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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
652 am CST sun Nov 29 2015

..updated aviation discussion...

issued at 345 am CST sun Nov 29 2015

Main concern this morning is area of light rain showers moving
through southeast Iowa/NE Missouri where surface temperatures are in the lower 30s.
Have a Special Weather Statement in effect for this area to
account for areas of light freezing rain. Fairfield-Iowa has been
reporting light rain over the last few hours with a surface temperature of
32 f. Dvn 88-d also showing isolated light showers pushing
eastward into west-central Illinois where temperatures are in the lower

Through 345 am CST...the most concentrated zone of showers has
been over Jefferson/Van Buren/Henry/and northwest Lee counties.

While elevated surfaces are most prone to a light glazing due to
Road surface temperatures a few degrees above freezing in most areas.
Untreated roads and sidewalks could become slick through 7 or 8
am CST this morning. Do not expect widespread travel issues due to
aforementioned Road surface temperatures and spotty nature of showers.


Short term...(today and tonight)
issued at 345 am CST sun Nov 29 2015

Today...scattered light showers will continue to the south of I-80
and to the west of I-74 this morning. Elevated layer of
isentropic lift has developed...producing rain showers with some
pockets of light freezing rain. The freezing rain threat will
diminish rapidly after 7 or 8 am CST as surface temperatures rise above

Models show 700-600mb warm air advection being responsible for the showers
across SC Iowa/north Missouri/southeast Iowa. NAM forecast time- height
sections indicate a decrease in negative Omega by the late morning
and probability of precipitation follow this trend. High temperatures today are forecast to be in
the upper 30s on average under mostly cloudy skies.

Tonight...precipitation will become likely especially after
midnight over the western third of the dvn County Warning Area as deep layered
q-vector convergence overspreads the area downstream of a large
upper-level low over Wyoming.

Freezing rain threat...analysis of the raw models surface dry and wet
bulb temperatures and sref ptype probabilities suggests the potential for
light ice accumulations. Current forecast favors counties along
and north of a Cedar Rapids-Iowa to Dubuque-Iowa line with the
best chance to receive a period of freezing rain between 12-6 am
CST Monday. Latest wpc ice accumulation forecast highlights this
same zone for possible light amounts.

At this time any accumulations should remain under 0.05 inches.
Elevated surfaces and untreated surfaces could become slick before
precipitation changes to rain late tonight or early Monday
morning. A Freezing Rain Advisory may be necessary for some
counties in the northwest one-third of the dvn County Warning Area but confidence is low
at this time due to marginal Road surface temperatures. Day shift will have
to evaluate new model data/trends. Uttech

Long term...(monday through saturday)
issued at 345 am CST sun Nov 29 2015

The main focus of the long term period is the storm system Monday
into Tuesday...which is expected to just glance the National Weather Service quadrant cities
forecast area.

Surface temperatures are expected to warm up enough Monday morning to
preclude much in the way of additional freezing rain. Bufr soundings
favor rain with perhaps some sleet mixed in at times over the far
northwest counties through the day. By Monday evening...the area of
rain/sleet mix is expected to expand over roughly the northwest
third as cooler air aloft works in. After midnight...the north will
be favored for some light snow accumulations...mixed at time with
sleet...but well under an inch. For Tuesday and Tuesday night...the
upper low will move through the region...with northern counties
again favored for additional light snowfall accumulations. Through
the snow/sleet amounts are forecast around an inch or
less...with the brunt of the storm impacting northern Iowa. Looking
ahead...expect dry conditions with moderating temperatures into the 40s by
Friday and Saturday.

The Hydro situation has settled down somewhat over the past day.
Flood warnings remain in effect for portions of the Iowa...skunk and
Rock River basins. Most points have leveled off or are
falling...with the exception of the Rock River...where Joslin is
still rising above flood stage and Moline is still rising but
forecast to crest below flood stage. Additional quantitative precipitation forecast through Tuesday
is not expected to have a significant impact on river levels.


Aviation...(for the 12z tafs through 12z Monday morning)
issued at 643 am CST sun Nov 29 2015

VFR conditions will prevail for the majority of this taf period.
As a large upper-level low approaches from the west late tonight
ceilings will begin to lower toward MVFR...after roughly
06z-09z/Monday. Forecast soundings show very dry air beneath the
overcast deck through the night.

Highest confidence in precipitation occurring late tonight is at kcid
then kbrl. Surface temperatures at or slightly below freezing at kcid support
chance for -fzra with light ice accumulations possible on
untreated surfaces. Uttech


Dvn watches/warnings/advisories...


short term...uttech
long term...rp Kinney

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