763
FXUS63 KILX 190434
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1134 PM CDT Tue Jun 18 2024

.KEY MESSAGES...

- Seasonably hot and humid weather will prevail this week. The
  hottest conditions will arrive Friday into Saturday when air
  temperatures climb into the middle to upper 90s and heat index
  values peak at 100-105 degrees.

- Isolated thunderstorms will be possible from time to time over
  the next few days...with a better chance for thunderstorms
  arriving late Saturday into Sunday.

&&

.UPDATE...
Issued at 744 PM CDT Tue Jun 18 2024

Extensive cirrus shield remains in place across much of the
forecast area, though is more sporadic across the Illinois River
Valley. Rainfall has been next to non-existent so far, though a
few showers are lifting northward toward the I-70 corridor in
south central Illinois. Latest SPC mesoanalysis and HRRR forecast
sounding for Effingham show some capping in this area, plus
temperatures have been lower with the thicker cloud cover down
there. Currently thinking thunder potential is minimal due to the
weak instability, though a few showers remain possible in the
eastern CWA through evening as a weak upper disturbance lifts
northeast out of Missouri. Updated grids recently sent to reflect
these thoughts, plus the usual minor tweaks to incorporate latest
observational trends.

Geelhart

&&

.SHORT TERM...(Tonight through Wednesday Night)
Issued at 329 PM CDT Tue Jun 18 2024

Deep-layer moisture continues to flow northward from the western
Gulf of Mexico on the back side of a prominent upper high centered
over the Carolinas. The corresponding thick cirrus shield has kept
temperatures a few degrees cooler than they were yesterday and has
limited instability. 20z/3pm satellite imagery shows mostly cloudy
skies along/southeast of a Bloomington to Jacksonville line...with
sunny skies to the northwest. Cannot rule out a stray shower or
storm over the next couple of hours, but areal coverage will
remain scant. CAMs are suggesting isolated showers may re-develop
overnight across the Wabash River Valley...with showers/storms
becoming a bit more numerous further west across Iowa/Missouri in
association with a slowing cold front. Overall think most
locations will remain dry as low temperatures only drop into the
lower to middle 70s.

The cold front will become stationary from Iowa into southern
Wisconsin/northern Illinois on Wednesday. The strongest forcing
and thus the greatest areal coverage of diurnal convection will
remain focused just N/NW of the KILX CWA: however, the HRRR continues
to suggest widely scattered convection along a pre-frontal trough
perhaps as far south as I-72. Have therefore included slight
chance PoPs as far S/SE as a Springfield to Paris line...but have
focused better rain chances northwest of the Illinois River in
closer proximity to the boundary. Otherwise Wednesday will be a
hot and humid day with considerably less wind than has been
experienced lately. S/SW winds will generally remain in the
10-15mph range as afternoon highs top out in the lower to middle
90s.

Barnes

.LONG TERM...(Thursday through Next Tuesday)
Issued at 329 PM CDT Tue Jun 18 2024

As the upper high retrogrades westward and upper heights rise,
rain chances will decrease and temperatures will increase by the
end of the week. Latest guidance suggests the hottest period will
be Friday and Saturday when high temperatures climb into the
middle and perhaps upper 90s in a few spots. Corresponding heat
index values will peak at 100-105 degrees...just shy of Heat
Advisory Criteria.

As has been advertised by the models for the past several runs, a
significant short-wave trough is expected to traverse the country
and push a cold front into central Illinois this weekend. 12z Jun
18 GFS and ECMWF are in relatively good agreement, showing the
front arriving Saturday night. As a result, have included high
chance to likely PoPs (40-60%) Saturday night into Sunday. Once
the front departs, slightly cooler and less humid weather is
expected early next week as highs drop back into the upper 80s to
around 90 degrees by Monday.

Barnes

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1134 PM CDT Tue Jun 18 2024

VFR conditions expected through the period. Most of the ceilings
will be near KDEC/KCMI early in the period, but above 12kft;
diurnal cumulus may result in some brief ceilings near 4000 ft
around midday. South/southwest winds increase again Tuesday
morning, but should be at or below 10 knots, then settle down with
sunset.

Geelhart

&&

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

$$