Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 151147

Area Forecast Discussion
547 AM CST Mon Dec 15 2014

.SHORT TERM...(Today)

Low pressure center of approaching storm system is located near
central KS this morning, heading northeastward. A band of rain ahead
of the low is approaching the Mississippi and will begin to spread
into the central IL forecast area in a few hours, just a bit later
than previously anticipated. Have adjusted PoPs for latest timing,
but otherwise forecast for rain likely this morning in west central
IL spreading into east central IL by around noon is on track. Once
the leading band of precipitation moves east in the early evening,
the upper level low and cold pocket will be approaching west-central
IL for another period of shower activity. This could bring enough
instability for some thunderstorms, and have included slight chance
of thunder in forecasts as a result. Mild temperatures will continue
through the afternoon with highs peaking in the early afternoon of
around 50. Breezy SE winds around 15 mph with gusts into the 20s
will continue through the afternoon due to a substantial surface
pressure gradient associated with the approaching low.

For the remainder of the morning, an increase in moisture and
clearing of high level clouds this evening led to development of
moderate to dense fog in the evening which has subsequently been
trending thinner as more high cloud has spread across the area. A
few pockets of dense of dense fog have continued so have kept the
dense fog advisory in place for now, but will be monitoring for
possible cancellation later this morning.


.LONG TERM...(Tonight through Sunday)

Vertically stacked low progged by the models to be near Chicago by
early Tuesday morning before moving across southern Michigan. Strong
upper wave/trough currently seen on water vapor imagery over
Manitoba will be closing off as it crosses the Minnesota border on
Tuesday, weakening the stacked low and booting it out of the region.
Have maintained likely PoP`s for much of the forecast area this
evening, with the low only making slow progress through the region,
and kept some chance PoP`s north of I-74 into Tuesday morning as

Remainder of the forecast period features a pattern change that
brings temperatures near or just below normal into the weekend. The
main branch of the jet stream will be across the southern tier of
states, with a surface high prevailing over the Great Lakes from
Wednesday into Friday. Most of the models have continued to trend a
bit further south with the Wednesday night storm system, as a weak
wave travels through the southern Plains, and the general model
consensus keeps the precipitation just to our southwest.

The late weekend system remains a bit problematic. Current upper
trough seen on water vapor imagery around 130W will be digging into
the southwest U.S. through midweek, before swinging into Texas by
Friday. The operational GFS remains the northernmost solution and
brings precipitation as far north as Peoria by late Friday
afternoon. The parallel GFS keeps us dry until Saturday, while the
Canadian bypasses us completely. The ECMWF is the strongest of the
model suites, spreading some snow across the southeast half of the
forecast area late Friday night through Saturday, although the
primary baroclinic zone remains well to our south. The forecast will
lean toward the ECMWF ensembles, which are not quite as strong with
the system. The main threat of snow will be south of I-72 Friday
night, but lingering across parts of the east/southeast CWA into
early Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)

Mainly LIFR conditions due to low ceilings across central IL this
morning, with mainly IFR in southeast IL. A band of shra has now
reached KMQB-KIJX in west-central IL and this will spread to
around the IL/IN border by 18Z. As the rain moves in, very little
degradation of flight category conditions is fact
some improvement is possible due to daytime heating and additional
cloud cover causing some improvement in low visibilities and low
ceilings. Overnight, showers expected to gradually diminish west
to east across central IL, however model time-height cross
sections and MOS guidance indicates little improvement in cigs
with IFR or worse likely to continue through the end of 24-hour
TAF forecast period.


DENSE FOG ADVISORY until 8 AM CST this morning FOR ILZ027>031-



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