669
FXUS63 KILX 190020
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
720 PM CDT Thu Jul 18 2024

.KEY MESSAGES...

- High temperatures will be in  the upper 70s to low 80s through
  the weekend, which is 5 to 10 degrees below normal.
  Humidity will also be unseasonably low through Saturday.

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

&&

.UPDATE...
Issued at 720 PM CDT Thu Jul 18 2024

Diurnal cumulus is fading off on schedule, and skies will be
mostly clear overnight. Temperatures are on track to drop into the
lower 50s over east central Illinois, which would threaten a few
record lows for Friday (see Climate section below). Forecast is
largely on track and only needed the typical minor tweaks based on
the latest observations.

Geelhart

&&

.DISCUSSION...
Issued at 238 PM CDT Thu Jul 18 2024

Expansive high pressure centered near northeast IA this afternoon
will continue to shift into northern IL for Friday. This feature
will bring dry conditions for the next few days as it parks over the
Midwest, while ushering in a dry air mass into central IL. The
air mass over central IL is already around 3/4 inch precipitable
water, around 10th percentile for this time of year, and forecast
to remain at least this dry for a day or two. The air mass is
also of cooler Canadian origin, and should produce highs in the
upper 70s to lower 80s, and lows dipping into the 50s the next few
days.

Late in the weekend, the pattern will begin to shift as high
pressure weakens over the Midwest and weak low pressure develops
over the Plains, working in tandem with high pressure off the coast
of the southeast U.S. to cause moisture to return to Illinois in
southerly flow. By Monday, long range ensemble guidance shows a mean
precipitable water value around 1.5 inches, or near 75th percentile,
lingering through much of next week. This should be adequate to
support occasional showers and thunderstorms in periodic
disturbances ejecting through the area guided by a weak upper level
trough over the central U.S. Temperatures look to trend slowly
upward, but remain a few degrees below normal in the lower to mid
80s, given increased cloud cover and showery conditions. As far
as severe weather and excessive rainfall, it is too early to rule
out a small threat. Overall weak 500 mb flow would provide weak
shear to limit any widespread severe weather threat, but
occasional shortwaves could locally enhance shear. Weak flow
could also promote slow storm motion for some localized heavy rain
threat, however latest ensemble guidance suggests 5 percent or
less chances for over 1 inch 24-hour rainfall accumulation
suggesting generally light to moderate rainfall rates.

37

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 609 PM CDT Thu Jul 18 2024

Once the breezier conditions in eastern Illinois fade out with
sunset, little aviation concern is expected the next 24 hours,
with just scattered daytime clouds around 4,000 feet.

Geelhart

&&

.CLIMATE...
Issued at 715 PM CDT Thu Jul 18 2024

Record lows for Friday morning:

Champaign..... 50 (1909)
Charleston.... 51 (1925)
Danville...... 52 (1984)
Decatur....... 48 (1909)
Lincoln....... 49 (1910)
Peoria........ 50 (1910)
Springfield... 54 (2009)

Geelhart


&&

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

$$