Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200529

Area Forecast Discussion
National Weather Service Lincoln IL
1229 AM CDT Tue Jun 20 2017

Issued at 932 PM CDT Mon Jun 19 2017

Widely scattered showers and thunderstorms continue to drift
southeastward through central Illinois this evening...with
02z/9pm radar imagery showing the cells approaching the I-70
corridor. Given very dry air below 750mb as evidenced by the 00z
KILX upper air sounding, evaporative cooling beneath the storms
led to gusty winds of 45 to 55mph with some of the strongest
cells earlier this evening. The storms have since weakened and no
longer pose a gusty wind threat. Have updated PoPs to continue
rain chances along/south of a Paris to Taylorville line for
another couple hours before the showers completely dissipate
toward midnight. Am expecting mostly clear and cool conditions
overnight with low temperatures dropping into the upper 50s and
lower 60s.


.SHORT TERM...(This evening through Tuesday)
ISSUED AT 224 PM CDT Mon Jun 19 2017

Deep cyclonic flow will linger across central and southeast
Illinois through the period. This flow regime, coupled with
unseasonably cool temperatures aloft, is supportive of deep
diurnal mixing/gusty winds and spotty diurnal convection. The
threat for isolated showers and storms will linger for a couple
hours early this evening before peak diurnal instability is lost.
The threat for isolated showers/storms will return by Tuesday
afternoon. The relatively dry air mass in place will help keep
storm coverage and CAPE values to a minimum, but the dry air
beneath cloud level could support some strong convective wind

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 224 PM CDT Mon Jun 19 2017

Upper-level flow flattens out for the middle of the week, allowing
temperatures to climb back above normal. A strong wave is progged
to track across Canada within this developing flow regime.
Shower/storm chances increase across at least northern portion of
the forecast area late Wednesday night into Thursday as an
associated storm complex may impact the area. Precipitation
chances increase across the entire forecast area Thursday night
into Friday as the wave tracks further east across Canada and a
trailing frontal boundary settles across the forecast area.

Beyond Friday, much more considerable uncertainty enters the
local precipitaton forecast. There are differences in exactly
where the trailing front eventually stalls, and how often it is
activated by disturbances riding along it. Further complicating
issues is the potential tropical system over the Gulf of Mexico
for late in the week, which may have impacts on the weather
pattern locally. Model trends will need to be watched closely as a
consensus is hopefully reached sooner rather than later.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1229 AM CDT Tue Jun 20 2017

Main TAF issue will be the development of scattered convection
again Tuesday afternoon. Much of the high-resolution guidance
suggests this arriving in KPIA/KBMI in the 20-22Z time frame, and
from KSPI-KCMI closer to 00Z. Have included VCTS mention at all
sites. Some of the heavier showers may produce gusty winds and
brief MVFR/IFR visibility reductions, but uncertainty in coverage
precludes trying to pin down details in the TAF`s this far out.
Remaining convection should be diminishing south of the TAF sites
by about 02Z with loss of daytime heating.




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