Severe Thunderstorm Warning 189, NWS Lincoln, IL

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1239 PM CDT Mon Jul 17 2023

.SYNOPSIS...
Issued at 1236 PM CDT Mon Jul 17 2023

Scattered thunderstorms will develop ahead of a slow-moving cold
front this afternoon. A few of the storms could become strong
along and south of I-70...producing gusty winds and hail. High
temperatures will range from the upper 70s northwest of the
Illinois River around Galesburg...to the middle 80s south of I-70.

&&

.SHORT TERM... (Today and Tonight)
Issued at 321 AM CDT Mon Jul 17 2023

A large cluster of convection has developed across eastern
Missouri into southern Illinois early this morning. While the main
area of storms is dropping southeastward and will not impact the
KILX CWA, additional scattered cells are forming N/NE of the Saint
Louis metro and some of these are expected to track into locations
south of I-70 over the next couple of hours. Further north, the
remainder of central Illinois will remain dry until a cold front
currently extending from near Milwaukee to just north of Kansas
City settles southward and triggers widely scattered convection
later this morning into the afternoon. As has been noted by the
past several model runs, it appears storms will become most
numerous south of I-72 this afternoon. The pre-frontal environment
will become moderately unstable with HREF ensemble mean CAPEs
reaching 2000-2500J/kg. In addition, 0-6km bulk shear values will
increase to around 40kt. These parameters will likely support a
few strong storms capable of producing gusty winds and marginally
severe hail...especially along/south of I-70 from mid-afternoon
into the early evening. After a few lingering showers/storms
across the SE CWA this evening, cooler/drier conditions will
filter southward overnight. High temperatures today will mostly be
in the lower to middle 80s, while lows tonight dip into the upper
50s and lower 60s.

Barnes

.LONG TERM... (Tuesday through Sunday)
Issued at 321 AM CDT Mon Jul 17 2023

The next chance for rain will materialize Tuesday/Tuesday night
as baroclinic zone extending from northeast Kansas into western
Kentucky energizes. Scattered showers/storms will develop along
and north of the boundary during the day Tuesday: however, a more
significant rain event will likely unfold Tuesday night. NAM shows
a vigorous 50kt 850mb nocturnal jet oriented from Oklahoma to
southern Illinois, which will help transport copious amounts of
moisture northward. Precipitable water values reach 2.50 south of
I-70 overnight, which would be record values for the date. Given
favorable synoptic set-up and impressive moisture flow, have
focused likely to categorical PoPs along/south of a Rushville...to
Decatur...to Mattoon line Tuesday night. Current projections suggest
rainfall across this area will range from 1 to 2 inches, which
could pose a flash flooding risk. There is still some uncertainty
as to exactly where the heavy rainfall axis will set up: however,
NAM/GFS/ECMWF all favor the S/SE CWA. The GEM remains the odd
model out with a much further north solution and has been
disregarded for this forecast package.

After morning showers/storms across the E/SE push into the Ohio
River Valley, mostly dry conditions are expected Wednesday
afternoon and night. Another cold front will drop southward
through central Illinois on Thursday, possibly triggering a few
more thunderstorms. After that, drier weather will arrive by the
end of the week as high pressure takes control.

Barnes

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1239 PM CDT Mon Jul 17 2023

Wildfire smoke will remain present for the time being, but near
surface smoke will start to clear out by later tonight. Visbys have
already shown signs of improvement this morning with all sites
reporting 6SM or higher as of 17Z. Scattered thunderstorms over west-
central IL early this afternoon will spread east/southeast along a
cold front, possibly clipping TAF sites near/south of I-72 (KSPI,
KDEC, KCMI). West-northwest winds below 12 kts will become light
overnight, gradually veering to a southerly direction by midday
Tuesday.

NMA

&&

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

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