing is late in the event...as the stronger lift exits to the east and some freezing drizzle settles in late Saturday night into Sunday.

The system in question is easily seen out over the eastern Pacific. Ahead of it... a return to winter temperatures will unfold steadily over the next couple of days as cold air builds south out of eastern/central Canada. This cold dry air will not have much time to moderate before WAA aloft starts to initiate precipitation in the return flow late Friday. As mentioned above... I see a mix early...before evap cooling cools the column to snow. The early soundings and storm track at 850mb argue for a mixed bag south of a line from Salem MO to near Mount Vernon, IL...for a good portion of the event...until the passage of the 850mb low turns on the cold air advection.

There are any number of wildcards... not the least of which is the potential for a long duration event ... with some models showing additional energy rotating through the open wave and maintaining light snow in the wake of the main surge Friday night and Saturday. This could prolong the snowfall well into Saturday night if not early Sunday in some areas...leading to additional accumulation.

Overall... I think widespread snow of 3" or more look likely for pretty much the entire viewing area...with snow starting after sunset Friday. The potential mix could extend as far north as a line from Salem, MO... to Farmington...to DuQuoin, IL...at least that's where I see it now. However, some decent accumulations still appear in order for those areas.

This storm is starting to get the look of a healthy mid-winter storm...

The size of the snow shield reminds me of the Christmas 2003 snowfall where the whole area got 3-6". That's what I'm leaning towards at this point.

I fully expect sleet contamination down here because...well, Perryville.

And never underestimate the power of the warm layer in a WAA situation. It could protrude north more than expected, thus, make for a lot of angry people in this here forum.

Totally agree. This probably won't end up being a bona-fide winter storm for most of us, but there should be a lot of haves and only a few have-nots with this one. Assuming we can make it inside the 36 hour window without any big surprises (never a given) then this usually means the bust potential is on the lower end of the spectrum. So while it might not be a high impact event it should at least be an event. I'll take it.

Hey Chris, do you guys use WSI? If so, how did you get your text to curve like that? I've been trying to figure it out.

We do use WSI. It is text loaded into the jet stream layer...with no motion

Well NAM is juiced up as usual. Already showing warning level accumulations and it's not even half done yet at the end of the run.

You may be right...it was one of those two years. I just remember the entire radar being filled with moderate echo all day and a nice area-wide snowfall.

Right now I think going within expectations of a 3-5 inch snowfall it's probably a pretty good play.


There will be multiple pieces of vorticity working together phasing as a destroyer of carbs itself out heads East and then eventually merges with the PV anomaly over Southeast Canada.


This system is coming with a very Stout moisture plume for this time of year the models show saturation taking place very quickly in spite of the ambient dry air.


The weather models also show the column being saturated all the way up tippy tippy top.

This means precipitation efficiency will be at near peak level again this time of year in this cold of an air mass.




Try to look at it like there has been times with clippers that we had incredible lift with compact energy.

There has been systems where we had Omega values in the -32 - 40 range. And yet we still didn't see that much snow.

Because moisture was lacking.

This system is loaded moisture wise and there's a chance it won't even pull in gulf of Mexico moisture as the system phases as they pass through the Mississippi valley.


Long story short there is a chance and we will see a slowing down facing digging system with a sharper trough that ends up closing off.

Even if the system only closes off at h5 or h7 for a half a day or a day.

With the amount of moisture in place that the system has large-scale ascent and meso scale lift could come into play.







Any ways to finish this off there's a chance we will see a dynamic system where we get an initial thump of 3-5" of WAA snow. Which will be widespread over most of the metro.

Then as the system phases deepens and organizes.


They will be a large area of generally light snow and sleet and freezing drizzle after that waa snow passes.

Then there will probably be some meso scale processes bands of snow or clusters of snow showers that will add some accumulation to the mix.

Given the current track of the system this would probably be along interstate 70 and possibly to the north a little bit.

But then lastly we might see a surge of gulf of Mexico and Pacific moisture laden precipitation coming from the large-scale is sent from the deepening closed off system.

This would probably look like a slug precip blowing up from South Central Missouri heading Northeast towards St Louis metro area.

As this general direction of precip will be slowly heading off to the east they'll be some precip intersecting it that is bubbling North and possibly North Northwest.

In fact this precipitation might even look stationary 4 time.

but it's only that way because of the pivot point of the deepening system as you all know it just so happened that in this case it looks like all signs are pointing to that taking place right over our area.


additional snowfall amounts from this process could range anywhere from one or two up to a half a foot.


So after that long-winded diatribe frivolous right now says his first broad forecast is 4-9".

This is for along 44/64 in I'll and no.

And along I 70 in I'll and mo out to warrensberg but West of there I expect less.

Also watch for a split or double maxima in precipitation and a general lowering of QPF amounts. It's all stuff we've seen before. Hopefully this one is different, but we can't bank on it.

I see an ever so subtle hint of a slightly warmer/further north solution. This needs to stop or I will be unpleased to say the least.

Still over 3000 miles away. Plenty of time for flips and flops. Not going to be fully sampled until Thursday 12Z runs at least.

I could see a slight adjustment north, but the ballooning upstream ridge/meridional flow should keep any big shifts in check and if anything, a slight S jog seems more likely with such a deep N flow digging into the trof.