309
FXUS63 KILX 181513
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1013 AM CDT Thu Jul 18 2024

.KEY MESSAGES...

- Seasonably cool and dry into the weekend, with high temperatures in
  the upper 70s to low 80s which is 5 to 10 degrees below normal.

- Precip chances return throughout next week, with a 20-50% chance
  each day.

&&

.UPDATE...
Issued at 1013 AM CDT Thu Jul 18 2024

High pressure and associated dry air continue to work their way
into central IL, and will result in dry weather and cooler than
normal temperatures today. A band of cloud cover has developed
over Lake Michigan drifting SSW-ward into central IL, creating a
broad band of scattered cloud cover mainly east of I-55, but
diurnally forced cumulus has already begun to develop as well.
Highs today in the upper 70s look on track. Updates this morning
have been to increase cloud cover slightly, but overall the
forecast is on track for today.

37

&&

.DISCUSSION...
Issued at 201 AM CDT Thu Jul 18 2024

An expansive 1024-mb sfc high pressure was centered over Minnesota
early Thursday morning, and this sfc high will slowly shift
southeast becoming centered over Illinois by Friday morning. With
this broad sfc high pressure in control, conditions will be
seasonably cool and dry through the weekend. Today will be the
coolest day of the stretch, with highs peaking in the upper 70s,
then gradual warming occurs through the weekend as highs return to
the low 80s, which is still below normal.

By the weekend, guidance continues to depict a slow-moving, closed
upper low developing west of the area on Saturday. This upper low
meanders about for a few days, with its associated forcing progged
to stay far enough west that the ILX CWA stays dry through the
weekend. Eventually though, that forcing shifts east and provides
a chance for showers/storms (20-50% chance, highest south of I-70)
early next week (Mon-Wed).

The forecast PWAT values have trended higher, and are now progged
to be near seasonable values (1.5") on Mon. Both PWAT and
instability values gradually trend higher each day next week, but
the instability values are still seasonably low, generally near or
below 1000 J/kg each day Mon-Wed. Deep layer shear also looks
weak, with 500 mb flow around or under 20 knots, and thus severe
storms continue to appear unlikely. Given the increase in PWAT
values and the potential for light flow in the cloud bearing
layer, slow storm motions (less than 15 mph) could lead to
localized instances of heavy rainfall. At any one location, the
odds of heavy rainfall are low, with only a 10-20% chance of
exceeding 1" of rain through next Thurs AM. Around mid-week, a
stronger shortwave digs towards the upper Midwest, resulting in
continued forcing for precip Wed night- Thurs. With continued
upper troughing over the Great Lakes, temps are favored to stay
near or below normal into the latter half of next week.

Erwin

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 542 AM CDT Thu Jul 18 2024

VFR conditions prevail through the period, with no precipitation
expected. Light winds start off northerly but gradually turn to
northeasterly today, with speeds below 10 knots. Scattered diurnal
Cu is possible during the day, around 4-5kft. Tonight, winds will
generally remain out of the northeast but fall below 5 knots,
becoming variable at times.

Erwin

&&

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

$$