160
FXUS63 KILX 112311
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
611 PM CDT Sat May 11 2024

.KEY MESSAGES...

- In the Monday to Tuesday timeframe, there is a 40-60% chance
  for more than an inch of rainfall south of I-74. This rain will
  contribute to area rivers and streams already running high,
  increasing the risk for localized inundation near riverbanks.
  This could perhaps also further delay planting and inhibit
  germination of agricultural seedlings.

&&

.DISCUSSION...
Issued at 137 PM CDT Sat May 11 2024

A beautiful and seasonably breezy spring afternoon continues across
central and southeast Illinois, offering a reprieve from the
excessive rainfall which has thus far delayed planting and
germination for many. Those traveling on rural stretches of
roadway should be aware, though, that in spots the topmost layer
of soil may be dry enough to get whisked up by these gusty
northwest winds and locally reduce visibility, as a few have
reported. Subsidence associated with the ridge expanding into the
region from the west has suppressed even fair weather cu
development, but the few that formed should diminish with
insolation loss in several hours, and with winds also dropping off
tonight lows will likely fall into the upper 40s in many
locations. The dry airmass, however, will also foster sharp
warming tomorrow, particularly when any low level moisture
attempting to creep up from the south gets mixed out (dewpoints
drop several degrees) during the afternoon as the 12z HRRR would
suggest. If the HRRR is right - and it has already this year done
a good job of handling these type of situations several times -
temps will climb into the low to mid 80s across much of the ILX
CWA tomorrow afternoon, warmest north of the I-70 corridor. One
thing to watch: Virtually all of the CAMs from the 12z HREF depict
at least isolated convection to our north and west, and a couple
of them even paint some simulated reflectivities in our area north
of I-72, tomorrow evening when the same ensemble`s mean MUCAPE
values exceed 750 J/kg northwest of the IL River. Given low levels
will be on the dry side, it would take a fairly hefty shower to
reach the sfc, but LREF does have 25+% chances for measurable
precip northwest of the IL River and 10+% north of I-72.

Dewpoints will increase again tomorrow evening, into the upper 50s
per HREF mean, given (1) southerly flow and (2) compression of low
level moisture with diurnal decoupling. Rain chances rise sharply on
Monday, as the cut off low (and associated moisture and forcing for
ascent) drifting our way from the Plains approaches. The LREF mean
wind field at 850mb suggested the low would track from roughly
Springfield, MO to Louisville, KY yesterday, but today that track
has shifted north to a roughly Columbia, MO to Cincinnati, OH
line, which suggests more rain for us. South of I-74, NBM would
suggest a 40-60% chance for more than an inch of QPF by the time
this system departs and its faucet finally turns off across our
area late Tuesday. This would increase runoff into rivers which
have been running a bit on the high side recently - a couple
points along the IL still in flood - perhaps contributing to some
localized inundation along creeks, streams, and rivers, and
perhaps further delaying planting or inhibiting germination of
crop seedlings.

The deterministic models suggest a shortwave ridge will build in the
wake of this low, but differ on how long we`ll be dry before the
arrival of the next system - the track of which is also nebulous at
this point. Unfortunately, the dry portion of the work week (Tuesday
night through Wednesday is the most likely rain-free time period)
could be quite short with NBM bringing rain chances back up to 40+%
by Wednesday night-Thursday morning. Behind the first system,
lingering cloud cover and cool advection will make Tuesday the
coolest day with forecast highs in the mid to upper 60s north of I-
70, with a gradual warming trend (though increasing model spread,
given uncertainty in storm track) the remainder of the week.

Bumgardner

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 611 PM CDT Sat May 11 2024

VFR conditions expected the next 24 hours, with mainly a few
clouds around 10kft at times. Gusty northwest winds have been
tailing off recently, and should be about 5-7 knots by sunset
(01Z). Expect a trend toward the west/southwest overnight with
winds picking back up to 10-15 knots by mid morning Sunday.

Geelhart

&&

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

$$