Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 202334
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
534 PM CST Mon Nov 20 2017

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 259 PM CST Mon Nov 20 2017

A low level jet ahead of an approaching cold front will aid in
producing strong winds through much of the night tonight. Despite
the strong south-southwest winds ahead of an approaching cold
front, moisture content of the air mass will only marginally
increase. Clouds will increase late tonight for areas northwest of
the Illinois river, with a band of mid-clouds progressing to the
southeast across central and southeast Illinois during the day
Tuesday. Bufkit analysis of GFS data is showing some sprinkles
developing just ahead of the front, mainly N of I-70. The depth of
saturation is quite lacking, but can not rule out a few rain
drops reaching the ground tomorrow with the enhanced omega/lift
indicated. For now, will keep the dry forecast in place for
Tuesday.

Low temps tonight will be held warmer than normal due to windy
conditions, despite mostly clear skies. Lows should bottom out in
the upper 30s in most areas, with low 40s in the west toward
Jacksonville, and mid 30s toward the Indiana border. Highs on
Tuesday will likely come early in the day, as the cold front
reaches I-55 by around 16z/10am, then exits to the southeast by
21z/3pm. So temperatures will peak in the morning for a large
portion of central Illinois, with falling afternoon temperatures
as northwest winds crank up to 15 to 25 mph. Morning/daytime
highs will range from the low 40s near Galesburg, to the low 50s
south of I-70.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 259 PM CST Mon Nov 20 2017

Gusty NW winds will linger for a few hours into Tuesday evening,
then diminish as a cold air mass settles into Illinois. Clearing
skies will help low temps Tuesday night dip into the low to mid
20s. Even light breezes will put wind chills in the mid-teens by
Wed morning.

The models continue to show a dry forecast for the rest of the
holiday week, as the storm track remains across southern Canada.
A northward shift of the polar jet will allow for some warming to
develop for Thursday and Friday, as high temps return to above
normal readings on Friday. The ECMWF is about 4 degrees warmer
than the GFS for Friday, but that is due to a slightly slower
frontal progression. The EC delays the arrival of clouds, allowing
for more insolation. The Canadian GEM and GFS are in better
agreement on clouds pushing into at least the NW half of our
forecast area by the end of the afternoon, so highs could be held
a bit lower than the EC shows if that scenario pans out.

The warm air will be short-lived, however, as another cold front
is projected to push across Illinois Friday night. Slight chances
of rain extend south toward Champaign and Danville, but the
overall consensus is for another primarily dry cold FROPA in our
forecast area. Dry conditions look to continue through the
Thanksgiving holiday weekend, under a moisture starved and cold air
mass. High temps on Saturday look to still approach normal, but
Sunday and Monday look colder than normal, with highs in the upper
30s to around 40 Sunday, and in the low to mid 40s on Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 525 PM CST Mon Nov 20 2017

VFR conditions are forecast to remain across the area through
this forecast period. Our main forecast concern will be with the
low level winds tonight into Tuesday. Forecast soundings continue
to show the low level jet will be centered over our area this
evening into the overnight hours with winds at 1200-2000 feet AGL
in the 40-50 kt range with a gradual decrease in speeds after 09z
as the core of stronger winds shifts to our northeast. We will
still be experiencing some gusts at the surface through the evening
but still enough of a spread in wind speed from the surface to
around 2000 feet to keep the LLWS going into the early morning
hours.

Mid level moisture/clouds will increase tomorrow morning ahead of
a cold front that will shift across the area during the late
morning and early afternoon hours. Surface flow will be south to
southwest at 12 to 17 kts during the morning and then shift into
the northwest at 12 to 20 kts after FROPA.

&&

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

$$

SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...Smith



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