063 
FXUS63 KILX 120457
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1157 PM CDT Mon Sep 11 2023

.SYNOPSIS...
Issued at 1141 PM CDT Mon Sep 11 2023

The threat of rain will diminish this evening north of I-72, but
will continue through the night south of there, finally ending
south of I-70 early Tuesday morning. After that, the remainder of
the week currently looks dry. High temperatures will run a few
degrees below mid September normals, but will still largely be in
the mid to upper 70s the next few days. 

&&

.UPDATE...
Issued at 737 PM CDT Mon Sep 11 2023

The steadier rain was centered roughly along the I-72 corridor
south to I-70 early this evening, though eastern areas are still 
seeing the rain remain quite light with ceilings up around 10,000
feet. No lightning has been observed for a number of hours. 
However, with our evening sounding still showing surface based 
CAPE's around 800 J/kg, I am hesitant to completely remove it from
the forecast. Recent grid update did dial it back to an isolated 
mention in these ares through late evening. Rain trends were also 
updated to remove most of the mention after midnight west of I-55,
but general timing trends still look decent. 

Geelhart

&&

.DISCUSSION...
Issued at 241 PM CDT Mon Sep 11 2023

Water vapor imagery depicts a large, positively tilted upper 
trough over the Midwest states early this afternoon. At the 
surface, a cold front is positioned from near Chicago 
southwestward toward Macomb. Scattered showers have been observed 
mainly near/north of I-74 so far today. Another wave of 
precipitation over Missouri/far west- central Illinois will spread
northeast through the remainder of the afternoon as a subtle 
shortwave embedded in the large-scale flow rotates through the 
area. The right entrance region of a 300 mb jet is in the process 
of positioning itself overhead, which paired with the shortwave 
will support large-scale ascent. A couple hundred J/kg of 
instability may lead to a few storms at times through this 
evening. QPF amounts should generally be light, but the 11.12Z 
HREF continues to show convectively driven pockets of ~0.50"+. The
front will push south of the area late tonight into Tuesday 
morning, though scattered shower activity may linger through most 
of Tuesday morning south of I-70.

The upper trough will work into the northeast US by the middle of 
the week as Canadian surface high pressure sinks south into the 
Midwest states. Cooler and drier weather will be seen through the 
end of the week with high temperatures in the 70s and lows in the 
upper 40s to 50s. By the weekend, upper troughing looks to swing 
through the middle of the CONUS with a cold front tracking through 
here sometime Saturday or Sunday. Precipitation chances with the 
frontal passage cannot be ruled out, though low-level moisture 
appears to be somewhat limited based on forecast soundings. The 
NBM keeps things dry this weekend, so did not sway away from that 
at this point due it still being uncertain and 6-7 days out.

Cooler temperatures look to stick around through early next week 
with the Climate Prediction Center's 6-10 day outlook highlighting a 
33-50% chance of below normal temperatures through the middle of 
next week.

NMA

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1141 PM CDT Mon Sep 11 2023

A chaotic sky currently exists across central Illinois as a cold 
front slowly slumps southward across the regional terminals. 
Despite occasional VFR/MVFR ceilings late tonight, the 
overwhelming majority of guidance supports mostly IFR/LIFR 
ceilings between 06z-12z. Further muddling the picture is the
potential for patchy dense fog, which can already be seen in
upstream obs across SE Iowa where visibility reductions are below
a mile in some cases. While this cycle of TAFs mostly emphasizes 
IFR/LIFR ceilings, we will make adjustments to visibility as 
needed.

MJA

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$