April 14-15 Snow Potential

[cyclone77]

A few days ago it looked like the snows would miss northwest, and now it looks as though they'll miss southeast.  Not surprising given such a thread-the-needle event that there could be such changes, even this close to the event.  Would have been nice to see MLI make a run at their all-time record though.  I'm just glad if it's gonna miss it misses to the southeast.  I've had enough of the cold rain events to last me till next winter lol.  Good luck to you guys out east.

[NegativeEPO]

I'm still skeptical we see much accumulating snow at all from this. Think the models are overdoing it, seems too warm at the surface. And I'm not just saying this because I don't like snow. I just can't see many areas getting more than maybe an inch.

[Hoosier]

Will be interesting to watch the trends tomorrow with the convection, etc.  I don't quite trust such a southeastward placement of tonight's GFS/GEM for some reason.  

[CoalCityWxMan]

Looks like models may be bumping back NW a tad after last nights south trend

[NTXYankee]

5 minutes ago, CoalCityWxMan said:

Looks like models may be bumping back NW a tad after last nights south trend

I thought I saw that occurring on the HRRR model now that it’s within range but looks to follow the same track as others once to Indiana.  I guess it’s possible though as it occurs more often than not with the nw trend, especially last minute.

[jrips27]

12z NAM and 3k NAM  definitely bumped NW

[CoalCityWxMan]

4 minutes ago, NTXYankee said:

I thought I saw that occurring on the HRRR model now that it’s within range but looks to follow the same track as others once to Indiana.  I guess it’s possible though as it occurs more often than not with the nw trend, especially last minute.

Yeah, like Hoosier mentioned above the SE trend was a little suspicious. Not too surprised 

[NegativeEPO]

Izzi didn't seem too enthusiastic at all stating that widespread accumulating snowfall looks unlikely at this point. I would have to agree with him.

[Hoosier]

From the LOT afd

Accumulating wet snow is likely for portions of the area on
Sunday April 14th. Below is some historical context for Chicago
and Rockford for accumulating snow this late in the season.

Chicago`s Largest Calendar Day Snowfall on or After April 14
------------------------------------------------------------
- 5.4" on Apr 16 1961
- 3.1" on Apr 23 1967
- 2.5" on Apr 25 1910
- 2.2" on Apr 14 1980
- 2.1" on Apr 23 1910
- 2.0" on Apr 19 1888
- 1.6" on May 01 1940
- 1.5" on Apr 15 1980
- 1.4" on Apr 14 2014
- 1.2" on Apr 14 1885 and Apr 16 1983


Rockford`s Largest Calendar Day Snowfall on or After April 14
------------------------------------------------------------
- 7.0" on Apr 18 1912
- 4.4" on Apr 16 1961
- 3.9" on Apr 14 1980
- 3.8" on Apr 23 1967
- 2.5" on Apr 15 1923 and April 15, 1949
- 1.5" on Apr 30 1907, Apr 24 1910, Apr 15 1928 & May 1 1940
- 1.0" on Apr 18 2018

[Chicago Storm]

Looking likely that there will be an axis of 3-6” across the area, with the main question being where that sets up.

Biggest April snow this late into the month definitely in play for ORD.


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[Chicago Storm]

Izzi didn't seem too enthusiastic at all stating that widespread accumulating snowfall looks unlikely at this point. I would have to agree with him.

Can pretty much toss all of what he had to say.


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[Baum]

31 minutes ago, Chicago Storm said:

Can pretty much toss all of what he had to say.


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Thank you.

[Hoosier]

Gino definitely playing it conservative but to be fair, he did acknowledge the higher end scenario of several inches.  

[Jonger]

15 hours ago, Powerball said:

I guess there's a first for everything. 

The relative lack of activity in this thread speaks for itself, lol.

My winter interests are -- big storms or nothing at all, with Christmas being the exception. My primary winter interest is always going to be for snow to my NW. I just can't do much with it locally.

[Hoosier]

Kind of looking like the progression could be rain, snow, rain, snow here, although that phase in the middle is subject to change... not out of the question it stays snow after it flips over.

[Hoosier]

For Chicago, there have only been 5 instances of not having a 1" calendar day snow in March followed by a 1" calendar day snow in April.  Here are the dates/amounts of the last Jan/Feb 1" snow and the dates/amounts of the April 1" or greater snow that broke each streak.  How about that stretch in 1910.

2/15/1903:  4.7" ------> 4/3/1903:  2.6"

1/14/1910:  1.6" ------> 4/23/1910:  2.1"

2/26/1936:  1.3" ------> 4/1/1936:  2.1"

2/18/2000:  11.1" ------> 4/7/2000:  1.6"

2/25/2007:  2.3" ------> 4/11/2007:  3.0"

2/18/2019:  1.8" ------> 4/14/2019:  ???

[Hoosier]

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
408 PM CDT Sat Apr 13 2019

.SHORT TERM...
340 PM CDT

Through Sunday night...

Rare late season accumulating snow event is on the way, with the
potential for amounts on colder surfaces that have not been seen
in decades in some locations this late in the season. Have
forecast overall amounts of 1-4" on colder surfaces. In the
heaviest swath wherever it sets up, 2-4" will be probable, with
localized accums of up to 5" or so not out of the realm of
possibility. However, travel impacts outside of sharply reduced
visibility at times are uncertain given the mild antecedent road
temps after full sun today. It`s certainly possible to get some
brief slushy accums on less heavily traveled roads during the
heaviest snowfall, but will not be issuing a Winter Weather
Advisory due to this uncertainty about magnitude of travel
impacts. To add to the possible items to consider, northerly winds
gusting to 25-35 mph could plaster elevated/colder surfaces with
the very wet and heavy snow, with some concern due to this for
tree damage despite leaves still being bare.

This system does have the necessary ingredients going for it to
produce appreciable accums at least on grassy surfaces this late
in the season. PWAT values will be over 0.7", with 0.6" generally
seen as favorable for heavy rates. Model cross sections indicate
strong low and mid-level frontogenesis favorably topped by saturated
negative EPV (instability). In addition, the mesoscale lift will
be augmented by strong synoptic lift from the negatively tilted
trough lifting across the region, with mid 990s mb surface low
tracking just north of Ohio River Valley. Finally, forecast
soundings show that steep mid-level lapse rates will be present,
with even some minor MUCAPE that could yield convective
enhancement to the rates and a non-zero chance for thundersnow.
The heaviest precipitation/snowfall rates will occur from Sunday
morning a bit prior to sunrise through mid day/early afternoon.
During the heaviest rates, snow could be coming down at 1"+ hour
at times for rate of fall but not necessarily in actual
accumulation rate given warm ground temps and air temps a few
degrees above freezing. For this reason, capped snow ratios at a
maximum of 7:1, though in the absolute heaviest rates ratios could
briefly be higher.

The initial surge of warm advection driven precip will quickly
spread northward tonight into pre-dawn Sunday, with p-type mixing
with or changing to snow except likely for far southeast areas
where it will be a bit warmer aloft and at the surface. The system
deformation, tied to the precip shield currently seen on radar
mosaic over parts of OK and west/central TX will then spread
northeast and will be narrower in focus and be accompanied by
f-gen driven banding. There could be a gap between the 2 slugs of
moisture, so precip rates between these two areas could tail off
for a time. Big wild card is exactly where the heaviest banding
sets up, because this will be the area in which the snow will
likely come down hard enough to overcome the warm ground
conditions to accumulate. Models do a good job of indicating
conditions favorable for mesoscale banding, but exact placement is
often a now-cast type item and we`re still about 18 hours out.
We`ll also have to see if the widespread intense convection in the
warm sector of the cyclone plays any role in modulating the
placement and intensity of banding.

Outside of the heaviest banding, lighter rates will limit
accumulation potential and p-type could oscillate between rain and
snow since thermal profiles are so close to the snow/rain line.
There also at times may be a loss of deep saturation aloft outside
of the heaviest banding, so drizzle mixed with snow or plain
drizzle may occur. Finally, the immediate lakefront of Chicago and
just inland is a wildcard for accumulations. With the strong
northeast winds coming over Lake Michigan water temps in the upper
30s to 40s, this may make it tougher to get an appreciable
accumulation, along with the urban heat island effect and
lingering warmest pavement temps from today.

During the afternoon, the magnitude of the forcing will gradually
wind down in the system deformation, so snow rates should taper
off and lower ratios farther/limit accum efficiency. Precipitation
will finally end by/during the evening as the system exits east,
with a small chance of brief lake enhancement into NW Indiana.
Temperatures will drop back to the upper 20s to lower 30s tomorrow
night, so any snow that doesn`t melt once rates taper off in mid-
late afternoon will stick around for one night and then quickly
melt on Monday. Will have to watch for some patchy fog in spots
after midnight Sunday night, especially where this any lingering
snow cover.

Castro

[Hoosier]

Hopefully this is the last snow call I make this season.

I'll go with 2-3" on the coldest surfaces here.  If it stays snow after flipping over, then amounts could be higher but I have low confidence in that as models want to bring in a bit of a warm nose for a while especially around 850-700 mb.  

Thinking back to April 18-19 last year when I got about 1", it eventually began to stick to paved surfaces despite temps being a bit above freezing.  I think there will be some sticking on the pavement this time as well, especially during heavier precip, but obviously not to the extent of colder/elevated surfaces. 

[beavis1729]

20 minutes ago, Hoosier said:

Hopefully this is the last snow call I make this season.

I'll go with 2-3" on the coldest surfaces here.  If it stays snow after flipping over, then amounts could be higher but I have low confidence in that as models want to bring in a bit of a warm nose for a while especially around 850-700 mb.  

Thinking back to April 18-19 last year when I got about 1", it eventually began to stick to paved surfaces despite temps being a bit above freezing.  I think there will be some sticking on the pavement this time as well, especially during heavier precip, but obviously not to the extent of colder/elevated surfaces. 

Pretty bullish given the time of year, but hard to argue with your call. 

I will go 2” for ORD and 3” here. If ORD happens to surpass 3.1”, it would be the 2nd largest calendar day snowfall on record so late in the season. 

[Jackstraw]

17 minutes ago, Hoosier said:

Hopefully this is the last snow call I make this season.

I'll go with 2-3" on the coldest surfaces here.  If it stays snow after flipping over, then amounts could be higher but I have low confidence in that as models want to bring in a bit of a warm nose for a while especially around 850-700 mb.  

Thinking back to April 18-19 last year when I got about 1", it eventually began to stick to paved surfaces despite temps being a bit above freezing.  I think there will be some sticking on the pavement this time as well, especially during heavier precip, but obviously not to the extent of colder/elevated surfaces. 

The snow we got back on the 30th last month stuck much quicker than expected with above freezing LL temps.  Roads were covered in 30 minutes at 34 degrees.  It also was plastered to everything due to the winds as was mentioned in the ORD discussion.  This one looks similar to what we had a couple weeks ago, albeit a little better modeled.  But those who get into the heavier bands enjoy, hopefully a bookender  

[Hoosier]

14 minutes ago, beavis1729 said:

Pretty bullish given the time of year, but hard to argue with your call. 

I will go 2” for ORD and 3” here. If ORD happens to surpass 3.1”, it would be the 2nd largest calendar day snowfall on record so late in the season. 

Not taking the snow maps at face value, but it is impossible to ignore the signal for accumulating snow.  I do still think that there will be a band of about 3-5", which I'd favor JUST north of here.

[Hoosier]

15 minutes ago, Jackstraw said:

The snow we got back on the 30th last month stuck much quicker than expected with above freezing LL temps.  Roads were covered in 30 minutes at 34 degrees.  It also was plastered to everything due to the winds as was mentioned in the ORD discussion.  This one looks similar to what we had a couple weeks ago, albeit a little better modeled.  But those who get into the heavier bands enjoy, hopefully a bookender  

Thanks for chiming in.  It is a couple weeks later in the season now but still, no reason to think it won't stick to paved surfaces with the kind of precip rates that look to occur.

[Chicago Storm]

Gonna go 3.5” ORD.

But feeling like that could be low.


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[Chicago Storm]

Nice strong banding signal showing up on a lot of guidance...




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[Jackstraw]

13 minutes ago, Hoosier said:

Thanks for chiming in.  It is a couple weeks later in the season now but still, no reason to think it won't stick to paved surfaces with the kind of precip rates that look to occur.

Honestly those were some of the heaviest snows I'd seen all winter and we had some decent 1-2 inch an hour rates this winter for once.  Was quite a surprise and folks up there may get surprised also lol.

[SchaumburgStormer]

3 minutes ago, Chicago Storm said:

Nice strong banding signal showing up on a lot of guidance...




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Regardless of accumulation on roads, it appears like it should be ripping for some folks. 

[cyclone77]

RAP gives us 0.80" of precip, while the GFS shows a trace lol.  Guess we'll have to see how radar trends evolve later tonight.  Could be getting anywhere from a few inches of snow with some nice rippage, or a heavy overcast with a biting breeze.

[Hoosier]

RAP has been hinting at dual snow maxes.

[Cary67]

Could make a run at 50" for seasonal total if we receive 3" or more

[ams30721us]

35 minutes ago, cyclone77 said:

RAP gives us 0.80" of precip, while the GFS shows a trace lol.  Guess we'll have to see how radar trends evolve later tonight.  Could be getting anywhere from a few inches of snow with some nice rippage, or a heavy overcast with a biting breeze.

Ha! Sounds about right. A literal nowcast, wait and see mode to how radar shapes up now.