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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
613 am CST Friday Nov 27 2015

issued at 554 am CST Friday Nov 27 2015

In coordination with surrounding weather forecast offices...increased probability of precipitation for the
middle/late morning into the early afternoon for the counties along and
south of Interstate 80. High-res models...hrrr/rap/nam12 are all
indicating another wave of light rain to expand over the region as
upper wave over NE Kansas moves from SW to NE. There could be some
snowflakes that mix in but thinking this precipitation will be mostly in
the form of rain...possibly light freezing rain where surface temperatures
are at 32 f. Do not expect travel impacts with Road temperatures above
freezing and overall light/patchy precipitation.


issued at 330 am CST Friday Nov 27 2015

Surface pressure continues to slide eastward through Illinois into
Indiana which has caused surface winds to turn around to the north.
This has resulted in cold air advection at the surface and up to
about 900mb. inversion is still present as winds are
southwesterly above this level with 850mb temperatures above 0c.
Therefore...precipitation has been plain rain through the night. The only
areas where surface temperatures are near freezing are across Buchanan and
Delaware counties but it looks like only some patchy
drizzle/freezing drizzle is possible there over the next few
hours. Elsewhere...any areas of light to moderate rain should
diminish over the next few hours along with a zone of 850-700mb


Short term...(today and tonight)
issued at 330 am CST Friday Nov 27 2015

Today...cold air advection via northerly surface winds will hold high
temperatures similar to the current temperatures. Expecting a temperature range from
the lower 30s across the northwest County Warning Area to the lower 40s over the southeast. Main
850-700mb frontogenetic band of rain will move eastward out of southeast
Iowa/NE Missouri/west Illinois early this morning. For this
reason...probability of precipitation will decrease from northwest to southeast during this time.

Areas along and north of an Iowa City Iowa to Freeport Illinois
line may receive a brief mix of light rain/freezing drizzle/sleet
where temperatures are near freezing through 8 or 9 am CST. Although
nothing significant is anticipated as precipitation should remain

Tonight...baroclinic zone takes on a west to east orientation
across the southern County Warning Area where slight chance probability of precipitation are in the
forecast tonight into early Saturday morning. 700mb winds are
forecast to increase out of the SW providing some isentropic lift
on the 300/305 k surface and possibly light precipitation. Forecast
soundings show much colder temperatures from the surface to 850mb...mostly
below 0c supporting the chance for some mixed light freezing
rain/sleet. With surface temperatures near to slightly below freezing there
could be some light icing on untreated surfaces.

The 00z/11.27 nmm-east and 06z/11.27 NAM are more aggressive with
this scenario unfolding compared to other models...something the day
shift will have to evaluate after the 12z/11.27 model runs. Uttech

Long term...(saturday through thursday)
issued at 330 am CST Friday Nov 27 2015

The main forecast issues in the long term period involve precipitation type
and coverage...especially Monday into Tuesday...and Hydro
concerns...which are discussed in section below.

On Saturday...expect below normal afternoon highs in the 35-40f
range. Weak isentropic lift may support some very light precipitation in
the extreme south Saturday night into Sunday...but the main precipitation
event will likely hold off until late Sunday or Monday. The 27/00z
GFS is the most aggressive among the operational model guidance in
developing precipitation before 12z Monday but have kept probability of precipitation at or below 40
percent for that period. Thermal profiles and surface temperatures indicate
some potential for freezing rain late Sunday night into early Monday

The main surface cyclone and upper low are expected to lift north
through the forecast area Monday and Monday night with high chance
to likely probability of precipitation reasonable at this time. There will again be the
potential for periods of mixed precipitation...with the finer
details to be hammered out as we get closer to the event. Rain
should be the main p-type during the day Monday with highs in the
upper 30s to middle 40s...ahead of a possible wintry mix Monday night
into Tuesday.

Precipitation should be ending Tuesday across the north followed by
slightly below normal high temperatures and dry conditions for Wednesday
and Thursday.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 554 am CST Friday Nov 27 2015

MVFR to continue at all terminals through the day with the
exception of kbrl where VFR is forecast. Secondary round of -ra
will mostly likely affect the southern terminals...kmli and kbrl
between roughly 16z-20z/ chance at kbrl. Therefore
included tempos in tafs during this time. Conditions will
gradually improve overnight. Although...there is a chance for
-fzra at kbrl after 06z-09z/Saturday. Uttech


issued at 238 am CST Friday Nov 27 2015

The long duration rainfall event is winding down this morning with
rainfall reports coming in about as expected in the 1-2 inch
range...locally higher. This recent rain...on top of fairly
saturated resulting in rises on many area rivers. Flood
warnings continue for the English River at Kalona and the north
Skunk River near Sigourney. Have issued a new Flood Warning for
Kalona as the stage has now risen above moderate flood stage.
Sigourney also topped minor flood stage early this morning. Several
points along the Iowa river...and the wapsi near DeWitt...are
forecast to rise above flood stage from later tonight into the
weekend. Will hold off issuing flood warnings for these points to
await new morning forecasts based on actual quantitative precipitation forecast.


Dvn watches/warnings/advisories...


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

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