Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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813
FXUS63 KDVN 132353
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
553 PM CST Mon Nov 13 2017

...00z AVIATION UPDATE...

.SYNOPSIS...
Issued at 255 PM CST Mon Nov 13 2017

Low clouds lingered north of Interstate 80 during the early
afternoon hours, with visibilities of 3 to 5 miles common in light
fog. The sky was partially clear south of Interstate 80. Early
afternoon temperatures ranged from the upper 30s along Highway 20
to the upper 40s in far southeast Iowa.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 255 PM CST Mon Nov 13 2017

The main forecast issues in the short term period are cloud, fog,
and drizzle/rain trends.

In the near term, high resolution models continue to favor areas
north of Interstate 80 for more fog development tonight, and this
makes sense given the light fog currently occurring. I don`t think
we are looking at another widespread dense fog scenario tonight
for several reasons: low stratus already in place, stronger
southeast winds, and drizzle expected to increase from the west
after midnight. Fog is mentioned along/north of Interstate 80 in
the forecast grids, along with the previously mentioned drizzle,
which will spread into eastern Iowa before daybreak. Lows tonight
are expected to say generally above freezing, precluding a
freezing drizzle threat.

For Tuesday, expect the drizzle to spread east of the Mississippi
river. Several models are also indicating some light rain, mainly
across the north in the afternoon. Have kept high temperatures
down in the 40s given the extensive cloud cover, and later shifts
may need to drop highs even more.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 255 PM CST Mon Nov 13 2017

Forecast focus on showers Tuesday night then an intense cyclone to
impact much of the Midwest/Great Lakes late this week and into the
weekend. Behind the system will be a blast of arctic air!

Tuesday night into Wednesday morning: A weak upper level trough will
swing across the area providing some light rain. Moisture looks to
be rather limited so rainfall amounts should be less than a tenth of
an inch at most locations. Have kept the mention of a slight chance
of elevated thunderstorms in our southern and eastern counties after
midnight. Forecast soundings indicate steep mid level lapse rates
sufficient for at least a few isolated non-severe storms.

Wednesday afternoon through Thursday afternoon: Zonal flow aloft and
between systems so a dry period, albeit brief. High pressure will be
over the area providing clear to partly cloudy skies. However, on
Thursday mid/high level clouds should increase, tempering the warm-
up. Highs will be in the 50s on Wednesday, and in the 40s Thursday.

Thursday night: Global models fairly similar in rapidly developing
warm air advection/moisture transport into the dvn cwa Thursday
night on a 40 knot southwest low level jet. This should increase the
coverage of showers and a few elevated thunderstorms, especially
after midnight. Too early to determine if any of these storms
produce hail.

Friday and Friday night: Models bring a potent negatively-tilted
trough out of the central Rockies and into the Midwest. This will
promote cyclogenesis in the central Plains early Friday, with the
surface low tracking into eastern IA near I-80 during the afternoon,
then reaching northern IL by evening. This is the track of the GFS,
but the ECMWF is farther south, while the Canadian is farther north.
Of course, the exact track of the system will be crucial to the
magnitude of the severe threat, and strength of the shear/CAPE. As
the week progresses we will have a better handle on the severe
potential. As of now, SPC has a 15% probability for severe in
eastern IA/northern IL all the way to the Arklatex.

This weekend: Cyclone will continue to deepen to about 985 mb as it
pushes into the Great Lakes region. This will sweep an arctic cold
front across the area with the GFS much colder than the ECMWF as it
has a much more amplified pattern. Either way it looks to be a
colder and windy Saturday with the chilly weather going into early
next week. The AO/NAO goes strongly negative so this would suggest a
much colder pattern ahead.

Haase

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 548 PM CST Mon Nov 13 2017

Challenging TAF cycle for exact timing of cloud trends. In general
a scouring of low clouds expected to continue this evening from
south to north, with generally VFR cigs at all sites by 04z while
some areas of IFR to MVFR fog possible. Overnight into Tuesday
expect low clouds to advect back into the terminals from the
west/southwest with lower MVFR to IFR conditions and perhaps some
spotty drizzle.

&&

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

$$

SYNOPSIS...RP Kinney
SHORT TERM...RP Kinney
LONG TERM...Haase
AVIATION...McClure



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