102
FXUS63 KILX 292300
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
600 PM CDT Mon Apr 29 2024

.KEY MESSAGES...

- Patchy fog will develop across much of central and southeast
  Illinois tonight...with a 30-50% chance of visibilities dropping
  below 1/4 mile in spots along/south of a Danville to Taylorville
  line.

- Above normal temperatures will prevail for the remainder of the
  week.

- The next significant chance for rain will arrive Thursday into
  Friday, followed by slightly cooler conditions by next weekend.

&&

.SHORT TERM...(Tonight through Tuesday)
Issued at 302 PM CDT Mon Apr 29 2024

19z/2pm surface analysis shows a weak cold front pushing slowly
eastward through the Illinois River Valley. Low clouds persist
east of the front, with persistent showers impacting locations
along/southeast of a Paris to Effingham line. Showers will
continue across the far E/SE KILX CWA through early evening before
gradually pushing further eastward into Indiana. The cold front
will eventually exit the CWA as well, but this will not occur
until late evening. While the upstream airmass behind the boundary
is considerably drier with current dewpoints only in the 40s
across Iowa/far western Illinois, this airmass will only gradually
trickle eastward after FROPA. As a result, there will be quite a
bit of lingering boundary layer moisture. Given clearing skies and
light winds, patchy fog looks to be a good bet...especially across
the E/SE where the drier air will be slowest to arrive.
HRRR/RAP/GFSLAMP all suggest the potential for locally dense fog
in a few spots across this area. In addition, the 12z Apr 29 HREF
indicates a 30-50% chance of visibilities dropping below 1/4 mile
along/south of a Danville to Taylorville line. Am not confident
enough to issue a Dense Fog Advisory at this time, but have
included areas of fog across the E/SE accordingly. After any early
morning fog dissipates, Tuesday looks to be a mostly sunny and
pleasant spring day with high temperatures topping out in the
middle to upper 70s.

Barnes

.LONG TERM...(Wednesday through Next Monday)
Issued at 302 PM CDT Mon Apr 29 2024

A short-wave trough is progged to eject northeastward out of the
Rockies on Tuesday, then track into the Upper Midwest by Wednesday.
While the strongest lift associated with this feature will remain
well northwest of Illinois, it will drag a weak cold front into
north-central Illinois by early Wednesday. Scattered showers and
perhaps a thunderstorm will precede the front Tuesday night with
any showers dissipating before daybreak Wednesday. Despite the
lingering weak boundary in the area, short-wave ridging aloft in
the wake of the system will ensure a warm/dry day on Wednesday
with high temperatures topping out in the upper 70s/lower 80s.

A more significant short-wave will cross the Rockies into the
Plains by Thursday...and this system will bring the next
significant chance of rain to central Illinois by the end of the
week. 12z models continue to be too fast with the eastward
progression of this amplifying system, so rain chances Wednesday
night/Thursday morning will likely be removed as models come into
better focus. The main window for the strongest forcing/deepest
moisture continues to look like Thursday afternoon through Friday
morning when GFS precipitable water values increase to 1.50-1.75.
Have therefore carried likely to categorical PoPs during that
timeframe.

Once the late week system passes, slightly cooler/drier weather
can be expected Friday night into Saturday before another short-
wave trough approaches by Sunday.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 600 PM CDT Mon Apr 29 2024

Clearing line has spread east across the central IL terminals and
is located just west of KCMI early this evening. Some cirrus
streaming northeast will affect mainly eastern IL overnight,
otherwise mostly clear skies through Tuesday afternoon. Cannot
rule out some patchy MVFR fog toward sunrise, but with drier air
advecting in from the west kept mention out of the TAFs for now.

25

&&

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

$$