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November 30-December 2 *Potential* Winter Storm


Hoosier
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2 minutes ago, Snownado said:

Is it safe to say that it's a lock that most of Indiana will at least some some flakes in the air next week ?

About as much of a lock as this

c06.jpg

 

In seriousness the GFS & ensembles seem to be trending more favorably compared to earlier today

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Euro looks a bit slower and weaker than it was 00Z last night.  It's cutting off from the northern jet much later this run.  A lot of those crazy totals on the previous runs were a perfect long lasting northerly fetch along almost the entire length of a warm Lake Michigan for upwards of 36 hours.  LES on steroids.  This run, still anaomolis for this time of year, makes a little more sense, to me anyways.  GFS is moving closer to this also.  I think in the end could see a foot in some places maybe a more wide spread 6-10.  Kuchera ratios are lower so a percentage could be sloppy.

500wh.conus.png

 

500wh.conus.png

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Well, I guess the season is here....might as well start it off with a tease followed by a kick in the N@!S

Good to have something to watch...

Two things strike me so far:

Like Stebo referenced: it definitely looks like it could stop and spin for a couple of days (consistent signal)...could be a N-S strip of jack-pot zone (Ohio/Ind border in general as of right now with W-E variance from Indy-CMH).

I also could see this evolve like Schaumburg mentioned --- Stung Out POS 

Happy Turkey Day!

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9AM Forecast Discussion - ILN

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Clearly the feature(s) and time period of interest during this
portion of the forecast will be the potential phasing of a southern
stream shortwave trough with a more progressive/dynamic northern
stream shortwave trough in the Monday/Tuesday timeframe, which could
lead to rapidly deepening/occluding low pressure tracking from the
southern Gulf Coast up the west side of the Appalachians. This would
bring a potential of cold sector precipitation /possibly the first
widespread accumulating snow of the winter/ and gusty winds. Outlier
/low probability/ solutions indicate that significant accumulating
snow could occur, but would take near ideal phasing for such an
event to occur.

What we feel somewhat confident in saying - is that ensembles means
have trended toward a wetter and colder overall solution for
Mon/Tue, so the chances of the first widespread accumulating snow
have risen over the last 24 hours. But overall probabilities of the
very heavy amounts seen in some recent deterministic runs of a few
models remain quite low - but something that has to be accounted
for. We will need to watch this closely as even a more conservative
snowfall forecast will bring travel impacts most likely Monday night
into Tuesday morning - but areas / amounts are still way too early
say with any measure of confidence.

Pre-storm mild temps - a key point about the quiet weather
Saturday/Sunday we need to mention is mild temperatures. Plenty of
sunshine both days should push temperatures well into the 40s on
Saturday, and 50s on Sunday. Cirrus thickens Sunday afternoon, and
mid clouds thicken Sunday night. The mild days Sat/Sun and clouds
Sunday night will keep soils/pavements quite warm, so snowfall will
need to overcome this to accumulate efficiently.

Phasing/low track -Timing of the potential phasing is key and
extremely low confidence at this time range, but some degree of
phasing is likely to occur between these systems - carving out a
deep longwave trough/closed low over the Ohio Valley by Tuesday
morning. Potential solutions run the gamut - from a rapidly
deepening low running from the Gulf Coast into western PA where it
slows to a stop and pivots, to a much weaker/progressive low riding
quickly through KY/WV/PA and into the northeast or off the Mid-
Atlantic coast.  The 26.00Z EPS and GEFS members /81 members in sum/
are all over the place with timing/track/precipitation coverage with
the various degrees of phasing which could occur. Still waiting to
see a clustering of surface low track/depth emerge from ensemble
systems. As of right now, the 31 members of the 26.00Z GEFS valid at
18Z Monday have surface lows scattered over thousands of square
miles from southeast Michigan, to upstate New York, to a number of
lows even down in the Carolinas. Each of these a viable solution -
and it is a representation of the sensitivity of phasing weather
systems separated /right now/ by thousands of miles. The 26.00Z
EPS/CMC ensembles also very similar - indicating surface low
pressure track/depth is variable and very low confidence at this
point in time.

Keys to remember about some of the extreme snowfall amounts being
seen on a few deterministic/ensemble members:  1) these static ratio
amounts do not account for the very warm ground temperatures
(remember Sunday`s temps in the 50s) 2) these do not take into
account the degree of compaction that would occur with a long
duration wet snow event that is leading to some of the very high
totals 3) boundary layer temperatures will remain 30-35 during any
snow that falls which means slower accumulation rates and more
compaction especially during daylight hours and 4) this storm has no
bitter arctic air in place or available to tap - unlike a very
similar setup 70 years ago when the Snow Bowl storm produced in
excess of 12-15" in the ILN CWA. That storm had surface temps in the
single digits and teens. Also pointing against the extreme solutions
is a very narrow dendritic growth zone - less than 100mb on forecast
soundings.  So we will need to watch ensembles closely in the next
couple of days to see if a trend emerges on a number of fronts.
Definitely a forecast to stay tuned to through the holiday weekend.

After the system pulls out on Wednesday, cold temperatures remain
with highs generally in the 30s.
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