March 23-24 Winter Storm

[Indystorm]

And I'm in the 4-6 inch range just ne of Indpls as my yellow daffodils have just started blooming in my front lawn.  Sheesh!  St. Louis is expecting convection with a high of 54 for Sat. as is PAH with a high of 66.  Am concerned as is Coal City Wxman regarding how this will affect snow intensity.  There were a number of reports of svr t storms in the San Joaquin Valley of California this afternoon.  I wonder if the storm will be stronger than currently anticipated with less weakening as it moves east.  12z data will be crucial.

[Jackstraw]

44 minutes ago, Hoosier said:

Tim in IKK gets buried and practically not a flake here.  Man.

 

Pingers revenge lol

[Jackstraw]

24 minutes ago, Hoosier said:

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
952 PM CDT Thu Mar 22 2018

.UPDATE...

948 PM CDT

No changes to going Winter Storm Watch. An early look at the
latest available guidance largely supports the current Watch
counties. The 00z NAM features very significant 1"+ liquid
equivalent amounts in a good chunk of the watch counties, which
would indicate potential for very heavy snowfall rates and
widespread 8"+ snowfall amount should things evolve close to what
is depicted. It also portrays an exceptionally sharp cut-off over
the northeast third of the CWA due largely to low level dry air.
This cut-off has been well advertised.

However, have some concern off this run alone that the magnitude
of forcing, especially mesoscale from mid-level frontogenesis, and
resulting strong lift, would cause heavy enough snow aloft to
saturate the low levels in parts of the area under the dry air
cut-off, especially sufficiently inland of Lake Michigan. This
would include portions of the western/southwest Chicago metro on
Saturday morning. A good way to visualize this potential is with
the simulated Composite Reflectivity, compared to 1km AGL
simulated reflectivity or the actual QPF output, which shows
strong 25+ dbZ echoes well north into the CWA, but little/no
reflectivity at 1km level and little/no QPF for part of area under
high reflectivity aloft/Comp Ref.

With the above being said, the verbatim outcome of the 00z NAM did
bring it into better agreement with the other operational guidance
after the 18z runs of the 12km and 3km NAMs were well north of
the consensus. On one final note, the 21z SREF did adjust
northward and increase mean QPF/snowfall from previous run (was
highest mean of previous 4 runs), but with still very significant
spread, especially among NMB members. All the above goes to say
that there is still uncertainty in the outcome of this event, such
as exact placement of the likely very sharp cutoff somewhere over
the northeast CWA, along with top end snowfall amounts in the
heavy snow swath. The current watch counties remain the highest
confidence for significant snowfall and impacts. The hope is that
full sampling by the 12z RAOBS of the southern stream short-wave
entering southern California will clear up lingering discrepancies
for the 12z guidance suite should there still be fairly large
spread with remainder of 00z suite.

Castro

Don't think I've ever seen LOT write that long about a NAM run 

[RCNYILWX]

Don't think I've ever seen LOT write that long about a NAM run 

Nothing else to write about at that moment other than 21z SREF and I got inspired. Of course the 00z RGEM is back way southwest and doesn't even get warning criteria snow into LOT CWA.

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[hawkeye_wx]

14 minutes ago, RCNYILWX said:

Of course the 00z RGEM is back way southwest and doesn't even get warning criteria snow into LOT CWA.

00z ICON, same thing... big sw jump.  This model has been inconsistent.

[Hoosier]

22 minutes ago, RCNYILWX said:

Nothing else to write about at that moment other than 21z SREF and I got inspired. Of course the 00z RGEM is back way southwest and doesn't even get warning criteria snow into LOT CWA.

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Barely a flake past the west/southwest row of LOT.  

[Hoosier]

Here are the SREF members and mean precip totals

[hawkeye_wx]

And the 00z GFS is generally a little sw as well.

[Radtechwxman]

Keep the south trend going! You guys gotta share the wealth. Lol. I80 has scored all winter. Time for I74 to cash in 

[cyclone77]

Hard to feel too secure with such a narrow, thread-the-needle type event, but growing more confident we see our first warning criteria event of the season.  I'm assuming it would be the last too lol.  That 12km NAM run was just sick from this area back towards Waterloo.  The RGEM makes me a bit nervous, as it would have us on the northeast edge of the main precip band.  All in all things are seeming to line up for a good 6-8" cement event.  The convective nature of the precip, the high PWATs, and the pivoting action of the storm may end up dumping a foot plus easy.

[Hoosier]

This is just one example of the sharp gradient/dry air we are dealing with on the northern edge. These are 3 NAM forecast soundings for O'Hare, Joliet, and Kankakee, in that order.  Notice the NAM sounding for O'Hare actually has some pretty decent omega and nearly saturated mid levels at 15z Saturday, but a nasty low level dry layer that prevents any precip from reaching the ground on the model. The Joliet and Kankakee soundings look a lot better in the low levels by comparison

[cyclone77]

Since the 00z HRRRx apparently never ran, I was forced to look at the long-range RAP.  This is only through 15z Sat with heavy snow still falling.  

[CoalCityWxMan]

4 minutes ago, cyclone77 said:

Since the 00z HRRRx apparently never ran, I was forced to look at the long-range RAP.  This is only through 15z Sat with heavy snow still falling.  

Lock it in...lol

 

Does anyone know if the long range rap can be trusted at all? I've never really used it before

[Hoosier]

6 minutes ago, cyclone77 said:

Since the 00z HRRRx apparently never ran, I was forced to look at the long-range RAP.  This is only through 15z Sat with heavy snow still falling.  

Just curious, what is your biggest storm in late March or later?

[cyclone77]

11 minutes ago, Hoosier said:

This is just one example of the sharp gradient/dry air we are dealing with on the northern edge. These are 3 NAM forecast soundings for O'Hare, Joliet, and Kankakee, in that order.  Notice the NAM sounding for O'Hare actually has some pretty decent omega and nearly saturated mid levels at 15z Saturday, but a nasty low level dry layer that prevents any precip from reaching the ground on the model. The Joliet and Kankakee soundings look a lot better in the low levels by comparison

Yeah that shows up nicely on the RH maps as well.

[CoalCityWxMan]

Also Cyclone, this is the 00z HRRRX at 36 hours FWIW. 

Hi-res vs. Globals

 

[cyclone77]

1 minute ago, Hoosier said:

Just curious, what is your biggest storm in late March or later?

I honestly can't remember an actual warning criteria event in mid to late March.  Not saying it didn't happen, but I can't remember one.  We did have a foot of snow in early April of 1997 IIRC.  That was a very impressive event, with quite a bit of it falling during the day as well.

[cyclone77]

1 minute ago, CoalCityWxMan said:

Also Cyclone, this is the 00z HRRRX at 36 hours FWIW. 

Hi-res vs. Globals

 

Nice.  Weatherbell and even the NOAA rapidrefresh site itself wasn't showing a 00z.

[Hoosier]

4 minutes ago, cyclone77 said:

I honestly can't remember an actual warning criteria event in mid to late March.  Not saying it didn't happen, but I can't remember one.  We did have a foot of snow in early April of 1997 IIRC.  That was a very impressive event, with quite a bit of it falling during the day as well.

That was the April 10-11 event, right?  I remember being so jealous lol. I think there was a band of snow on the evening of the 10th that hammered areas from around PIA to IKK.  I still remember watching the radar and how that thing wouldn't come north.  

[Justin]

5 minutes ago, cyclone77 said:

I honestly can't remember an actual warning criteria event in mid to late March.  Not saying it didn't happen, but I can't remember one.  We did have a foot of snow in early April of 1997 IIRC.  That was a very impressive event, with quite a bit of it falling during the day as well.

I was just going to say for the Quad Cities it has to be that storm... it was around tax day too I thought as well.  That was about as wet as snow can get without it being rain, lol.  I think we had something like 14-15" with that storm.  It was gone in like two or three days too.  This set up is very similar in nature as we are going to need the dynamic cooling to over come snow falling during some daylight hours also.   I just cannot buy the widespread double digits being spit out.  Still think high end amounts of 8-9" will be in more narrow/isolated spots.  Should thundersnow occur then all bets are certainly off and there would certainly be swaths of 12"+.  I still feel like across my area the axis of heaviest snow will be roughly from Charles City Iowa to around/just North of Clinton Iowa then thru the La Salle area in IL.  

[hlcater]

10 minutes ago, CoalCityWxMan said:

Also Cyclone, this is the 00z HRRRX at 36 hours FWIW. 

Hi-res vs. Globals

 

Looks like it's on board with the NAM with the aggressive warm nose. Ew.

[cyclone77]

2 minutes ago, Hoosier said:

That was the April 10-11 event, right?  I remember being so jealous lol. I think there was a band of snow on the evening of the 10th that hammered areas from around PIA to IKK.  I still remember watching the radar and how that thing wouldn't come north.  

Yep, that's it.    https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=lotrad&java=script&mode=archive&frames=150&interval=5&year=1997&month=4&day=11&hour=6&minute=55

[CoalCityWxMan]

Well, once again there’s pretty big placement differences of the axis of heavy snow (what else is new) 

The NAM, RAP, HRRRX(lol), SREF are north while the GFS, GEM, EURO are further south. Let the nail biting begin 

[cyclone77]

7 minutes ago, NWLinnCountyIA said:

Looks like it's on board with the NAM with the aggressive warm nose. Ew.

Gambling with the snow/mix line is gonna pay off for whoever gets in on that.  The pivot point will dump buckets of snow near where that mix/snow line ends up.

[hawkeye_wx]

00z UK

[Hoosier]

3 minutes ago, hawkeye_wx said:

00z UK

Odd, I was just looking at the Ukie precip on the meteocentre site and the map looks different.  Both have the correct date stamp so who knows

[cyclone77]

3 minutes ago, hawkeye_wx said:

00z UK

Wow, what a cutoff.  Always fun when you're worried about potential mixing issues on one model, and an extreme dry cutoff on another.  

[SchaumburgStormer]

29 minutes ago, NWLinnCountyIA said:

Looks like it's on board with the NAM with the aggressive warm nose. Ew.

Never discount the warm tongue of death.

[hawkeye_wx]

22 minutes ago, Hoosier said:

Odd, I was just looking at the Ukie precip on the meteocentre site and the map looks different.  Both have the correct date stamp so who knows

Hmm.  That is odd.  I didn't notice until you mentioned it.

[cyclone77]

New Euro alarmingly southwest compared to it's past 10 runs.  QC 10", 3" here, and 0" about 20 miles northeast of here.  The southern/western QC metro has had two warning criteria events this season while we haven't had one, so this would be pretty irritating lol.  

Hopefully the 12z runs correct back northeast a bit.