2/23 - 2/24 Central Plains/Midwest Blizzard

[ToastedRavs]

6z NAM holding steady for Des Moines metro. Bisects the state of Iowa from corner to corner. Steady NAM, for a few runs now. That is probably not a good thing. Ha!

[Bellona]

6z NAM holding steady for Des Moines metro. Bisects the state of Iowa from corner to corner. Steady NAM, for a few runs now. That is probably not a good thing. Ha!

Has 12 imby. I'd take that!

[Grizzcoat]

[CentralNebWeather]

06z GFS stays solid north. Dream run for myself, gabel23 and Clint. Not good for southeast Nebraska. Lots of moving parts, what model wins out?

[jcwxguy]

EPS has a 6-7" bullseye right through Omaha/Lincoln. Though there's still a fair amount of variance between the 51 members, especially for only 36-48 hours out. Models still don't know what's going on.

[CentralNebWeather]

ISSUED: 4:39 AM FEB. 22, 2019 – NATIONAL WEATHER SERVICE

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO

6 AM CST SATURDAY...

...WINTER STORM WATCH REMAINS IN EFFECT FROM SATURDAY MORNING

THROUGH SATURDAY EVENING...

 

* WHAT...Mixed precipitation expected. Heavy snow possible. New

snowfall accumulation of up to one inch and ice accumulation of

around one to two tenths of an inch expected this afternoon

into tonight. The heaviest snow will be possible on Saturday

with new snowfall accumulation of 3 to 6 inches with perhaps a

little more light ice accumulation Saturday morning prior to

turning over to snow. North winds around 30 mph could gust as

high as 45 to 50 mph on Saturday leading to poor visibility in

blowing and drifting snow.

 

* WHERE...Portions of south central Nebraska.

 

* WHEN...For the Winter Weather Advisory, from noon today until 6

AM CST Saturday. For the Winter Storm Watch, from 6 AM CST

Saturday morning through Saturday evening.

 

* ADDITIONAL DETAILS...Power outages and tree damage are possible

due to the ice. Travel could be nearly impossible at times on

Saturday. Areas of blowing snow could significantly reduce

visibility. The hazardous conditions could impact weekend

travel.

[jcwxguy]

Rdps shifted southeast a little

[Minny_Weather]

I'd expect blizzard warnings for every county that MIGHT get the band in the afternoon shift.

[gosaints]

Tonight is shaping up to be quite interesting. I think someplace in the la crosse forecast area will get thunder. Now weather that is snow, sleet, zr, or rain or all of the above I have no idea. Location is also gonna be variable

[DSM WeatherNut]

Wow...Des Moines NWS has a lot to say, but in the end still a lot of uncertainy. May answer model forecasts in this post though with a higher degree of technicality.

 

Tonight-Saturday AM Icing potential...

Key Points:
This is a dynamic, very sensitive/touchy target... meaning if
current sfc temperatures shift north or south by a few degrees,
the current advisory area would likely need to be shifted and/or
expanded as well.

Winds will likely be in the 10 mph or less range with this
event, meaning impacts will be completely precipitation-driven.

Forecast ice accumulations in the 0.05" to 0.10" range may lead
to ice-covered and slippery surfaces... especially untreated ones.

Forecast notes:
The 00z Fri GFS has been essentially tossed out for Saturday
morning. From the 06z Fri-12z Fri timeframe, this model produced
almost 1 inch of QPF (mostly rain). Trying to trace the root-cause
of this high amount, the GFS seems to be keying on some sort of a
bizarre mid-level feature that can be traced back to the Permian
Basin of Texas. This feature then phases with a 850mb LLJ
currently over the Gulf of Mexico to seemingly produce some sort
of convection. The problems here are that the Permian Basin
feature has not initialized as indicated, and the GFS is an
outlier with bringing the nose of the LLJ into SE Iowa. So, have
ultimately stuck with much lower QPF in the quarter-inch or so
range.

With the 32 degree line cutting right through Iowa, sfc temperatures
will need to be watched closely. At 06z, the 00z GFS initialized
several degrees too warm with air from the source region. Other
models were a few degrees to warm as well, though it was somewhat
sporadic. This suggests there may be a slight
southward/southeastward nudge that is needed for the area of likely
highest ice accumulations. If this occurs, Polk and Jasper counties
may need to be added to the Advisory. As hi-res data + 12z data
comes in, hopefully confidence on locations will increase.

Important to note that if you plan to run errands, travel, etc. with
the intention of trying to "sneak your travel in" before the big
system arrives Saturday evening, you may run into travel impacts
Saturday morning. so if you plan on heading out Saturday morning, be
sure to check the forecast and check 511ia.org for the latest road
condition updates.


Saturday PM - Sunday Blizzard potential...

Key Points:
Have upgraded wording for this event to "blizzard potential*.
Winter Storm Watch still in effect, so emphasis on the word
*potential*.

Strong winds will be the main driver of the worst impacts of
this system. These winds will begin in western Iowa Saturday
evening, and spread eastward throughout the state, making it to
I-35 by Midnight Sunday morning.

Accumulating snow will likely exit the DMX CWA by sunrise Sunday
morning. However, very strong winds will continue through Sunday
afternoon. In places of snow accumulations, especially higher
amounts, this will cause significant blowing and drifting snow.

In locations that receive less than 1 inch of snow (likely to be
in SE Iowa), hazardous winds will likely still have impacts-
blowing vehicles, especially high-profile vehicles.


Forecast Notes...

Track: Heavily favored the 00z Fri ECMWF for track of this
system. Ultimately, the 00z Fri GFS & GEFS runs have become
outliers in placing the track of this system north and west. ECMWF
has had the best run-to-run continuity of this system over the
past few days. The 00z NAM *really* slams in dry air at and above
the DGZ on the backside of this system. Tracing this dry air back
to Manitoba at 09z, this dry air from the NAM is not initializing
well. With the RAP and hi-res models beginning to reach out to 12z
Sat, where the sfc low is positioned somewhere over the OK
Panhandle, the ECMWF solution has been favored, with the GFS
continuing to look like an outlier. The UKMET and Canadian models
are also pointing towards the ECMWF track solution.


Amounts: Strong cold air present on the backside of this low
will quickly change precip to snow, starting from northwest to
southeast. Have removed mixed precip from forecast for Saturday
evening-Sunday morning in northwestern Iowa where the cold sector
is locked in. Once this cold air arrives, the precipitation types
will not "wobble" between ice/snow/ice/snow/etc... rather it will
likely change to snow and stay snow for the event duration.

The current forecast amounts remain very touchy. Have left current
Winter Storm Watch counties in place. Confidence certainly not high
enough at this point to where it is justifiable to confidently
add/remove counties. Please note that there still may be a shift in
the track of the system, which would cause a shift in the location
of blizzard impacts. As mentioned in last night`s Forecast
Discussion, it is not value-adding to go chasing singular model
solutions. There could very well be variance in the track of the
highest snow amounts up through Saturday morning model runs.
Catching the trend is where value can be added. At this point,
IMHO, the value is to trend towards the ECMWF.

[Minny_Weather]

OAX is completely throwing out GFS even though SREF is on its side as well.

 

 

 

There is still a large spread in the model solutions for round
3...the main event...Saturday/Saturday night related to the
latitudinal location of the heavy snow. For this forecast, used
the EC/NAM/UKMet/Canadian solution for snow placement as the GFS
track has been more of an outlier. Noticed the SREF also is
farther north though. The storm system is a fast-mover which will
limit snow amounts. The greatest lift appear during the afternoon
hours. Snow totals range from 2 to 6+ inches with mostly 4 to 8
inches the watch area. The Garcia method is supportive of 3 to 6
inches. The current watch is consistent with the
EC/NAM/UKMet/Canadian, so did not adjust the watch.

As the surface low tracks from central Kansas eastern Iowa,
northwest winds increase 20 to 30kts with gusts 35 to 45kts. Will
continue to mention blizzard conditions possible due to the strong
wind gusts. The bulk of the snow ends by midnight, however the
blowing will last until Sunday.

[Tom]

This is one of the more difficult systems we have tracked this season given the high uncertainty and high impacts it will deliver.  The trend among the models has been for a fairly narrow band of heavy snow and some consistency between the GEFS/EPS.  Here's a comparison between both models and I also threw in the 00z Euro Control in the mix.  The big difference across NE is the Euro covers most of SE NE with the heavy snow band while the GEFS are farther NW.  Most ensemble members off the EPS show a larger defo band developing much earlier across KS than the GEFS members.  Given how dynamic this system is going to be, I'd right the Euro/EPS due to much better physics in the modeling.

 

 

 

 

[jcwxguy]

Euro continues the nw shift (for Nebraska anyways)

[Madtown]

Looks like a good ol fashioned blizzard in N. Wi. green Bay office has me down for 14"

[gosaints]

With the dynamics at play someone progged for rain could so easily end up with concrete surprises.....

[Tom]

Not much talk about the Freezing Rain potential, but both the Euro and NAM are showing a lot of ice in N WI.

 

@BrianJk, this may be a bigger problem than the snow that falls for your roof as it may carry more weight.  Not sure what you would rather see happen.

[Madtown]

pretty sure between the snow and ice I wont be coming home Sunday

[Tom]

06z Euro still likes the idea of heavy snow across E NE and trending NW across IA but maintaining across S MN and into the far Northwoods region.

[Tom]

GoSaints, you got your magnet out???  I think your going to reel in this one and be close to where the Blizzard conditions develop on the backside of the SLP.

[gosaints]

GoSaints, you got your magnet out??? I think your going to reel in this one and be close to where the Blizzard conditions develop on the backside of the SLP.

we shall see. Best snows could end up west of here but still in the game in this range....

[BrianJK]

Not much talk about the Freezing Rain potential, but both the Euro and NAM are showing a lot of ice in N WI.

 

@BrianJk, this may be a bigger problem than the snow that falls for your roof as it may carry more weight. Not sure what you would rather see happen.

Yeah it’s very worrisome either way. Beginning to think I may have to make a trip up there. Many of the folks I spoke with seem to dismiss the concern of roof issues but I think this is a unique situation. Yes they’ve had ton of snow up there in the past, but the present snow pack is anything from powder. And this current storm to hit will likely be laying down some sort of wintry cocktail before flipping to heavy snow.

[BrianJK]

pretty sure between the snow and ice I wont be coming home Sunday

That’s my dilemma. The back roads to my place will not be plowed in time for me to leave on Sunday. Likely not to Monday afternoon/evening.

[Stormhunter87]

The wpc ensemble maps shooting for 4-8 that hasnt really changed. The grided output is like a roller coaster though.

[BMT]

well, i'm alright with missing this one, as long as we don't get heavy rain here.  The 6z HRRR looks a lot like the NAM, (as far as Low placement) but they are the only two far enough east for a chance at any snow here.  That snow band on the NAM is so thin that it could track perfectly for eastern Iowa and most areas still don't get much because its moving so fast.  Nasty Winds look like the only sure bet with this one.        

[Minny_Weather]

Long range HRRR so take this with a grain of salt. Late changeover from sleet to snow hampers totals for here.

[St Paul Storm]

Let’s see what the 12z NAM does. The NAM is making MPX pause a bit.

[Minny_Weather]

NAM looks to be about 50 miles North & 1mb stronger @ hr 30.

[CentralNebWeather]

Let’s see what the 12z NAM does. The NAM is making MPX pause a bit

It is putting some snow into my area of Nebraska that it really hasn't done before.  That is a start I guess.

[CentralNebWeather]

NAM looks to be about 50 miles North & 1mb stronger @ hr 30.

I was just going to say I thought it had ticked north just a little.  Nice catch.

[St Paul Storm]

It is putting some snow into my area of Nebraska that it really hasn't done before.  That is a start I guess.

Things are looking a bit different at hr 30 for sure.

[BMT]

further NW for sure

[Minny_Weather]

NAM with a noon changeover for here. That's big. Precip shield is definitely North as well. Therefore, I will get nothing. I always get nothing when NAM does well a day before a storm lol.

[East Dubzz]

Yeeesh, NAM is bringing an inch of rain through my area by noon tomorrow.

[CentralNebWeather]

If the NAM has come a little north, what do you guys think will be the trend of the models?  Should be a fun day of tracking.

[East Dubzz]

If the NAM has come a little north, what do you guys think will be the trend of the models? Should be a fun day of tracking.

I think they’ll all stay pretty consistent. NAM was due to come north eventually.

[St Paul Storm]

The NAM showing tonight’s snow bleeding into Saturday’s bigger storm up this way. Keeps the precip going without a break. That’s interesting.

[OmahaSnowFan]

The wpc ensemble maps shooting for 4-8 that hasnt really changed. The grided output is like a roller coaster though.

I noticed they’ve removed the heavy snow wording in my grids which is peculiar. I’m at 3-7 total. Also noticed they reduced the max winds down to 50 mph

[St Paul Storm]

I think they’ll all stay pretty consistent. NAM was due to come north eventually.

I agree. The other models have been relatively consistent and I’d expect that to continue. The NAM has been a hot mess trying to figure this one out.

[East Dubzz]

Snow shield looks a little more expansive on this run, I think.

[CentralNebWeather]

I agree. The other models have been relatively consistent and I’d expect that to continue. The NAM has been a hot mess trying to figure this one out.

I am cheering like crazy for the GFS to verify but that may be a little too robust.  Probably the Euro is the most realistic.  We'll see.