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Hoosier

April 14-15 Snow Potential

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Could end up not being much, but there is at least some possibility of a band of heavy, wet snow to the tune of several inches.

Discuss

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Whether it's rain or snow at onset, precip looks to arrive here in the wee hours of Sunday morning.  If it's snow, could lay down a layer prior to any possible sun angle factor.

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Will be in Milwaukee Saturday-Tuesday for some family stuff. As someone from down south who doesn’t see much snow I’ll be keeping a close eye on this. Would love to see a couple of inches. 

 

Euro looked like a pretty good hit. Looked a little colder for the Milwaukee area but I think that was a byproduct of the low being a little SE of the 12z run. If anyone’s got the Kuchera map, would love to see it. 

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5 hours ago, jrips27 said:

Will be in Milwaukee Saturday-Tuesday for some family stuff. As someone from down south who doesn’t see much snow I’ll be keeping a close eye on this. Would love to see a couple of inches.

Trade ya for some of Dixie Alley's severe. :P

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NAM quite a bit snowier..pretty high totals with kuchera method still. Wonder how much would melt/compact right away with most of it falling during the day  

32930618-9217-44B4-89C1-C617083555CE.png

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good to see the winter trend of snowing just to my north and west is not just a seasonal thing.

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2 minutes ago, michsnowfreak said:

Hoosier, was Chicago's last 1" snow in Feb a record if it holds?

No, there have been like 9 times when the last 1" snow happened earlier than the currently valid last 1" snow.  It would be very unusual to have a 1" snow in mid February and then skip over March and basically go 2 months until getting the next one... more on that later.

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NAM is still running on the northern end on this 12z cycle, with other models farther south.  We'll see about Euro.

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2 hours ago, Baum said:

good to see the winter trend of snowing just to my north and west is not just a seasonal thing.

Locking it in for next years El Nino

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Numerous questions with this

850 mb temps are cold enough on the nw flank going in, but how long will it take to cool the lower levels to support snow?  What will precip rates be like?  Exactly how warm will it get during the daytime on Sunday?  

All in all, I'd still say a band of 2-5" is in play, but it will probably be pretty narrow if it occurs.  Even those amounts could be enough to make this the biggest snow this late in the season in about 40-50 years for some areas.

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imo it looks like there could be rates around 1" per hour at  times... as long as temps get close enough to freezing.  Realizing those heavy rates will be important to the overall forecast and whoever can get that during the daytime would help since we have an August like sun angle.  

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43 minutes ago, Hoosier said:

Numerous questions with this

850 mb temps are cold enough on the nw flank going in, but how long will it take to cool the lower levels to support snow?  What will precip rates be like?  Exactly how warm will it get during the daytime on Sunday?  

All in all, I'd still say a band of 2-5" is in play, but it will probably be pretty narrow if it occurs.  Even those amounts could be enough to make this the biggest snow this late in the season in about 40-50 years for some areas.

Agree - good summary at the moment.  In such a marginal set-up, it will probably come down to nowcasting...or, at a minimum, another 1-2 sets of model runs.

Still a lot of uncertainty in modeled QPF for being only 36 hours out.  12z NAM shows 1.00+" liquid in Chicago metro, with the GFS and FV3 around 0.5" (although quite a bit more further south).  Not sure about the Euro, although you mentioned that ORD gets hit pretty good verbatim.  The track seems to be converging on a general solution...but of course even 10-20 miles can make a big difference for the metro.

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5 minutes ago, beavis1729 said:

Agree - good summary at the moment.  In such a marginal set-up, it will probably come down to nowcasting...or, at a minimum, another 1-2 sets of model runs.

Still a lot of uncertainty in track for being only 36 hours out.  12z NAM shows 1.00+" of liquid in Chicago metro, with the GFS and FV3 around 0.5" (although quite a bit more further south).

The city is in a good spot if you blend everything together.  Another thing I'm wondering is if lake temps have warmed up enough to be a factor in keeping temps a bit warmer there.  Hard to say for sure... there is a huge difference in current water temps between the Chicago shore and Chicago crib (48 vs 37).  I'm guessing the shore temps are very sensitive and could drop by several degrees in the next few days so my guess is that if the lake ends up being a factor, it would only be right near the shore and not out toward MDW or ORD.

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Looks like the 18z NAM ticked a *bit* SE from the 12z NAM, but is still not nearly as far SE as the Euro/GFS/FV3.  From a liquid precip standpoint, looks like a nice hit for Chicago metro...around 1" QPF. 

Is it worth analyzing NAM soundings at 36-60 hours to determine precip type?? :ph34r:

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RC afd

 

.LONG TERM...
400 PM CDT

Saturday Night through Friday...

The main concern and focus is on the potential for a rare mid
April accumulating wet snow event late Saturday night into Sunday.
After this, we`ll quickly warm back to above normal on Tuesday,
followed by the active pattern resuming in the mid to late week
period. The message for Sunday`s snow is that a fairly narrow
swath of noteworthy accums of 2+" is becoming increasingly likely
across portions of northern Illinois, with possibility of some
road impacts where it snows heaviest.

Backdoor cold front passage will flip winds to north/northeast
Saturday evening, and allow colder air to bleed in at the low
levels. At the same time, strong negatively tilted trough/ULL and
attendant sub 1000 mb surface low will be ejecting northeastward.
This system will be accompanied by widespread intense convection
in the warm sector (note SPC Day 2 Moderate Risk for areas near
Gulf Coast) as it lifts northeast toward our area Saturday night.
It appears that the ingredients could be in place for moderate to
heavy precip rates in the cold sector of the surface low, aiding
in dynamic cooling of otherwise fairly marginal thermal profiles
that you would expect for mid April. Potentially supporting
factors include: steep mid-level lapse rates; high PWAT values
above 0.6" for a snow producing system; and likelihood of strong
low and mid-level frontogenetically driven banding given tight
baroclinic zone that system will be interacting with/intensifying.
There are some lingering uncertainties and possible red flags,
however, that will be discussed below.

Precipitation shield will rapidly spread northward through
Saturday night and into early Sunday, with northern extent
dependent upon exact track and strength of the surface low.
Overall trend on the global models and ensembles has been for a
more southeastward track of the surface low and perhaps a hair
weaker system. Suspect that the most recent 12km NAM runs are
stronger and wetter outliers vs GFS/ECMWF consensus. Temperatures
by early Sunday should fall to the mid to high 30s and arrival of
steady to heavy precip rates by Sunday morning should even cool
them slightly. All in all readings should largely flatline given
the precipitation, clouds and strong northeast winds gusting to
30-35+ mph. These strong northeast winds off a now fairly mild
Lake Michigan could also make it very tough for snow to accumulate
immediately lakeside, including downtown Chicago.

One of the largest sources of uncertainty is exactly where the
heaviest f-gen driven banding sets up in the system deformation
axis. In this likely narrow swath will be the best chance to
overcome the strong mid April sun, above freezing temps and mild
antecedent ground temps for snow to even accumulate on road
surfaces, with event totals of 2-4" or even higher. Dynamic
cooling will be a necessity to enable more than non-accumulating
wet snow, which seems like a distinct possibility outside of
wherever the heaviest banding occurs. Lowered ratios to 7:1 or
less considering the aforementioned factors, with possibility of
locally higher ratios again wherever the heaviest banding occurs.

Another concern I have is that the intense convection in the warm
sector could ultimately rob some of the moisture and dynamics in
the cold sector, which could be playing a role in much farther
southeast and weaker system on 12z Canadian. Everything discussed
above will also determine where rain/snow line is, which is
currently indicated south of a Valpo to Pontiac line. Ultimately,
suspect that the extreme totals on some of the models are
overdone, but once we have honed in the specifics, it is possible
a headline may be needed for counties where confidence is highest
in travel impacts. Official forecast snow amounts of 1-4"
along/north of I-80 in IL will certainly be refined as trends
become more clear.

After the storm exits, Monday`s temps will recover to just shy of
seasonable and likely melt any lingering snow. Then strong
southwesterly warm advection Tuesday will bring temps all the way
back up to the upper 60s to lower 70s, quite a change from Sunday!
The next stronger weather system in what continues to be an active
pattern across the CONUS will be during the Tuesday night/Wednesday-
Thursday period, when periods of showers are probable, along with
the threat for some thunderstorms. Unseasonably cool temps will
likely return Friday in the wake of the mid week storm system.

Castro

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45 minutes ago, CoalCityWxMan said:

The long range RAP looks pretty good for N IL

0A1B4BEB-3D48-4E83-A3DA-E8A5FFA8F870.png

Sleet would be particularly cruel at this time of year.  I am expecting the rain/snow line to not be too far away, one way or another.

Will be interesting to see how much daytime warming the RAP and HRRR have on later runs.  Be aware that they could be too aggressive with that.

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3 minutes ago, Hoosier said:

Sleet would be particularly cruel at this time of year.  I am expecting the rain/snow line to not be too far away, one way or another.

Will be interesting to see how much daytime warming the RAP and HRRR have on later runs.  Be aware that they could be too aggressive with that.

Pulled a few forecast soundings and some of that sleet area could actually be snow.  I think the model could be having trouble resolving the precip type because saturation aloft is a bit iffy and there is a relatively deep layer aloft with temps like 0C to -1C.  

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3 hours ago, Jonger said:

Not sure if I really want this.

20190412_182819.thumb.jpg.332bc2db0414d28c46a020668e01ccaa.jpg

I guess there's a first for everything. :lmao:

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

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7 minutes ago, Baum said:

when you don't really want snow bet on snow.

I probably would've bet money a week or two ago on accumulating snow being done.  Have had some nice spring days, stuff is blooming and locally, snow has almost shut off entirely for the past couple months.  Oops

This one is a little more tolerable than other April snows because of the likely period of heavy rates, possible historical aspects and the quick warm up coming early next week.

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