Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 232006
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
306 PM CDT SAT JUL 23 2016

.SHORT TERM...(This evening through Sunday)
ISSUED AT 305 PM CDT Sat Jul 23 2016

19z/2pm surface analysis shows stationary frontal boundary extending
from southern Lake Michigan northwestward into the Dakotas.
Widespread convection is ongoing along/north of the boundary in
advance of a well-defined short-wave trough evident on water vapor
imagery over southern Manitoba.  Latest radar mosaic shows bulk of
thunderstorms focused from Minnesota and northeast Iowa across
Wisconsin...however a few radar echoes extending southwestward into
central Illinois will have to be watched as they may impact parts of
north-central Illinois this evening.  Models are handling the
convective evolution differently...with the WRF-ARW and GFS
depicting a dry forecast across the KILX CWA tonight...and the NAM
and HRRR showing the central Iowa convection tracking into the
northwest counties around Galesburg early this evening.  Based on
current radar/satellite trends...will follow the NAM/HRRR most
closely for the immediate short-term.  As such...have brought low
chance PoPs into the Illinois River Valley from the Canton area
northward early this evening...with the PoPs spreading eastward
along/north of I-74 through the overnight hours.  Further south
across the remainder of the CWA...have gone with a mostly clear
forecast with patchy fog developing along/southeast of a Paris to
Shelbyville line where dense fog was observed last night.

Cold front currently over the western Plains will push slowly
eastward on Sunday...eventually reaching the Mississippi River by
late afternoon.  Airmass ahead of the front will remain capped...as
evidenced by 700mb temps around 12C.  As a result, most model
guidance suggests dry conditions until the cap weakens late in the
day.  Have tailored PoPs accordingly to go with 30-40 PoPs
along/west of I-57 by afternoon...with only slight chance PoPs
further east and south.  High temperatures will once again reach the
lower to middle 90s...with heat index values topping out between 100
and 110 degrees.  Will continue the current Excessive Heat Warning
along/south of a Rushville to Danville line through Sunday
evening...and may need to include the northwest CWA in a headline
as well if current trends continue.

&&

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 305 PM CDT Sat Jul 23 2016

Cold front will sink into central Illinois Sunday night...bringing
scattered showers and thunderstorms to the entire area.  Have gone
with 50 PoPs across the board accordingly.  Boundary will then drop
slowly southward into the Ohio River Valley on Monday...gradually
taking the rain chances with it.  Have gone with chance PoPs
everywhere during the morning...then only south of I-72 by
afternoon.  Temperatures behind the front will be slightly
cooler...with highs dropping back into the middle to upper 80s.

High pressure will build into the Great Lakes for Tuesday, pushing
the front into Missouri/Kentucky.  While a warm/dry day will be on
tap across all of central and southeast Illinois, the front will
quickly begin to return northward as the high departs the region.
Models have continued the trend of bringing rain chances back into
central Illinois faster, with chance PoPs now in place across nearly
the entire area by Wednesday.  After that, the boundary will become
nearly stationary across the Midwest, resulting in daily rain
chances through the end of the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1255 PM CDT Sat Jul 23 2016

Latest forecast models show more low level moisture and cumulus
clouds over eastern IL this afternoon, which support the broken
ceilings of 2.5-4k ft from CMI eastward. Some broken cirrus
clouds as well especially from I-74 north from MCS over northern
IA, sw WI and se MN that is tracking east. A band of convection
over western IA from I-35 west is projected to track east into the
IL river valley after 00Z, reaching PIA by sunset and BMI by 03Z
as it weakens later this evening. Added VCSH for this convection
and may need to add TS this afternoon especially at PIA. Models
keep more widespread convection north of central IL especially
over WI through Sunday morning. Have light fog/haze from 09-14Z
with vsbys 3-6 miles as more widespread fog with vsbys under 2
miles stays over southeast IL again. SSW winds of 4-8 kts this
afternoon become light SSE after sunset, and SSW 7-11 kts after
14Z Sunday.


&&

.ILX Watches/Warnings/Advisories...
Excessive Heat Warning until 7 PM CDT Sunday for ILZ040>057-
061>063-066>068-071>073.

Excessive Heat Warning until 7 PM CDT this evening for
ILZ027>031-036>038.

&&

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...07



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