1/10 - 1/11 Possible Severe Frontal Passage with intense snow showers

[Grizzcoat]

From OMA-

 

Main forecast concern is the impending winter weather event tonight
and Thursday. In the meantime, expect clouds to only increase today,
with particularly grungy low clouds and some visibility restrictions
in western IA and easternmost NE. Temperatures will remain mild
under continued southerly surface to mid-level warm air advection.
Meanwhile, the southwestern upper-level trough will deepen today as
it moves toward the TX panhandle, with the Canadian trough dropping
toward the Dakotas. Think that other than some mist in the grungy
areas, precipitation will hold off during the day today until both
systems are closer. Toward the early side of this evening, as
southern low opens and ejects to the central Plains, models
consistently break out showers and perhaps even an isolated rumble
of thunder in the warm sector (funny to use that phrase in January).
Later in the evening, the post-frontal precipitation (rain or mix,
then quickly changing to snow) approaches the northeastern CWA.
Have backed off on POPs in the evening hours in between those
areas and have slowed the approach of the post-frontal
precipitation a bit. As the two systems phase, the focus for
heaviest precipitation becomes the frontal zone as it reaches
north central IA to east central and southeast NE. Post-frontal
winds continue to look strong, with speeds around 25-30 mph and
gusts up to around 35 mph. The northwestern CWA ends up missing
the sustained frontogenetic lift, and thus think most of that area
will see lighter snowfall amounts of 1-3". As a result, and given
earlier start time to snow, will convert watch to an advisory for
snow and blowing snow north of a line from around Wayne to David
City to Fairbury.

Have some confidence in a 4-7" snowfall band likely extending from
some part of the CWA eastward into IA, with amounts supported by
snow- liquid conversion of QPF as well as by the Garcia method, as
frontogenetic forcing is sustained from Wednesday night into
Thursday morning. As with any banded snowfall situation, the
confidence on the placement of that likely rather narrow band is
on the low side, though current indications would say it would end
up within a county or two of I-80 in Nebraska and I-80 to Highway
30 in Iowa. Naturally, this is an awfully high visibility segment
of our forecast area, with Lincoln on the western fringe,
Omaha/Council Bluffs potentially in the swath, and both I-80 and
I-29 at risk for the higher-end amounts. Think some part of the
remaining watch area may eventually need a warning, but would like
to give the next shift another chance to look at the model trends
regarding placement of the mid-level frontogenetic band,
especially since snow won't begin there until after midnight. Have
left a watch, and added a few counties on the southern side to
capture potential for the higher swath and trends a bit further
south.

[Grizzcoat]

No major change from DMX- (not surprising) 

 

Tonight into Thursday:
Scenario remains similar as in past nights
with overall precip types, frontal passage, amounts etc. Biggest
changes continue to be on placement with the models coming in a bit
further east/south with the track of the heavier snow band. The
biggest issue regarding this system though continues to be the
strong push of cold air and gusty winds on the back side of this
system. Given overall snow amounts in the light to moderate range,
the gusty winds creating the blowing and drifting snow and reducing
visibilities especially in rural areas will make for hazardous
travel conditions across much of the northern/western portions of
the forecast area. Even in areas that are not expected to receive
much snow toward the DSM/ALO metro area and points southeast, there
will be a period of time where icy conditions can be expected and
some reduction in visibilities as the snow sets in and northwest
winds increase. With snow amounts generally around an inch or less
in the aforementioned areas, prolonged visibility reductions from
blowing snow not expected but a few hour period surrounding the time
of transition to snow is possible. Additional travel headaches
outside the watch area possible as temperatures rapidly fall behind
the front and icy conditions occur from the initial wintry mix/snow
freezing to surfaces including walkways and roads. This timing is
expected to happen during the morning commute hours in both the
Waterloo/Des Moines areas.

Further northwest in the watch area, a band of heavier snow expected
to develop along a line from around the Denison area northeastward
toward Fort Dodge, Algona and Forest City. Still some possibility of
this heavy band to shift some in the next 12-24 hours, as the track
of the sfc low becomes more defined as it lifts across western and
central Iowa late Wednesday night. Deformation zone then in place
across the western/northwestern half of the state into early
Thursday as the mid-level trough moves through aloft. Strong push of
CAA and strong pressure rises on the backside to contribute to the
increasing winds. Largest isallobaric push will come across the
southwest but overall NAM has around 6-8mb 3 hr pressure rises which
are all decent to get blustery conditions. Much of the area could
see advisory criteria sustained winds and gusts, which could lead to
considerable amounts of blowing and drifting snow in the watch area.
Concern though centers around the type of snow expected as thermal
profiles suggest initial onset of snow to be more wet, heavy with
snow ratios of around 6 to 8:1, with increasing snow ratios as the
column cools and the lift taps into the DGZ. Therefore not sure how
well the heavier wet snow will blow. This should still only result
in maybe a difference of widespread 1/2 mile vsbys versus 1/4 mile
to near zero if the snow was drier, lighter but the near
blizzard/blizzard conditions can't be completely ruled out.
 

[jcwxguy]

Hope this is right

http://maps3.pivotalweather.com/maps/models/rdps/2018011006/036/snku_acc.us_c.png

[Tom]

00z/06z GEFS...notable shift SE trend has commenced and now may impact our IA members...looking good for OMA/LNK members and into SE MN...

 

 

[St Paul Storm]

3-5” in the point. May only get 1-2” if the band sets up SE of where most models currently show. Nowcast and radar watching in effect. I’m thinking leafblower as opposed to snow blower.

[Tom]

3-5” in the point. May only get 1-2” if the band sets up SE of where most models currently show. Nowcast and radar watching in effect. I’m thinking leafblower as opposed to snow blower.

LOL...ah man, that's funny...could be worse...I was teased by the Euro just 24 hours ago that has all but vanished any chances of snow.  Maybe some LES.

[Minny_Weather]

OAX issued advisory for Western and Northern counties. Kept the watch from Lincoln Eastward. Smart move.

[St Paul Storm]

LOL...ah man, that's funny...could be worse...I was teased by the Euro just 24 hours ago that has all but vanished any chances of snow. Maybe some LES.

I don’t think I’ve ever tracked a 1-2” snowfall as long as this one. It is what it is. The trend so far this winter has been southern stream dominant. The northern pieces of energy look good in the models up until 24-36 hours and then they crap out. This is no different. Still the potential for nice surprises tonight/tomorrow, but I’m not banking on it.

[Minny_Weather]

Even with model trends, I still think this will be a nowcast thing. It's nice that models are showing the band back over us 24 hours out, but really it all comes down to what happens in 24 hours. We have seen models crap the bed plenty. Who knows? The band could end up being over Grand Island. This is the type of thing that the radar will probably make the models look stupid.

[Tom]

@ Madtown, RPM model looked good for your trails up in N Wisco...keeping your trip up north alive...

[Madtown]

gfs has the heaviest where im headed... the nws isn't too impressed. 4-6 when most models show 7+

 

looks like should be a go just need to get it on the ground now.

[Minny_Weather]

NWS going 2-5 here. With recent trends I think a max amount of 5 is appropriate

[Tom]

12z NAM keeps trending SE across NE/KS/IA...looks weaker...DSM/N IA area looks like some intense "thump" snow with heavy hourly snowfall rates...2"/hr stuff showing up...

[CentralNebWeather]

12Z NAM will not make most Nebraskans on here happy.  Not good.  

[Tom]

12Z NAM will not make most Nebraskans on here happy.  Not good.  

It's almost looking like a summer time "training" thunderstorm frontal event...good luck to whoever is lucky enough to be underneath this thing...razor thin that's for sure....

[Minny_Weather]

NAM is still wrong I think. Where does that dry air in the middle come from?

[gosaints]

trending turdier

[Minny_Weather]

3km is thin. Let's see if it thickens out as it progresses.

[gabel23]

OLU-

THU 06Z 11-JAN   1.4     0.2    1004      85      90    0.00     550     547   

THU 12Z 11-JAN  -7.4    -9.6    1014      63      97    0.12     546     535   

THU 18Z 11-JAN  -8.1   -13.1    1023      45      42    0.01     545     527 

                                                                                                    was .23" at 12Z

 

JYR-

 

THU 06Z 11-JAN   1.6     0.2    1004      85      92    0.00     550     547   

THU 12Z 11-JAN  -7.3    -9.6    1014      64      97    0.15     546     535   

THU 18Z 11-JAN  -7.8   -12.3    1023      45      34    0.02     546     528

                                                                                                    was .23" also at 12Z

Boy, looking like maybe 2" of snow. Amazing and painful how this thing goes from giving me 3-6" to now a trace to 2". 

[gosaints]

The opposite of spreading the wealth

 

http://maps1.pivotalweather.com/maps/models/nam/2018011012/033/snku_acc.us_mw.png

[Minny_Weather]

3km literally looks like a Spring time severe squall line. Only difference is it's snow.

[Tom]

3km literally looks like a Spring time severe squall line. Only difference is it's snow.

My exact thoughts...it could be pound town for a couple hours if you get underneath the best frontal banding...

[Snowshoe]

They are going to need a good wet 5"-6". Terrible year so far in most of Wisconsin. 

@ Madtown, RPM model looked good for your trails up in N Wisco...keeping your trip up north alive...

 

http://dx1webcamhosting.com/lolrec/trail.jpg

[Minny_Weather]

Okay, where is this dry slot on the NAMily coming from? It's actually annoying.

[Tom]

They are going to need a good wet 5"-6". Terrible year so far in most of Wisconsin. 

 

http://dx1webcamhosting.com/lolrec/trail.jpg

 

#Craptastic

[Minny_Weather]

HRRR isn't looking too awful so far. Nice area of rain at the end of the 12Z run.

[CentralNebWeather]

I am going to follow the short term models more closely.  Maybe they lend some good news, or more of the same.  Dreaming of Colorado Lows.

[Madtown]

Lando is bad right now....got friends in the Mercer area atm ans its a little better. This should be enough to make it enjoyable and get to the UP if need be.

[NH4NU]

We have all been here before and we all should know by now that models this close to event should not be taken as literal. 

[Minny_Weather]

NAM 3KM is literally the NAM except those outside the band fare slightly better

[Snowshoe]

Hope you're able to have a great trip.

 

Lando is bad right now....got friends in the Mercer area atm ans its a little better. This should be enough to make it enjoyable and get to the UP if need be.

[bud2380]

just got to check the NAM and haven't read through the thread yet.  I have to imagine there are some meltdowns going on.  That is one narrow deformation band.  

[St Paul Storm]

Gonna end up right between the band to the north and the one to the south. Bare ground coming up after 43F today.

[Minny_Weather]

I still don't see the dry slot that the short range American models are showing happening. Seriously, for a frontogenic system filled with moisture, I just don't see it. Dew points and RH values are fine throughout the system.

[NH4NU]

This question is for eastern Nebraskans. If the GFS remains exactly the same from last night and this morning and pretty much every run since Monday morning, do we get to finally stop talking about the NAM? GFS has been arguably the most consistent model from the beginning. If 00z falls in line with NAM I rest my case and this thing is a bust. It’s like a new run comes out and everyone forgets every single model prior to it. It’s confusing and makes no sense.

^^This includes attention to NAM over the EURO which has now been consistent for 2-3 runs as well.

[Minny_Weather]

This question is for eastern Nebraskans. If the GFS remains exactly the same from last night and this morning and pretty much every run since Monday morning, do we get to finally stop talking about the NAM? GFS has been arguably the most consistent model from the beginning. If 00z falls in line with NAM I rest my case and this thing is a bust. It’s like a new run comes out and everyone forgets every single model prior to it. It’s confusing and makes no sense.

We're paying attention to trends. Since last night, almost every model (including GFS) has trended Southeast. I comment on every run of every model because I feel it is important to do so in case it's a new trendsetter.

[Jaycee]

I think if the NWS was believing the southeast trend they would have placed the Falls City area in a watch as well. I don't think they're buying the last minute changes with the models-- they're clearly thinking the band will setup from Lincoln to Omaha somewhere.

[Minny_Weather]

I think if the NWS was believing the southeast trend they would have placed the Falls City area in a watch as well. I don't think they're buying the last minute changes with the models-- they're clearly thinking the band will setup from Lincoln to Omaha somewhere.

It's encouraging to see they left us in a watch. Means they're actually watching this.

[NH4NU]

Monitoring trends is completely fine with a model that has been consistent! Folks, the NAM had us in like 8”+ a day and a half ago. GFS hasn’t deviated more than 2” since 00z Monday.

[Minny_Weather]

Monitoring trends is completely fine with a model that has been consistent! Folks, the NAM had us in like 8”+ a day and a half ago. GFS hasn’t deviated more than 2” since 00z Monday.

Just because a model is consistent now doesn't mean it will stay consistent. Now, I hope GFS stays consistent cuz it has 8" for me. Like I said earlier, though, I'm not buying NAM's and HRRR's idea of a slot. The DPs are literally gonna be the exact same as the temps.