022 
FXUS63 KILX 140949
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
349 AM CST Mon Jan 14 2019

.SHORT TERM...(Today and tonight)
ISSUED AT 349 AM CST Mon Jan 14 2019

Skies have cleared across much of central Illinois early this
morning...resulting in the formation of patchy fog. The fog has
occasionally reduced visbys to 1/4 mile or less, creating
hazardous driving conditions in some locations. Will therefore be
issuing a Dense Fog Advisory everywhere along/west of a Champaign
to Shelbyville line. Further east closer to the Indiana border, 
persistent low clouds will prevent fog development. The fog will 
dissipate by mid-morning:however, as boundary layer flow becomes 
increasing southwesterly, low clouds currently poised upstream 
across Missouri will advect into the area as the day progresses. 
End result will be a mostly cloudy day with highs in the upper 20s
and lower 30s. 

As warm advection increases over the cold snow-covered ground, fog
and/or drizzle will likely develop late tonight into Tuesday
morning. Forecast soundings show a 2000-2500ft thick saturated
boundary layer with weak lift...indicative of a period of drizzle.
With temperatures well below freezing, may see some minor icing
for the Tuesday morning commute. A Winter Weather Advisory may be
needed, but decided to delay issuance and allow the next shift to
examine the latest model data before making the final decision. 

&&

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 349 AM CST Mon Jan 14 2019

Patchy freezing drizzle will come to an end by midday Tuesday,
followed by milder conditions with highs in the lower to middle
30s by afternoon. A weak cold front will pass through Illinois
Tuesday night with little fanfare other than a shift in the wind.
The front will then become stationary along the Ohio River on 
Wednesday before an approaching upper disturbance produces a wave 
along the boundary. Most models suggest a period of isentropic
lift and light precip along/north of the track of the wave
late Wednesday night into Thursday morning. With moisture 
profiles initially being shallow, ice crystals likely will not be 
present as the precip begins. As a result, think freezing rain 
will be the primary precip type until temperatures warm
sufficiently to support rain by Thursday afternoon. Initial
indications suggest minor ice accumulations of less than one tenth
of an inch.

Once this system departs, all eyes will be on yet another system
developing in the lee of the Rockies on Friday. All models 
produce a surface low over eastern Colorado by Friday morning,
with the system then tracking E/NE into the Tennessee/Ohio River
Valleys this weekend. The exact track remains in question:
however, a few points can be gleaned from the 00z Jan 14 suite.
First, the GFS continues to be the most inconsistent model and its
solution has therefore been largely ignored. Second, the ECMWF/GEM
remain in very good agreement from prior runs...lending credence
to their forecast. Third, model consensus has shifted slightly
northward with the low track...which seems reasonable given the
likely presence of a differential heating boundary along/south of
the deep snow cover over central Illinois. Based on these points,
think snow will develop across much of the area Friday night and
continue through Saturday night. Locations south of I-70 may be
warm enough for a rain/snow mix or even just rain at times.
Further north across the remainder of the KILX CWA, another
potentially significant accumulation of snow seems probable next 
weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1146 PM CST Sun Jan 13 2019

Skies have cleared across the central IL terminals which will lead
to strong radiational cooling and a good chance of fog, which will
be locally dense. IFR or worse visibilities can be expected to
develop overnight as a result. Fog will diminish by around 16Z,
however low cloud cover will return, and cigs better than low-end
MVFR are not expected through the forecast period. Winds N up to 
6 mph initially, then becoming light and variable as high pressure
moves into the region overnight. Winds becoming SW 4-8 kts after
16Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...37