299
FXUS63 KILX 101758
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1258 PM CDT Fri May 10 2024

.KEY MESSAGES...

- In the Monday-Tuesday timeframe, there is a 20-30% chance of
  greater than 0.75" of rainfall in 24 hours. Should this occur,
  one impact would be additional runoff into area rivers already
  running high.

&&

.UPDATE...
Issued at 957 AM CDT Fri May 10 2024

Mid level water vapor satellite imagery shows an upper
trough sinking southeast across the Ohio Valley and towards the
Appalachians this morning. As a shortwave ridge builds into the
Prairie State in its wake, mid levels will dry and become
increasingly stable this afternoon, though steep lapse rates off
the surface will provide a shallow layer of stout instability
favoring continued cu development (HREF probs for low clouds
remain 40-60% through the evening). Can`t rule out a couple
sprinkles with this activity, though most, if not all, precip
falling from the more robust towering cu should evaporate through
the dry "inverted V" below the LFC. A better chance (> 30% north
of a Macomb to Paris line) for showers will arrive tonight as a
compact upper trough and associated trailing cold front pass
through the region.

Bumgardner

&&

.DISCUSSION...
Issued at 237 AM CDT Fri May 10 2024

An upper level wave is diving southeast across IL this morning.
There have been a few showers associated with this wave as it
traversed IA and moved into northwest IL, but the latest high res
models indicate these showers won`t make it deep into central IL.

We will see brief upper ridging this afternoon before another
upper wave dives southeast into IL tonight in the northwest flow
aloft. An associated surface low will dive southeast across the
Great Lakes with an accompanying cold front passing through IL
Friday night. We`ll see a chance for showers with this system
Friday night, but instability looks rather weak. Believe thunder
chances will be rather slim as MUCAPEs look to be less than 100
J/kg according to the HREF mean.

Expect benign northwesterly flow aloft for the weekend. We`ll have
breezy northwest winds on Saturday with a surface ridge of high
pressure moving through the area Saturday night. By Sunday night,
an upper low will be passing to the east across Ontario with a
southern stream upper low approaching to the southwest.
Precipitation chances increase across IL from this southern
system Sunday night, with some moderate chances for thunder
expected as MUCAPEs are as high as 500 J/kg in west-central IL.

The upper low will slowly make its way east across the mid MS
River Valley on Mon/Tue and the track will play a key role in how
far north the rain extends. Showers with embedded thunderstorms
are expected for the start to the week, with the southern half of
IL having the best chance for measurable rainfall. Right now, the
rainfall ensemble mean for Mon-Tue ranges from around 0.25" in
Galesburg to 0.75" in Lawrenceville. Models also have a 20-30%
chance for 0.75" of rain in 24 hrs in our southern zones, around
I-72 and south, which could add some additional runoff to area
rivers that are already running high.

Sometime in the Wed-Thu timeframe, we`ll likely see an upper
ridge move into the area once again, providing a break from the
precip for at least part of the period. There are model
differences in the timing of this ridge, but sometime on Thu or
Friday, another upper wave is expected to bring showers and storms
back to the region. Stay tuned for updates to this late week
system as the picture becomes clearer with subsequent model runs.

Knutsvig

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1254 PM CDT Fri May 10 2024

Aside from marginal MVFR ceilings around BMI (which should be
lifting over the next hour or two), VFR conditions should be
predominant throughout the forecast period, barring a brief vis
drop with scattered showers overnight. Low VFR ceilings should
break up behind the cold front, when a pronounced wind shift (from
southwest to northwest) will also occur. Northwest winds will
increase, gusting frequently over 20 kt, by mid to late Saturday
morning when surface heating aids in mixing.

Bumgardner

&&

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

$$