Jump to content

  • Member Statistics

    17,508
    Total Members
    7,904
    Most Online
    joxey
    Newest Member
    joxey
    Joined

December 24-25 Snow Potential

Hoosier

By Hoosier,
in Lakes/Ohio Valley

Recommended Posts

pondo1000

pondo1000

Posted
Posted
9 minutes ago, snowlover2 said:

Technically speaking from Dayton south in ILN CWA its the possibility of 3" and they are only saying 2. That being said in the past they would issue a WWA for the first widespread snowfall of the season and being Christmas I thought they would have and they eventually might.

Yeah, just a SWS for now out of ILN for this area. 1-2 inches.

Link to comment
Share on other sites
  • Replies 343
  • Created
  • Last Reply
Hoosier

Hoosier

Posted
  • Author
Posted

Solid discussion by LOT

  

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
310 PM CST Sat Dec 23 2017

.SHORT TERM...
308 PM CST

Through Sunday...

Main forecast concerns/challenges are with the snow expected
early Sunday morning into Sunday evening across much of the CWA.
Have expanded the winter weather advisory north into parts of the
I-88 corridor, and have replaced the advisory for Lake IN and
Porter counties with a warning for higher amounts likely owing to
additional lake enhancement/effect.

In the near term, relatively quiet conditions across the CWA.
Cloud cover to the north has reached the northern half of the CWA,
providing some partly sunny/partly cloudy skies. This will
continue to pass through but likely further scatter with time.
Precip not expected this afternoon into the evening.

Trends today for most guidance coming in today have been for a
more robust system to move across the region on Sunday. A system
that will likely provide higher snowfall amounts than previously
forecast across much of the CWA. Feeling fairly confident with
placement and timing of highest snow amounts/rates, with this
confidence also including this trend for higher snowfall amounts.
This higher confidence in place also given the fact that this
system was sampled by 12z RAOBs today. Large trough expected to
swing/dig across the central CONUS tonight into Sunday with a
fairly stout vort max likely pushing through the area. Out ahead
of it, will see low/mid level flow back to more of a southerly
direction, with a period of WAA helping to set the stage for
developing snow over IA/MO and western IL after midnight tonight.
Initial dry air in the lower levels should not have any trouble
saturating, as this strongest forcing continues into the
west/southwest CWA around the 3-4 AM CST time frame. Should see
this light snow continue to expand and increase in intensity
across most locations south of I80 around 6 AM CST, especially
with vort max and deepening surface reflection swinging through.
Further expansion of this snow into remaining areas in northern
Illinois and northwest Indiana then expected through mid morning,
with this large scale ascent spreading over the area.

With this snow expected within the next 24 hours, able to get a
glimpse into the mesoscale features which could be at play.
Guidance becoming more focused not only with this system, but with
the mesoscale features that are appearing likely to provide
periods of higher intense snowfall and amounts. Deep area of
frontogenesis expected to push through portions of east central IL
and northwest Indiana during Sunday morning. As this occurs, will
see low level flow become oriented off the lake with lake
enhancement/effect becoming highly probable. This is especially
the case by mid/late morning into midday, once again, with
frontogenetical forcing increasing. This will likely provide
increasing snowfall rates along the Kankakee river valley in the
IL and IN up to locations near the lake in northwest Indiana.
While this moderate to at times heavy snow occurs along this axis,
light to at times moderate snow will occur elsewhere across the
remaining CWA. A period of snowfall appearing likely for much of
the day Sunday, with a window of more intense snow likely during
the 14z-19z time frame. High snow efficiency also appearing
probable with a deep dendritic growth zone, forcing likely
situated in this zone for a longer period of time, and then with
slant wise and upright instability likely in place.

Several of the previously mentioned factors have led to growing
concerns for higher amounts and possible larger impacts. So have
increased snow amounts over much of the CWA with 1-3 inches
possible north of I-88, 2-4 between I88 and I80, and with 3-6
south of I80 (especially in the Kankakee river valley in IL and
IN). For locations near the lake in northwest Indiana, high delta
Ts, High inversion heights, and strong low level convergence will
help to offset a lacking longer fetch and produce higher amounts
of 5-8 inches. Once again, have replaced the advisory in Lake IN
and Porter counties with a warning with the expected higher
amounts and with the fact that its quite possible for 1-2 inch
hourly snowfall rates to occur at times. This would provide
visibilities at or below 1/4 mile at times, and snow covered
roads. Will need to continue to monitor this location, as it is
definitely possible that I am under forecasting the snow amounts
in this location. If more intense snow were to really set up in
this location, its possible for isolated amounts of 8-12 inches
somewhere in this area. For the Kankakee River Valley locations,
have continued the Advisory but did strongly contemplate replacing
the advisory with a warning from Livingston- Kankakee-
Newton/Jasper counties and areas south. Although the more robust
system and highlighted features will bring amounts higher closer
to around 6 inches, felt that could keep the advisory going but
mentioning these higher amounts and larger impacts. The higher
amounts in this location will be due to mesoscale features that
could still move slightly or change and with that also in mind,
did not change to a warning. That being said, it is still possible
for a stronger band to develop in these locations and if this
were to occur, could see amounts in the 6-8 inch range. If this
scenario were to seem more likely, than a change to a warning
would be necessary. Evening/overnight updates will continue to
look at this possibility.

Did expand the advisory up to along the I-88 corridor, with
periods of higher snow intensity also appearing possible in this
locations. This along with amounts approaching 2-4 inches will
provide some hazardous travel. With this reasoning, felt
comfortable issuing an advisory in these locations. Expect snow to
exit later in the afternoon, but with lake effect likely continue
for locations in northwest Indiana. Will eventually see a
weakening trend and more shift to the east of this development by
the evening.

Rodriguez
Link to comment
Share on other sites
Hoosier

Hoosier

Posted
  • Author
Posted

The HRRR Kuchera map has ratios even >20:1.  That would be nice.  With the DGZ, lift, moisture profiles and relatively light winds, 15:1-20:1 should be a good bet in many areas.  The area that gets under the enhanced frontogenetic banding may have the best shot at something higher, at least in a transient sense.  

Link to comment
Share on other sites
RCNYILWX

RCNYILWX

Posted
Posted
Yeah there are some that do the split. I'm not sure if they could just do it or if it would have to go through some sort of approval process.  Maybe Ricky could provide some info.
We would have to go through an approval process. Cook County would be ideal to split into separate zones because of its shape and it's something I'd like the office to do. I also think LaSalle County would be a candidate for a north half and south half zone because of its size.

Sent from my SM-G935V using Tapatalk

Link to comment
Share on other sites
ConvectiveIA

ConvectiveIA

Posted
Posted
11 minutes ago, StormChaser4Life said:

Is it just me or did 0z nam seem to shift the heaviest band south? 

Slightly. But the 01, 02 etc HRRR and RAP are juicing up big time north and heavy. Im not quite expecting their outcomes but on the other hand, the 0z NAM is a southerly outlier in comparison to those and the GFS. Radar trends seem promisingly early with flurries for us here now before the main event. Some signs the current radar echos are beginning to lift north a little on their northern reach across eastern NE

Link to comment
Share on other sites
cyclone77

cyclone77

Posted
Posted

Gonna be interested to see how the LSRs turn out.  Further north in the snow band where we are the DGZ is pretty respectable; at about 200mb of depth.  However, soundings show the best lift is mostly above that layer.  There is still some decent lift at the top of the DGZ though, so not really sure how things will play out.  I think a conservative 15:1 may do it, but wouldn't be surprised if it turned out closer to 20:1.  

With all that being said, the 00z model consensus for us is around 0.11-0.14", with the RAP coming in the highest with around 0.17".  I think I'm gonna bump my call up for here to around 2".  

Link to comment
Share on other sites
Radtechwxman

Radtechwxman

Posted
Posted
50 minutes ago, ConvectiveIA said:

Slightly. But the 01, 02 etc HRRR and RAP are juicing up big time north and heavy. Im not quite expecting their outcomes but on the other hand, the 0z NAM is a southerly outlier in comparison to those and the GFS. Radar trends seem promisingly early with flurries for us here now before the main event. Some signs the current radar echos are beginning to lift north a little on their northern reach across eastern NE

Just seems like actual radar is a bit further south than simulated radar and the movement is more se than models showing. But that one band arcing ahead is showing some signs of lifting more north and as that wave deepens and approaches the snow should really blossom

Link to comment
Share on other sites
Kaner88

Kaner88

Posted
Posted
1 hour ago, Hoosier said:

The recent HRRR runs are trying to swipe the Illinois shore with that lake enhanced band for a while.  Something to watch if we have anybody on here from near the lake from Chicago southward.

Nice look at a little tail of that in the latest HRRR, in the midst of its attempt to drag the 4" line north to ORD and beyond.

HRRRCHI_prec_kuchsnow_018.png

Link to comment
Share on other sites
Hoosier

Hoosier

Posted
  • Author
Posted
1 minute ago, Kaner88 said:

Nice look at a little tail of that in the latest HRRR, in the midst of its attempt to drag the 4" line north to ORD and beyond.

HRRRCHI_prec_kuchsnow_018.png

Mentioned it before but for some reason there is a noticeable difference between the Kuchera map at COD compared to the one at Pivotal.  The COD one seems a bit inflated to me but may need to observe them over a period of time to be sure.

Link to comment
Share on other sites
Kaner88

Kaner88

Posted
Posted
2 minutes ago, Hoosier said:

Mentioned it before but for some reason there is a noticeable difference between the Kuchera map at COD compared to the one at Pivotal.  The COD one seems a bit inflated to me but may need to observe them over a period of time to be sure.

Good eye, looks like you're right. Would be interested to know why that is- maybe different Kuchera calculations? 

snku_acc.us_mw.png

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...