Area Forecast Discussion
Issued by NWS Central Illinois

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474
FXUS63 KILX 161045
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
545 AM CDT Wed Aug 16 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 300 AM CDT Wed Aug 16 2017

Developing storm system over western Kansas early this morning
will be lifting northeast and strengthening today, with the
synoptic models centering the low over southeast Minnesota by late
tonight. Clusters of thunderstorms seen on regional radar mosaics
at 2 am over southern Missouri, and these will be lifting
northeast into central Illinois. Areas from about Jacksonville-
Flora should see them arrive toward 9 am or so, but it will likely
take until early afternoon to reach the I-74 corridor. A few of
the afternoon storms may be on the stronger side, with 0-6km bulk
shear values reaching the 30-35 knot range.

A line of thunderstorms associated with the cold front itself
should begin to take shape by mid afternoon from western Iowa into
Kansas. The ARW has some of the leading storms moving into the
northwest corner of the forecast area as early as sunset, but a
mid to late evening arrival seems a bit more likely. The stronger
part of the line will be tracking southeast across Missouri and
should bypass us, with most of the models featuring more of a
weakening trend by midnight or so. Have continued with likely
PoP`s over much of the forecast area, except for closer to 50% in
the southeast third of the CWA due to the weakening trend.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 300 AM CDT Wed Aug 16 2017

The low will continue to strengthen as it lifts northeast across
Wisconsin on Thursday, with the front itself crossing the forecast
area Thursday afternoon. The eastern part of the CWA will still
have decent instability into the afternoon, while shear remains a
bit marginal, but some stronger storms along and east of I-57 will
be a threat through early afternoon. Any lingering rain should
exit early evening as the storm system slowly lifts northeast.

A shortwave remains progged to sharpen over the western Great
Lakes into the Plains on Friday, and should be centered over
Illinois by early Saturday. This fast moving system will bring
showers and a few storms to the area, although the GFS lingers
some decent rain into the afternoon. Think this is a bit too
aggressive, so will only carry some slight chance PoP`s over the
east by afternoon.

Eclipse update (Monday): The GFS remains consistently inconsistent
with the strength of the next wave, and the evening model run has
reverted back to a more widespread wet pattern over much of the
state. The ECMWF fires off some storms in the afternoon closer to
the Ohio Valley, while the Canadian model keeps high pressure in
control. Not the type of pattern that specifics can be drawn at
high confidence this far out. However, there is more of an
agreement with a strong frontal boundary dropping southeast Monday
night into Tuesday with healthy rain chances.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 545 AM CDT Wed Aug 16 2017

Clusters of showers and storms have crossed the Mississippi River
into southwest Illinois, but have been showing a weakening trend
over the last half hour. Will include a mention of VCSH for
KSPI/KDEC at the start of the TAF period, but better chances of
convection over central Illinois will be later this morning as
storms currently in central Missouri move northeast. Have included
a period of VCTS at all sites for about 6-8 hours, then a short
period of dry conditions before storms move in from the west late
evening, ahead of a cold front.

&&

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

$$

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



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