Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201735

Area Forecast Discussion
National Weather Service Lincoln IL
1235 PM CDT Thu Apr 20 2017

Issued at 1220 PM CDT Thu Apr 20 2017

Cold front draped across Central Illinois today making slow
progress to the SE. Have updated some of the high temps as well as
the hourlys as areas NW of the IL River Valley will have very
little in the way of warming behind the boundary. Showers and
scattered thunder sparse at midday...with better coverage in the
SE as well as expected later in the eastern half of the CWA ahead
of and along the fronts afternoon progression. Minor updates
across the board.


.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 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 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 18Z TAFS through 18Z Friday afternoon)
Issued at 1220 PM CDT Thu Apr 20 2017

Low cigs invof the boundary and associated with scattered thunder
and SHRA until the front clears Central IL. Winds a bit gusty
today as little needed to mix down some higher winds just off the
surface. Thunder threat still more of an issue in eastern
terminals and have pulled back to VCSH in PIA and SPI...will watch
carefully as some weak showers are still lagging behind the front.
Otherwise, forecast largely a veering wind forecast to more
northerly post-frontal.




LONG TERM...Barnes
AVIATION...HJS is the U.S. government's official web portal to all federal, state and local government web resources and services.