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Hybrid Clipper Event 1/27-1/29

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Just now, RCNYILWX said:

NAM has been really struggling with this air mass with dry air issues. If soundings otherwise look as good as previous runs, then should be good to go.

Sent from my SM-G965U using Tapatalk
 

Ever think of a side career as a counselor/therapist? :-) Forecasts like this have to be hard for your office. People go to bed with one message and wake up with “reality” (either way it’s hard to be right on the nose...)

Thanks for your posting, love the actual expert views and insight into thinking...

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25 minutes ago, michaelmantis said:

Don’t post that cr*p here... ;-) Debbie downer type map right there for NE IL.

Have a feeling people are going to wake up many places surprised (both with more and less snow than expected). Lots of variables here.

You start posting global runs on top of hi-res runs there's enough analysis paralysis to find clunkers and fantasy runs alike

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2 minutes ago, Cary67 said:

You start posting global runs on top of hi-res runs there's enough analysis paralysis to find clunkers and fantasy runs alike

I am sure there are different schools of thought on this, but is there a point of diminishing returns with the increasing number of models out there? Not sure what that number is (or could also see the view of more data never hurts).

Going back to someone’s post from a few hours ago, my total layman’s view is that “forecasting” risks becoming just “averaging the models” vs. intuition, climatology, and training.

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Snow creeping closer toward my direction. P&C still listing potential of 4-9 inches. I’ll stay on the low end of that & throw out an ORD prediction of 5.7 inches.

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I'll freely admit that I've always been aggressive in terms of wanting to issue advisories/warnings for events that may not quite get to criteria but will have an impact and that not everyone agrees with it.  But, I feel like this is a good case where an argument could be made for a Winter Storm Warning for another row of counties south in IL and include Chicago...

1) Amounts will push criteria anyways. 

2) The snow will be moderate to heavy into the rush, and potentially through much of it.

3) It will be 10 degrees and breezy until the start of the commute.  This along with rates will make roads a mess.

Then after a high-impact, borderline warning criteria snow it shoots above freezing for a few hours and likely just drizzles, so everything starts compacting/melting, then the bottom falls out with gusty winds and snow showers in the afternoon, causing a lot of issues with stuff turning icy and roads/lots not cleared quickly enough becoming very hard to deal with.  This is all followed by record cold.  It's quite a storm.  There may not be the conventional 80% confidence in 6"+ for a warning in Chicago, but I think there are a lot of complicating factors.  This isn't to single out LOT as their snow amounts are fine, and by convention, their headline decision is fine (especially given an advisory already out and amounts only inching up a bit as their AFD mentioned), but is a broader argument that advisories/warnings, in general, should be more impact based.  

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2 minutes ago, OHweather said:

I'll freely admit that I've always been aggressive in terms of wanting to issue advisories/warnings for events that may not quite get to criteria but will have an impact and that not everyone agrees with it.  But, I feel like this is a good case where an argument could be made for a Winter Storm Warning for another row of counties south in IL and include Chicago...

1) Amounts will push criteria anyways. 

2) The snow will be moderate to heavy into the rush, and potentially through much of it.

3) It will be 10 degrees and breezy until the start of the commute.  This along with rates will make roads a mess.

Then after a high-impact, borderline warning criteria snow it shoots above freezing for a few hours and likely just drizzles, so everything starts compacting/melting, then the bottom falls out with gusty winds and snow showers in the afternoon, causing a lot of issues with stuff turning icy and roads/lots not cleared quickly enough becoming very hard to deal with.  This is all followed by record cold.  It's quite a storm.  There may not be the conventional 80% confidence in 6"+ for a warning in Chicago, but I think there are a lot of complicating factors.  This isn't to single out LOT as their snow amounts are fine, and by convention, their headline decision is fine (especially given an advisory already out and amounts only inching up a bit as their AFD mentioned), but is a broader argument that advisories/warnings, in general, should be more impact based.  

I think its a 50/50 call.. but with the high Impact on the morning commute I thought they would pull the trigger as well

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LOT update

 

National Weather Service Chicago/Romeoville, IL
901 PM CST Sun Jan 27 2019

.UPDATE...
901 PM CST

Winter storm continues to take shape to our northwest this
evening. Latest guidance continues to support a several hour
period of heavy snow across the area last tonight and very early
Monday morning, with snowfall rates of an inch or more per hour
likely especially across far northern Illinois. Had considered
adding another tier of counties to the Winter Storm Warning along
the I-88 corridor, though 00Z runs of the HRRR/NAM and 3km WRF all
appear to support going headline delineation with respect to
expected snowfall amounts. Main message continues to be that
several inches of snow will come at bad time for Monday morning
commuters, and that the morning rush will likely be significantly
impacted especially north of I88.

Evening GOES-16 water vapor imagery depicts a vigorous mid-level
short wave trough digging southeast across the northern Plains.
Strong surface pressure falls, in excess of 4 mb per 3 hours, were
developing downstream into the mid/upper Mississippi Valley in
response to strong low level warm advection and height falls. This
in turn was resulting in an expanding precipitation shield across
much of Minnesota and Iowa, and into western parts of Wisconsin
and Illinois. Model guidance has locked into a solution which
takes the track of the surface low southeast into central Iowa
through midnight, then eastward across far northern Illinois near
the Wisconsin border through Monday morning. This low track would
typically not favor heavy 6+ inch snowfall amounts for northern
IL. However, very strong baroclinicity and dynamics with this
system in addition to the initial southeasterly propagation of the
storm support a period of impressive snowfall rates across
northern IL. In addition, presence of cold arctic air mass will
also likely support higher than usual snow/liquid ratios during
the period of strong isentropic ascent from around midnight
through sunrise. Overall, tweaked QPF amounts and snow ratios
slightly, though basically am maintaining the same forecast
snowfall amounts ranging from 1-3 inches across the southern
couple tiers of counties to 6 to 9 inches across far northern IL
closer to the Wisconsin border.

The heaviest snow should be winding down as the morning rush hour
begins, with intensity tapering of from sunrise through mid-
morning. Mid-level dry slot develops which will likely result in a
period of mixed light snow or drizzle. Surface temps, which will
rise through the night and into Monday morning, will bring temps
slightly above freezing across the east/southeast parts of the cwa
for a time, though temps will then fall as the low and cold front
move east of the area by early afternoon. This will result in the
potential for a period of light freezing drizzle before cold
advection cools the column enough for any lingering precip to
change back over to light snow/flurries. Winds gusting 30-35 mph
initially from the south in the morning, and then from the west-
northwest in the afternoon, will likely cause some blowing and
drifting of snow especially in open areas. Temperatures will fall
into the teens and lower 20s behind the departing system in the
afternoon, with wind chills dipping toward zero by nightfall.

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3 minutes ago, OHweather said:

I'll freely admit that I've always been aggressive in terms of wanting to issue advisories/warnings for events that may not quite get to criteria but will have an impact and that not everyone agrees with it.  But, I feel like this is a good case where an argument could be made for a Winter Storm Warning for another row of counties south in IL and include Chicago...

1) Amounts will push criteria anyways. 

2) The snow will be moderate to heavy into the rush, and potentially through much of it.

3) It will be 10 degrees and breezy until the start of the commute.  This along with rates will make roads a mess.

Then after a high-impact, borderline warning criteria snow it shoots above freezing for a few hours and likely just drizzles, so everything starts compacting/melting, then the bottom falls out with gusty winds and snow showers in the afternoon, causing a lot of issues with stuff turning icy and roads/lots not cleared quickly enough becoming very hard to deal with.  This is all followed by record cold.  It's quite a storm.  There may not be the conventional 80% confidence in 6"+ for a warning in Chicago, but I think there are a lot of complicating factors.  This isn't to single out LOT as their snow amounts are fine, and by convention, their headline decision is fine (especially given an advisory already out and amounts only inching up a bit as their AFD mentioned), but is a broader argument that advisories/warnings, in general, should be more impact based.  

Trust me, there has been an internal debate on this else where. I'll let @RCNYILWX explain more if he wants to.

But for now it stays WWA, and an upgrade may or may not happen.

I fully agree a WSW should be n effect though. Amounts will be near or exceed criteria, combined with winds, commute on a Monday morning...

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Just now, Chicago Storm said:

Trust me, there has been an internal debate on this else where. I'll let @RCNYILWX explain more if he wants to.

But for now it stays WWA, and an upgrade may or may not happen.

I fully agree a WSW should be n effect though. Amounts will be near or exceed criteria, combined with winds, commute on a Monday morning...

I've heard there's some debate and I'm sure both sides have merit...my lean is this should definitely be a warning, though given they just updated their grids to bump downtown Chicago to slightly over 6" and held with an advisory my guess is at this point there won't be an upgrade.  I don't want to come off as looking for a reason to complain about a random NWS office.  I discussed the Chicago forecast with the met putting it together at work late this afternoon and was surprised by no warning, and was wondering if anyone here was chiming in or not. 

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24 minutes ago, OHweather said:

I've heard there's some debate and I'm sure both sides have merit...my lean is this should definitely be a warning, though given they just updated their grids to bump downtown Chicago to slightly over 6" and held with an advisory my guess is at this point there won't be an upgrade.  I don't want to come off as looking for a reason to complain about a random NWS office.  I discussed the Chicago forecast with the met putting it together at work late this afternoon and was surprised by no warning, and was wondering if anyone here was chiming in or not. 

I would go warning in every borderline case especially if timing is right at rush hour. People hear warning much stronger than advisory. If I am going to bust I'd much rather bust high than low.

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Just now, Stebo said:

I would go warning in every borderline case especially if timing is right at rush hour. People hear warning much stronger than advisory. If I am going to bust I'd much rather bust high than low.

The flip side of that is if it doesn’t materialize you get chronic nay saying. Although I don’t think this would be one of those cases. 

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Just now, Maneee said:

The flip side of that is if it doesn’t materialize you get chronic nay saying. Although I don’t think this would be one of those cases. 

I think gone are the days of stuff not materializing. Being weaker sure, but outright not materializing, no.

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4 minutes ago, Stebo said:

I would go warning in every borderline case especially if timing is right at rush hour. People hear warning much stronger than advisory. If I am going to bust I'd much rather bust high than low.

A 6” fluffy synoptic snow falling over 10 hours with no wind on a Saturday can probably slide with no warning, but no mitigating factors here and a lot of compounding ones.  I know MQT factors in ratios and may grudgingly put out an advisory for 6” of fluffy upsloped LES but will warn 6” wet synoptic.  At least that’s what a tv met up there once told me.  Hard to come up with flexible criteria that make sense for any possible given storm, but I don’t love the rigidity of the current criteria.  Too many factors other than snow amount over a 12 or 24 hour period. 

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Just now, OHweather said:

A 6” fluffy synoptic snow falling over 10 hours with no wind on a Saturday can probably slide with no warning, but no mitigating factors here and a lot of compounding ones.  I know MQT factors in ratios and may grudgingly put out an advisory for 6” of fluffy upsloped LES but will warn 6” wet synoptic.  Hard to come up with flexible criteria that make sense for any possible given storm, but I don’t love the rigidity of the current criteria.  Too many factors other than snow amount over a 12 or 24 hour period. 

Agree completely.

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