Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230951

Area Forecast Discussion
National Weather Service Lincoln IL
351 AM CST Fri Feb 23 2018

.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CST Fri Feb 23 2018

Some light to moderate rain showers were arched across central IL
early this morning, generally east of Macomb to Jacksonville line
and lifting ne. Larger area of heavier rains were along and se of
the Wabash river and pulling out of southeast CWA by dawn.
Lawrenceville received a 0.33 inch rain during the night, while
heavier rains of half to 1 inch with a few thunderstorms set up
se of Lawrence county. This band of convection stretched from sw
OH through southern IN, far southeast IL and into se MO and
central AR. Areas of fog prevailed during the night across central
IL north of I-70 with pockets of dense fog with vsbys down to 1/4
to 1/2 mile especially along I-74 corridor. Temps were nearly
steady or slower rising during the night, with current readings in
the lower 40s northern CWA and around 50F along highway 50.

Will hold off on a dense fog advisory this morning as just have
pockets of dense fog and vsbys are improving over western CWA as
rain showers moved through. Peoria went from 1/4 mile to 3 miles
past hour. Areas of fog and drizzle along with rain showers to
diminish from the west during the morning with most areas dry by
afternoon, though a fair amount of low clouds will remain through
the day with nw CWA having best chance of seeing some peaks of
sun this afternoon. Highs today range from 45-50F nw CWA to mid
to upper 50s in southeast IL.

A weather system to eject ne from the southern plains tonight and
spread rain showers back ne across the area during tonight,
reaching areas south of I-70 by late evening and northern CWA
overnight. Areas north of Peoria could see mix pcpn including
light glaze over Knox and Stark counties overnight into early Sat
morning. Meanwhile isolated thunderstorms possible south of I-70
overnight. Rainfall amounts tonight of a quarter to half inch from
I-72 south. Lows tonight range from lower 30s nw of the IL river,
to the low to mid 40s in southeast IL.


.LONG TERM...(Saturday through Thursday)
ISSUED AT 340 AM CST Fri Feb 23 2018

Surface low pressure emerging over the OK panhandle Sat morning to
strengthen as it lifts ne toward Lake MI overnight Sat night. A
warm front will lift northward into central/se IL by mid to late
Saturday, then a cold front sweeps eastward across IL during Sat
evening. Periods of showers and some thunderstorms Sat and Sat
evening, then diminishing overnight Sat night behind cold front.
SPC has marginal risk of severe storms in southeast IL Sat evening
and this will also be the time for heaviest rainfall of half to 1
inch. A strong 60 kt low level jet ahead of cold front Sat evening
and 90 kt mid level jet to give stronger wind shear to support
marginal risk of severe storms. Also will see stronger winds
during Sat night over area. Rainfall totals of 1.5-2.2 inches
expected over southeast IL with highest amounts in Lawrence county
from Friday night through Sat night. Precipitable water values
peak quite high again from 1 to 1.5 inches in southeast IL. Held
off on flood watch for areas southeast of I-70 as these amounts
are still shy of flash flood guidance values of 1.9-2.4" in 12 hr
and 2.2-2.7" in 24 hrs. Though WPC day 2 for Sat/Sat night does
have southeast counties in a moderate risk of excessive rainfall,
so this will need to be monitored closely. Highs Sat range from
upper 40s northern CWA to lower 60s along highway 50.

A welcomed stretch of dry weather expected over CWA from Sunday
through Tuesday. High pressure to drift east into the mid MS river
valley by midday Monday and near the mid Atlantic coast by Tue
afternoon. Temps are cooler Sunday but still above normal with
highs in the mid to upper 40s in central IL and lower 50s
southeast IL. Looks like return of sunshine finally on Sunday and
will be about a week since we last had a mostly sunny day last
Sunday. Highs Monday in the low to mid 50s, and moderate into the
upper 50s and lower 60s Tue with increasing ssw flow and continued
mostly sunny skies Mon/Tue.

00Z models dig a strong upper level trof over the sw states into
nw Mexico and then eject a southern stream system ne from southern
plains into mid MS river valley by dawn Wed. This to spread rain
showers ne over CWA during Tue night, mainly after midnight and
continue rain chances on Wed. Then likely chances of rain showers
Wed night and then diminishing chances of rain from sw to ne
during Thu morning. Knox and Stark counties could see light snow
mix with the rain late Wed night into early Thu morning. Highs Wed
in the upper 50s and lower 60s. Highs Thu cool to upper 40s
northern CWA and mid 50s in southeast IL. Dry conditions from Thu
afternoon through Friday as weather system moves ne of IL into the
Great Lakes region. Highs Friday in the mid to upper 40s.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1148 PM CST Thu Feb 22 2018

Widespread LIFR ceilings will continue overnight and possibly into
Friday morning, as light rain and drizzle approach the TAF sites.
Visibility conditions are generally IFR due to drizzle and light
fog, with LIFR vis at PIA and CMI to this point. Forecast
soundings and HRRR output show that vis could become dense
(VLIFR) at PIA, BMI and CMI tonight, for a period of time into the
early onset of rain. Have kept the forecast more pessimistic with
clouds overnight, as the consensus has converged toward that
solution. Rain/drizzle should quickly diminish from west to east
early Friday morning, with cloud ceilings rising to MVFR by early
afternoon, then VFR by late afternoon.

Winds will start out southeast at 8-12kt, then become southwest
by Friday morning, and eventually west Friday afternoon after a
cold frontal passage. Speeds will generally remain in the 8-12kt
range Friday and Fri evening.





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