Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 172111
Area Forecast Discussion
National Weather Service Lincoln IL
311 PM CST Tue Dec 17 2013
ISSUED 300 PM CST Tue Dec 17 2013
The short term will be highlighted by a warming trend through mid
week. Fog may become an issue as the snow melts over the next few
days. A cold front is still slated for Friday morning, with a
major winter storm taking aim on the area for the weekend. Precip
type issues remain the biggest challenge with that storm. The 12z
guidance has generally trended warmer on Sat and Sat night, which
means rain longer and farther north, with a band of freezing rain
in our northern area. Snow chances may hold off until very late
Sat night and possibly until Sunday as the colder air finally
flows into central IL. Snow amounts on the NW side of this system
could be very high, with the latest trends putting that band just
to our northwest. Any shift in the placement of the stationary
front and track of the low up along the front will be critical to
precip type distribution and amounts of snow and ice.
SHORT TERM...Tonight through Friday night.
The quick clipper snows from today should be out of our southeast
counties by evening. We will not mention any snow in the worded
zones as a result.
Fog potential tonight does not appear as high as previous model
runs, although the models have not been handling the ground level
moisture very well at all. We kept a mention of patchy fog in our
grids for tonight, but do not expect any widespread dense fog
despite very light winds and clear skies.
Wednesday will see high pressure sliding east of IL and southerly
winds increasing. Warm advection flows will intensify in the
afternoon, helping to push temperatures into the 40s in many
areas. Snow cover will reduce the effective heating of the sun,
with energy going to melting the snow. That may keep highs in the
upper 30s over areas with deeper snow. The additional ground level
moisture should help fog develop Wed night, despite some steadier
south winds overnight.
Fog should linger Thursday morning as mid and upper level moisture
increases ahead of the approaching cold front. Rain showers should
hold off until afternoon when isentropic lift intensifies due to
45kts of flow up the 295k surface. Rain should generally remain
north of Lincoln in proximity to the developing mid-level warm
front and nose of the theta-e ridge.
There remains some concern as to the extent of freezing rain later
Thursday night into Friday morning as surface temps northwest of
Peoria dip below freezing behind the cold front. We kept a mention
of FZRA in that area, with a thin layer of icing possible.
Precipitation chances should become confined mainly to the
southeast half of our area Friday afternoon and Friday night as
the cold front and shortwave shift east. Once again, any rain
falling into the night could transition to freezing rain along
and north of I-72.
The cold front is projected to stall out just to the southeast of
Illinois, in prep for a return push northward when the weekend
LONG TERM...Saturday through Tuesday.
A surge of warm air and moisture in the mid levels will strengthen
on Saturday, pushing the front back north as a warm front. Rain
will re-develop or advance northward during the day, with freezing
rain possible in the morning north of I-72 before surface temps
climb above freezing. All or our forecast area except maybe around
Galesburg should climb above freezing during the afternoon,
keeping all precipitation as rain. The timing and speed of the low
riding up the front will dictate how soon that colder air will be
drawn into the northern edges of the storm and change the rain to
freezing rain and eventually snow. Saturday night could see an
extended period of freezing rain in a band from SW to NE across
our counties, including areas from Rushville/Jacksonville/
Springfield north to Canton/Peoria and east to Bloomington and
Champaign. Ice amounts could reach over a quarter inch in some
areas, depending on how soon the cold air arrives at low levels.
Snow is expected to develop on the NW fringes of our area as soon
as Saturday evening, but more likely after midnight into Sunday. A
couple of inches of snow could accumulate on Sunday in areas west
of I-57, with lesser amounts toward I-57 and east. A band of
deformation snows could increase those amounts in bands west of
There remains a great deal of uncertainty with the weekend storm
system, but the trends have been for a warmer solution in our
counties, even from the previously colder ECMWF.
Dry and colder conditions will follow the storm, and should set up
better travel conditions for Christmas Eve day through Christmas,
and possibly longer.
ISSUED 1151 AM CST Tue Dec 17 2013
Band of snow-showers with visbys down to 1SM or less is currently
moving across central Illinois. 1744z radar indicates that the
snow-showers are mainly along and east of I-55, with areas to the
northwest now dry. Based on radar timing tools, will carry -SN
through 19z at KBMI, KSPI, and KDEC, and through 20z at KCMI. Once
the snow ends, VFR ceilings will persist for a couple hours before
clearing arrives from the northwest. Clouds have already scattered
at KGBG and will clear at the TAF sites between 19 and 21z. After
that, mostly clear skies will prevail tonight into Wednesday.
Winds will generally be from the west today/tonight, but will
become southerly at 10 to 12kt by Wednesday morning.