Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 181555
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1055 AM CDT Fri Aug 18 2017

.UPDATE...
Issued at 1055 AM CDT Fri Aug 18 2017

Abundant sunshine prevails across central Illinois this morning:
however, mid and high clouds associated with low pressure over
western Iowa will spill into the Illinois River Valley this
afternoon. Forecast soundings remain relatively dry through the
day, so think any precip triggered by the approaching wave will
hold off until evening. Latest run of the HRRR continues to show
scattered showers/thunder entering the far NW KILX CWA around
Galesburg by 23z/6pm. Have therefore maintained a dry forecast
through the afternoon, with skies becoming partly to mostly cloudy
west of the Illinois River by mid to late afternoon. Scattered
showers and thunderstorms will then develop/spread eastward across
the entire area tonight. High temperatures this afternoon will
generally reach the middle 80s...with a few upper 80s possible
south of I-70.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 227 AM CDT Fri Aug 18 2017

Quiet weather expected for a short time today as a narrow ridge of
high pressure drifts eastward. Main concern is with the shortwave
currently seen on water vapor imagery across the Dakotas. Latest
model runs continue the earlier trend of this mainly being focused
on tonight, rather than spread into the first part of Saturday.
Temperatures will still remain on the warmer side, mainly mid 80s,
although dew points in the 60s will make it more comfortable.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 227 AM CDT Fri Aug 18 2017

Main concerns for this period involve the Monday sky cover, as
well as the storm system expected in the Monday night through
Tuesday night time frame.

Eclipse update (Monday):
A frontal boundary will be draped from the Nebraska panhandle into
northern Wisconsin Sunday night, initially moving little due to it
being parallel to the upper flow. Best thunderstorm chances will
be focused along it late Sunday night into Monday, and while rain
would largely stay to our northwest, the cirrus blowoff will be
more of a concern through the Illinois River valley around midday.
However, it is close enough to warrant some 30% PoP`s northwest
of the river in the afternoon. Across the southeast half of the
CWA, the GFS and ECMWF models are more on the optimistic side that
any cirrus that far south would not be a significant impact, with
the cu-rule showing minimal cumulus development.

Going beyond Monday, the GFS is a bit faster in the arrival of the
rain Monday night ahead of the earlier mentioned cold front, but
is a bit slower than the ECMWF with the passage of the front
itself. In either event, likely PoP`s appear warranted over the
CWA Tuesday and into the evening south of I-72. By midnight, the
slower GFS has the front exiting the southeast CWA, and a quick
drying trend is expected behind it. Dry weather will prevail
Wednesday into Thursday, as sprawling high pressure drifts east
into the Great Lakes region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 535 AM CDT Fri Aug 18 2017

VFR conditions will prevail the next 24 hours. Main TAF concern is
with scattered thunderstorms mainly this evening, ahead of an
incoming cold front. Will maintain VCTS mention at all sites for
about a 4-5 hour period, with some minor adjustments in timing
from the previous TAF set.


&&

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

$$

UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Geelhart


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