March 23-24 Winter Storm

[Hoosier]

12z vs 18z

 

[hawkeye_wx]

The nam and euro are certainly not on the same page.

[Baum]

18 minutes ago, CoalCityWxMan said:

The nam spreads much more snow further north, looks good for many. 

Thanks for throwing me a bone. 

[Hoosier]

Fairly stout easterly 925 mb flow in the snow area.  Granted it may be tough to even mix to that level.

[snowlover2]

If there was ever a time for NAM to be right.

[buckeye]

Honestly I'd be more surprised if the nam didn't pull this at some point...especially an 18z run.   Is the nam sniffing a last minute shift...

Or is the nam being the nam?  My money on the latter.

[OHweather]

1 minute ago, buckeye said:

Honestly I'd be more surprised if the nam didn't pull this at some point...especially an 18z run.   Is the nam sniffing a last minute shift...

Or is the nam being the nam?  My money on the latter.

I was about to throw away any lingering hope for Athens (which would require a decent NE shift) given the trough/confluence downstream of this storm over the northeast.  I tend to agree this is probably just NAM noise...if it’s not I’d expect the globals to catch on 0z as we aren’t that far out at this point. 

[snowlover2]

18z GFS stays south.

[buckeye]

15 minutes ago, snowlover2 said:

18z GFS stays south.

I'd be shocked if the nam didn't settle back at 00z.   Nam has been a cruel b*tch to central Ohio this winter.   I think its given us 5' in digital snow.

[cyclone77]

Last night I felt the main band would be northeast of us, and now it's possible the heaviest could be a bit southwest of us more towards the QC.  That's usually a good problem to have, so I'm starting to feel more confident of a nice 5"+ cement event.  8"+ certainly looking possible in the heart of where the main axis sets up.  

[cyclone77]

54 minutes ago, Hoosier said:

Fairly stout easterly 925 mb flow in the snow area.  Granted it may be tough to even mix to that level.

Yeah 50kts not far off the deck with heavy precip.  Could get some 45mph gusts, and if there is any convective element I suppose gravity waves could be possible with even higher gust potential.  Wondering if the frisky winds may actually help reduce power outages to some extent.  With winds staying up it may actually keep a lot of the snow from sticking to the smaller branches/twigs.  Something to consider anyway.

[Malacka11]

The HRRR seems to be fairly NE, doesn't it? (For what it's worth)

[Baum]

23 minutes ago, cyclone77 said:

Last night I felt the main band would be northeast of us, and now it's possible the heaviest could be a bit southwest of us more towards the QC.  That's usually a good problem to have, so I'm starting to feel more confident of a nice 5"+ cement event.  8"+ certainly looking possible in the heart of where the main axis sets up.  

I'd  love to see you get a nice hit.

[Hoosier]

23 minutes ago, cyclone77 said:

Yeah 50kts not far off the deck with heavy precip.  Could get some 45mph gusts, and if there is any convective element I suppose gravity waves could be possible with even higher gust potential.  Wondering if the frisky winds may actually help reduce power outages to some extent.  With winds staying up it may actually keep a lot of the snow from sticking to the smaller branches/twigs.  Something to consider anyway.

Timing might be a factor... like how much snow comes down before the stronger winds arrive.  Not sure... haven't really looked closely enough to see how those details line up.

[cyclone77]

42 minutes ago, Hoosier said:

Timing might be a factor... like how much snow comes down before the stronger winds arrive.  Not sure... haven't really looked closely enough to see how those details line up.

Good point.

WPC showing a slight chance at a foot plus for parts of northeast IA.

[Hoosier]

For the RAOB sampling crowd, the 00z runs will be important, and definitely 12z Fri as we'll really have everything in there then.

[RCNYILWX]

18z RGEM did have a substantial shift north from 12z run, probably similar in distance of shift to NAM, but since it was much farther south with 12z run, outcome was not NAM like. Just very impressive in the heavy snow swath, particularly across northeast IA and the QCA. I think the potential is fairly high for a narrow swath of 8"+ amounts with locally 1'+, most favored in northeast IA and western/NW IL.

My gut feeling is that here in the west and southwest Chicago burbs north of 80, we have a near miss to the south with probably some minor accums, and little/none in Chicago proper. With that being said, the lingering differences in the operational models and large ensemble spread (especially in SREF) means that uncertainty is still rather high. It can almost be looked at as the individual operational runs fitting within the ensemble spread even including 18z NAMs.

If I were to assign arbitrary probs as things stand now, I'd say 60-70% favored consensus swath plays out, 20-30% the axis shifts northeast and we get into solid accums in this part of Chicago area, and 10% or less something like the 18z NAM happens. Hopefully partial sampling of southern wave this evening for 00z suite and full sampling for 12z runs better clears things up.




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[Baum]

^

cherry on top of a near miss year.

[Snowless in Carrollton]

In the last 24 hours, weather.com has changed their forecast from 1-3" to 5-8" to 3-5" and now back to 1-3" for this area.

[Baum]

4 minutes ago, Snowless in Carrollton said:

In the last 24 hours, weather.com has changed their forecast from 1-3" to 5-8" to 3-5" and now back to 1-3" for this area.

Your better off spinning a roulette wheel, my friend. 

[Hoosier]

1 hour ago, RCNYILWX said:

18z RGEM did have a substantial shift north from 12z run, probably similar in distance of shift to NAM, but since it was much farther south with 12z run, outcome was not NAM like. Just very impressive in the heavy snow swath, particularly across northeast IA and the QCA. I think the potential is fairly high for a narrow swath of 8"+ amounts with locally 1'+, most favored in northeast IA and western/NW IL.

My gut feeling is that here in the west and southwest Chicago burbs north of 80, we have a near miss to the south with probably some minor accums, and little/none in Chicago proper. With that being said, the lingering differences in the operational models and large ensemble spread (especially in SREF) means that uncertainty is still rather high. It can almost be looked at as the individual operational runs fitting within the ensemble spread even including 18z NAMs.

If I were to assign arbitrary probs as things stand now, I'd say 60-70% favored consensus swath plays out, 20-30% the axis shifts northeast and we get into solid accums in this part of Chicago area, and 10% or less something like the 18z NAM happens. Hopefully partial sampling of southern wave this evening for 00z suite and full sampling for 12z runs better clears things up.




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21z SREF still looks like it has a more northern solution.  At least the mean. 

[Malacka11]

00z is calling our names

[Hoosier]

Huge Minneapolis screwjob on the 00z NAM.

It's a little slower and the precip shield is south of 18z.

[hlcater]

1 minute ago, Hoosier said:

Huge Minneapolis screwjob on the 00z NAM.

It's a little slower and the precip shield is south of 18z.

It's also super juiced. It's putting out 20-24" totals across eastern Iowa.

Yea. Right.

[Hoosier]

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

[Hoosier]

2 minutes ago, NWLinnCountyIA said:

It's also super juiced. It's putting out 20-24" totals across eastern Iowa.

Yea. Right.

The jacked 18z NAM came a run late.  

[CoalCityWxMan]

5 minutes ago, Hoosier said:

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

Has me right in the middle of a 14-16” jackpot. Never thought I’d see the day lol. 

 

But the cutoff sucks, wish something like the 18z would happen for your guys’ case

[Hoosier]

Just now, CoalCityWxMan said:

Has me right in the middle of a 14-16” jackpot. Never thought I’d see the day lol. 

 

But the cutoff sucks, wish something like the 18z would happen for your guys’ case

Never thought I'd say this in late March but I'd honestly consider a little road trip if something like that happened.  

[CoalCityWxMan]

13 minutes ago, Hoosier said:

Never thought I'd say this in late March but I'd honestly consider a little road trip if something like that happened.  

Feel free to come on down lol. With the convective look to the snow, wouldn’t be surprised to see some thundersnow in my area

[Hoosier]

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