Area Forecast Discussion
Issued by NWS Central Illinois

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247
FXUS63 KILX 210548
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1148 PM CST Sat Jan 20 2018

.UPDATE...
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
focused.

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 06Z TAFS through 06Z Sunday night)
Issued at 1148 PM CST Sat Jan 20 2018

A gap in low cloud cover roughly aligned along portions of I-72
west of KDEC is providing the main complication in TAFs this
evening. Otherwise, a region of IFR/LIFR cigs/vsbys is spreading
northwestward across the area and will likely affect most of
central IL overnight. In general, guidance suggests general
decrease in ceiling heights overnight along with increasing
drizzle and fog as continued warm advection and plentiful low
level moisture continue. Little improvement is expected through
the end of the 24 hour TAF period. Winds generally S-SE 5-10 kts
through the forecast period.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

UPDATE...37
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...37



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