Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 161759

Area Forecast Discussion
National Weather Service Lincoln IL
1259 PM CDT Wed Aug 16 2017

Issued at 1005 AM CDT Wed Aug 16 2017

Morning upper air shows digging trof/low center over southwest NE.
This system to continue to deepen as it moves to the northeast.
Surface low in eastern NE to deepen and move to the northeast into
MN. Airmass over CWA has limited instability, as best unstable air
with upper support and frontal boundary to affect MO today. Expect
showers and weak storms with initital weak wave to move through
region early today. Additional chance of weak showers and storms
in early evening. Best pcpn possible with the movement of the
frontal zone into the region after 10pm and overnight. More
significant convergence on and ahead of the front, however with
instability decreasing diurnally and the main upper level forcing
well to the north of region, scattered brief heavy rain with
scattered storms will be the main threat overnight, as main best
severe potential over MO.


.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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1255 PM CDT Wed Aug 16 2017

Areas of scattered showers and a few thunderstorms to continue to
move over the region from this afternoon into the overnight hours.
Manly VFR conditions with the storms, as weak instability the rule
throughout the period. After the front moves through late tonight,
some mvfr and scattered IFR cigs comes in behind the front, which
may last over the western TAF sites through midday Thursday.




SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Goetsch is the U.S. government's official web portal to all federal, state and local government web resources and services.