Area Forecast Discussion
Issued by NWS Central Illinois

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601
FXUS63 KILX 230153
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
853 PM CDT FRI JUL 22 2016

.UPDATE...
Issued at 843 PM CDT Fri Jul 22 2016

00z ILX sounding showing the strong cap has weakened some but
still rather significant across our area this evening. Quite a
bit of elevated instability present with the latest ILX objective
analysis indicating MUCAPES ranging from 3500 J/KG in our
northwest to around 2000 J/kg over southeast Illinois. Have been
seeing quite a bit of ACCAS to our west and northwest this evening
an indicator of the instability present above 700 mb. No notable
shortwave around our area until you move out into west-central
Nebrask where a complex of storms was tracking east. Will continue
to carry slight chances for most of the area overnight with a
trend towards a bit higher POPs across the north as we approach
dawn on Saturday. Should have the updated zones out by 900 pm.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 314 PM CDT Fri Jul 22 2016

19z/2pm surface analysis shows stationary frontal boundary from
Michigan westward into the Northern Rockies...while outflow boundary
from previous convective complex extends from Kentucky northwestward
into central Iowa.  The airmass across central Illinois remains
quite stable...as evidenced by current LAPS SBCAPE values of
1500J/kg or less.  Further west along/ahead of the outflow boundary,
the atmosphere is considerably more unstable across Iowa where
SBCAPEs are greater than 3000J/kg.  Isolated showers and
thunderstorms are beginning to develop across northern and central
Iowa, and this activity will gradually shift into west-central
Illinois this evening.  Have therefore included slight chance PoPs
across the Illinois River Valley by 00z...then further east across
the entire KILX CWA overnight.  Low temperatures will remain in the
lower to middle 70s.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 314 PM CDT Fri Jul 22 2016

As upper-level ridging begins to weaken and mid-level temps cool
slightly, areal coverage of thunderstorms will 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 22 models have
continued to delay FROPA, so have increased rain chances along/south
of I-72 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 00Z TAFS through 00Z Saturday evening)
Issued at 602 PM CDT Fri Jul 22 2016

Other than some patchy MVFR fog after 08z tonight, VFR conditions
are expected for the remainder of this forecast period. Weak high
pressure will shift off to our east tonight with mainly some mid
and high level clouds streaming across the area from time to time.
A weak frontal boundary located to our north this evening will
act as a focus for scattered TSRA over northern Iowa tonight and
then spread southeast. Will carry VCTS late tonight into early
Saturday morning to take into account the potential for a few of
the storms to make it into our forecast area. Winds again will
be light southeast to south tonight at 3 to 7 kts, and south winds
are expected again on Saturday at 10 kts or less through the day.


&&

.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.

&&

$$

UPDATE...Smith
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith



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