December 10-12 Potential Snow Event

[LoveSN+]

14 minutes ago, Chambana said:

Kind of a bummer to miss 2 systems in a row to my north. My focus turns to next weekend 12/18 timeframe. Enjoy everyone!!!

I think we will see some flakes, just accums will be minimal.

[ConvectiveIA]

25 minutes ago, Chambana said:

Kind of a bummer to miss 2 systems in a row to my north. My focus turns to next weekend 12/18 timeframe. Enjoy everyone!!!

Feeling similar dread in DSM IA but for different reasons. Would be all snow anywhere in IA as that line is well to our south, but DSM is right at a tight gradient and border between little (snow) precip here points west and south, and deep snows just to our northeast. That latest UKMET graphic continues that fear.

[Chicago Storm]

12z ECMWF with another step back. Even weaker and more disorganized than the 0z run.

[Hoosier]

1 minute ago, Chicago Storm said:

12z ECMWF with another step back. Even weaker and more disorganized than the 0z run.

[Hoosier]

Seriously though, and maybe it won't be the case this time, but I remember multiple storms before where the consensus was wetter than the ECMWF and the consensus won.  Obviously would be nice to have it on board.

[Chicago Storm]

Only 0.30-0.40" QPF around here this run.

Quite a difference between it and the 1"+ QPF on over half of the GEFS members.

[Deck Pic]

3 minutes ago, Chicago Storm said:

Only 0.30-0.40" QPF around here this run.

Quite a difference between it and the 1"+ QPF on over half of the GEFS members.

 

Yeah...The Euro sucks

[HillsdaleMIWeather]

6 minutes ago, Hoosier said:

Seriously though, and maybe it won't be the case this time, but I remember multiple storms before where the consensus was wetter than the ECMWF and the consensus won.  Obviously would be nice to have it on board.

The Euros been acting weird this whole winter.

[Stebo]

9 minutes ago, Hoosier said:

Seriously though, and maybe it won't be the case this time, but I remember multiple storms before where the consensus was wetter than the ECMWF and the consensus won.  Obviously would be nice to have it on board.

Euro's tendency to be overtly dry is certainly in play. 

[RyanDe680]

Ratio guesses?  12:1?  I-80 corridor could hold to  10:1

[Hoar_Frost]

1 minute ago, RyanDe680 said:

Ratio guesses?  12:1?  I-80 corridor could hold to  10:1

I'd say 15-20:1 in the first round and 10:1 (or perhaps less - especially south and near Lake Michigan) in the second round. 

[HillsdaleMIWeather]

New NWS point forecast calling for 5-11  inches of snow

[RyanDe680]

The NAM may not be in total agreement, but its better.  It's slowly caving.

[HillsdaleMIWeather]

IWX preferring the stronger solutions, holding off on the Winter Storm Watch until probably morning

LONG TERM...(Saturday Night through Friday)
Issued at 242 PM EST Fri Dec 9 2016

Just enough spread in solution scope aloft...esp with thermal
profiles tied to general intensity differences among individual
model solutions to prevent an agreeable watch coordination this
aftn. That said... did bump pops much higher in consideration of
general agreeable consensus scope. While details still sketchy...
satellite depiction of upstream sw over the nepac ocean this aftn
gives a preferred nod toward stronger solutions aloft. This would
yield to a threat of mixed precip through srn areas by Sun
aftn/evening yet also point to a period of heavy snow potential
Sun morning through Sun aftn (north). In the least will issue a
Winter Storm Outlook this aftn to highlight the potential for
significant snowfall accumulations (6-10") late this weekend
especially US 30 north.

[Hoosier]

Average model QPF running around .5-.75 here, with the GFS higher and the NAM lower (though the heavier band would only have to shift/expand about 20 miles south) and of course the ECMWF.  I like the blended approach so I'd currently favor something like 7-9" for totals in the southern Chicago burbs and my area, possibly ending as a bit of rain. Would have potential to touch double digits in a GFS/GEFS outcome but don't want to go all in on that.  

[Stebo]

I'll go with a local storm total of 5-8" maybe a bit more if Lake Huron gets involved.

[TravisWx]

Long time lurker here. I'm in Rogers City, MI (basically right on Lake Huron). Any chance the models aren't fully picking up the potential for lake enhancement for NE lower MI? Seems like APX never mentions LE for NE MI. I remember a few years ago there was a weak-ish low that moved over. We had 3 inches forecasted for our area, ended up getting over 18+ inches from lake enhancement. The local news even did a special on it. 

[Hoosier]

18z NAM still has good qpf overall.  

[IllinoisWedges]

From LOT. 

[HillsdaleMIWeather]

From IWX

[hlcater]

I like 6-9" total here. Let's see how this verifies.

[Hoosier]

LOT afternoon afd gave good reasoning for why they went on the snowier side.

[Stebo]

DTX AFD:

Quote

Attention then turns to winter storm late Saturday night into Sunday
night. Strong consensus exists in a pop sense, warranting an
increase to 90 to 100 pops area wide. NWP struggles with regard to
lead energy have largely been resolved as GFS/NAM/GEM trended toward
the more consolidated look of the EC and UKMET, although noteworthy
initialization errors appear to plague the 12z NCEP suite per Suny
Stony Brook ensemble sensitivity analysis.

Expectation of system evolution remains unchanged with lead
isentropic ascent within a strengthening right entrance region
drives the first half of the event followed by a transition to more
dynamic lift upon the approach of the wave aloft. 12z NAM cross-
sections reveal high static stability throughout the column, calling
into high question its stronger surface low and high QPF output.
Largely for this reason, preference is given to EC/Canadian
solutions which depict a weaker cyclone overall.

Light snow is expected to be begin late Saturday night as lead
energy enhances the jet streak overhead. Aforementioned high static
stability will effectively limit the vertical response during this
time, although the initially cold column favor will still maximize
efficiency. Expect At least one half to one inch by 12z Sunday
morning across the southern half of the CWA. Peak snowfall will
occur as the low-level jet slides by to the south. Substantial
moisture advection and increasing dynamic support aloft will favor
profilic hydrometeor production. However, model progs of the
resultant warming column elevate the dendrite growth zone well above
10,000 feet. Nonetheless, 1 inch per hour rates over a 4 to 6 hour
period will be plausible during the day Sunday along the nose of the
jet.

The more phased Canadian and GFS suggests a lower snow ratio
scenario courtesy of a stronger LLJ warming the column. The
resulting habitat would support a mix of crystal types that would
then undergo notable riming upon decent, particularly across the
southern CWA. The primary change noted in the 12z EC was a less
phased solution over the northern Great Plains. Snow density in that
case would be much more favorable for overachieving. The official
forecast calls for snow ratios of 12 to 15:1 across the north and
falling to 8 to 10:1 across the south. The going forecast therefore
3" to 7" north of I-69 and 5" to 9" to the south. Confidence is
highest across the central CWA between Detroit and Flint which are
less likely to be impacted by small fluctuations in track. Assuming
no major changes, the primary considerations for tonight will likely
be snow density and potential for headline issuance.

Very good and thorough discussion from them.

[RyanDe680]

Quote

 Ratios of 14:1
to 19:1 may support a quick 2-4 inches by midnight, especially in
any evident bands that setup

wow.  14:1 to 19:1

[Chicago Storm]

Don't want to end up south of that band, going to be a sharp cutoff as we always see in these situation...

[Deck Pic]

For ORD (concentrating there since that's where I'll be), 18z GFS may mix around hour 54-55, but precip mostly done then, and it is low level warmth, so could be snow and 34 rather than flip/mix.  

This is sounding at 51 hours - you can see it is totally clean - sfc is 30.

 

Here is liquid through 54.  Maybe some is mix toward the end, but probably snow through 53 hours

 

[homedis]

6 minutes ago, Chicago Storm said:

Don't want to end up south of that band, going to be a sharp cutoff as we always see in these situation...

Jeez that's really close.

[HillsdaleMIWeather]

18 minutes ago, homedis said:

Jeez that's really close.

The NAM has kinda been that black sheep of models though

[cyclone77]

Still a bit early, but my first call for here is 3-5", with 2-4" for the QC.  Heaviest amounts look to ride the highway 20 corridor in IA, and angle down toward Chicago in IL.  Amounts south of I-80 in the DVN cwa are going to be very difficult to forecast, as there will likely be a pretty steep drop-off.  Lower ratios with whatever falls on Sunday won't be helping the accumulation rates any, particularly in the southern half of the area. 

Looks like an interesting event overall, and it will be nice to get a little fresh cover down over top of that 1" of arctic crust out there right now.  

[Hoosier]

I'd be concerned in northern IN/southern MI if the LLJ configuration looks like this on Sunday.  The NAM has more of a direct punch into those areas while the other models shunt it more toward the OV.  If this NAM type solution were to pan out, there would be a pretty good chance that the warming aloft would be underestimated and those areas would change over to mix/rain faster than progged.