Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241751

Area Forecast Discussion
1151 AM CST Wed Dec 24 2014

Many updates to the forecast already throughout the morning. Small
system that was threatening snow indeed took a more easterly path
in addition to several nuances that added up to less, if any,
significant snowfall for the area. Wave aloft remained open
instead of closing and becoming more dynamic. Snowfall rates,
therefore, remaining low if they even get started, and surface
temperatures well above freezing. SFC dwpts well back into IA very
warm and barely at or below freezing. Majority of precip out there
expected to be rain. Some flakes certainly possible and will see
an increasing mixture of ra and sn through the afternoon, slowly
becoming all snow on the back edge as the system pulls out to the
NE. However, as fast as the precip becomes all snow, it comes to
an end. As a result, have pulled the advisory...Also, have warmed
the MaxT and adjusted the forecast here and there. Areas east of
Interstate 55 may see some light dusting this evening, with more
falling, but much of it will be melting as it hits the ground.
Along the Illinois Indiana border, some minor accumulations up to
an inch are possible under some of the more productive showers.


.SHORT TERM...(Today)

Latest surface analysis indicating the storm system of interest for
us was located over northwest Alabama and is now forecast to track
further east than earlier thought and should be in extreme eastern
Indiana or western Ohio by this afternoon. This will push the
band of heavier precip east as well which would suggest the
accumulating snow will set up east of I-55, more like along and east
of I-57 for any significant accumulations. Forecast soundings off just
about any model you look at was indicating boundary layer temperatures
still too warm to support any long duration of accumulating snow
until this afternoon or early this evening over extreme east central
Illinois. Even in these locations, wet bulb zero heights were above
1200 feet, so we will need to see some significant forcing associated
with the shortwave trof/upper low to produce some dynamic cooling that
may be able to overcome the warm boundary layer temperatures. Not
seeing any strong trends back to that solution with the past couple
of model runs, as a result, have started to trim back on the advisory
across our west for now. Have added some counties across extreme east
central Illinois due the eastward shift to the storm track and where
the better and longer duration lift will set up this afternoon and
early this evening. As far as snowfall is concerned, very low end
advisory snowfall totals across the area with generally 1 to 3 inches
east of I-55, and if model trends continue to shift the surface low
track further east, the better setup for accumulating snow will be
east of I-57.


.LONG TERM...(Tonight through Wednesday)

Snow to diminish from west to east during the evening with around
a half inch of additional snow from 6-9 pm from Champaign and
Paris northeast. Surface low pressure deepens nne to 988 mb at 6 pm
near Detroit and to 980 mb near Georgian Bay Canada by midnight
tonight. Blustery west winds 15 to 20 mph and gusts of 20 to 30 mph
this afternoon/evening to gradually diminish late tonight as deep
low pressure pushes into western Quebec by dawn Thu/Christmas morning.
Low stratus clouds to gradually decrease from sw to ne during day
on Thu with surface ridging into IL from southeast states. Above
normal highs in the lower 40s on Thu. This should melt most of the
snow by Thu afternoon. Even milder highs of 45-50F on Friday as
breezy ssw winds develop, with clouds increasing especially by Fri

Models have been trending slower on low pressure ejecting ne from
CO into the western Great Lakes by dawn Sat and pulling a cold
front se through IL Sat. Have chance of light rain Friday night,
though may hold off in eastern/se IL until overnight Friday night.
Then have light rain changing to light snow Sat over central IL
with mix over southeast IL. Any snow accumulations look fairly
light with this system over central IL. Highs Sat range from mid
to upper 30s over IL river valley to mid to upper 40s in southeast
IL. Cooler highs in the 30s on Sunday across region behind the
cold front which pushes into KY/TN. Models differ with
disturbances tracking ne along the frontal boundary and stuck
close with superblend pops this weekend, with highest pops in
southeast IL. Appears cold enough for mainly light snow chances by
Sunday and Sunday night in southeast IL. Temps to cool further
behind system early next week with below normal temps expected by
middle of next week.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Not much in the way of major changes to the TAFs. Some minor
tweaks to lessen impacts to vis as precip not as heavy or
widespread. Still more than enough moisture to keep IFR through
the overnight, slowly breaking out by morning. In the shorter
term, however, terminals mainly MVFR/IFR and a couple of dips down to
LIFR cigs in BMI. For the most part, kept the MVFR/IFR cigs and
vis as consistency is difficult to assess based on obs and sat
info. Northwesterly and gusty today, losing gusts in the
overnight.  More southwesterly in the morning hours.




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