Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 092340

Area Forecast Discussion
National Weather Service Lincoln IL
540 PM CST Sat Dec 9 2017

.SHORT TERM...(This evening through Sunday)
ISSUED AT 305 PM CST Sat Dec 9 2017

A 524 dm 500 mb low over northeast IN was within a strong upper
level trof over the central Ohio river valley. Stratocumulus
clouds lingered over much of IL into eastern IA and far ne MO at
mid afternoon, along with scattered flurries and isolated light
snow showers over central and ne IL. As upper level low/trof pulls
further away from IL by early evening, expect clouds and brisk NW
winds of 15-25 mph and gusts 25-35 mph to diminish. Though some
mid/high clouds will increase from the nw during overnight. A cold
night ahead with lows around 20F.

Increasing sw winds on Sunday to moderate temperatures into the
upper 30s and lower 40s for highs, close to seasonable levels. A
partly to mostly sunny day overall with more clouds ne of I-74
where the next clipper system dives se into the central Great

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 305 PM CST Sat Dec 9 2017

Lows Sunday night in the low to mid 20s as winds diminish light
and clouds increase from the NNW overnight Sunday night. A
stronger clipper systems dives se into our area on Monday, though
the brunt of its precipitation skirts just ne of CWA across
northern/ne IL. SW breezes brings milder highs in the 40s Monday
with far SW CWA over Scott and Clay counties approaching 50F.
This will likely be our mildest day during the next 7 days.

Colder air filters back into the area behind this clipper system
during Monday night and Tue on brisk nw winds. Highs Tue similar
to todays readings in the upper 20s and lower 30s, coldest ne CWA.

12Z models differ with handling a clipper system during mid week
around Wed and stayed close to consensus of models until
differences sorted out. This places slight pops in sw CWA on Wed
afternoon. Then 20-40% chance of light snow overnight Wed night
from I-72 north with highest pops over northern/ne IL. Highs Wed
in the lower 30s ne CWA and upper 30s sw CWA. Highs on Thu
moderate a bit more to mid 30s northern CWA to around 40F
southern reaches of CWA.

The persistent upper level trof over the eastern states much of
next week appears to break down toward the end of the week as
upper level flow tries to flatten out somewhat by Friday. This to
keep clipper system further ne of IL while our area enjoys a dry
and milder weather for Friday into next Saturday. Highs Fri in
the upper 30s and lower 40s, warms into the mid 40s to around 50F
for Saturday.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 540 PM CST Sat Dec 9 2017

VFR conditions will prevail at all TAF sites next 24hrs. Skies
will quickly clear this evening, through there could be a a little
bit of stratocu going across the sites next couple of hours.
Models then indicate that a broken deck of could around 10kft will
advect over each site overnight but then be gone by morning.
However, another patch may come into the area so will keep
scattered mid clouds through the morning. By afternoon, HiRes
models show lower clouds advecting into the area. Models differ on
amount of moisture so have only gone with scattered clouds around
2.5kft for now. If models come into better agreement this evening,
may have to increase amounts to broken. These lower clouds are in
conjunction with a sfc trough that is forecast to move through
the area tomorrow afternoon, reaching CMI close to end of TAF
period. Winds will be west-northwest, but become southwest
tomorrow. Could be some gusts to around 20kts, but unsure, so left
off for now. Winds become northwest during the afternoon behind
the sfc trough.




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