479
FXUS63 KILX 290123
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
823 PM CDT Tue May 28 2024

.KEY MESSAGES...

- Isolated showers and breezy northwest winds will continue to
  diminish this evening.

- Fair weather and overall quiet conditions are expected during
  the latter half of the week. A more unsettled pattern returns
  this weekend into next week.

&&

.UPDATE...
Issued at 823 PM CDT Tue May 28 2024

A shortwave that promoted scattered thunderstorms centered over
northeast IL this evening has passed into Indiana, with shower and
thunderstorm activity diminishing in the subsident region behind
the shortwave. Diurnal heating is also fading with the setting
sun, and favors diminishing activity as well. With mesoanalysis
showing around 100 J/kg MLCAPE and trending downward,
thunderstorms have been removed from the forecast the remainder of
the evening. Winds look to rapidly decrease after sunset as well.
As even cooler air spreads into the area in northwest flow, lows
are forecast around 50 degrees tonight.

37

&&

.DISCUSSION...
Issued at 204 PM CDT Tue May 28 2024

This afternoon, long wave trough is in place over the Great Lakes
with northwest flow over central Illinois. This is driving steep
low to mid level lapse rates while a shortwave trough digging
across southern WI/northern IL is allowing a few storms to
develop. Some of this activity will build south into portions of
central Illinois this afternoon, but coverage should remain
isolated to widely scattered (20 to 30 percent), and chances will
fade with loss of daytime heating this evening. Severe storms are
not anticipated in part due to weak instability (dew points in
the lower 50s contributing to MLCAPE values of around 300-400
J/kg. That said, isolated stronger wind gusts may still be
possible given the steep lapse rates down low.

High pressure over the northern Great Plains and Canadian Prairies
today will overspread the Midwest through the latter half of the
week with the surface ridge axis passing over central Illinois
Thursday. Temperatures will undergo a very gradual warming trend
during this time frame with low 70s in the forecast for Wednesday
and upper 70s by Friday. The air mass will be quite dry with dew
points mixing down into the 40s for portions of the area, possibly
dipping into the 30s in spots Thursday. The dry air will help
keep skies clear and allow large diurnal swings with overnight
lows generally in the upper 40s to lower 50s.

Upper pattern will transition to more zonal by this weekend and
continue into the first part of next week with several low
amplitude waves bringing periodic chances for showers and a few
storms. Surface ridge will shift to the mid Atlantic coast
Saturday allowing return flow into the Midwest. The warming trend
will continue into the weekend with widespread 80s back in the
forecast for Sunday and mid to upper 80s early next week. Gulf
moisture also returns to the region with dew points back into the
60s and pushing 70 by early next week. With the jet stream
migrating well to our north, and at least initially modest dew
points, a severe weather threat does not seem apparent, but as
humidity builds early next week, some stronger storms could be
possible, especially during the afternoon and evening hours with
any waves that coincide with peak heating. Given the fast moving,
low amplitude shortwaves, timing details for precip chances
remains uncertain and the extended portion of the forecast is
broad-brushed with slight chance to chance PoPs due to model
timing differences.

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 642 PM CDT Tue May 28 2024

A shortwave trough will promote isolated to widely scattered
showers and thunderstorms until 02Z-03Z this evening. With low
coverage, have only placed 1-3 hours of VCTS in area TAFs and will
amend if any storms approach any terminals. Any storms could
produce brief MVFR cigs/vsbys and gusts as high as 40 kts.
Otherwise, VFR conditions expected for the upcoming 24 hours.
Winds NW 12-16 kts with gusts 22-28 kts until 02Z, becoming NW
5-10 kts overnight. Winds shifting to northerly by 16Z.

37

&&

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

$$