Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 270835

Area Forecast Discussion
National Weather Service Lincoln IL
335 AM CDT TUE SEP 27 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 335 AM CDT Tue Sep 27 2016

Flow across central and southeast Illinois will become more cyclonic
into this evening as a surface low pressure area and associated
cutoff upper level low drops south through the Great Lakes region.
Today`s weather should be a repeat of yesterday`s, with mostly sunny
skies, westerly winds gusting up to 25 mph at times, and temps
rising into the lower to middle 70s by this afternoon. As the cutoff
low drops toward the area, clouds will begin to increase this
evening in the north and northeast parts of the CWA. Short term
models also bring a short wave around the back side of the low
pressure area tonight. So will need to add a slight chance of
showers along and north of I-74 for tonight.


.LONG TERM...(Wednesday through Monday)
ISSUED AT 335 AM CDT Tue Sep 27 2016

Cooler than normal temperatures, diurnal cloudiness and a few
periods of light rain showers - mainly in eastern Illinois - will be
the main weather features from mid-week into the weekend. The medium
range models are in slightly better agreement on the position of the
main weather maker, an upper low expected to settle into parts of
the Midwest through the end of the week.

The latest 00z model runs show excellent agreement in dropping an
upper low from Lake Superior to southern Lake Michigan Wednesday,
and then just south of the lower Ohio Valley Thursday. This will
bring a reinforcing cold front and strong low level cold advection
into Illinois. The result will be unseasonably chilly temperatures
for Wednesday with highs struggling to reach the mid 60s. Plenty of
diurnal cloudiness will also develop with the cold air aloft. Will
continue with low chance PoPs for scattered showers in extreme east
central IL/Danville area, with isolated showers/slight chance PoPs
from Galesburg-Lincoln-Mattoon-Lawrenceville and eastward for

Increased the chance for light rain showers in most of east central
Illinois for Thursday as diurnal cloudiness increases and spokes of
energy rotating around the upper low in central KY provide upper
support. This will also keep temperatures in the upper 60s in
eastern IL, with somewhat warmer readings closer to the IL River

Model solutions begin to diverge on the specifics of the upper low
center for Friday and Saturday, with the European continuing to be
further to the west. However, each run of the GFS is also a bit more
to the west. Thus, there is more confidence that eastern IL will
have scattered showers and continued cool temperatures through
Friday. Despite the differences in model solutions for the position
of the upper low, they are also starting to agree that the low will
pull out toward the eastern Great Lakes during the day Saturday.
This should result in only spotty showers late Friday into early
Saturday in eastern IL, followed by a decreasing cloud trend and
gradually warmer temperatures the rest of the weekend. By early next
week, upper level ridging and a southerly low level flow will bounce
us right back into warmer than normal temperatures for the first
full week of October.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1145 PM CDT Mon Sep 26 2016

Very dry air in place across central IL overnight into Tuesday
with dewpoints in the upper 30s/lower 40s. 1025 mb high pressure
over the central Rockies and ridging eastward into the mid MS
valley and KY and providing the fair wx. This will continue VFR
conditions with clear skies across central IL through Tue. Any
patchy shallow fog that develops later tonight will stay focused
along major rivers like the MS and Ohio, and south of I-70 where
higher dewpoints in the upper 40s/lower 50s. SW winds of 4-8 kts
overnight will veer WSW and increase to 10-15 kts with gusts of
17-24 kts between 15-16Z Tue, then diminish to 4-7 kts around
00Z/Wed. Scattered mid/high clouds to arrive from the north after
sunset Tue evening while lower clouds should not arrive along I-74
until after 06Z Wed. This due to strong 543 dm 500 mb low spinning
just north of Lake Superior tracking southward across Lake MI and
far eastern WI during Tue evening.


.ILX Watches/Warnings/Advisories...


LONG TERM...Miller
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