556
FXUS63 KILX 110054
AFDILX

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

.KEY MESSAGES...

- In the Monday to Wednesday timeframe, there is a 30-40% chance
  for more than an inch of rainfall south of I-72, with decreasing
  chances further north. This rain will add runoff to area rivers
  already running high, increasing the risk for flooding along
  riverbanks and adjacent low-lying areas.

&&

.UPDATE...
Issued at 755 PM CDT Fri May 10 2024

In a flashback to the solar eclipse, the sky cover forecast is
heavily scrutinized this evening. Extreme geomagnetic storm
conditions (G5 as of 7 pm) would highly favor appearances of the
Northern Lights tonight, but there will be some clouds to deal
with.

Latest satellite imagery shows the earlier diurnal clouds over
eastern Illinois fading off some, though an extensive area of
cirrus was present north of I-72. Upstream, a band of mid level
clouds, ahead of the upper trough over the upper Mississippi
Valley, extends from eastern Wisconsin to northern Missouri.
Timing tools bring this band into areas northwest of the Illinois
River toward 10-11 pm and the I-55 corridor around midnight. A
band of scattered showers accompanies these clouds, though there
will only be about a 2 hour window for rain chances at any given
location. With the higher cloud bases, amounts should not be of
consequence. Some quick clearing is expected behind this cloud
band. Thus, most favorable weather periods for seeing Northern
Lights are broken up as such:

* West of Illinois River -- 1 am to 4 am
* I-55 corridor -- Sunset through about 11 pm, and after 3 am
* South of I-72 -- This evening, and again after 3 am west of I-55
* East central Illinois -- This evening, then deteriorating after
  midnight
* South of I-70 -- Sunset through about 3 am

Note that Northern Lights appearances can be finicky and may not
be visible in these entire periods.

Geelhart

&&

.DISCUSSION...
Issued at 140 PM CDT Fri May 10 2024

Visible satellite shows a sea of cumulus percolating across
central Illinois, driven by surface heating and destined to perish
after its loss at sunset. Deterministic models are in agreement
500mb heights will continue their sharp rise and winds back
across the region through the evening as a shortwave ridge briefly
builds in, favoring a stable mid level atmosphere. Nevertheless,
given breaks of sunshine favoring efficient radiational warming,
mixing will be deep and surface based instability rather portly
which could lead to a brief shower/sprinkle or two, though
coverage should remain less than 15%. The better chance (> 30%
north of a Macomb to Paris line) for showers will arrive tonight
as a fast-moving, compact trough clips the northeast portion of
our area with cooling temps aloft leading to elevated instability
and low level shear increases along a trailing cold front. Between
11pm (NW of the IL River) and 4am (E of I-57), stamps on SPC`s
HREF page show various CAMs bring a narrow ribbon of
reflectivities across the area along that front, with the highest
values (and greatest chance for something to actually reach the
surface through a relatively dry atmosphere) north of I-74, where
40-60% of membership depicts measurable precip.

Behind that departing trough, another ridge will build gradually in
its wake through the weekend to foster dry and gradually warming
conditions. By Sunday, we`ll see a return to above normal temps
(normal high in Lincoln is 74 degF), though mid to high clouds will
be on the increase ahead of the next system - a cut off low
meandering our way from the Great Plains. While that feature doesn`t
properly arrive until Tuesday, moisture advection ahead of it could
lead to rain activity by late Sunday night, though this will be
delayed at least a little by the dry low level airmass in place at
that time.

Depending on the exact track of that low (and when the next system
approaches behind it), precip chances could linger through Wednesday
and possibly even into Thursday, particularly south of I-72 given
the closer proximity of the surface low`s center which the ensemble
mean tracks between Springfield, MO and Louisville, KY from Monday
night to Thursday morning. NBM suggests the same areas (south of I-
72) will have a 30-40% chance for seeing more than 1 inch of rain
for the 48-hour period ending at 12z (7am CDT) Wednesday, which will
increase run-off into rivers already running high and hence flooding
potential along riverbanks.

Bumgardner

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 606 PM CDT Fri May 10 2024

VFR conditions to prevail the next 24 hours. Main feature of note
will be a front that sweeps across Illinois in the 04-09Z time
frame. This will bring a period of ceilings around 7,000 feet, as
well as scattered showers. Winds swing around to the northwest
behind the front, and sustained winds of 15-20 knots are expected
by midday Saturday, especially near KBMI/KCMI.

Geelhart

&&

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

$$