Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210243

Area Forecast Discussion
National Weather Service Lincoln IL
843 PM CST Sat Jan 20 2018

Issued at 843 PM CST Sat Jan 20 2018

Cloudy conditions will continue across most of central IL
overnight although a band of partial clearing has moved into areas
along the I-72 corridor this evening. The next region of low
cloudiness is currently expanding from along and south of the I-70
corridor and should expand into most of central IL overnight. This
latter area of low cloudiness is associated with slightly higher
dewpoints and will likely develop some fog and drizzle late
tonight. Have delayed onset of fog and drizzle west of I-57 with
the evening update, but otherwise forecast is largely on track
with cloudy conditions and mild temperatures in the upper 30s and
lower 40s predominant through tonight, as well as areas of fog and
drizzle developing.


.SHORT TERM...(This evening through Sunday)
ISSUED AT 215 PM CST Sat Jan 20 2018

Large expanse of stratocumulus has overspread most of the CWA
except for the extreme southeast, and that will fill in soon from
the south. Despite some thin spots this afternoon, the clouds
won`t be going anywhere for awhile. So far, upstream observations
have remained dry. However, the potential for drizzle will
increase this evening, as ceilings lower. Think this will
initially be more over the eastern half of the forecast area, then
expand after midnight. Will continue to mention areas of fog, with
the high-resolution guidance focusing more on the eastern half of
the CWA.

An upper level low will carve itself out of the trough currently
pushing across Nevada, lifting northeast Sunday and Monday. Precip
chances will ramp up as this system approaches. Forecast soundings
don`t really moisten up above 850 mb until Sunday evening, so
drizzle still will be the predominant precip type. With a warm
front sharpening just to our north, upper 40s to mid 50s are still
expected in the warm sector.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 215 PM CST Sat Jan 20 2018

Temperatures expected to keep edging upward Sunday night as the
cold front approaches from the west. Most of the models are
suggesting formation a line of showers with some embedded
thunder immediately ahead of the front, sweeping from west to
east after midnight, and this is where the highest PoP`s are

On Monday, the models are in good agreement with a nearly stacked
system centered near the Iowa/Missouri border at midday, slowly
tracking across northern Illinois through the evening. Some dry
conditions expected for a time late morning and early afternoon,
before the wraparound showers arrive. The NAM and ECMWF models are
slowest in pulling the system out of the region, lingering light
rain or snow showers into Tuesday morning over a large part of the
area. Went with a bit more faster solution, and will generally
limit any PoP`s Tuesday morning to slight chances in the
northeast CWA.

Quiet weather is still on tap for the middle of the week, with a
broad upper trough passing through dry. Upper ridging across the
Rockies will shift east and be centered over the Midwest by
Friday, bringing temperatures back up to the 40s and 50s for us
late week. Early next weekend, a cold front is expected to arrive,
bringing the next precip chances. Currently, it looks to be warm
enough for rain.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 529 PM CST Sat Jan 20 2018

Fairly uniform MVFR cigs around 2000 ft AGL across central IL
this evening, while low clouds are generally absent from SW
Illinois westward. Slow progress northward of the improved
ceiling area may reach KSPI-KDEC in a few hours, however because
of the low certainty of this possibility, have kept MVFR cigs
through the evening at these sites. Otherwise, guidance suggests
general decrease in ceiling heights overnight along with
increasing drizzle and fog as continued warm advection and
plentiful low level moisture continue. Incorporated IFR or worse
cigs beginning by 3-8Z this evening, with little expectation of
improvement through the end of the 24 hour TAF period. Winds
generally southerly 5-10 kts through the forecast period.




SHORT TERM...Geelhart
LONG TERM...Geelhart
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