Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251728

Area Forecast Discussion
1128 AM CST Tue Nov 25 2014


Large area of stratocumulus continues to sag southeast across the
forecast area, with the last holdouts near Lawrenceville now
clouding up. A narrow area of clearing from Peoria southeast has
been shifting toward Bloomington and Champaign, although this is
also starting to show a bit of filling in on the latest visible
satellite imagery. At present, the northern edge of the cloud deck
is advancing across northwest Illinois and is approaching
Galesburg from the north. The latest RAP and HRRR guidance shows
some additional development in that area over the next couple
hours, so we will need to keep an eye on that. For now, it looks
like the bulk of the clearing will begin across the southwest CWA
soon and slowly pull northeast.

Have made some adjustments to the high temperatures across the
northern CWA, where it`s still only in the lower 20s, and the
latest sky grids have been sent as well.


.SHORT TERM...(Today)

Low pressure that brought widespread rain to central Illinois on
Sunday is now over Quebec, with trailing cold front approaching the
East Coast.  Despite the parent low being so far away from the
region, lingering upper troughing is keeping cloud cover locked in
place.  08z/2am IR satellite imagery shows low clouds covering all
of central/northern Illinois and as far west as eastern Iowa.
Timing tools are indicating only a very slow eastward progression of
the clearing line, so have delayed the clearing across the KILX CWA
accordingly. The day will start out overcast across the board, then
a slow west-to-east clearing will occur as the day progresses.
Based on latest satellite loop and 00z forecast soundings, think
locations along/northeast of a Bloomington to Mattoon line will
remain cloudy for the entire day.  Further west and south, skies
will become partly to mostly sunny this afternoon.  Will be a cold
day with highs only in the 30s, but it will not be nearly as windy
as yesterday with westerly winds generally around 10 mph.


.LONG TERM...(Tonight through Monday)

Main weather challenge in the extended continues to be clipper
system expected to track through the region on Wednesday.  00z Nov
25 models are in excellent agreement with the timing and track of
the system, but display minor differences with their QPF fields.
All models take low pressure currently over Alberta and track it
southeastward into western Iowa by 12z Wed, then into southern
Illinois by 00z Thu. This represents a continued southerly trend
in the track, which means portions of the far N/NE CWA may see
little or no precip with this system.  NAM is the most
concentrated with its QPF, keeping it confined very near the low
track.  Meanwhile, both the GFS and ECMWF are more generous and
spread light precip further north across the entire area.  Have
updated Wednesday precip chances to focus likely PoPs along/south
of a Rushville to Decatur to Robinson line, tapering down to low
chance northeast of I-74.  Given the more southerly track, WAA
ahead of the wave will be weaker than previously thought, so high
temps will not be quite as warm.  Afternoon readings will range
from the middle 30s far north to the lower 40s south of I-70.
Forecast soundings support snow: however, surface temps will be
warm enough for a rain/snow mix across much of the area and
perhaps mainly rain across the far southeast.  Snowfall amounts
will be mitigated by the marginal temps and overall light QPF,
with perhaps a half inch along/southwest of Macomb to Springfield
line where the precip will begin during the morning hours when it
is still cold enough to support all snow reaching the ground.
System will quickly track into the Appalachians Wednesday night,
with just a few lingering snow-showers across the E/SE into the

Once Wednesday clipper departs, the remainder of the extended
appears to be quiet.  A shot of cold air behind the system will drop
high temps into the upper 20s/lower 30s on Thursday: however, a
marked warming trend is still expected for the end of the week as
eastern CONUS upper troughing relaxes and a zonal pattern develops.
As southerly winds develop on the back side of departing high
pressure, high temperatures will soar well into the 50s on Saturday
before a cold front sags southward into the region late in the day.
Still some discrepancies further out concerning how far south front
will make it, with overall consensus taking it into the Ohio River
Valley by Sunday.  High pressure initially along the Gulf Coast will
limit northward moisture return, so showers will likely not develop
along/ahead of the boundary until it sinks into the SE CWA Sunday
afternoon/night.  All model solutions point to a cool/dry day on
Monday before southerly flow resumes and precip chances slowly begin
to increase by Tuesday.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)

Main forecast concern is with the timing of the MVFR conditions
this afternoon. All TAF sites currently with ceilings at or below
2000 feet. Clearing line advancing eastward from far western
Illinois, with AWIPS timing tool showing it reaching KSPI around
20Z, but not reaching KCMI until toward 00-01Z. Once skies clear,
VFR conditions are on tap the remainder of the forecast period.
There will be lowering ceilings late Wednesday morning ahead of a
fast moving storm system, but any MVFR conditions would likely be
after 18Z. Westerly winds this afternoon will become light and
variable for a time early this evening, before a southeast flow
sets up and persists the remainder of the forecast period.




LONG TERM...Barnes
AVIATION...Geelhart/EJL is the U.S. government's official web portal to all federal, state and local government web resources and services.