Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 040906
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
306 AM CST Mon Dec 4 2017

.SYNOPSIS...
Issued at 305 AM CST Mon Dec 4 2017

A warm night ongoing with early morning temperatures in the 50s
due to strong southerly winds gusting to 33 mph. Warm air advection
was occurring across the Midwest and showers were covering much
of the cwa. In the stronger forcing there were also thunderstorms
in extreme northeast IA into sw WI. A few brief lightning strikes
have been noted in far nw IL also. 3 hr pres falls of 2-4 mb were
over IA/WI and MN. Strong pres rises were noted in CO/WY as
cyclogenesis was taking place in the western high Plains. The
surface map showed 55-60 dewpoints from southern IA to OK with mid
60s dews in TX.

Very cold air was lurking in the northern Rockies and northern
Plains with early morning temperatures in the 20s and snow was
flying in the northern Rockies.
HAASE

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 305 AM CST Mon Dec 4 2017

Forecast focus on intensifying storm system with much colder air
ready to sweep into the area tonight.

Today: One final warm day ahead which we won`t see again for quite
some time. Highs will push well into the 60s despite plenty of
cloud cover. However, considering how warm it already is early
this morning, these warm readings should be easily achieved. The
current grids indicate we will be short of record highs by about
5 degrees and have included the records in the climate section
below. If more sunshine is realized then it may be warmer than
expected for the day shift to monitor. By noon the cyclone should
be nearing the Twin Cities (991 mb) and then to near Duluth by
sunset (987 mb).

Warm air advection showers and a few thunderstorms should push off
to our northeast this morning, followed by a break in the rain for
a time later this morning and early afternoon. Will only have
chance pops during that time frame. However, later in the
afternoon pops are increased to likely ahead of an approaching
strong cold front and showers and a few thunderstorms should
erupt. Deep layer shear strengthens but instability will be
limited (assuming a cloudy day). SPC has shifted the marginal risk
south of the dvn cwa based on lack of this instability but later
shifts can monitor for any changes.

Tonight: This is when big changes occur as the cyclone deepens
rapidly to 975 mb as it tracks just north of Lake Superior by
sunrise Tuesday. The strong cold front will sweep eastward across
the dvn cwa during the evening. NAMNEST shows a narrow line of
thunderstorms with the front in eastern IA early this evening,
then rapidly pushing east of the cwa as the evening progresses.
Can`t rule out some strong winds up to 50 mph with some of the storms.
The airmass dries quickly behind the front so not expecting any
precipitation after frontal passage.

West winds will increase rapidly behind the cold front as the
cyclone deepens. Gradient will tighten and have increased winds in
the grids to gusts up to 45 mph. I have not issued a wind advisory
yet but the day shift may need to consider one for at least a
portion of the cwa. Used CONSMOS for wind speeds as other models
were too low. Much colder air will be pouring into the area
behind the front with lows by sunrise Tuesday dropping into the
mid to upper 20s. Wind chills will be lowering into the teens, if
not a bit lower than that. Needless to say this will be quite the
shock to the system after the past few days of mild weather.
HAASE

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 305 AM CST Mon Dec 4 2017

Tuesday begins the long term, and with it the brutal reality of
"normal" temperatures.  While much of the extended will in fact be
below to well below normal, Tuesday should be a transition day with
highs in the lower 30s north to lower 40s south, which is pretty
close to normal for the first week of December.  The wind Tuesday
will be very strong, and the widespread near advisory wind event
should be taking place over the Midwest already the beginning of the
day, but the strongest winds are likely during the early afternoon
hours when we see the deepest mixing as sun combines with strong
cold advection and a tight pressure gradient. West winds sustained
at 20 to 30 mph are possible, with gusts around 40 likely. This is
extremely close to advisory levels, and will need to be watched for
a potential headline.

This same set up is expected Wednesday, but with less winds aloft,
we should top out in the 20 to 25 mph range, gusting to 30 to 35,
which is of course, windy and cold! Wednesday night and Thursday,
winds will decrease, along the the temperatures aloft, resulting in
colder weather, but a bit more tolerable with less wind.

The cold, and relative quiet weather will then turn to the first of
what could be several clippers in the next 10 to 14 days on Friday.
This pattern will support colder than normal temperatures, and
frequent low probability snow events. So, while pops for snow are
appropriately low due to timing and locations of clippers, the over
all outlook is probably going to see some snow accumulation over the
Midwest, including much if not all of the eastern Iowa and northwest
Illinois.

Temperatures are held towards the cooler end of guidance in general
which is the CONSMOS blend. That hopefully will allow for the best
fit in a pattern where we are seeing an onset of winter season
conditions.

ERVIN

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
ISSUED AT 1147 PM CST Sun Dec 3 2017

Band of warm advection clouds and light sprinkles is moving
through the area currently but posing little or no impact to
aviation. Of more concern is the MVFR deck back in southwest Iowa
which could advect quickly northeast into the area later this
mornings. Gusty southeast winds becoming strong southwest off the
deck, and strong surface winds veering from southeast this morning
to west later this evening are anticipated with gusts as high as
30-35 kts later in the day. As the cold front moves through the
area, the atmosphere will be unstable enough to generate a some
showers and possibly a thunderstorm, but chances of thunder at any
one TAF site is low so kept it out of the forecast.

&&

.CLIMATE...
ISSUED AT 305 AM CST Mon Dec 4 2017

Record Highs for December 4...

Moline.........71 in 1998
Cedar Rapids...69 in 1998
Dubuque........67 in 1998
Burlington.....73 in 1998

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Ervin
AVIATION...Wolf
CLIMATE...Haase



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