Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201125
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
625 AM CDT Thu Apr 20 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 329 AM CDT Thu Apr 20 2017

08z/2am surface map shows 1008mb low over northeast Iowa with a cold
front trailing southwestward to Oklahoma.  Most of the convection
associated with this system has either pushed well to the northeast
into Wisconsin/Michigan or is clustered further south over eastern
Kansas.  Only widely scattered showers are noted in between, so am
not expecting much precip to arrive across the Illinois River Valley
early this morning.  The eastward progression of the front is
slightly slower than previously forecast...with the 18z position
progged to bisect central Illinois.  Only scattered showers/thunder
will precede the boundary this morning: however, as the atmosphere
destabilizes, convection will become more widespread across the E/SE
KILX CWA later today.  Have therefore carried likely PoPs along/east
of a Champaign to Shelbyville line this afternoon.  High
temperatures will range from the upper 60s northwest of the Illinois
River around Galesburg...to the upper 70s to around 80 degrees south
of I-70.  The front will continue southward tonight, eventually
dropping south of the Ohio River overnight.  Will carry some
lingering PoPs along/south of I-70 this evening, then will go dry
everywhere after midnight.  Lows will range from the lower 40s far
north...to the lower 50s far SE.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 329 AM CDT Thu Apr 20 2017

As has been advertised for the past several days, a stronger upper
wave is expected to cross the Rockies into the Plains by the end of
the week, causing a surface low to develop along the front.  Models
have been consistently shifting the low track further south and the
00z Apr 20 suite is no exception.  In fact, the GFS/ECMWF/GEM are
now in relatively good agreement with low pressure tracking from the
northern Texas on Friday to eastern Tennessee Sunday morning.  With
this more southerly track, central Illinois will be on the
cool/stable side of the system...with rain showers spreading across
mainly the southern two thirds of the CWA beginning Friday afternoon
and continuing through Saturday night.  It now appears areas from
Peoria northward will remain completely dry through the
weekend...with the most significant rainfall occurring along/south
of I-70.

Once the low passes to the southeast, dry weather will return for
Sunday and Monday.  A northern stream short-wave is expected to
track across the Northern Plains on Monday, then dig into the Great
Lakes on Tuesday.  As it does, it will push a weak cold front into
central Illinois Monday night into Tuesday.  Deep-layer moisture
will likely be limited, so will only mention low chance PoPs for
showers across the far N Monday night.  After that, another fast
moving wave embedded within the predominant zonal flow pattern will
approach by mid-week, potentially bringing a few showers into the
picture by Wednesday.  As always, timing of these weak features
within the fast flow will be tricky, so timing of PoPs will likely
change as well.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 625 AM CDT Thu Apr 20 2017

Scattered showers and thunderstorms are currently developing
upstream across central/western Missouri and will spread into
central Illinois over the next 2-4 hours. Based on radar timing
tools and latest HRRR data, have included VCTS at KPIA/KSPI/KBMI
between 12z and 18z. Further east at the remaining terminals,
started VCTS after 15z...but continued it through 21z as
additional scattered thunderstorms are expected along the
advancing front across east-central Illinois this afternoon.
Mostly VFR conditions are expected: however, will need to keep an
eye on a large area of MVFR ceilings immediately behind the cold
front across Iowa. HRRR shows these clouds spilling into north-
central Illinois later this morning...primarily impacting KPIA and
KBMI. The lower ceilings will be fleeting...with ceilings
improving and eventually scattering out later this afternoon.
Winds will initially be southwesterly with gusts to 20-25kt this
morning, then will veer to the W/NW later this afternoon into
tonight.

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Barnes



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