Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 190737
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
237 AM CDT Sun Aug 19 2018

.SHORT TERM...(Today and tonight)
ISSUED AT 236 AM CDT Sun Aug 19 2018

Rather quiet across the forecast area early this morning. GOES-16
nighttime fog imagery shows some patches of thick fog southwest of
Effingham and also in the Illinois River valley of west central
Illinois, with a broader area of light fog over the northern third
of the forecast area. Some of the high-res guidance suggests
potential for some dense fog toward sunrise, mainly across the
western and northeast parts of the forecast area. Otherwise, high
pressure over the Great Lakes should keep us dry today.

With a narrow upper ridge overhead, the thick smoke layer aloft
should remain in place today. The experimental smoke forecast from
the HRRR suggests this should lift out overnight, as the surface low
swings into Missouri.

The upper low over Wyoming early this morning should drop into
southeast Nebraska later tonight, as the surface system develops
over the Plains. Have backed off on the evening rain chances, as a
substantial dry layer will be in place above 850 mb. However, have
gone with likely PoP`s over the southwest CWA after midnight, and
chances as far east as Decatur.

&&

.LONG TERM...(Monday through Saturday)
ISSUED AT 236 AM CDT Sun Aug 19 2018

The storm system will become vertically stacked over the mid-
Mississippi Valley on Monday, before the upper low weakens to an
open wave. With the surface low moving northeast toward the
Wisconsin border by late evening, a dry slot will begin to cut off
the rain. Before this occurs, precipitable waters in excess of 2
inches will begin to move in before sunrise, and overspread the
area. Northern portion of the CWA are in a slight risk of
excessive rainfall, though the rain/storms should be progressive
enough to prevent a widespread flood risk. Meanwhile, most of
Illinois is in a marginal risk of severe weather. Main wild card
will be with the amount of clouds expected, as the GFS and NAM
both suggest decent low level shear and some healthy CAPE`s above
1500 J/kg. Main time frame for any strong/severe storms appears to
be from mid afternoon until around sunset.

Scattered showers and a few storms will linger into Tuesday, as
a secondary trough swings across the region. After that, high
pressure will dominate for mid week. A couple days of pleasant
temperatures are on tap through this period, before the next storm
system moves in from the Plains. With the low track in this system
further north, the best rain chances will be over the upper
Mississippi River valley. However, scattered showers/storms are
still expected this far south.

As the weekend begins, the upper level winds will shift more out
of the southwest, helping to transport the western heat dome
toward the middle of the U.S. 850 mb temperatures around 20C are
expected as early as Saturday afternoon. Current blended
temperatures give highs in the mid 80s for the weekend, though the
latest ECMWF MOS guidance suggests some lower 90s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1146 PM CDT Sat Aug 18 2018

Main concern for aviation remains the potential for VLIFR fog
between 10z-13z. Dewpoint depressions will likely drop to zero in
our NE counties at least, with spotty areas all across central IL.
Low temp forecast is in the low to mid 60s, in areas where current
dewpoints are in the upper 60s to near 70. Have included some LIFR
fog at BMI and CMI, with IFR at PIA and DEC. The period of dense
fog would be short lived, with vis improving to VFR by 14z.

Cloud levels in the afternoon should generally remain SCT025-035,
so not anticipating BKN ceilings during peak heating.

Winds will remain easterly through tomorrow evening, with speeds
prevailing less than 10kt.


&&

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

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon


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