Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 222358
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
558 PM CST Thu Feb 22 2018

.SHORT TERM...(This evening through Friday)
ISSUED AT 137 PM CST Thu Feb 22 2018

Some welcome dry weather is occurring across the forecast area
early this afternoon, and temperatures in the 30s and 40s have
melted off the lingering ice. Next surge of rain is currently
approaching the western border of Missouri, with the upper wave
moving northeast from the Oklahoma area. Forecast soundings show a
dry wedge in the mid levels that lingers for a time this evening,
so PoP`s have been adjusted downward a bit to slow the onset of
the rain by a few hours. All areas will have at least categorical
PoP`s for a time, though, but rain chances by Friday morning
should be limited to areas south of I-70. A few rumbles of thunder
possible in that area after midnight, with a few hundred joules of
elevated MUCAPE.

While most of the area will be dry by morning, the clouds won`t be
in any hurry to leave, due to a persistent low level inversion.
With little cold air behind the boundary that passes by early
tomorrow, temperatures in the 50s still seem reasonable east of
I-55, with mid-upper 40s west.

.LONG TERM...(Friday night through Thursday)
ISSUED AT 137 PM CST Thu Feb 22 2018

Main focus for heavy rain into the weekend remains focused across
the southeast CWA. The frontal boundary will be hanging up from the
Ohio Valley into the southern Plains on Friday. Several waves of
energy will ride northeast, culminating in a strengthening storm
system over the central Plains this weekend. The track of the
surface low from this system will take it into Wisconsin late
Saturday evening, with the trailing cold front crossing us
Saturday night. Once that passes, a few welcome days of dry
weather are on tap.

In regards to the timing and details, rain will be spreading into
the area once again Friday evening, though locations north of
I-72 will see it arrive later in the night. With the colder
northeast surface low persisting into early Saturday, a transition
to some sleet, freezing rain or snow is possible on the northern
periphery of the rain shield. Current indications are that areas
north of a Quincy to Bloomington line are most favored for this
transition zone. Any icing there will be short lived, as
temperatures rise to near 50 degrees on Saturday. Precipitation
chances remain very high until the passage of the front.

Regarding the heavy rain, precipitable water will frequently be
in the 1-1.5 inch range across the southeast CWA into Saturday
evening. An upper wave riding northeast into the Ohio Valley will
help enhance thunder chances as well as heavy rain potential.
Current thinking is for 2-2.5 inches south of I-70 for the period
from tonight through Saturday evening. May need a flood watch down
there eventually, but will hold off for now as the rain tonight
should be an inch or less.

Temperatures through the period should remain on the milder side,
with no significant cold surges expected.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 558 PM CST Thu Feb 22 2018

Widespread IFR and LIFR ceilings have developed, with the onset of
drizzle at the TAF sites, and those cloud conditions should
continue overnight and into Friday morning. Visibility conditions
are generally IFR due to drizzle and light fog, with LIFR vis only
at PIA to this point. Forecast soundings show that vis could
become dense (VLIFR) at PIA and BMI tonight, before steady rains
arrive and help with some mixing of the boundary layer. Have kept
the forecast more pessimistic with clouds overnight, despite MAV
guidance pointing toward some MVFR cloud heights during the period
of rains later tonight. Rain/drizzle should diminish Friday
morning, with cloud ceilings rising to MVFR by early afternoon,
then VFR by late afternoon.

Winds will start out east-southeast at less than 10kt, 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.

&&

.HYDROLOGY...
Issued at 137 PM CST Thu Feb 22 2018

Many of the rivers are in flood at the moment, courtesy of the
2.5 to 5 inches of rain that has fallen this week. Danville
(Vermilion River) has crested at its 3rd highest level on record,
and the highest value since 1994. Moderate flooding is projected
on the Illinois and Wabash Rivers. The crest on the Illinois River
is currently near La Salle, with areas downstream rising into the
weekend. Heaviest precipitation over the next few days will be
focused more on the areas along and south of I-70, with potential
for 2-2.5 inches through Saturday evening. That will be more of an
impact for the Wabash, Embarras and Little Wabash Rivers.

&&

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

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon
HYDROLOGY...Geelhart


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