Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 211735
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1135 AM CST Sat Jan 21 2017

.UPDATE...
Issued at 945 AM CST Sat Jan 21 2017

Large expanse of clear skies covering much of central Illinois
this morning, with high clouds along and east of I-57.
Temperatures already in the 50-55 degree range in most areas. Some
diurnal cumulus development possible, but this should not be
enough to significantly impact the temperatures, which will
largely reach the 60-65 degree range. Zones/grids were updated to
reflect the latest sky trends and to remove the fog mention from
earlier.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 339 AM CST Sat Jan 21 2017

Southerly flow behind a warm front which has lifted north of the
forecast area early this morning has brought warmer air and a steady
south breeze around 10 mph which in turn has dissipated much of the
fog that was seen earlier in the night. Nevertheless, mild
temperatures in the upper 40s to lower 50s and dewpoint depressions
less than 3 degrees continues to bring patchy fog and haze mainly
north of I-72.

The shortwave ejecting northeastward out of the central Plains into
Iowa this morning will bring  breezy southerly winds through early
afternoon...with mixed layer momentum suggesting gusts should exceed
20 mph early this afternoon then decreasing as the wave moves
further northeast. The warm southerly flow should cause temperatures
to exceed 60 degrees for most of central and southeast Illinois,
which would be close to records in a few areas (see climate section
below).

The trough over the southwest is progged to propagate quickly
eastward reaching the southern Plains late tonight. Deformation to
the northeast of the feature combined with weak instability could
result in showers and isolated thunderstorms mainly south of I-72.
Warm lows to continue south of I-72, with mid to upper 40s, while
temperatures begin to cool to the north with upper 30s/lows 40s as
winds turn northerly due to the influence of the low.

.LONG TERM...(Sunday through Friday)
ISSUED AT 339 AM CST Sat Jan 21 2017

The southern stream storm system, with a 538 dm 500 mb low tracks
into nw Mississippi by 18Z/noon Sunday and near the Smokies by
midnight Sunday night. 00Z models have trended further northward
with qpf/rain into central and southeast IL on Sunday, especially
southeast of the IL river. ECMWF models is further southeast with
qpf mainly in southeast IL, while GFS and NAM bring qpf over entire
CWA Sunday while GEM has qpf southeast of the IL river. Have trended
the forecaster wetter Sunday. Thunder chances should be southeast of
CWA by Sunday. Lingered chances of showers Sunday night se of the IL
river, with small chances of showers still over eastern IL Monday
morning. QPF ranges from less than a tenth inch along and nw of the
IL river to near 0.40 inch in southeast IL. Clouds linger into
Monday as well, though low clouds to start decrease during Monday
afternoon sw CWA. Temps start to cool on Sunday, but still well
above normal for late January. Highs Sunday range from the upper 40s
nw of the IL river, to the upper 50s in southeast IL from I-70
southeast. (Normal highs for late Jan are 33-35F in central IL and
upper 30s in southeast IL). Lows Sunday night range from mid 30s
over IL river valley, to lower 40s southeast of I-70. Cooler highs
Monday in the low to mid 40s, with upper 40s near Lawrenceville.

A weak upper level ridge still slated to build into IL/MS river
valley by Tue morning. This should bring a period of dry wx Monday
night and Tuesday. This should bring partly sunny skies Tue though
clouds will be increasing again later in the day, and become mostly
cloudy over IL river valley/nw CWA by sunset Tue. Lows Monday night
in the lower 30s central IL and mid 30s southeast IL. Highs Tue 45-
50F with mildest readings near 50F over southeast IL and sw of
Springfield.

Models dig a strong upper level trof into the Rockies Tue and eject
a strong surface low pressure ne from central KS into northern IL
Tue night and east of Lake Huron by sunset Wed. This will bring a
chance of light rain to the IL river valley Tue night and Wed and
could be mixed with light snow nw over IL river late Tue night/early
Wed morning but no accumulations expected. Light precipitation
chances could get as far south as I-70 Wed afternoon/evening while
areas south of I-70 appear drier. Could be a mix of light rain/snow
over northern CWA Wed night. Highs Wed range from lower 40s over
northern CWA, to around 50F in far southeast IL.

Pattern change expected during 2nd half of the week, as large upper
level trof shifts east across the Midwest and Great Lakes region
Thu/Fri cooling temperatures closer to normal (highs in the 30s Thu
and Fri and lows in the low to mid 20s for Thu and Fri nights). Can
not rule out periodic chances of light snow showers or flurries as
northern stream disturbances rotate through the upper level trof
late this week. Better chances of light snow will be northeast of
CWA over the Great Lakes region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1135 AM CST Sat Jan 21 2017

VFR conditions to prevail into the first part of the evening. Main
forecast focus involves a storm system lifting northeast out of
the southern Plains tonight. Despite the afternoon sunshine, a
fair amount of low level moisture will remain in place to reduce
visibilities down to a few miles by mid-late evening, but a more
pronounced lowering is expected overnight. Ceilings will also
lower from south to north as the system tracks into the lower Ohio
Valley by midday Sunday. Will need to watch areas from KSPI-KCMI
for potential IFR conditions after 12Z as rain spreads north from
the storm system, but confidence is not high enough to include
that just yet.

&&

.CLIMATE...
Issued at 339 AM CST Sat Jan 21 2017

Record highs for Today (Jan 21):

Bloomington............ 62F (1906)
Champaign.............. 62F (1906)
Decatur................ 69F (1906)
Galesburg.............. 66F (1957)
Lincoln................ 60F (1964)
Olney.................. 68F (1986)
Peoria................. 62F (1957)
Springfield............ 63F (1986)

&&

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

$$

UPDATE...Geelhart
SHORT TERM...37
LONG TERM...07
AVIATION...Geelhart
CLIMATE...Geelhart


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