December 11-13th MW/GL Snowstorm

[Grizzcoat 3790]

N shift on GFS - with more coverage. Concern here is N shift holding and continuing N to even NW. I think the later. This system moved too much S from previous guidance 3-4 days ago. A shift N- to NW is expected. Twin Cities are not out.

[dubuque473 272]

DVN giving me hope for at least something..

 

Northern stream energy will be onshore Thursday night and its
strength and evolution with lead southern stream trof will help
determine how strong our Friday-Saturday system will be. Both the
00z NAM/00z ECMWF show a negative tilt wave developing which results
in a stronger and slower dynamic system and in contrast the 00z
GFS/GEM show more a neutral tilt to this incoming system, which
would be somewhat weaker and faster moving. Surface low track has
come into slightly better agreement with 00z runs and their
ensembles, with a consensus track from SGF at 00z Sat, to STL, to
northern IN by 18z Sat. This normally would favor the local area
receiving heavy snowfall. However, the complicating factor with
this system as mentioned in previous discussion is that we will
have no cold arctic air in place. We will have to depend on strong
dynamics and high snowfall rates to get snow to accumulate on
warm ground/pavement. This is still a possibility, but confidence
still remains low.

QPF/Snowfall...

Model PWs will be rising above 0.75" which is 2-3 standard
deviations from the climatological mean per NAEFS output. Strong
lift ahead of the wave will result in rainfall totals over a half
inch by Saturday, especially in our southeast half of CWA. Lighter
amounts are expected further north and west. NBM weather type progs
have been trending further south with the rain/snow line late Friday
night, with most areas north of a Fairfield to Quad Cities line
seeing a changeover to all snow early Saturday. Latest 00z NAM and
WPC internal snowfall guidance would suggest a def zone snowfall
region and potential accumulating snow to set up somewhere over
south central IA through the Cedar Rapids/Iowa City metro, to
Freeport,IL on Saturday, with little to no accumulating snow south
and east of this line. Any deviation or change in low track in later
forecasts will shift this snowfall area. Wide range of possible
snow totals still exist and will be further addressed in later
forecasts.

[Grizzcoat 3790]

30 minutes ago, dubuque473 said:

DVN giving me hope for at least something..

 

Northern stream energy will be onshore Thursday night and its
strength and evolution with lead southern stream trof will help
determine how strong our Friday-Saturday system will be. Both the
00z NAM/00z ECMWF show a negative tilt wave developing which results
in a stronger and slower dynamic system and in contrast the 00z
GFS/GEM show more a neutral tilt to this incoming system, which
would be somewhat weaker and faster moving. Surface low track has
come into slightly better agreement with 00z runs and their
ensembles, with a consensus track from SGF at 00z Sat, to STL, to
northern IN by 18z Sat. This normally would favor the local area
receiving heavy snowfall. However, the complicating factor with
this system as mentioned in previous discussion is that we will
have no cold arctic air in place. We will have to depend on strong
dynamics and high snowfall rates to get snow to accumulate on
warm ground/pavement. This is still a possibility, but confidence
still remains low.

QPF/Snowfall...

Model PWs will be rising above 0.75" which is 2-3 standard
deviations from the climatological mean per NAEFS output. Strong
lift ahead of the wave will result in rainfall totals over a half
inch by Saturday, especially in our southeast half of CWA. Lighter
amounts are expected further north and west. NBM weather type progs
have been trending further south with the rain/snow line late Friday
night, with most areas north of a Fairfield to Quad Cities line
seeing a changeover to all snow early Saturday. Latest 00z NAM and
WPC internal snowfall guidance would suggest a def zone snowfall
region and potential accumulating snow to set up somewhere over
south central IA through the Cedar Rapids/Iowa City metro, to
Freeport,IL on Saturday, with little to no accumulating snow south
and east of this line. Any deviation or change in low track in later
forecasts will shift this snowfall area. Wide range of possible
snow totals still exist and will be further addressed in later
forecasts.

Dmx talking several inches C and S IA. ( Potentially) 

Thursday.

.LONG TERM.../Friday through Tuesday/
Issued at 410 AM CST Wed Dec 9 2020

Attention then shifts to the evolution of the weekend system as
it opens and lifts northeast into the Midwest. 00z deterministic
model output has shifted the storm track slightly to the NW
compared to runs 24 hours ago now putting the best band of snow
across generally the southern half of IA. Additionally, less
variability was noted amongst model solutions which has added to
confidence in the Friday-Friday night period. Open-wave reaches
the central plains around midday Friday, with initial moisture
surge arriving into southern IA at around the same time. Have
continued following the NBM trend boosting precipitation chances
into likely category across the south. Precip type on Friday will
be tricky and depend on the amount of cold air in place along w/
wet-bulbing if rates are sufficient. For now, have kept the
hedged forecast on Friday, maintaining -SN OR -RA. Cold air will
certainly be sufficient for snow accumulations mainly for Friday
night and Saturday morning, before the system departs Saturday
afternoon. Too early to get detailed on amounts, but some areas
across central and southern IA have the potential for several
inches of snow from this system. Storm track and amounts will
continue to be refined over the next few days, so those w/ travel
interests late Friday into Saturday morning will certainly want to
monitor future forecast updates.

[bud2380 3520]

The 6z RGEM is like a dream come true. 

[CentralNebWeather 4714]

Local ABC meteorologist. 

 

[james1976 3976]

Ill be in St Paul so of course my backyard will get blasted.

[dubuque473 272]

Off with a back injury so kind of expect a lot.

[bud2380 3520]

6z Euro looking even better

[Stormhunter87 969]

OAX is only going 1-3 for the area and the metro thinking 0-1 inches. Hmmm

[Tom 16887]

06z Euro...nail biter around these parts...5-10 miles is going to make a big difference I think...sorta reminds me of the Nov '15 snowstorm that rocked the NW burbs while the city got zilch...

 

[Tom 16887]

Come to think of it, this storm is actually trending towards more of a "share the wealth" TX Panhandle cutter....we usually don't see much snow up into NE/ from these type of storms so consider this a win if it does happen.

[Stacsh 904]

Another cold December rain for SMI.  This is getting old.  

[bud2380 3520]

The majority of the snow in Iowa from I80 on north comes Friday night.  There are two waves with this.  The first wave comes through Friday with rain changing to snow and then looks pretty heavy at times, then a bit of a lull before the 2nd wave comes in Saturday morning.  That one hits southern Iowa harder and then into Illinois, which is why you are seeing the heavy totals in Northern Illinois and Southern WI.  

[Hawkeye 4600]

It's looking ok for Iowa, but models generally show the best moisture/dynamics/cold air coming together a bit farther east.

[Tom 16887]

1 minute ago, bud2380 said:

The majority of the snow in Iowa from I80 on north comes Friday night.  There are two waves with this.  The first wave comes through Friday with rain changing to snow and then looks pretty heavy at times, then a bit of a lull before the 2nd wave comes in Saturday morning.  That one hits southern Iowa harder and then into Illinois, which is why you are seeing the heavy totals in Northern Illinois and Southern WI.  

This could be a trend towards a more robust second wave which was one of the features in the LRC pattern.

[bud2380 3520]

I meant to reference, that is what the 6z Euro showed.  For my backyard it could come down to how quickly the rain transitions to snow and then how long does it take to accumulate.  It will require some heavy rates early on to get the accumulation going. 

[bud2380 3520]

6z Canadian

 

http://img.meteocentre.com/models/gemglb_amer_06/accum/SN_000-084_0000.gif

[bud2380 3520]

12z NAM is running and out to 54 hours.  Looks very similar to 6z at this point. 

[Clinton 4427]

31 minutes ago, Tom said:

This could be a trend towards a more robust second wave which was one of the features in the LRC pattern.

It wouldn't take much this first wave is weak, warm, and +tilted.

[bud2380 3520]

NAM going way north with the 2nd wave.  

[Hawkeye 4600]

I have to think the NAM is too amped.  It cuts the surface low almost due north at the end, which seems unlikely.

[bud2380 3520]

Yeah, I haven't seen a solution bringing several inches all the way into SE Minnesota like this.  I like the strength of the storm  here, but hopefully it doesn't go this far north.

 

[Madtown 1092]

Maybe a bit too north, but I gotta believe the lack of cold air, the lack of snow cover and still somewhat early in winter makes this thing end up farther north than what everything was showing yesterday. Who knows.

[james1976 3976]

It will since I won't be home

Don't be mad at me though lol...

[Hawkeye 4600]

12z RGEM

[St Paul Storm 4028]

49 minutes ago, Madtown said:

Maybe a bit too north, but I gotta believe the lack of cold air, the lack of snow cover and still somewhat early in winter makes this thing end up farther north than what everything was showing yesterday. Who knows.

It may come down to how much cold, dry air tries pushing in from the NW. Models the last few days had really been hitting the dry air hard, thus forcing the storm south. Now they seem to be backing off. While I don't think it's coming all the way back up this way, it's safe to assume there are more changes coming. 

[bud2380 3520]

2 minutes ago, Hawkeye said:

12z RGEM

Nice weird bullseye on the RGEM right in my backyard.  

[St Paul Storm 4028]

Milwaukee slammer on the 12z GFS. 

[Hawkeye 4600]

GFS going more amped.

[bud2380 3520]

GFS would have it snowing through the Iowa - Wisconsin game Saturday 

[Madtown 1092]

Thats about as classic as it gets!

[GDR 665]

Looking more and more share the wealth storm!

[Hawkeye 4600]

I would like to see the storm amp up earlier so Iowa can get into the heavier snow.  Models are split on this.  The GFS doesn't really get going until farther east.

[james1976 3976]

Canadian has snow in my backyard by noon Friday. Definitely quicker and further north than GFS.

[bud2380 3520]

Canadian a little warmer this run with wave 1 and brings a lot of rain to CR and IC.  Then the secondary wave is further north than the GFS and brings some decent snows to eastern Iowa.  Further north fairs better since they stay snow the whole event.

 

[Hawkeye 4600]

12z Canadian is stronger, but marginal temps keep it all rain in se WI.

[bud2380 3520]

I really hope the Canadian is on the right track.  it would be fun to wake up to this Saturday morning.

 

[Hawkeye 4600]

Canadian snow map is very different than the GFS.  The two are only off by 12+ inches over southeast WI.

 

[bud2380 3520]

All I can say is I hope the UK is showing snow in Iowa.  Based on the SLP path it should be.  

 

http://img.meteocentre.com/models/ukmet_amer_12/P1_GZ_D5_PN_072_0000.gif

[Grizzcoat 3790]

Those 1000-500 thicknesses are borderline, W IA looks ok, further E may be mix or rain

[MIKEKC 413]

Looks like KC will see some rain(not much) and maybe a few wet snowflakes Saturday.(We really need moisture(moderate drought here) The data never shows us getting below 33-34 degrees while the precipitation is here. Even in the snow areas, temps look just cold enough. Likely a really wet snow for the ones that get it. 

For the ones that get the snow, enjoy it, as the GFS goes back to a flame thrower across the country in the mid range. No deep cold anywhere to be found. Hopefully that changes soon. 

[jaster220 8344]

7 hours ago, Tom said:

00z EPS and Control...

 

 

 

 

Crazy to see the Euro Op run so far removed from it's own Ensemble Mean. The Ens map seems in line with other models leaving the Op on it's own island. I see 6z finally fell in line with others but wow it was way off for several runs with the S track tease.

[Grizzcoat 3790]

J'aime la france 

[jaster220 8344]

3 hours ago, Stacsh said:

Another cold December rain for SMI.  This is getting old.  

Don't forget the part where we wait another 50 days for our next chance hoping it's actually cold enough then. We aren't getting a "winter" this year. Maybe a random storm in April when we don't want one, but not a winter. If it does get cold, track will prolly move over to the EC or such.

[Grizzcoat 3790]

Ukie 850 at 72.

[snowstorm83 2042]

12z GEFS

[Grizzcoat 3790]

Uk is pretty consistent.

[gabel23 1603]

Hoping the king EURO jumps on board with the Ukie! 

[Stormhunter87 969]

Ukie is sticking to it's guns and a solid track for here. It appears weaker though from earlier runs or trouble getting moisture.

[bud2380 3520]

Loving the UKIE.  Man that would be about as good as I can hope for with this storm.  I'm guessing the NWS will wait until at least tomorrow morning to post any headlines.  Even though model consensus is tightening there is enough variance yet to be cautious.