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Midwest/Ohio Valley/Great Lakes Snow January 24-26


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DTX "confidence higher than normal" due to consistency of GEFS/EPS at 500 mb

Attention during the coming days will be affixed on the mid latitude
cyclone/winter storm system that appears set to track through the
Lower Mississippi to Ohio River Valley Wednesday. Will not get into
details much since the storm system remains some 84 hours out,
rather will offer some commentary on the predictability of the
system. Definitely think its noteworthy to remark on the little to
no variability in the 500mb EOF patterns of the 22.12Z GEFS cluster
analysis. This lack of difference is between both eof1 and eof2 and
in the 500mb height difference signal at both Day3 and Day4. It is
also interesting, or maybe should not be surprising then, to not see
much d(prog)/dt variability in the 500mb vorticity field through
roughly the first 60 hours. Generally looking at a low variance,
strong closed off 500mb anomaly that digs clear through the Desert
SW into northern Mexico. Thereafter, variability does begin to
increase with the structure and timing of as many as 3 shortwave
centers that push into portions of western Canada, but do not see
much to suggest these vorticity anomalies will impact the phasing or
strengthening of the low pressure system as it tracks northeastward
out of the Lower Mississippi River Valley. Survey of 22.00Z EPS
member postage stamps is also suggestive of low solution variance.
The EPS members are showing a single mode characterized by heart of
cold side deformation/trowal impacting Lower Michigan (to varying
extents) with warm conveyor missing well to the south and east. What
will need to be sorted out is the quality and magnitude of moisture
that will advect meridionally into the system here locally rather
than just get shunted eastward. There are some indications in the
deterministic solutions that suggests convection and latent heating
over the Southeast United States could impact the low track. With
that stated, the forecasted structure and placement of the coupled
upper level jet into Ontario and Quebec supports a higher confidence
in a second low pressure center hanging close to Southeast Michigan
even if some east coast transfer wants to happen. Taking the lack of
solution variability in the EPS and GEFS in account, confidence is
higher than normal that the system will impact the area Wednesday
morning through Wednesday evening. The uncertainty is how far
northward the deformation snow will impact and what sort of snow
gradient will exist on the northern edge.
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14 minutes ago, Cary67 said:

Despite the outlier NW 12Z GFS track; main snows still stay SE from Central IL over to DTW. As Euro seems fairly locked in will go 1.5" far NW, 2-3" downtown and southside, 5" Kankakee

 

 

 

Mid level low tracks would argue for a more expansive shield (higher QPF) on the northwest side, *IF* the GFS played out as the actual outcome. Dubious to that though. 
My first guess for MBY is 2-4”. Should increase fairly quickly just to the south/southeast.

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5 hours ago, Stevo6899 said:

6zrgem also looks similar, strengthening as it heads NE. That's key here and the difference between an 8-12 and 3-6. If it weakens as it head NE, it'll transfer alot quicker

Could still "go south" ofc like many times for DTW, but trends to keep strengthening longer are coming together, which the 20.0z GEM had shown already Thur evening. 

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4 minutes ago, RogueWaves said:

@Powerball for you

Have been focusing on a
strong impulse that will eject out of the base of the upstream
trof and reach the area Wednesday. This will be a fast hitting
type of system with just snow (expected at this time). There is a
high likelihood of travel impacts Wednesday into early Thursday

 

Why for me? lol...

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10 minutes ago, RogueWaves said:

Thought it was you that always complained about weak rates and mix issues with SEMI storms. 

Not so much mixing issues as of late, but definitely rates for sure, since the vast majority of the "big" events have been low-amped (weak lift/instability) and northern-stream dominant (limited moisture).

That said, this storm definitely has potential given its gulf origins, the trough taking on a negative tilt and ULL possibly closing off.

 

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4 minutes ago, Powerball said:

Not so much mixing issues as of late, but definitely rates for sure, since the vast majority of the "big" events have been low-amped (weak lift/instability) and northern-stream dominant (limitrd moisture).

That said, this storm definitely has potential given its gulf origins, the trough taking on a negative tilt and ULL possibly closing off.

 

I'm actually a fan of wetter snow, but a few degrees colder would've been nice, lol. Real-deal cold and this could've had the rare bliz potential for SEMI. Still looking ok for an impactful event. Anything to get plow piles around so when the inevitable melt-off occurs, it at least looks the season. 

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25 minutes ago, RogueWaves said:

I'm actually a fan of wetter snow, but a few degrees colder would've been nice, lol. Real-deal cold and this could've had the rare bliz potential for SEMI. Still looking ok for an impactful event. Anything to get plow piles around so when the inevitable melt-off occurs, it at least looks the season. 

Honestly, the solution from a couple days ago that showed a major winter storm / blizzard up there still isn't entirely out of the realm, even with marginal temps.

The questions over the next 24-48 hours will be:

1. Whether the models are shearing the southern wave apart too fast given how much it digs and the strength of the jet streak, which has happened in the past (see 2/5/11 as an example).

2. Whether the models are overestimating the amount of confluence over Canada from today's lead wave.

The 12z GFS was definitely a small step in the right direction.

 

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2 hours ago, Powerball said:

Honestly, the solution from a couple days ago that showed a major winter storm / blizzard up there still isn't entirely out of the realm, even with marginal temps.

The questions over the next 24-48 hours will be:

1. Whether the models are shearing the southern wave apart too fast given how much it digs and the strength of the jet streak, which has happened in the past (see 2/5/11 as an example).

2. Whether the models are overestimating the amount of confluence over Canada from today's lead wave.

The 12z GFS was definitely a small step in the right direction.

 

I remember that one. GHD-1 round-2 for Detroit metro is was a nice surprise hard smack-down. I think it was you that said the PV Bliz was a lame storm and the PV did all the work. Well, with like zero cold infusion, this will be the complete opposite. Can't possibly get both here, lol

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Izzi with the afternoon afd for LOT

 

.LONG TERM...
Issued at 300 PM CST Sun Jan 22 2023

Tuesday through Sunday...

No big changes in forecast reasoning or guidance with the 12z
suite of model runs. Primary highlights of the long term portion
of the forecast include:

* Accumulating snow likely to overspread the area from south to
  north overnight Tuesday into Wednesday morning.

* Should be north-south gradient in snowfall accumulations across
  the CWA, with current data favoring higher accumulations south.

* Intermittent snow showers likely to persist through the end of
  the week with threat for swaths of light accums and hazardous
  travel conditions.

Water vapor imagery early this afternoon shows a well defined
southward moving upper low over the Intermountain West that will
be our weather maker mid-week. Secondary player in our mid-week
weather is a strong Pacific storm system over the Gulf of Alaska
that is progged to ride the polar jet stream across western Canada
before digging south into the northern Plains later this week.

The 12z operational runs and their respective ensembles really
didn`t depict any changes that graduate from the noise level to
something that is noteworthy with the mid-week system. The 12z
operational runs of the GFS and ECMWF are actually in remarkably
good agreement with each other through 12z Wednesday. Later
Wednesday into Wednesday night, the operational GFS does bend the
surface low track back a bit farther west than most of its
ensemble members and the ECMWF and EPS.

As far as sensible weather conditions go, really no meaningful
differences between these models, both have the swath of heavier
snow just to the south and east of our CWA. However, both also
have a broader area of lighter snow blanketing most of our CWA
farther to the north and west of the band of heavier snow than is
typical with most of these mid-latitude cyclones. This is likely a
result of constructive interaction with the aforementioned
northern stream shortwave trough digging south just to the
northwest of the southern stream cyclone to our southeast.

Current model QPF for late Tuesday night into Wednesday combined
with the somewhat marginal thermal profiles, looks to favor a 1-3
or 2-4 inch type snow along and north of I-80. Farther south,
particularly across northwest Indiana, if current runs were to
verify, accums would get solidly into advisory level criteria.

Some guidance is showing some enhanced QPF over northeast IL
associated with some lake enhancement, particularly Wednesday
afternoon and evening. Guidance is in good agreement that air
temps will probably be a hair above freezing by then, and if
today is any indication, snow may struggle to accumulate much
during the afternoon. In addition, lake effect parameters appear
quite marginal for lake enhancement with shallow tops to the lake
induced convective layer and weak instability owing to the lack of
any strong push of cold air. This makes me somewhat skeptical of
the models showing significant enhancement to the QPF as a result
of the lake.

Finally, while there is (and has been for a couple runs) pretty
solid model and ensemble agreement in the handling of this system,
it is still quite plausible that guidance could change. While
guidance never really truly phased that northern stream shortwave
with the cut off low over the southwest, there certainly seems to
be some interaction with the northern stream wave perhaps pulling
the southern stream wave a bit farther north, and this certainly
seems to be resulting in a broader snow area on the NW side of
this cyclone. Models are notorious for struggling both with the
movement and timing of cut off lows (like the one digging into the
southwest) and also can struggle at times handling the interaction
of northern and southern stream waves, like is progged mid-week.
All of this to say, that current strong model agreement doesn`t
necessarily equate with high confidence in the forecast. If the
timing or amplitude of either wave changes much, then the degree
of interaction could change. Less interaction could result in a
sharper cut off to the snow on the northwest flank of the system,
or a track farther south could lessen our snow amounts. Conversely,
more interaction/phasing and the heavier snow with the TROWAL
could result in higher impact accumulations farther north into our
CWA.

Beyond this southern stream wave`s snow, maintained/nudged up pops
Wednesday night into Thursday associated with the northern stream
shortwave. Combination of forcing with this trough and instability
resulting from the very cold air aloft (-33C at 500mb), should
result in a pretty favorable set up for at least scattered snow
showers.

Some indication that we could see a brief break in the snow
shower chances (at least in these latest runs) Thursday night,
before the next northern stream trough moves across the region
Friday. Guidance remains rather inconsistent with the handling of
the individual waves, and to an extent, with the overall pattern
by Friday into next weekend. Given the lower confidence, made no
changes to NBM, which does have snow shower chances with the
shortwave Friday then potentially another more impressive system
later in the weekend or early next week.

- Izzi
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50 minutes ago, Hoosier said:

Izzi with the afternoon afd for LOT

 

.LONG TERM...
Issued at 300 PM CST Sun Jan 22 2023

Tuesday through Sunday...

No big changes in forecast reasoning or guidance with the 12z
suite of model runs. Primary highlights of the long term portion
of the forecast include:

* Accumulating snow likely to overspread the area from south to
  north overnight Tuesday into Wednesday morning.

* Should be north-south gradient in snowfall accumulations across
  the CWA, with current data favoring higher accumulations south.

* Intermittent snow showers likely to persist through the end of
  the week with threat for swaths of light accums and hazardous
  travel conditions.

Water vapor imagery early this afternoon shows a well defined
southward moving upper low over the Intermountain West that will
be our weather maker mid-week. Secondary player in our mid-week
weather is a strong Pacific storm system over the Gulf of Alaska
that is progged to ride the polar jet stream across western Canada
before digging south into the northern Plains later this week.

The 12z operational runs and their respective ensembles really
didn`t depict any changes that graduate from the noise level to
something that is noteworthy with the mid-week system. The 12z
operational runs of the GFS and ECMWF are actually in remarkably
good agreement with each other through 12z Wednesday. Later
Wednesday into Wednesday night, the operational GFS does bend the
surface low track back a bit farther west than most of its
ensemble members and the ECMWF and EPS.

As far as sensible weather conditions go, really no meaningful
differences between these models, both have the swath of heavier
snow just to the south and east of our CWA. However, both also
have a broader area of lighter snow blanketing most of our CWA
farther to the north and west of the band of heavier snow than is
typical with most of these mid-latitude cyclones. This is likely a
result of constructive interaction with the aforementioned
northern stream shortwave trough digging south just to the
northwest of the southern stream cyclone to our southeast.

Current model QPF for late Tuesday night into Wednesday combined
with the somewhat marginal thermal profiles, looks to favor a 1-3
or 2-4 inch type snow along and north of I-80. Farther south,
particularly across northwest Indiana, if current runs were to
verify, accums would get solidly into advisory level criteria.

Some guidance is showing some enhanced QPF over northeast IL
associated with some lake enhancement, particularly Wednesday
afternoon and evening. Guidance is in good agreement that air
temps will probably be a hair above freezing by then, and if
today is any indication, snow may struggle to accumulate much
during the afternoon. In addition, lake effect parameters appear
quite marginal for lake enhancement with shallow tops to the lake
induced convective layer and weak instability owing to the lack of
any strong push of cold air. This makes me somewhat skeptical of
the models showing significant enhancement to the QPF as a result
of the lake.

Finally, while there is (and has been for a couple runs) pretty
solid model and ensemble agreement in the handling of this system,
it is still quite plausible that guidance could change. While
guidance never really truly phased that northern stream shortwave
with the cut off low over the southwest, there certainly seems to
be some interaction with the northern stream wave perhaps pulling
the southern stream wave a bit farther north, and this certainly
seems to be resulting in a broader snow area on the NW side of
this cyclone. Models are notorious for struggling both with the
movement and timing of cut off lows (like the one digging into the
southwest) and also can struggle at times handling the interaction
of northern and southern stream waves, like is progged mid-week.
All of this to say, that current strong model agreement doesn`t
necessarily equate with high confidence in the forecast. If the
timing or amplitude of either wave changes much, then the degree
of interaction could change. Less interaction could result in a
sharper cut off to the snow on the northwest flank of the system,
or a track farther south could lessen our snow amounts. Conversely,
more interaction/phasing and the heavier snow with the TROWAL
could result in higher impact accumulations farther north into our
CWA.

Beyond this southern stream wave`s snow, maintained/nudged up pops
Wednesday night into Thursday associated with the northern stream
shortwave. Combination of forcing with this trough and instability
resulting from the very cold air aloft (-33C at 500mb), should
result in a pretty favorable set up for at least scattered snow
showers.

Some indication that we could see a brief break in the snow
shower chances (at least in these latest runs) Thursday night,
before the next northern stream trough moves across the region
Friday. Guidance remains rather inconsistent with the handling of
the individual waves, and to an extent, with the overall pattern
by Friday into next weekend. Given the lower confidence, made no
changes to NBM, which does have snow shower chances with the
shortwave Friday then potentially another more impressive system
later in the weekend or early next week.

- Izzi

looks like they gave him the script and said not to stray.

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