Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 240542
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CST Mon Feb 23 2015

.UPDATE...
ISSUED AT 850 PM CST MON FEB 23 2015

Quiet weather is expected across central and southeast Illinois
overnight, although it will still be quite cold. Winds will trend
southwesterly over the next few hours as a ridge of Arctic high
pressure moves east of the area. These southerly winds should help
stall the temperature fall for the rest of the night once they
develop, although some areas with the deeper snow cover have
already fallen below zero.

Going forecast is in good shape overall. Only tweaks to hourly
trends are required at this time.

&&

.SHORT TERM...(Tonight)
ISSUED AT 240 PM CST MON FEB 23 2015

1040+ mb Arctic ridge centered over eastern Missouri and western
Illinois this afternoon.  This has produced temperatures just above
record cold highs for the date across central Illinois this
afternoon, with most areas reaching 8-15 degrees by 2 PM, or around
25 degrees below normal for late Feb.  As the high continues to sink
southeast towards the Ohio Valley by 12z, light north/west low level
winds will back to southwest and strengthen towards daybreak, in
response to low pressure tracking north of the Great Lakes.  This
should lead to a quick temp drop-off this evening, with readings
steadying out after midnight.  Skies will remain mostly clear
overnight due to the dry/subsident airmass.  Expect coldest readings
east of I-57 where winds remain light longer, a degree or two above
zero.  Meanwhile, farther west where return flow kicks in sooner,
lows around 4-7 will be more common in west-central IL.  These
temperatures combined with winds at 10-15 MPH towards daybreak, will
lead to wind chills close to -15 east of a Bloomington to Mattoon
line after 09z.  Since this is marginal and would only last a few
hours, will not be issuing a wind chill advisory with this forecast
package.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 240 PM CST MON FEB 23 2015

A strong area of low pressure will be pushing north of the Great
Lakes on Tuesday bringing our area gusty southwest winds which
should help to push afternoon temperatures into the low to mid
30s. Most of the stronger lift and deeper moisture will remain to
our north but a few flurries are still possible later in the
afternoon as the front sweeps across the area. Colder weather will
once again move into the area for the middle and latter portions
of the work week with daytime highs on Wednesday about 10 degrees
colder than Tuesday, and even colder for Thu and Fri. A weak
shortwave is still forecast to slip southeast into the middle of
the country on Wednesday spreading some light snow southeast into
parts of the Plains and Midwest. Highest POPs (chance) will be
over west central Illinois with slights to the east. Current
indications suggest the more significant accumulations of an inch
or two will remain west and southwest of our area Wednesday night
into early Thursday. The shortwave will push southeast of the area
by late Thursday taking any lingering low chance POPs with it with
cold and dry weather prevailing for the rest of the week.

Longer range models continue to indicate a significant pattern
change to start across the lower 48 next weekend as our upper flow
transitions from northwest to southwest resulting in a moderating
trend but also a more active pattern with respect to precipitation
chances. Only problem is timing of each of the shortwaves ejecting
out of the developing long wave trof to our west and associated precip
chances and type with each. With the 12z runs, the GFS was quite
a bit slower than the latest ECMWF with the ensembles still
exhibiting quite a bit of spread later Saturday into Sunday. Will
continue to keep slight chances going during the day Saturday and
then increase the POPs quite a bit Saturday night into Sunday as a
wave of low pressure moves northeast towards the area. Latest forecast
soundings and thicknesses suggest precip will start out as light snow
Saturday night with a gradual transition to rain south and central,
and snow far north on Sunday. Still many details to be worked out
with the weekend system but it does appear we will see at least a
couple of days of thawing temperatures. We should warm into the
30s north to mid 40s south on Sunday with most areas seeing 30s on
Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1141 PM CST MON FEB 23 2015

Predominantly VFR conditions expected across the central Illinois
terminals through the 06Z TAF valid time. High pressure will
slowly pull away from the area tonight, allowing a clipper system
to approach from the northwest. The approach of this system will
see a steady increase in southwest winds later tonight, with the
winds becoming quite gusty Tuesday morning. The winds will shift
more westerly as the cold front associated with the system passes
through Tuesday afternoon. Little precipitation is expected with
the clipper, as the best forcing/moisture stay well north of the
area. However, would not be surprised to see a few flurries in the
vicinity of FROPA. Some guidance also suggests CIGS may drop to
MVFR along and behind the front, but confidence in this occurring
is too low to carry at this time. Will continue to monitor model
trends.

&&

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

$$

UPDATE...Bak
SHORT TERM...25
LONG TERM...Smith
AVIATION...Bak






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