270 
FXUS63 KILX 071114
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
514 AM CST Sun Nov 7 2021

.SYNOPSIS...
Issued at 155 AM CDT Sun Nov 7 2021

Mostly clear skies and mild temperatures will continue for today
and Monday. Southwest winds will be gusty at times, especially
during the afternoon hours.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 155 AM CDT Sun Nov 7 2021

Early morning surface analysis indicated high pressure stretched
from the lower Mississippi Valley northeast through the Ohio
Valley, while unorganized low pressure was in the lee of the
Rockies. This resulted in light south winds keeping temperatures
several degrees warmer than 24 hours ago in the mid 30s to lower
40s. Aloft, 500 mb map showed ridging expanding east from the
Plains into the Upper Midwest.

The stretch of excellent fall weather continues in the short term
as upper ridging expands east today. MSLP gradient tightens with 
the high shifting farther east and a low pressure trof tracking 
into the Plains and Upper Midwest. So breezier southwest winds 
expected which could gust over 20 mph west of I-55 this afternoon.
The stronger low level warm advection may be offset a bit by 
increased high clouds, but should still be sufficient to see 
widespread mid 60s highs. The gradient will keep the boundary 
layer mixed overnight for milder lows in the mid 40s west of I-55,
while lighter winds in SE IL and associated decoupling to drop 
lows in the upper 30s.

.LONG TERM...(Monday through Saturday)
ISSUED AT 155 AM CDT Sun Nov 7 2021

Positive 500 mb height anomaly bullseye shifts overhead as the 
upper ridge leans across the region on Monday. Southwest gradient 
flow continues and will contribute to highs in the mid/upper 60s, 
or 10-15 degrees above normal. 

A low amplitude shortwave pushes a cold front into the area on
Tuesday. The column appears pretty dry due to expansive high 
pressure north of the Gulf coast, and the better forcing is shown 
to our north. This should mainly cause an increase in clouds and a
few sprinkles or brief light showers, and only have slight chance
pops. Highs only a couple degrees cooler than Monday from the 
increased clouds.

A much stronger system will develop over the Plains on Wednesday
when a 140 kt upper jet punches east from the Pacific into the
Rockies. 500 mb shortwave is forecast to close off over the upper
Midwest Wednesday into Wednesday night, eventually sending a cold
front through the region late Wednesday into Thursday. Due to the
stronger forcing and better moisture return, a widespread rainfall
should be seen. Better instability remains to our south so no
thunder mentioned, but this could change with the dynamic nature
of the system.

Global ensembles are in good agreement that the large upper low
will be centered near the Great Lakes on Friday, bringing deep
layer northwest flow and cold advection to the Midwest. In fact 
negative 500 mb height anomalies are centered over the state 
Fri/Sat. Steep low level lapse rates could combine with waves 
embedded in the northwest flow to produce scattered showers. But 
the bigger story will be the return of well below normal 
temperatures and breezy conditions. GEFS mean 850 mb temps drop as
low as -7C late Friday, and the blended guidance drops highs to 
the mid 40s Friday and lower 40s Saturday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 514 AM CST Sun Nov 7 2021

VFR conditions will continue for another 24 hours as high pressure
remains in control of the sensible weather. Winds will be the main
concern to aviation, with wind gusts this afternoon climbing into
the 15-20KT range from the S-SW. Winds will generally diminish
below 10kt this evening. However, a 40-45KT southwesterly low 
level jet will advance into IL from the west overnight, producing 
LLWS conditions at the terminal sites. The target height looks to
be around 1200FT AGL.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...25
SHORT TERM...25
LONG TERM...25
AVIATION...Shimon