884
FXUS63 KILX 082353
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
653 PM CDT Sat Jun 8 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 00z TAFs through 00z Sunday Evening)
Issued at 653 PM CDT Sat Jun 8 2024

2330z/630pm satellite/radar mosaic shows a cold front from near
KPNT southwestward to KUIN. Winds ahead of the front will remain
westerly at both KDEC and KCMI for the next hour or two, then will
veer to NW and gust 15-20kt at all terminals through the evening.
As the front settles south of the I-70 corridor, winds will
further veer to N/NE and decrease to less than 10kt overnight.
Patches of low clouds at 1500-2500ft will accompany the front:
however, do not think MVFR ceilings will develop. Instead, a large
mass of mid/high clouds upstream across Iowa/northern Missouri
will stream eastward, resulting in mostly cloudy conditions
through much of the night. Clouds will tend to thin/dissipate by
Sunday morning, followed by just SCT high clouds through the day.
Winds will return to NW and once again gust 15-20kt at the I-74
terminals after 17z/18z Sun.

Barnes

&&

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

$$