Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 120442

Area Forecast Discussion
National Weather Service Lincoln IL
1142 PM CDT Wed Oct 11 2017

Issued at 825 PM CDT Wed Oct 11 2017

Extensive low clouds cover central IL and surrounding areas and
won`t clear out through much of the day Thursday as high pressure
and light winds dominate the weather pattern. Patchy drizzle and
fog will accompany the low clouds through tonight. With all the
clouds and moisture, temperatures won`t fall much through the
night, reaching the low to mid 50s at most locations, down from
the mid and upper 50s at 8 p.m. Current forecast depicts this
scenario, so no significant updates are needed this evening.


.SHORT TERM...(This evening through Thursday)
ISSUED AT 305 PM CDT Wed Oct 11 2017

20Z/3 pm surface analysis shows 1013 mb low pressure over north
central Ohio with a trof extending into central IL near I-74. A
few spotty very light rain showers and drizzle was near this trof
by I-74. WNW winds shift more northerly behind this trof as it
has been sinking slowly southward today. Low stratus blankets IL
with clearing over western IA/MO and northern WI/MI. Aloft a
weakening 575 dm 500 mb low was near Detroit MI. Despite low
pressure system pushing eastward away from IL tonight, low level
moisture will stay trapped in a strong inversion, keep low stratus
clouds around into Thu. As low stratus clouds lower during
tonight, it will form some fog on surface with patchy drizzle
overnight into Thu morning. Lows tonight mostly in the lower 50s.
The stratus clouds are expected to decrease from sw to ne during
Thu afternoon as upper level ridge builds into the Ohio river
valley. Highs Thu in the mid to upper 60s, coolest over east
central IL where low clouds linger longest.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 305 PM CDT Wed Oct 11 2017

Dry conditions expected on Thu night with mostly clear skies and
light winds, with lows again in the lower 50s. A frontal boundary
sets up from central KS ne across central portions of IA/WI by
Fri morning and presses into nw IL during Fri night. Still dry
over CWA on Fri with warmer highs in the upper 70s to around 80F,
warmest in sw CWA. The frontal boundary pushing into nw IL Fri
night will bring a chance of showers and thunderstorms to the IL
river valley along and nw of I-55 by overnight Fri night. SPC day3
outlook has marginal risk of severe storms during that time over
far nw CWA in western parts of Schuyler, Fulton and Knox
counties. Have likely chances of showers/thunderstorms on Saturday
over the IL river valley, especially nw of the IL river, with
chance pops over heart of CWA while areas south of I-72 likely
remain dry Sat. Areas along and south of I-70 will continue dry on
Sat night. SPC day4 outlook has a risk area just west of CWA on
Sat and Sat night. An unseasonably warm day Sat with highs in the
low to mid 80s, expect upper 70s north of Peoria with more clouds
and convection around. Low pressure to eject ne into western Great
Lakes Sat night pushing cold front se into central IL by dawn
Sunday and across southeast IL during Sunday morning, with chances
of showers/thunderstorms spreading into southeast IL on Sunday.

High pressure to settle eastward into IL on Monday with dry and
cooler weather returning Sunday night through next Wed. Highs
Sunday range from mid 60s nw of IL river, to the mid to upper 70s
in southeast IL. Highs Monday in the low to mid 60s, in the upper
60s to near 70F on Tue and lower 70s next Wed. Still not frost or
freeze in sight as coolest lows are in the low to mid 40s early
next week, so growing season likely continues. In fact CPC`s 8-14
outlook for Oct 19-25 continues at 65-70% chance of above normal
temperatures over CWA with 40-45% chance of above normal
precipitation. So the mild and wetter pattern of late looks to
continue next two weeks.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1142 PM CDT Wed Oct 11 2017

Extensive low level moisture is trapped over the region due to
high pressure and light low level winds. This is resulting in
IFR and LIFR cigs this evening, and cigs will tend to lower
overnight, resulting in most areas having LIFR cigs until around
15Z. Patchy drizzle and fog will result in MVFR and IFR vsby
conditions increasing overnight as well. Expecting slowly
improving conditions after 15Z as daytime heating slowly erodes
the lowest cigs. By around 00Z, expecting conditions to improve
to VFR as drier southerly flow develops.





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