Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
757 PM CST Monday Jan 26 2015

issued at 754 PM CST Monday Jan 26 2015

Radar/observation and reports suggest freezing drizzle over northwest Illinois County Warning Area has
largely diminished to very spotty attim. Anticipate a renewed
round of very light precipitation developing southward from WI... and
affecting far northeast/east central Iowa and northwest Illinois over the
next few hours as vorticity maximum drop southeastward from WI. Being in and out
of ice in clouds looks like precipitation will be flurries/light snow with
also some freezing drizzle. Have added low chance probability of precipitation northwest Illinois
for very minor measurable precipitation potential.


issued at 305 PM CST Monday Jan 26 2015

Strong warm front extended from extreme western WI to near Ottumwa
Iowa and then into North Texas. Ahead of the front temperatures were in
the 20s while to the west readings have soared into the 50s in
central/western Iowa and MO and in the 60s and lower 70s in the Great

Doppler radar/surface observation were indicating the snow has shifted
into southeast WI/NE Illinois with an area of freezing drizzle in SW WI.


Short term...(this evening through tuesday)
issued at 305 PM CST Monday Jan 26 2015

Forecast focus on some freezing drizzle early this evening
otherwise milder temperatures.

Tonight...areas of light freezing drizzle in northwest Illinois should end
early this evening but clouds should linger across much of the County Warning Area
during the night. Our far western counties will be partly to
mostly cloudy. Forecast soundings indicate a strengthening
inversion at 900 mb which should trap the low level moisture below.
The warm front will continue to push west to east across the County Warning Area
which will bring a warmer night...compared to last night. Minimum
temperatures should range from the middle 20s in northwest Illinois to around 30
in our far southern County Warning Area.

Tuesday...inversion and northeast winds should keep clouds lingering
into the morning with decreasing clouds in the afternoon. However...
some of the guidance keeps skies cloudy all day so this will be
challenging. I will forecast maximum temperatures in the lower 30s
NE to the lower 40s SW.

Long term...(tuesday night through monday)
issued at 305 PM CST Monday Jan 26 2015

Two main forecast concerns for the extended forecast. The first is
a weather producer that brushes the area Wednesday night and
Thursday and another low that moves through the region this
weekend. The first event looks to a rain/fzdz event across the area
and the other a snow event this weekend.

After a mild week last week and snow this past weekend...we have
another taste of mild weather through Wednesday night and then
winter weather looks to return to the area.

Wednesday night into Thursday...two shortwave in rapid succession
will move through the area. The first one will move through south of
our County Warning Area on Wednesday PM into Thursday am. This will help to
continue 850 mb warm air advection through 06z on Thursday. With warm air in place
across the area the dominant precipitation type will be rain early on
Wednesday night. The second wave moves through between 15z and 21z
on Thursday. However before this on Thursday am we see cold air advection begin and
a cooling column...especially at the surface. With most of the
column saturation occurring at temperatures above will not be snow looks unlikely. Instead model soundings suggest
that fzdz will occur...especially across north zones. With low quantitative precipitation forecast
and probability of precipitation only a Glace...0.01 inches of ice is forecast. This could
be enough to ice up roads...across that area. The initial surge of
cold air is tempered enough that temperatures will rise diurnally to above
freezing County Warning Area wide...meaning that the glaze of ice should melt by
later in the afternoon. 12z guidance did pull this system further
north and there is a potential for this event to be
refined further in future events.

A period of northwest flow then dominants through the end of the week and
into Saturday where temperatures stay near freezing for highs.

A trough and developing surface low develops and moves into our area
for the weekend. There are discrepancies between the GFS and Euro
as far as timing and location/strength of surface features. The GFS
brings well developed surface low to our north..whereas the Euro and
Gem keep the lower pressure south. Regardless...temperatures will be cold
enough for all snow. The system this weekend bears watching through
the week. It is important to note that 00z Euro and other previous
runs of the Euro kept US dry and has been trending towards this
system...the GFS has done the same thing. So we will see what
happens with the next few runs.


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 548 PM CST Monday Jan 26 2015

Warm front extends just west of the Mississippi River to start
the taf cycle. Generally VFR conditions on northwest winds
being found west of the boundary... while along and east of the
boundary MVFR to IFR conditions prevail. The warm front is
expected to push east of the Mississippi River and the taf sites
by late evening with conditions likely settling mainly into
MVFR and VFR. Some patchy freezing drizzle will be possible at
kdbq and kmli until the boundary passes. Forecast overnight into
Tuesday am is siding toward latest rap and hrrr cloud forecasts which
show stratus migrating southward from Minnesota in northerly flow and
have ceilings at all sites becoming mainly MVFR in 1500-3000ft above ground level
range. May see some partial clearing by Tuesday PM as flow turns
easterly and Ushers in slightly drier air.


Dvn watches/warnings/advisories...


short term...haase
long term...Gibbs

National Weather Service Glossary of Abbreviations