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fxus63 kdvn 111149 

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
549 am CST sun Dec 11 2016

..12z aviation update...

issued at 323 am CST sun Dec 11 2016

Snow event ongoing, but overnight trends suggest brunt of best
forcing and thus snowfall has shifted even further north acrs far
southern Minnesota, far northeastern Iowa and into WI. The next low pressure
center that will roll up toward the area and bring warmer air in the
south, taking shape acrs the southwestern plains.


Short term...(today and tonight)
issued at 323 am CST sun Dec 11 2016

Ongoing snows from the eastern Dakotas, southeastward along the
Minnesota/Iowa border into the northern third of Illinois and southern WI, will
move out of the northern and northeastern cwa, or at least diminish
after 5 or 6 am. Then as the low pressure and inverted trof system
rolls up acrs the mid to upper MS River Valley through this afternoon,
more precip and possibly a def zone type band of precip will take
shape acrs more of the southeastern half to 2/3's of the County Warning Area from
late morning and into the afternoon, before shifting east of the County Warning Area
this evening. All in all, latest thinking with snowfall amounts of 1-
3 inches that have already fallen north of i80, and system trends
with additional projections suggest that just Winter Weather Advisory
headlines warranted and mainly east of an Iowa City to Dubuque
line...the warning areas marginal at best.

New snowfall amounts after 12z Sunday west of the MS river and north
of i80 only half inch to an inch, while areas east of the MS river and
along/north of i80 get another 1-2+ inches today. Areas along and
south of i80, with warming profiles being pulled up acrs the area by
the incoming system and southerly low to mid level flow will make
for mixed precip acrs those areas. Thinking rain-snow mix trending
to mainly a cold rain, with bouts of sleet from time to time. This
will make it tough for any snow to accumulate in those areas today.
Warming sfc temps over cold ground and snow cover, and possible
convergent flow may allow for some areas of fog to form through the
day, until northwest Post-system flow increases this evening. But
with complexity of the fcst, will leave out mention for now. The
current philosophy will keep the current headlines going for now
while it is still snowing, but then start to trim from the west
after 5 or 6 am this morning, as well as having to assess trending
the warning areas in northwest Illinois to advisory. Will probably keep at least
the eastern half tier of the advisory going for the snow later today
when people are out and about for slick roads and reduced visibility,
although those parameters may be marginal as well. All precip winding
down early this evening. ..12..

Long term...(monday through next saturday)
issued at 323 am CST sun Dec 11 2016

The extended remains cold, and marginally active with possible light
snow with any passing wave though the Arctic air. There have been
problems with model blends tonight, but the over all trends are
reflected in the grids as best can be collaborated.

For the early to late work week, we will have snow cover over
roughly the north 1/2 of the cwa, and likely bare ground south.
Thus, there will be a temperature challenge day and night, with
true Arctic cold over the north, and a modified airmass in the
south. Below zero lows are likely over snow, while the south see 5
to 15 for lows. The next system will spread warm advection snow
over the Midwest again by Friday, lasting possibly into Saturday.
Models have shifted this low well north of any track indicated 24
hours ago, making p-type questions enter into the challenges for
late week. For now, that system looks very progressive and any mix
or rain could be very short lived before a dry slot arrives, thus
it is not Worth timing a 2-4 hour window of low confidence mix in
on day 6. We can approach that potential challenge after this
storm system in the short term gets out of the region.



Aviation...(for the 12z tafs through 12z Monday morning)
issued at 531 am CST sun Dec 11 2016

With overnight bands of snow moving out of the area currently,
there will be a temporary lull and VFR period thru mid morning.
Then the next system will lift up toward the area out of the
Central Plains and bring lowering ceilings and more precip to the
area from late morning and into the afternoon. Snow along and
north of i80, and rain-snow mix possibly going over to all rain
for a period south of i80 at brl. The heavier snow/IFR to LIFR
conditions may have the best chance to set up midday through mid
afternoon along the i80 corridor and effect the mli terminal.
Lighter snow then with MVFR to IFR conditions at times for Cid
and dbq this afternoon until early evening when the precip is then
expected to move off to the east. Lighter south winds and milder
air over cold ground may produce rounds of MVFR to LIFR fog today
even when precip is not falling. Increasing west to northwest
winds from west-to-east later this evening will help scoop up
cigs some and improve visibilities. ..12..


Dvn watches/warnings/advisories...
Iowa...Winter Weather Advisory until 6 PM CST this evening for Benton-

Winter Storm Warning until 6 PM CST this evening for Buchanan-

Illinois...Winter Weather Advisory until 6 PM CST this evening for Bureau-
Henry Illinois-Putnam-Rock Island-Whiteside.

Winter Storm Warning until 6 PM CST this evening for Carroll-Jo



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