Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231708
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1208 PM CDT Mon Apr 23 2018

.UPDATE...
Issued at 1030 AM CDT Mon Apr 23 2018

Band of light rain showers continues to edge slowly to the north
and northwest late this morning. 12z ILX sounding depicting quite
a bit of dry air remaining in place below 12000 feet so initially,
the rain will have a difficult time progressing very far north
into the forecast area early this afternoon. However, as a weak
shortwave associated with the upper low, currently over southeast
Missouri, shifts north and northwest late this afternoon into
early this evening, we should see a gradual shift north with
the rain as well. Have made only minor adjustments to the timing
of the rain further north and northwest late this afternoon with
areas along and east of I-55 having the better chances for see
some light rain.

The warmest temperatures this afternoon will be across the west
and northwest where some sunshine is expected helping to push
temperatures close to 70 along and west of the Illinois River.
Coolest readings this afternoon will be where the more persistent
rain and thicker cloud cover exists, across east central and
southeast Illinois where afternoon highs will settle into the
upper 50s to lower 60s. Updated ZFP should be out by 11 am.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 321 AM CDT Mon Apr 23 2018

Northeasterly winds continue today and most of tonight for
Central Illinois as a low stalls just to the south at the
confluence of the Ohio River. That low aloft is cut off and making
very slow forward motion, if any. Overnight, it has shown some
signs of brief retrograde. At any rate, the slow motion will
likely keep some cloudiness over the southern half of the state at
the very least. Some precip finally working its way into
southeastern IL up to Interstate 70, having had plenty of lower
level dry air to saturate. Spreading of the precip to the north is
expected through the day, though the northern extent is the bigger
question. NW of the Illinois River Valley is least likely to see
the precip, and as a result will have the higher max temps in the
upper 60s. Further to the south with the cloud cover and precip,
high temps will be confined to the low 60s. Temps only dropping
into the upper 40s overnight as that low makes very slow progress
and keeps the clouds in place with some showers through the
overnight.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 321 AM CDT Mon Apr 23 2018
Extended forecast remains largely unchanged. Slight precip
chances mainly in the east continuing through tomorrow with the
slow progress of the upper low into the Appalachians. Forecast
dries out as the GFS comes around to a more ECMWF/NAM solution
with the evolution of the kicker/next system. Previously phasing
the two shorter waves moving into the Plains/Midwest midweek...the
GFS et al are now keeping the two smaller waves separate,
resulting in a drier forecast through the middle of the week.
First pushes through the Great Lakes mid week, although its effect
as a kicker is a little less than, and the current low remains cut
off and a bit wobbly over the mid eastern seaboard. Another wave
dives into the southeast, bringing a wet end of the week to the
Gulf states. Illinois ends up between them and mid week stays dry.
However, that second wave sets up a more northwesterly flow aloft,
and the next trof is a bit more pronounced and brings a shot of
cooler air into the region. Showers move in with the frontal
boundary Thursday night into Friday as the surface low starts to
develop just to the south. Weekend looking dry and warmer on the
other side of precip for Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1205 PM CDT Mon Apr 23 2018

MVFR and local IFR cigs that have been south of the TAF sites into
early this afternoon were slowly shifting north and west as low
pressure over southeast Missouri tracks south of the area this
afternoon and tonight. Forecast soundings continue to suggest
that PIA will be the last to see the MVFR cigs move in late this
evening, probably closer to 05z. Once MVFR and local IFR cigs
finally move into the entire area by late tonight, it appears
they will hold across the area through at least 18z Tuesday.
An east to northeast wind is expected to continue this afternoon
through tonight with a gradual backing of the winds into a
northeast to north direction late tonight and Tuesday. Speeds
this afternoon will range from 10 to 15 kts with an occasional
gust up to 23 kts and then hold around 10 to 15 kts tonight.

&&

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

$$

UPDATE...Smith
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Smith



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