Expires:No;;034741
FXUS63 KILX 111838
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
138 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 18z TAFs through 18z Sunday Afternoon)
Issued at 1233 PM CDT Sat May 11 2024

VFR conditions will continue through the forecast period, with
diurnal cumulus, along with northwest winds gusting to 25 kt, 
diminishing after sunset this evening. Tomorrow, low level winds
will turn to southerly, gusting 15-20 kt near the end of the
forecast period.

Bumgardner

&&

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

$$