Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
309 am CST Monday Dec 29 2014

issued at 104 am CST Monday Dec 29 2014

At 230 am CST...a weak cold front extended along the Iowa/Missouri
border and through northern Illinois. Light snow was confined
mainly to northwest Iowa. Early morning temperatures ranged from
the upper teens across northern the 20s in eastern Iowa
and northwest Illinois.


Short term...(today and tonight)
issued at 104 am CST Monday Dec 29 2014

A few flurries and sharply colder temperatures tonight are the
main issues during the short term period.

A cold front has dropped south of the U.S. Highway 34 corridor
early this morning. Significantly colder air is lagging well to the north
of the forecast area as abundant cloud cover is helping keep early
morning temperatures in the 20s across eastern Iowa and northwest
Illinois. Expect continued cold air advection today and tonight
with an increasing northeast breeze. Northern counties should only
see a modest rise today with highs in the 20s...while the
southeast should see a bit more sunshine with high in the low/middle

Bufr soundings indicate rather sparse low level moisture and
measurable snow is not likely. However...with weak short wave
energy translating east across the forecast expecting
flurries with the lower ceilings today and tonight...especially
west of the Mississippi. Recent radar trends indicate weak
reflectivity increasing across central Iowa...and Independence was
reporting -sn out of a deck around 2500 feet above ground level.

Long term...(tuesday through sunday)
issued at 104 am CST Monday Dec 29 2014

Dry and cold conditions will be seen across the area Tuesday through
Wednesday as Arctic high pressure moves through the Midwest. High
temperatures should average 10 to 15 degrees below normal.

Wind chills very late Tuesday night/Wednesday morning may push into
the 15 to 20 below range west of a Dubuque to Oskaloosa line. These
numbers are just above criteria for headlines.

Wednesday night dry conditions will continue as the Arctic high
moves into the Ohio Valley.

Thursday on...
the model consensus has dry conditions for Thursday/Thursday night.
Temperatures will average slightly below normal. Attention then
turns to the next storm system.

The model solutions and run to run continuity of the models has been
highly variable for this storm system. Looking at everything from a
large scale perspective...the overall flow pattern would suggest the
storm tracking more to the south and east.

Dprog/dt of the models has indicated an overall slowing down of the
storm system...which given the large scale picture...appears
reasonable if the southern stream remains separated from the
northern stream. If this trend is correct...then Friday and possibly
Friday night may end up being dry for the area. Additionally...the
return flow is pushing out the cold air suggesting more of a
rain/snow mix during the daylight hours.

The model consensus now has the northern half of the area dry Friday
with only slight chance probability of precipitation across the south half for Friday.
Chance probability of precipitation remain for Friday night but the model consensus has
lowered them by nearly 10 percent.

The model consensus has slight chance/chance probability of precipitation for the area on
Saturday and slight chance probability of precipitation Saturday night/Sunday for
differences in timing of the storm system.

If the trends of the European model (ecmwf)/Gem and dprog/dt trends of the GFS
continue...the possibility does exist that this system will pass to
the south and east of the area. As such...this storm system bears
watching in case it does affect the area next weekend.


Aviation...(for the 06z tafs through 06z Monday night)
issued at 1134 PM CST sun Dec 28 2014

A weak east-west oriented cold front over southern Iowa will
continue moving south and exit the area early Monday morning. Light
winds near the boundary become northeast overnight...but remain
light. Middle/high clouds will remain over the area through Monday
evening. Some light snow/flurries developing over western and
central Iowa could expand east into east central Iowa by Monday
morning. However if the snow makes it into eastern
should stay west of the the i380/Highway 218 corridor and should
not restrict visibilities much. An area of low clouds over
southwestern Minnesota and northwest Iowa will have to be watched to see
if they expand into east central Iowa Monday morning. The latest
model solutions show the clouds breaking overnight and were not
included in this set of tafs.


Dvn watches/warnings/advisories...


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

National Weather Service Glossary of Abbreviations