553
FXUS63 KILX 090507
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1207 AM CDT Sun Jun 9 2024

.KEY MESSAGES...

- A low chance (25% probability or less) that isolated
  thunderstorms develop this evening between 4pm - 9pm; severe
  weather and/or flooding not anticipated.

- Heat stress returns Thursday and Friday as Wet Bulb Globe
  Temperatures (WBGT) climb to 82F-84F; risk level 4 of 5.


&&

.DISCUSSION...
Issued at 1227 PM CDT Sat Jun 8 2024

Afternoon water vapor imagery depicts an upper-level low
positioned over Lake Superior with multiple shortwaves digging
along its southern periphery. These features will ultimately help
drive a surface cold front through central Illinois this evening.
While large-scale forcing is better to the north and south of the
area, there does appear to be enough moisture convergence along
the front to support scattered showers, at least.

The CAPE/Shear parameter space is somewhat underwhelming this
evening, such that the severe storm risk is low, but there is
enough support within CAMs (i.e. HRRR, RAP) to suggest we could
see a feisty updraft or two anchored to the front where a few
uncapped parcels (SBCAPE 1500 J/kg) coexist with 40 kts of
effective- layer shear. While narrow CAPE profiles and straight
hodographs should preclude a large hail and tornado risk, the
threat for damaging wind is a little better. But again, coverage
will be sparse since the more favorable forcing is displaced away
from our region.

Cooler and more stable air will build into the region Sunday
through Monday as an upper ridge and its associated area of
surface high pressure keep the pattern quiet. Overnight
temperatures Sunday night and Monday night will be on the chilly
side, with deterministic NBM guidance offering lows in the upper
40s in some spots.

Low-impact weather will persist through the middle of next week,
but an influx of heat and humidity is anticipated across the Mid-
Mississippi Valley beneath increasing mid-level heights. Recent
NBM guidance supports afternoon highs near 90 degF for both
Thursday and Friday ahead of the next frontal system. Wet Bulb
Globe Temperatures (WBGT), or simply the heat stress index, are
forecast to be 82-84 degF which equates to a level 4 of 5 heat
risk.

Convective chances for next week are muted among blended and
ensemble guidance, with PoPs generally below 20%. While we do
appear to be entering a drier period, `tis the season for ridge-
rider convection. And, with a series of diffuse synoptic fronts
dropping through the area next week, it would not be wise for us
to advertise a prolonged dry stretch.


MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1207 AM CDT Sun Jun 9 2024

A cold front has pushed south through all TAF sites late this
evening with some pockets of 2-4k ft stratus behind it leading to
brief MVFR ceilings. Winds are generally out of the north and will
gradually back to northwest by later this morning. Wind speeds ramp
up between 16-18Z with occasional gusts of 20-25 kts expected
through the afternoon. Otherwise, mid to high clouds will stream
across the area through the period.

NMA

&&

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

$$