Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Quad Cities Iowa Illinois
1149 am CST Tue Dec 6 2016

..aviation update...

issued at 1103 am CST Tue Dec 6 2016

Dense fog advisory has expired as conditions rapidly improve with
the passage of a cold front pushing eastward across NW and western
IL, with decent pressure rises in eastern Iowa.

Update issued at 1010 am CST Tue Dec 6 2016

Cold front was nearing the MS river with rapidly improving
conditions occurring west of the front. However, dense fog with
frequent visibilities of 1/4 mile or less was still evident east
of the front. Due to this we have extended the dense fog advisory
to 11 am east of the MS river.

Cold air advection will be kicking in by afternoon with a
colder/drier airmass arriving on brisk northwest winds. There will
be plenty of sunshine this afternoon but temperatures will also
begin falling as the afternoon progresses. Current readings were
in the upper teens in NW Iowa.

Update issued at 836 am CST Tue Dec 6 2016

Cold front pushing across eastern Iowa this morning will rapidly dissipate
the dense fog/low stratus that's ahead of the front. The front should
be east of the dvn cwa by noon with sunshine and brisk winds this
afternoon over much of the cwa.


issued at 312 am CST Tue Dec 6 2016

At 230 am CST...areas of fog and low clouds cover the region with temperatures
around freezing north to the mid 30s south. A cold front with scattered
flurries just behind the front north of I-80 is approaching northwest
sections of the area. AWIPS distance-time feature supports the front
with clearing conditions will pass through the area by 11 am with any
flurries along and north of Highway 30. Colder and drier air will continue
into the region the few days.


Short term...(today and tonight)
issued at 312 am CST Tue Dec 6 2016

Short term forecast confidence assessment...good or above average with
main issue the dissipating fog and if temperatures start falling by
afternoon. Area highs and lows should be within 3 degrees of forecast.

Today...cold front should pass from west to east roughly between 6 am
and 11 am with fog rapidly dissipating and clearing skies. Highs most
locations will tend to be mid day all but far east as falling temperatures
by afternoon with 20s most locations by sunset. West to northwest winds
of 10 to 20+ miles per hour will be the case late morning through the afternoon.

Tonight...fair skies with increasing clouds late and continued brisk
northwest winds. Mins to fall into teens northwest to mid 20s southeast.
This will mark the coldest night of the early winter season with wind
chill values falling to 5 to 15 degrees above zero by daybreak.

Long term...(wednesday through monday)
issued at 312 am CST Tue Dec 6 2016

Zonal to northwest 500 mb flow will dominate the long term period. A number of
disturbances will move through this flow leading to a highly dynamic
forecast period. Highly energetic jet across the US along with the
500 mb flow will lead to an active forecast period with high run to run
variability in the models. As a result, overall confidence in
forecast is low.

The beginning of the long term features a vort Max rotating around
cyclonic flow across our area. Previous forecast had light snow for
southern two tiers of counties. Latest guidance suggests that the
threat for snow across this area continues to diminish. If it
wasn't for the Gem and ECMWF, we would have a dry forecast. Think
that the next run of the blends will remove this schc pop for the
southernmost tier of counties. The main story will be the winter
temperatures across the area. Nighttime wind chills will be around
0 for most of the area Wednesday and Thursday night as Arctic air
makes its return to the upper Mississippi River valley. Latest run
of guidance continues 850 mb temps in the -12 to -14c realm, so little
change to temps this shift.

Into this weekend, Friday night looks as though the chance for snow
returns to the area as a clipper type system overruns 850 mb warm air advection. The
GFS and Gem produce quantitative precipitation forecast across the northern County Warning Area. The European model (ecmwf) does
not. So model inconsistencies begin the weekend. The Gem and GFS
have a stronger 500 mb wave eject out of The Rockies and produces
another round of snow for Saturday night across the area. The European model (ecmwf)
does not have this wave. Current forecast has chance pops across
the area. That said, there is definitely more time for this to
change. What does seem more certain is the well-advertised cold air
to end the workweek.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1149 am CST Tue Dec 6 2016

VFR conds through the taf cycle as high pressure builds into the
mid MS valley. Northwest winds around 15 knots with gusts to 25
knots this afternoon then west around 10 knots tonight into
Wednesday morning.


Dvn watches/warnings/advisories...


short term...Nichols
long term...Gibbs

National Weather Service Glossary of Abbreviations