Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
601 PM CST sun Dec 21 2014

issued at 245 PM CST sun Dec 21 2014

At 245 PM CST...a brisk southerly breeze continued across eastern
Iowa...far northeast Missouri...and northwest Illinois. Despite
the abundant cloud cover...the warm air advection was boosting
afternoon temperatures into the upper 30s to middle 40s. Some patchy
drizzle was lingering...mainly north of Interstate 80.


Short term...(this evening through monday)
issued at 245 PM CST sun Dec 21 2014

In the near term...the focus is on probability of precipitation...fog potential...and
eventually precipitation type late across the far north.

Winds will stay up in the 8-15 knots range tonight...which will maintain
dewpoints in the 30s...highest west of the Mississippi River. Expect
more patchy fog and drizzle...with some light rain possible...especially
late in the far west. The southeast wind should preclude any dense fog
overnight. American model BUFKIT soundings all indicate the near
surface layer will cool off enough toward daybreak for a rain/snow
mix...mainly along the U.S. Highway 20 corridor. This mix may persist
in the far north through late morning before a change back to all rain.
However...little or no accumulation is expected. Through Monday
afternoon...most areas could pick up 0.1-0.2 inches of rain.
Afternoon highs Monday should peak about 10 degrees above normal
for the date...ranging from the upper 30s north to middle/upper 40s south.

Long term...(monday night through sunday)
issued at 245 PM CST sun Dec 21 2014

The models continue to indicate an active weather pattern for the

The first storm system will move across western Iowa and into
Wisconsin Monday night/Tuesday. The passage of the low to the west
and north means that precipitation will be in the form of all rain
Monday night into Tuesday.

Forcing weakens late Monday night and into Tuesday with some drying
aloft. Thus rain will likely taper to drizzle and probably end late
Monday night into Tuesday across the area. Temperatures will average
above normal.

The main energy for the next storm system is just getting sampled by
upper air flights in the Pacific West Coast. As a result this system
has developed much further to the south and east.

Tuesday night forcing initially remains weak but slowly becomes
stronger prior to sunrise. Initially precipitation will start out as
rain and slowly mix with and change over to snow by sunrise
Wednesday as colder air gets pulled south. Snowfall amounts Tuesday
night should range from a trace to a dusting at best.

On Wednesday the main storm system moves north into the Ohio Valley
and the eastern Great Lakes. A rain/snow mix will slowly change over
to all light snow during the day. Since the better moisture will be
well east of the area...snowfall amounts should be no more than a
dusting of accumulation.

Wednesday night on...
the model consensus has dry conditions across the area Wednesday
night and Thursday as high pressure quickly moves through the
Midwest. Temperatures should average slightly above normal.
Attention then turns to the next storm system.

The track of the storm system late in the week has been varying
considerably. Trends with the models have been to slowly move it a
little further north over time. If this trend continues...then the
better forcing and snow would be across Minnesota and Wisconsin.

As a result the model consensus has slight chance probability of precipitation across the
northern half of the area Thursday night with slight chance to low
chance probability of precipitation across the entire area on Friday.

What the models do reasonably agree upon is that a strong cold front
associated with the storm system will sweep through the area late
Thursday night and Friday. Based on what is being suggested by model
trends...temperatures may be steady or slowly falling on Friday
under strong northwest winds.

Friday night through Sunday the model consensus has dry and cold
conditions across the area as strong high pressure builds into the
Midwest. Temperatures will average below normal.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 547 PM CST sun Dec 21 2014

Moderate southeast winds of 10 to 15 kts to keep visible at or above 5 miles tonight with
mostly MVFR ceilings ahead of storm system developing in the Southern
Plains. After 22/12z...areas of rain to overspread the region with
MVFR to IFR conditions with several hours Worth of rain and drizzle.
Brief periods of non-precipitation possible as surface low approaches
that are unable to be identified this far out.


Dvn watches/warnings/advisories...



Synopsis...rp Kinney
short term...rp Kinney
long term...08

National Weather Service Glossary of Abbreviations