Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 220753
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
253 AM CDT FRI JUL 22 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 252 AM CDT Fri Jul 22 2016

Last evening, storms blasted their way southward through a +14C 700mb
cap, taking advantage of around 6000 J/kg MUCAPE. Although the
remaining CIN did keep the strength of the storms in check once they
reached central IL. The now dying MCS across central Illinois will
start out the day, with precip eventually coming to an end as the
system loses lift and upper support and drifts south.

A couple versions of the HRRR are showing dry conditions for a
majority of the day today, with a small cluster of storms developing
after 20z in our northern counties. The storms are projected to
progress slowly south into the evening, oriented in a NW to SE line
across central IL. The other operational models have differing
solutions on timing and coverage, but will stick closer to the HRRR-
CR for this short-term forecast update.

Temperatures plummeted about 10-15 degrees with the MCS arrival last
evening. However, still expect clouds to dissipate by mid to late
morning, allowing for plenty of time for sunshine to produce high
temps in the low to mid 90s again today. Due to the additional
moisture from last nights convection, dewpoints should have no
problem climbing back in the mid to upper 70s, with a few low 80s
possible. Those numbers should support peak heat index values in the
107 to 112 range this afternoon. Low temps will remain very mild
again tonight, with some cooler locations where any evening storms
develop. Overall, temps should bottom out in the low to mid 70s again
tonight.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 252 AM CDT Fri Jul 22 2016

A couple more days of heat and humidity expected, before some relief
arrives in the form of a cold front Sunday night. Main challenge
before that will be with any convection and its impacts on the
temperatures. With the main synoptic boundary still off to the
northwest until late in the weekend, the primary focus for
convection will be with mesoscale boundaries which are not handled
very well in the larger scale models. Have not changed PoP`s much
from the previous forecast, mainly 30-40% range this weekend during
the daytime hours. Still keeping the heat indices in the 105-110
range, but the convection could thwart those plans. No changes
planned to the headlines at this time due to the uncertainty.

Moving on to early next week, the movement of the front slows some
as it gets caught in the west-east high pressure axis aloft. Have
updated the PoP`s on Monday to linger about 30% chances as far north
as I-72, until the passage of an upper wave across the mid-
Mississippi Valley. As another trough moves through the Plains mid
week, it will sharpen and provide more of a focus for showers and
thunderstorms. While the GFS and ECMWF are not too different in the
upper level features, the synoptic boundaries are much more
uncertain, as well as the precipitation chances. Thus, will not go
any higher than 40% at the end of the current forecast period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1106 PM CDT Thu Jul 21 2016

Complex of storms affecting the PIA and BMI TAF sites will
gradually shift south and affect our further south sites over the
next 2 to 4 hours. Wind gusts to 35 kts will be possible with
some of the stronger cells along with torrential rainfall and
brief MVFR and possible IFR cigs/vsbys. We look for the complex of
storms to settle south of the southern TAF sites by 09z. After
that, there may be some fog that develops and brings vsbys down to
MVFR category til 13z, and then VFR conditions are expected during
the day Friday along with some more oppressive heat and humidity.
Chances for additional storms continue on Friday but coverage
looks to be quite spotty again so will not include anything with
this forecast issuance for tomorrow afternoon/eve. Surface winds
will be light southerly tonight, but variable in direction and
quite gusty in and near the thunderstorms. Look for south to
southwest winds of 8 to 13 kts on 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...Shimon
LONG TERM...Geelhart
AVIATION...Smith



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