Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 180845

Area Forecast Discussion
National Weather Service Lincoln IL
345 AM CDT Thu Jul 18 2019

Issued at 307 AM CDT Thu Jul 18 2019

The Excessive Heat Warning remains in effect for the western
portion of the CWA, and will begin today for the eastern half of
the CWA. Southwesterly winds will increase today, ushering in
warmer temperatures and more humid air.


.SHORT TERM...(Today and tonight)
ISSUED AT 307 AM CDT Thu Jul 18 2019

Currently monitoring a developing system in northeastern Iowa, for
potential southward dropping into Illinois this morning. This
system is forecast to develop a linear band from the southwestern
edge, which could clip counties along and north of I-74. However,
not much instability is available to say it`s going to happen.
Almost like a repeat of what occurred with the storms that moved
through the region yesterday, as they developed earlier and slide
through western Illinois.

Otherwise, today will feature the return of an increasing
southwesterly airflow. As High pressure remains off the east
coast, with a weak Low in the Rockies, pressure gradients will
tighten through the day. This will help usher more humid air into
the region, lifting temperatures and heat index values above 105
to the region, with some locations reaching upwards of 115 degrees
this afternoon. Even though winds will increase, in this
situation it will not help to make the air feel cooler.

With flattened out 500mb heights along and north of the nations
mid latitudes, any weak disturbances that form are expected to
remain north of the Midwest overnight. This will keep dry weather
in place around central Illinois, however temperatures will
remain mild as the southwesterly airflow continues.


.LONG TERM...(Friday through Wednesday)
ISSUED AT 307 AM CDT Thu Jul 18 2019

The hot and humid weather pattern will continue into and through
the weekend across the central US and Midwest, before a cold front
slides through to end the weekend and shift the airmass east.

Temperatures and heat index values will remain dangerously
elevated Friday and Saturday. Heat index values will peak above
105 degrees, with many locations reaching 110 to 115. This will
only be made worse, by upper level High pressure settling
overhead, bringing mostly sunny conditions to the area. Heat index
values are a measurement in shaded locations, so with the sunshine
expected, it will make it feel near 120 to 125 degrees in direct

Heading into the second half of the weekend, High pressure will
begin to breakdown allowing for a Low pressure system to drop into
the northern Midwest and Great Lakes. This will swing a cold front
through the Midwest and Ohio Valley. Models are starting to come
into agreement on a Sunday afternoon passage, although how much
precipitation is still in the air. The NBM model run had no
precipitation present, however thoughts are that with the
excessive moisture in the atmosphere, there will be some to
provide lift for development of showers and thunderstorms.

Frontal passage will bring the return of a cooler, less humid
airmass into the region. And longer range models indicate that
this could linger through mid-week, as a Canadian High stalls out
over the region.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1130 PM CDT Wed Jul 17 2019

VFR conditions expected to prevail the next 24 hours. Primary
concerns are with convection chances near KPIA/KBMI early Thursday
morning. Late evening satellite and radar showing some storms
starting to develop over northern Iowa. Some of the evening models
suggest a potential for this to expand and move east, scraping by
portions of central Illinois. Will only include a VCSH mention for
now at these sites, but will need to watch this closely over the
next several hours. After these showers/storms pass, southwest
winds will increase to above 10 knots, which should last a good
portion of the afternoon and early evening.


Excessive Heat Warning from 1 PM this afternoon to 7 PM CDT
Sunday for ILZ038-043>046-053>057-061>063-066>068-071>073.

Excessive Heat Warning until 7 PM CDT Saturday for ILZ027>031-



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