Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 171129
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
629 AM CDT Thu May 17 2018

.SHORT TERM...(Today and tonight)
ISSUED AT 337 AM CDT Thu May 17 2018

Very warm and generally dry weather will prevail across central
Illinois today...with afternoon high temperatures topping out in
the middle 80s. As an upper-level low evident on 08z/3am water
vapor imagery near Kansas City tracks E/SE, it will interact with
an old frontal boundary draped across the Ohio River Valley to
trigger scattered showers and thunderstorms mainly along/south of
the I-64 corridor this afternoon. A few showers may impact the
far SE KILX CWA, so have included low chance PoPs along/southeast
of a Robinson to Flora line. The low will then track into
southern Illinois by 12z Fri...helping deep-layer moisture over
the Ohio River Valley pivot W/NW. As a result, showers and
isolated thunderstorms will spread as far north as the I-72
corridor tonight. Overnight low temperatures will mainly be in the
lower 60s.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 337 AM CDT Thu May 17 2018

00z May 17 models are now in good agreement concerning the track
of the upper low, with most solutions meandering it slowly E/NE
into Indiana by Saturday morning. This particular track will mean
mostly cloudy skies with scattered precip across much of the area
on Friday. Instability parameters are quite paltry, with MUCAPES
of only 100-200J/kg across the far SE CWA. Have therefore
confined isolated thunder mention to locations south of a
Martinsville to Taylorville line. Highs on Friday will be
considerably cooler than today...ranging from the lower 70s
along/east of I57...to the upper 70s in the Illinois River Valley.

The low will slowly exit the region on Saturday, resulting in
partial clearing and temperatures rebounding back into the 80s.
Meanwhile, the next system progged to impact central Illinois will
be taking shape across the southern Plains. Surface low pressure
will develop over the Oklahoma/Texas panhandle on Friday...then
will slowly track northeastward into the southern Great Lakes by
early next week. Considerable model spread still exists concerning
the exact track/timing of the low, so forecast confidence remains
average to slightly below average late in the weekend. It appears
the low will reach northeast Kansas Saturday afternoon, where it
will interact with a highly unstable/moderately sheared
environment to produce strong to severe thunderstorms from Kansas
City to Des Moines. As the low slowly shifts further E/NE, the
potential for strong thunderstorms will increase across portions
of central Illinois on Sunday. However, timing discrepancies among
the models make it difficult to pinpoint any areal/spatial severe
threat at this time. Will however increase PoPs Saturday night
through Sunday evening as the low approaches.

Once the low moves east of the region, it will pull a weak cold
front southward into central Illinois. Given zonal flow pattern in
place and weak mid-level winds, think boundary will stall
somewhere in the vicinity...perhaps just south of the CWA on
Monday/Tuesday. After that, the front will begin to shift back
northward...resulting in increasing rain chances by the middle and
end of next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 629 AM CDT Thu May 17 2018

VFR conditions should prevail at all TAF sites next 24hrs. All
sites will start with high cirrus this morning continuing into
this afternoon and early evening. Then as the next weather system
approaches the area, mid clouds will advect into the area from the
south, reaching SPI/DEC/CMI first and PIA/BMI last. Later
overnight lower clouds at around 5kft will advect in, again first
at SPI/DEC/CMI and last at PIA and BMI. Precip could arrive at
same time, but think it will hold off til around 12z...so did not
add at this time. Winds will be northeast through the period at
around 10-15kts.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Auten



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