691
FXUS63 KILX 191708
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1208 PM CDT Thu Sep 19 2024

.KEY MESSAGES...

- Summer-like warmth continues the next few days with more
  seasonal temperatures returning for the start of the new week.

- A more unsettled pattern arrives beginning tonight as a few
  upper systems bring periodic chances for showers and storms
  through at least early next week.

&&

.UPDATE...
Issued at 947 AM CDT Thu Sep 19 2024

An area of mid-level clouds has been clipping the extreme
southeast parts of the forecast area near Lawrenceville recently,
but has begun an eastward push and should move out soon. In
general, skies expected to remain mostly sunny across the forecast
area, with some increase in high clouds during the afternoon ahead
of the front west of the Mississippi River. Temperatures have been
on a quicker climb than forecast and required some updates for the
remainder of the morning, but overall temperatures are still on
track to top out around 90 degrees this afternoon.

Geelhart

&&

.DISCUSSION...
Issued at 243 AM CDT Thu Sep 19 2024

An upper Rex block is in the process of breaking down late this week
as a series of upper disturbances from the western CONUS work
through the Upper Mississippi Valley and Midwest states in the
coming days. Satellite imagery shows exiting cirrus over eastern
parts of the state, with clear skies west of there. Temperatures as
of 2 am range from the upper 50s to low 60s. Dewpoints in the 50s
should allow air temperatures to drop a few more degrees through
daybreak. Daytime temperatures will continue to run seasonally high
the next several days with highs peaking in the middle 80s to around
90 degrees.

After a rather dry start to the month, precipitation chances return
late tonight into Friday as an upper shortwave lifts from the
northern Plains into the southern Canadian Prairies. A cold front
will approach from the west late tonight, bringing scattered
showers and storms to areas mainly near/west of I-57 through
Friday morning. A lull in precipitation will be seen late Friday
morning as the front stalls out across the area. Showers and
storms may redevelop along the front Friday afternoon as daytime
heating and seasonably high dewpoints result in 1000-1500 J/kg of
instability. Although the upper wave will be north of here by this
time the stalled out boundary paired with increasing mid-level
flow should allow some stronger storms to develop from mid
afternoon through early evening. A SPC marginal risk has been
introduced with the threat of damaging downburst winds and large
hail being the main concerns.

A stronger upper wave currently spinning off the coast of California
will bring better chances for precipitation and beneficial
rainfall this weekend into early next week. A couple shortwaves
will work through the area Saturday night into Sunday before the
main wave approaches late Sunday night. Periodic chances for
showers and storms will exist through at least Monday night with
the heaviest push of rainfall coming late Sunday night into Monday
morning as a ~30 kt LLJ noses feeds into a warm front. QPF
amounts look beneficial from this second system, though likely
won`t come close to erasing our ongoing deficit. The NBM shows
favorable probabilities (50-70%) of seeing at least 1 inch of rain
west of I-55, with about a 30-40% of 2 inches or more.

Temperatures turn cooler for the start of the new week with highs
Monday through Thursday looking to stay near or below 80s degrees.

NMA

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1208 PM CDT Thu Sep 19 2024

VFR conditions expected to prevail during the forecast period.
Main aviation concerns will be in the 06-12Z time frame, when a
band of showers and scattered thunderstorms moves southeast across
central Illinois. Thunder chances are expected to diminish with
time, so for the moment, will only include a mention at KPIA/KSPI
for a few hours from 08-11Z. Once the showers exit, skies clear
out again. Further into Friday, some convection is expected to
develop over east central Illinois with the arrival of a cold
front, but this is most likely after the current TAF forecast
period.

Geelhart

&&

.CLIMATE...
Issued at 947 AM CDT Thu Sep 19 2024

Rainfall over the last 30 days across much of central and
southeast Illinois has been about 25% or less of normal, with the
impacts of post-tropical Francine mainly limited to parts of
Richland and Lawrence Counties southward. Going back 2 months,
only a few pockets generally along the I-72 corridor have had
above normal rain, though far enough back that its impacts have
largely faded. Burn bans have been implemented in Crawford,
Richland and Lawrence Counties.

This morning`s Drought Monitor introduced D1 (moderate) drought
conditions across the southern third of the state generally
near/south of I-70, as well as in west central Illinois from about
Havana to Quincy. While prospects of some decent rain have been
increasing for the weekend and early next week (>50% chance of
over an inch of rain north of I-72), prospects south of I-70 are
more in the 20% range, with only a 40-50% chance of even a half
inch. Latest CPC 8-14 day outlook for September 26 to October 2
lean near or slightly below normal for rainfall.

Geelhart


&&

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

$$