Area Forecast Discussion
Issued by NWS Central Illinois

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387
FXUS63 KILX 200849
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
349 AM CDT Thu Jul 20 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Thu Jul 20 2017

Not much of a shift in the forecast overall as Central IL sits on
the edge of a dome of very hot air and a more active pattern just
to the north for the upper Midwest and the northern tier of IL.
The main message remains the heat, with advisories and warnings
active across the region. Periodic chances for showers and
thunderstorms... particularly for areas north of I-74 as remnant
outflows from the northern storm systems drift a bit further south
before they weaken. This morning, for example, the HRRR continues
to develop some showers on the SWrn flank of the convection moving
through northern IL in the next few hours. As a result...have
pulled some chance pops in for areas mainly north of a line from
Peoria to Danville. May see little more than an increase in clouds
however, as the storms will be weakening this far south.

Hot air continues to push into the Midwest and by this afternoon
h85 temps will climb to 21-23C and surface temps respond up to the
mid to upper 90s. With the muggy airmass in place with dwpts in
the 70s, afternoon heat indices will climb into the 105-110F range
for a large portion of the state. Please exercise extreme caution
if outside in the heat of the day. Tonights temps will not provide
much in the way of cooling off, only dropping into the mid 70s in
a stagnant and muggy airmass.

&&

.LONG TERM...(Friday through Wednesday)
ISSUED AT 330 AM CDT Thu Jul 20 2017

The forecast for Friday and Saturday will be much the same as the
previous discussion. Hot and humid, and more thunderstorms passing
to the north. The strength of the upper ridge is once again the
deflecting force to keep the storms to the north...and is the
question mark with the abundant mesoscale influences. Friday has
shifted to a better chance to see some relief from the heat,
albeit briefly, with a stronger wave moving precip into the center
of the state. Either way, heat continues through Saturday.
Saturday night, the front that has been developing for the last
few days finally makes its way to the south and spreads precip
chances through the state...and cooler temps on the back side of
it for Sunday. Forecast expected to be dry for the start of next
week, with temperatures far more moderate in the low to mid 80s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1245 AM CDT Thu Jul 20 2017

VCSH for PIA with weakening convection edging closer... but
otherwise guidance keeping with a VFR forecast. Given mix of llvl
moisture, and the outflow from storms to the north, cannot rule
out patchy drops in vis to at least MVFR, but confidence not
strong enough anywhere until the boundary moves through. Expect
another update may be necessary at 09z for a few of the sites at
least. Winds tomorrow taking on a more southwesterly direction,
but still less than 10kts overall.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM CDT Saturday for ILZ027>029-
036-037-040>042-047>054-061-062-066>068-071>073.

Heat Advisory until 8 PM CDT Saturday for ILZ030-031-038-043>046-
055>057-063.

&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...HJS



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