853
FXUS63 KILX 021453
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
953 AM CDT Thu May 2 2024

.KEY MESSAGES...

- Level 1 (marginal) risk of severe weather continues from mid
  afternoon into mid evening from McLean, DeWitt, Logan and
  Sangamon counties west.

- Warm, more humid and breezy today with highs in the mid 80s,
  except closer to 80F by Galesburg. This will be the warmest day
  since Apr 14th over much of central IL.

- Numerous chances for showers and thunderstorms through
  Wednesday, though brief drier periods expected Friday night and
  Saturday morning and overnight Saturday night and Sunday
  morning.

&&

.UPDATE...
Issued at 952 AM CDT Thu May 2 2024

Earlier convection has lifted northeast into northern Indiana,
with a large part of the forecast area now mostly sunny. A large
band of showers and embedded thunderstorms extends from western
Wisconsin to south of Kansas City, though cloud tops have steadily
been warming with this activity. Early look at the morning high-
res models has slowed some of the eastward progression of this
activity, though a few still pop up a few showers/storms east of
I-57 before late afternoon. However, they`re in better agreement
with an uptick in activity west of the Illinois River before mid
afternoon. Afternoon PoP`s above 60% are generally limited to this
area, with scattered showers/storms elsewhere, though areas south
of I-70 may stay dry the entire time.

Geelhart

&&

.DISCUSSION...
Issued at 400 AM CDT Thu May 2 2024

Predawn surface map shows 1002 mb low pressure over southeast
Nebraska with a warm front extending eastward over central MO and
into sw IL. Very small/isolated shower and thunderstorm over
eastern Shelby county and nw Macon county lifting ne ahead of warm
front and along an old outflow boundary originating from
convection that was near St Louis area Wed evening. Temps were in
the mid 50s to lower 60s over central IL with mid 60s along and
south of highway 50. Drier dewpoints in the low to mid 40s from
Macomb to Rantoul north while more moist dewpoints in the lower
60s over Clay, Richland and Lawrence counties.

Latest CAMs show warm front lifting northward over central IL
during this morning and only isolated convection possible as it
moves through with much of morning being dry over the area. Breezy
south winds by afternoon to bring warmer highs in the mid 80s over
much of area, with Galesburg closer to 80F. Getting more humid too
as dewpoints rise into the low to mid 60s across the area by
midday and afternoon. Air mass gets more unstable during this
afternoon as CAPES peak from 1000-1500 j/kg by mid afternoon with
wind shear values of 15-25 kts, highest over western CWA. SPC day1
outlook has marginal risk of severe storms from McLean, DeWitt,
Logan and Sangamon counties west from mid to late afternoon into
mid evening where wind shear values will be higher than in
eastern IL. Isolated convection early this afternoon to become
more scattered over the IL river valley by late afternoon. Higher
chance of showers and thunderstorms spreads eastward during
tonight as cold front moves thru central IL overnight. Lows
overnight mostly in the lower 60s over central IL, but range from
upper 50s nw of the IL river to near 65F se of I-70.

Best chances of convection will be over eastern IL on Friday
especially Fri morning. Models have trended faster with pushing
convection eastward during Friday afternoon and much of CWA should
be dry by sunset Friday with just isolated showers near the Wabash
river early Fri evening. We are not in any outlook for severe wx
on Friday as wind shear and instability is weak. Cooler highs
Friday in the low to mid 70s and becoming partly to mostly sunny
over the IL river valley during Fri afternoon as drier air moves
in behind the cold front.

A brief period of dry weather expected over most of area Friday
night and Sat morning. Then a disturbances ejects eastward from
the central plains and returns chance of showers and thunderstorms
Sat afternoon/evening. A bit more instability develops Saturday
afternoon especially sw CWA with CAPES around 500 j/kg and still
rather weak wind shear values 15-25 kts. A few stronger storms
possible from mid Sat afternoon into early Sat evening mainly sw
CWA. Highs Saturday in the upper 70s in central IL and near 80F in
southeast IL. More humid again as dewpoints elevate into the lower
60s as day progresses.

Drier conditions expected overnight Sat night and Sunday morning
though can not completed rule out an isolated shower or
thunderstorm south of I-72. Diurnal heating could develop isolated
to scattered convection late Sunday afternoon especially southern
CWA, then convection chances increase northward during Sunday
night into Monday as short wave moves into the mid MS river
valley. Highs Sunday in the low to mid 70s in central IL and upper
70s southeast of I-70. CAPES increase to 500-800 j/kg Monday
afternoon with wind shear values around 25 kts, so a few stronger
thunderstorms possible Mon afternoon.

Stronger mid/upper level trof develops over the Rockies Sunday and
ejects strong low pressure system into western ND by Tue morning.
Models agree on a swath of convection moving into IL later Monday
night and Tuesday. CSU machine learning and CIPS analogs shows
risk of severe storm on Tuesday into Wednesday over IL and will
need to monitor this period. Highs Monday in the upper 70s and
80-85F Tue/Wed.

The Climate Prediction Center (CPC) 6-10 Day outlook for May
7-11th shows 60-70% chance of above normal temperatures over
central IL with 40-45% chance of above normal precipitation. The
8-14 day outlook for May 9-15th also trending toward wetter
conditions. So the mild and active wx pattern looks to continue
next two weeks.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 555 AM CDT Thu May 2 2024

A warm front will lift north across central IL during this
morning, with isolated showers and possibly a thunderstorm
occuring. Current radar shows isolated showers from BMI and DEC
eastward and lifting ne. Have VCSH to account for this next few
hours. As warm front lifts north later this morning, East to ESE
winds at 7-12 kts to turn south and increase to around 15 kts with
gusts 23-28 kts by late morning and continue through the
afternoon. Isolated convection to develop during mid and late
afternoon with better chances of convection at PIA by late
afternoon. MVFR conditions are possible as band of showers and
scattered thunderstorms shift eastward across central IL during
this evening, with MVFR ceilings likely overnight even as showers
diminish from the west. SSW winds to diminish to around 10 kts
during this evening and shift west to NW during overnight at 5-10
kts.

07

&&

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

$$