Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 160214

Area Forecast Discussion
National Weather Service Lincoln IL
914 PM CDT Tue Oct 15 2019

Issued at 310 PM CDT Tue Oct 15 2019

A cold front will depart to the east this evening, bringing an end
to the rain showers and isolated storms. The front will usher in
another cold air mass, with low temperatures tonight in the upper
30s to low 40s. Highs on Wednesday will struggle to climb into the
50s in many areas, under cloudy skies, with brisk northwest winds
gusting to 25 mph.


Issued at 914 PM CDT Tue Oct 15 2019

Skies are mostly clear over most of the CWA this evening except
for areas to the east and southeast. Thinking those will hang
around little longer in those areas. However there are more clouds
across IA that are moving toward the area tonight. Question is how
far south and will it be scattered or broken when it gets
here...and when. Lots of uncertainty at this point but think some
of the clouds will advect into the area overnight. So have made
some adjustments to sky cover for overnight. Front is finally
through CMI, DNV, MTO and will be getting into southeast IL, south
of I-70 next hour. Think remainder of forecast is fine. Update
will be out shorlty.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 310 PM CDT Tue Oct 15 2019

The cold front is making steady progress across Illinois, and is
on track to depart to the east of our counties by 03z/10pm. 0-6km
wind shear values are climbing to 50-60 mph ahead of the front,
with MLCAPE values only around 50-200 J/kg. Better instability
will reside farther south along the cold front in Missouri and
southern Illinois. However, the steep mid-level lapse rates may be
enough to support a few thunderstorm updrafts in central IL.
Therefore, have continued with the mention of thunder until cold

While there will be a clearing line behind the cold front for a
few hours, satellite images are showing a well defined area of low
clouds that will pivot southward into Illinois by Wednesday
morning. Lows tonight will be held a little warmer than they
could drop to due to gusty W-NW winds all night. Lows will still
be chilly, in the upper 30s to low 40s, and wind chills below
freezing at times.

Expansive clouds on Wednesday will couple with the cold air mass
to limit high temps to the low to mid 50s. NW winds will remain
gusty through the day on Wed.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 310 PM CDT Tue Oct 15 2019

A weakening pressure gradient Wed evening will allow for a more
complete decoupling of the boundary layer winds, setting the stage
for an even colder night. Clearing skies will allow some areas to
see some patchy frost, especially in traditional cold spots.

Dry conditions will prevail in the extended forecast through
Friday evening, under gradually warming conditions. The warming
will be attributed in part to nearly zonal flow aloft, as well as
prevailing southerly flow during that time. High temps will
rebound upward each day after Wednesday, reaching the mid-upper
60s Friday and Saturday. Sunday could even see widespread 70s in
central IL.

The next chances of rain look to come with a weakening cold front
later Friday night through Saturday evening. Limited moisture and
weak forcing for precip should limit rainfall amounts to a quarter
inch or less during that time.

However, a more dynamic storm system is taking aim on the Midwest
for early next week. A deep trough will progress from the central
Plains on Sunday to northern Lake Superior by 12z/7am Tuesday.
During that time, a strong cold front will push across Illinois,
with a moisture tap off the Gulf of Mexico ahead of the system.
That will increase precipitable water values into the 1.5" to
1.75" range. Locally heavy rainfall will be possible from Sunday
night through Monday night, with a couple of inches of rainfall
possible. Rain should taper off on Tuesday, as drier and colder
air return to the area.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 635 PM CDT Tue Oct 15 2019

VFr conditions will prevail at all TAF sites to start with
scattered mid clouds around 10-12kft moving across the area.
Satellite loop shows a break in the clouds to the northwest and
west but a large area of clouds around 4-5kft is advecting toward
the area and will move over the sites this evening. Timed these
clouds into PIA around 03z and then progressing to the east and
southeast. Toward morning, cig heights will drop to around 1.5kft
and then slow rise during the day to around 2-2.5kft toward the
noon hour. Expecting clouds to continue through the day. Winds
will be west-northwest tonight with FROPA occurring at 00z at DEC
and 01z at CMI. Breezy conditions around 20kts expected this
evening but then overnight should loose gusts. Gusts over 20kts
expected again tomorrow during the day.




LONG TERM...Shimon
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