Area Forecast Discussion
Issued by NWS Central Illinois

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926
FXUS63 KILX 212000
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
300 PM CDT THU JUL 21 2016

.SHORT TERM...(This evening through Friday)
ISSUED AT 300 PM CDT Thu Jul 21 2016

A warm and muggy night is in store across central Illinois tonight.
After high temperatures in the lower to middle 90s this afternoon,
lows tonight will only drop into the middle to upper 70s.  Aside
from an isolated thunderstorm along/east of the I-55 corridor this
afternoon, dry conditions will be the rule into this evening.  As is
typically the case this time of year, models are struggling to
accurately forecast convective evolution.  Solutions vary
greatly...with some models going completely dry tonight and others
suggesting a potential MCS across northern Illinois late.  Current
analysis shows an outflow boundary from storms that rolled through
the Great Lakes earlier today extending from southern Wisconsin into
northwest Indiana.  With a weak 20-25kt 850mb jet flowing into the
boundary, think clusters of thunderstorms may develop along/north of
I-80 after midnight.  These storms will tend to sink S/SE toward
dawn, potentially spilling into the N/NW KILX CWA.  Have tailored
PoPs accordingly...with dry conditions everywhere through the
evening followed by low chance along/north of I-74 well after
midnight.

&&

.LONG TERM...(Friday night through Thursday)
ISSUED AT 300 PM CDT Thu Jul 21 2016

A few showers and thunderstorms may be ongoing across the northern
KILX CWA Friday morning, but these will likely dissipate after
sunrise.  Additional convection may develop along outflow boundaries
left behind by the morning storms:however, with warm mid-level
capping in place, do not think convection will become widespread.
Most models suggest widely scattered thunderstorms everywhere except
the SW CWA where cap will be strongest.  Main story on Friday
will be the continued heat and humidity, as high temperatures once
again reach the middle 90s and heat index values climb into the
105-110 degree range.

As upper-level ridging begins to weaken and mid-level temps cool
slightly, areal coverage of thunderstorms may become a bit more
robust on Saturday.  Synoptic frontal boundary will remain well to
the N/NW, so main forcing mechanism will be mesoscale outflow
boundaries left behind by previous convection.  Have carried low
chance PoPs everywhere with highs topping out in the lower to
middle 90s.

Best rain chances still appear to be setting up Sunday/Sunday night
as cold front approaches from the northwest.  12z Jul 21 models have
now delayed FROPA, so rain chances will likely linger across at
least the southern half of the CWA into Monday.  After that, a
cooler/drier airmass will settle into central Illinois on Tuesday
and Wednesday with highs dropping back into the middle to upper 80s.
As such, have maintained the Excessive Heat Warning everywhere
through Saturday evening...and along/south of a Quincy to Danville
line through Sunday evening.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1250 PM CDT Thu Jul 21 2016

VFR conditions generally expected across the central IL airports
next 24 hours. The exception will be isolated convection possible
near BMI and CMI this afternoon. Some models show more convection
developing and tracking se into northeast IL and central IN late
tonight into friday morning and close to I-74. If slight chance
of convection occurring then could get brief MVFR
ceilings/visibilities with the rain. Also MVFR visibilities of
4-5 miles possible with light fog/haze from 09-14Z Friday similar
to early this morning due to very moist tropical airmass in place
with dewpoints in upper 70s to around 80F. Winds remain fairly
light next 24 hours. SSW winds of 6-10 kts this afternoon to
become south 3-6 kts after sunset and sw 7-10 kts after 14Z
Friday.


&&

.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 Saturday for ILZ027>031-
036>038.

&&

$$

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



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