Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 230353
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1053 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
Nebraska 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 06Z TAFS through 06Z Saturday night)
Issued at 1050 PM CDT Fri Jul 22 2016

A band of mid level clouds (7000-10000 ft) continues to slowly
drift southeast and may produce an isolated shower or storm along
the I-55 corridor over the next hour or so which would affect BMI
and SPI. For now, will keep any mention out and keep an eye on the
radar and surface obs before TAF issuance and make any changes if
needed. Otherwise, temp-dew points spreads were down to between 1
and 3 degrees most areas which suggests at least a brief period of
MVFR or possible IFR cigs and vsbys in the 08z- 13z time frame.
Any fog or lower clouds that do develop should quickly dissipate
btwn 13z-14z with mainly VFR conditions thereafter. Rain chances
at this point appear to be too small to mention in the TAFs for
this issuance. Winds will be light and variable tonight and
southerly at 5 to 10 kts on Saturday.

&&

.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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