Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230454

Area Forecast Discussion
National Weather Service Lincoln IL
1154 PM CDT Tue May 22 2018

Issued at 942 PM CDT Tue May 22 2018

High pressure centered over the southern Great Lakes is dominating
the weather across central Illinois this evening...providing
mostly clear and dry condtions. Meanwhile, an old frontal boundary
extending from eastern Nebraska into the Ozarks is producing a
band of mid-level cloudiness and some widely scattered convection
across portions of Nebraska into western Iowa. The activity across
Nebraska will become more widespread with time, aided by a 35-45kt
850mb jet streak over the Plains: however, the showers across Iowa
will not be able to make much eastward progress as they track
further away from the jet energy and try to push into the
prevailing surface ridge axis. Am not expecting any showers to
reach the KILX CWA tonight: however, it does appear clouds will be
on the increase along/west of the Illinois River toward dawn.
Further east, clear skies will prevail across the remainder of
the area. Overnight low temperatures will range from the middle to
upper 50s along/north of the lower 60s south of I-70.
Some patchy fog will be possible as well: however, do not think it
will become much of an issue.


.SHORT TERM...(This evening through Wednesday)
ISSUED AT 300 PM CDT Tue May 22 2018

High pressure will migrate across northern Illinois tonight
producing mostly clear skies with light north to northeast winds.
With crossover temperatures this afternoon just over 60 degrees
across the area and lows expected to drop into the upper 50s to
around 60 in many areas north of I-70, patchy fog still seems
possible overnight, especially given that most model and MOS
guidance is hinting at areas of fog development. Additionally, a
region of 1 to 2 inches of rainfall from Jacksonville up through
the Illinois River Valley fell yesterday, and should contribute to
low level moisture. For Wednesday, light northeast winds will
continue, with ridging amplifying into central IL. Highs will
trend upward into the mid 80s.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 300 PM CDT Tue May 22 2018

A large scale high pressure ridge will continue relatively
stationary over the Plains for the upcoming week. The result will
be warm temperatures, trending to the upper 80s to around 90
degrees late this week through the weekend. Any chance for
precipitation will come from weak shortwave features trying to
progress through the Plains ridge. Models suggest enough Gulf
moisture drawn into the Plains to produce precipitation,
primarily diurnally modulated, Friday through the weekend into
early next week. At this point, precip chances vary from slight
chance to chance during the afternoon and evening periods Friday
through Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1154 PM CDT Tue May 22 2018

Overnight fog development is looking less and less
04z/11pm temp/dewpoint spreads of 4-10 degrees are common across
the area. Despite diminishing winds and continued mostly clear
skies, think the very dry airmass will keep widespread fog from
forming. High-res model output agrees, with most solutions
focusing the fog close to Lake Michigan. Will maintain some slight
visby reductions overnight, but do not think they will be
significant or long-lived. A band of mid-level clouds is still
expected to develop into the Illinois River Valley early Wednesday
morning, but model RH fields suggest these clouds will dissipate
by midday. Winds will initially be from the NE at less than
5kt...then will become E/SE at 5-10kt after sunrise.




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