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No big wave, no buldge, its pretty much flat and coming straight from the Pacific across the U.S... Add arctic air at the mid levels and boom, snow with Pacific energy.
Lastly... Water Vapor loop to see where the moisture is in the atmosphere.. You can see the 1st snow wave coming across
The main storm may go into the Great Lakes then transfer the energy into a new coastal storm. You'll see this happen on the maps.
Like watch todays GFS say this storm heads to Montreal, then transfer to a coastal storm off Maine Monday night
See the update? Exactly what I was seeing with the GFS. Storm heads to Great Lakes then transfers its energy into a coastal storm off Maine.
If we wanted a full fledge snowstorm we needed that transfer down in Virginia/Delware area! Or NJ. OR 1 storm that doesn't head towards the Great Lakes
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
551 AM CST Sat Dec 10 2016
Through Sunday night...
Challenging forecast tonight through Sunday evening with potential
for a long duration snow event with significant totals, especially
northern half of the CWA. Questions remain about how much precip
will fall and potential for mixed precip and much lower snow:liquid
ratios (SLRs) Sunday into Sunday night. This event absolutely does
not fit the conceptual model of a warning worthy snowfall event
locally, so given the expected very long duration of the event and
primarily light to moderate snowfall accumulation rates, we`re
opting to upgrade the winter storm watch to a winter weather
advisory. Since we are teetering along the edge of warning
criteria over northern most CWA, it is possible that some areas
may need to be upgraded to a warning, but after collaboration
internally and with DVN felt this was the best course of action.
Meteorologically, a fairly strong Pacific jet stream will
translate eastward into the the Great Lakes region later today
and through Sunday. Height falls in advance of a fairly low
amplitude short wave will result in back low/mid level flow across
the area today, tightening up the thermal gradient with
strengthening isentropic ascent/warm air advection likely to
result in a swath of snow developing east into northern IL late
this afternoon and into northwest Indiana by early evening.
Guidance is in pretty good agreement with QPF through 12z Sunday,
with maybe up to an inch or so of snow possible between 2-6pm
western CWA. Tonight (00z-12z Sunday) guidance paints a swath of
QPF over northern half of the CWA in the neighborhood of 0.25",
which given fairly efficient ratios should fluff up to 2 to
perhaps 5 inches of snow. Time-height cross sections suggest that
while the dendritic growth zone will be deep, especially the first
half of the night, ascent within that layer is not expected to be
particularly strong and progged RH wrt to ice is not super
saturated, so extremely efficient dendrites appear unlikely to be
the primary/dominant crystal type, none the less it should be a
dry snow that should fluff up to 15 to perhaps 20:1 ratio.
GFS and NAM both show transient waves of modest f-gen, but
neither model suggests that a deep sustained frontogenetic
circulation will become established and park overhead like last
weekend.
QPF from the various models varies more substantially heading
into Sunday.
Generally looking for snowfall totals in the 6 to locally 10"
range along and north of the I-88/I-290 corridor, but the snowfall
rates look to generally remain below the 6"/12 hour and 8" in 24
hour warning criteria. Also, hitting on a weekend and likely
peaking in the middle of the night tonight could lessen the
impacts some, which given the borderline warning criteria supports
starting with an advisory and upgrading when/if it becomes clear
heavy snow will materialize. In the heavier accumulating snow
swath (generally along north of I-80) expecting up to an inch of
so through 6pm this evening, 2-5" tonight, an additional 1-4"
Sunday. Snow or mix should end from west to east by late
afternoon west and during the evening Sunday over NW IN.
Monday Through Saturday...
Main concern for the long term forecast period will be temperature
trends with the coldest air of the season expected.
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