Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 170900

Area Forecast Discussion
National Weather Service Lincoln IL
400 AM CDT Wed Jul 17 2019

Issued at 330 AM CDT Wed Jul 17 2019

Dangerous heat will shift into the Midwest beginning today,
lasting through the upcoming weekend. This will be the first major
heat wave of the year for the region, as heat index values will
peak between 105 and 110 degrees during the afternoons. Overnights
will remain mild, as heat indicies will remain near or above 80


.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Wed Jul 17 2019

The remnants of Barry shifted eastward overnight, as upper level
winds quickly carried the system towards the east coast. With
significant moisture in the air, and clearing skies, some areas of
light fog are expected to develop early this morning.

High pressure will begin to slowly build back into the region
during the mid-week. Another Low pressure system in Canada will
interfere with the full development of High pressure today and

WAA is expected to increase today, ushering warmer temperatures
back into the area. This in combination with sunshine will aid in
the rapid temperature rise across the central US and western
Illinois. As temps climb into the 90s today, with dewpoints in the
70s, heat index values will peak out near 100 to 105 across west
central Illinois. This is the lower level Excessive Heat Warning
criteria for our office, and therefore we have continued the EH.W

Overnight a Low pressure system will slide through Canada,
sweeping a cold front through the upper Midwest. On the southern
edge, models favor MCS development, dropping this complex through
Illinois. The main area of concern appears to be along and north
of the I-74 corridor, however some model uncertainty exists with
the exact track and strength of this system.


.LONG TERM...(Thursday through Tuesday)
ISSUED AT 330 AM CDT Wed Jul 17 2019

Heading into the second half of the work week, the oppressive heat
and humidity will be the story. High pressure will dominate the
weather pattern, bringing clear skies and dry weather across the
central US. This pattern is expected to continue through the end
of the work week and into the weekend.

Southerly airflow will continue throughout the entire duration of
the heat wave, helping to increase the heat index values.
Temperatures will top out in the 90s, with heat index values
reaching 105 to 110 degrees, with some isolated locations climbing
to near 115 degrees...especially on Friday and Saturday. Cooler
temperatures will filter into the region Sunday, however heat
index values near 105 will be possible across eastern and
southeast Illinois.

The Excessive Heat Watch in eastern Illinois was upgraded to an
Excessive Heat Warning with this package, due to heat index values
increasing across eastern and southeastern Illinois with the
latest model runs. Although surrounding offices did not upgrade,
this was not an issue due to the location and eastern edge of the
warmest air.

A break from the heat comes at the end of the weekend. Models
indicate a larger Low pressure system sliding across the upper
Midwest through the Great Lakes, swinging a cold front through the
region. However, at this time, some discrepancy in model data is
evident with respect to timing of fropa. Some models show a Sunday
passage, while others have a Monday passage.

Cooler temperatures look to prevail next week, as CPC models hint
at a below average 6 to 10 day outlook.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1117 PM CDT Tue Jul 16 2019

Main forecast concern will be potential for some MVFR conditions
overnight due to light fog, although far eastern Illinois may also
see lower ceilings. 05Z observation showing IFR conditions at
KDNV, and latest HRRR model showing potential for lowering
ceilings west to near KCMI over the next several hours. Will bring
ceilings below 2,000 feet at KCMI on the upcoming TAF set. As
diurnal cumulus begins to form around mid morning, sites may see a
few hours of MVFR ceilings before the cloud heights start to lift
around midday. Later in the forecast period, evening models are
showing some potential for thunderstorms diving southeast out of
Iowa. Timing is rather scattered, with more of a late evening
potential near KPIA, but too much uncertainty to mention at this


Excessive Heat Warning from 1 PM Thursday to 7 PM CDT Sunday for

Excessive Heat Warning from 1 PM this afternoon to 7 PM CDT
Saturday for ILZ027>031-036-037-040>042-047>052.



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