Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 300929

Area Forecast Discussion
National Weather Service Lincoln IL
329 AM CST Wed Nov 30 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 329 AM CST Wed Nov 30 2016

A strong cold front has cleared central and southeast Illinois to
the east overnight, ushering much cooler but climatologically normal
air into the area. However, the parent very slow moving surface low
is centered over the upper Midwest, and deep cyclonic flow will
persist across the area through the period. While skies are
currently clear across the forecast area, wrap around low clouds are
steadily making their way toward Illinois. These clouds will provide
considerable cloud cover later today through tonight. Main question
today is if these clouds will contain any precipitation locally. The
majority of the model guidance keeps the splotchy QPF in the wrap
around clouds north of the forecast area. This seems reasonable
given the forecast soundings depicting a shallow moist layer that
is likely to be devoid of ice crystals. With this scenario in mind,
plan to keep the local forecast dry.


.LONG TERM...(Thursday through Tuesday)
ISSUED AT 329 AM CST Wed Nov 30 2016

The vertically stacked low pressure system over the upper MS river
valley (998 mb surface low pressure and 532 dm 500 mb low pressure
near Minneapolis) will track east across the northern Great Lakes,
and into southern Quebec and northern New England by Thu night. A
few short wave pivoting around this large low pressure system will
keep a fair amount of low clouds around especially north of I-70
Thu and Fri, though light precipitation should stay north of CWA.
Southeast IL will have best chances of seeing some sunshine on Thu
and Fri. Seasonably cool temperatures expected with highs 39-45F Thu-
Sat and lows 28-32F Thu night and Fri night.

Dry conditions expected to continue through Saturday evening across
CWA as cool high pressure noses into IL. Still a partly to mostly
cloudy day Sat with mid/high clouds increasing by Sat afternoon
ahead of next storm system. 00Z models show a southern stream short
wave moving into nw Mexico while a northern stream short wave moves
into the Midwest by 12Z/Sunday. Have 20-40% chance of light snow
overnight Sat night, especially late, and possibly mixed with light
rain in southeast IL. Light mixed precipitation early Sunday morning
to change to light rain by late Sunday morning/afternoon with little
or no snow accumulations. ECMWF and GFS models are more similar with
keeping heavier qpf southeast of our CWA on Sunday and also quicker
returning drier weather Sunday night. ECMWF has some lingering light
qpf in eastern IL Sunday evening while consensus of models are dry
and leaned in that direction. Lows Sat night and Sunday night in the
lower 30s. Highs Sunday of 40-45F.

Some weak upper level ridging into IL by 12Z/Mon with a dry day
expected Monday and a bit milder highs of 43-48F, mildest sw CWA.
Another short wave trof approaches IL Monday night/Tue bringing next
chance of precipitation, which appears to be in the form of rain.
Lows Mon night in the mid to upper 30s with highs Tue in the mid to
upper 40s over central IL and around 50F in southeast IL.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1111 PM CST Tue Nov 29 2016

Westerly winds and mostly clear skies will follow a cold front
overnight...followed by MVFR ceilings starting 16-20Z Wednesday.
An area of low cloud cover containing MVFR cigs is expected to
wrap around a deep low over the upper Midwest...eventually
affecting central IL terminals after 16-20Z Wednesday. Slightly
higher cloud ceilings in model guidance at KSPI-KDEC-KCMI suggests
potential that ceilings will remain in VFR category through the
period so have kept ceilings at 3500 feet there...while MVFR cigs
are still included at KPIA-KBMI starting 16-17Z. Winds WSW
generally under 12 kts until 18Z...increasing to 10-15 kts with
gusts to around 20 kts around 16-18Z.




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