048
FXUS63 KILX 191951
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
251 PM CDT Thu Sep 19 2024

.KEY MESSAGES...

- Main period of shower and thunderstorm activity with the first
  front would be after midnight through early Friday morning,
  though amounts remain on the low side.

- The front itself may trigger a few strong to locally severe
  storms Friday afternoon, favoring the area from about Decatur
  eastward.

- An extended period of rain chances is expected from Saturday
  night through Monday night, highest Sunday-Sunday night.
  Greatest chances for rainfall amounts over an inch are highest
  north of I-72 (60-70% chance).

&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 250 PM CDT Thu Sep 19 2024

Skies remain mostly sunny across the forecast area this afternoon,
with just a few high-based cumulus recently developing from
Decatur southward. Looking upstream, surface analysis showed the
cold front extending from west central Minnesota into south
central Kansas. Scattered convection should expand across Iowa
this evening as the front pushes further east, though morning
high-res models continue to advertise a weakening trend as the
showers/storms move southeast to the Illinois River valley.
Highest PoP`s remain focused west of I-55 and mainly in the
post-midnight period. By sunrise, what`s left of the rain should
generally be in areas near and southwest of Decatur, with the
forecast area expected to be dry by about 10 am.

Some scattered redevelopment is possible early Friday afternoon
ahead of the front, which by midday should be located near the
Illinois River. Latest SPC Day2 outlook maintains a level 1 severe
risk across east central Illinois. Parameters overall don`t look
especially impressive, but 1000-1500 J/kg of MLCAPE and peak
heating would favor a few strong to severe storms. Anything that
forms should quickly weaken toward sunset.

With the front seeing an arrival later in the day, temperatures in
the upper 80s will be common once again. However, more of a
moisture surge ahead of it will result in a heat index in the
low-mid 90s ahead of the front.

Geelhart


.LONG TERM...  (Saturday through Next Thursday)
Issued at 250 PM CDT Thu Sep 19 2024

Prominent upper low seen on water vapor imagery south of San
Francisco this afternoon is still progged to reach the Desert
Southwest early this weekend, before tracking northeast. With the
persistent upper level high over Texas flattening but not
completely going away, a front will lay out from the Texas
panhandle into the western Great Lakes region Saturday night.
Little movement in this boundary is expected until Tuesday, when
the low has finally opened up and the associated wave gets kicked
eastward as a deepening trough digs into the upper Mississippi
Valley. Latest NBM highlights about a 60-70% chance of greater
than 1 inch of rain north of I-72 during this period, with only a
20-30% chance south of I-70. Rain chances will be highest Sunday
and Sunday night (60-80% range). However, showers will remain in
the forecast through Monday night, finally fading on Tuesday with
the front pushing east.

Getting toward midweek, the models build a rex block pattern over
the Rockies and nudge it eastward toward Thursday. However, both
the GFS and European models close off a sprawling upper low over
the Great Lakes or mid-Atlantic states, which persists into late
week. This would put us in the position of being too far west for
any significant wraparound showers from the low, but too far east
for the heat building underneath the ridge. Thus, midweek
temperatures in the mid 70s would be more common. Blended guidance
does have some silent 20 PoP`s for Wednesday and Thursday right
now, but dry conditions should prevail.

Geelhart

&&

.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.
&&

$$