061
FXUS63 KILX 171738
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1238 PM CDT Mon Jun 17 2024

.KEY MESSAGES...

- An extended period of hot and humid weather will prevail across
  central and southeast IL through Saturday. Heat index values
  will peak at or above 100 degrees this afternoon, upper 90s to
  around 100 degrees Tuesday afternoon and 95 to 100 during the
  afternoon hours Wednesday through Saturday.

- Isolated showers and thunderstorms are possible from this
  afternoon through early Tuesday evening, especially in eastern
  IL. The risk of severe storms is low, though lightning hazards
  and isolated/brief heavy rains exist along with gusty winds.

&&

.DISCUSSION...
Issued at 345 AM CDT Mon Jun 17 2024

Predawn surface analysis shows 996 mb low pressure over central CO
with a frontal boundary extending ne across central Nebraska, nw
Iowa, southeast MN and nw WI. A warm front had pushed well east of
IL over eastern lower MI, western Ohio and far eastern KY. A
tropical airmass covered IL with warm temps in the mid to upper
70s and muggy dewpoints in the upper 60s and lower 70s. Clear to
mostly clear skies prevailed over central IL/CWA while clouds were
streaming ne over southeast MO bootheel into far southern/se IL,
central/western KY and far southern IN. Small MCS was over
south central and southeast lower MI that brought severe winds to
parts of northern IL Sunday afternoon. Larger MCS complex was over
central and northern Nebraska, southeastern SD, sw MN and far nw
Iowa.

Breezy southerly flow prevails today over central/se IL with 1025
mb high pressure anchored off the mid Atlantic Coast. Deeper
tropical moisture plume to advect northward over central and
southeast IL during this afternoon and evening with PW values of
1.5-2 inches. Not much lifting mechanisms around today aside from
diurnal heating of tropical airmass that will develop isolated
showers and thunderstorms during this afternoon and continue
slight chances tonight mainly in eastern/se IL. Best chance of
convection today appears to be in southeast IL by late afternoon
where deeper moisture will arrive sooner. Developing cumulus
clouds late morning/midday to give partly sunny skies this
afternoon with more sunshine nw of the IL river. Hot and humid
today with highs in the mid 90s and dewpoints in the lower 70s to
give afternoon heat indices of 99-104F. Breezy south winds to gust
20-25 mph by afternoon especially nw of I-70. Sensitive and
vulnerable groups should take the necessary precautions to avoid
the potentially hazardous temperatures. This is shy of heat
advisory criteria of 105F but will issue another Special Weather
Statement to address the extended heat wave expected through
Saturday. Mild lows tonight in the mid 70s over much of the area.

A 594 dm 500 mb high in the southeast states this morning to
strengthen to near 600 dm on Wed as it centers near NJ and
southern New England shore and ridging back into the mid MS river
valley. This will continue the hot and humid weather pattern much
of this week as it holds in place through Saturday and even builds
upper level heights over IL late this week.

Isolated convection again on Tue especially in afternoon and
early evening hours. Hot and humid Tue with highs in the lower
90s, with areas from IL river nw approaching 95F where more
sunshine possible again. Heat indices peak in the upper 90s to
around 100F Tue afternoon, highest over the IL river valley in nw
CWA. Lows Tue night in the mid 70s.

The main synoptic frontal boundary to be over central Iowa and
central WI Wed with isolated convection possible Wed afternoon nw
of the IL river. Can not rule out an isolated shower/thunderstorms
Wed afternoon in eastern IL but currently pops are less than 20%
on Wed for areas east of the IL river. Highs Wed in the lower 90s
with Peoria approaching 95F again. Heat Indices Wed afternoon in
the mid to upper 90s. Sensitive and vulnerable groups should
especially take the necessary precautions to avoid the potentially
hazardous temperatures.

As subtropical ridge strengthens late this work week, temperatures
get back into the mid 90s for highs Thursday-Saturday with
afternoon heat indices in the upper 90s to near 100F. Will need to
watch for possible heat advisory criteria if we get 4 or more
consecutive days of heat indices of 100-105F. None the less, a 7
day heat wave in mid June is unusual for this early in the season.
Sensitive and vulnerable groups should especially take the
necessary precautions to avoid the potentially hazardous
temperatures. Isolated convection possible mainly during afternoon
and early evening hours north of Peoria Thu and Fri and northern
CWA Sat afternoon. Extended models continue to show upper level
trof digging into the upper Midwest/Great Lakes during this
weekend with increasing chances of showers/thunderstorms from
north to south Sat night and Sunday along with temps cooling a bit
into the upper 80s to around 90F early next week (Sun/Mon).

The Climate Prediction Center (CPC) 8-14 Day outlook for June
24-30th continues to favor above normal temperatures across all
but the Pacific Northwest in lower 48 with IL having 50-60% chance
of above normal temperatures.


07

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Jun 17 2024

VFR conditions will prevail through the entire 18z TAF period.
Isolated convection will develop this afternoon...primarily
along/east of the I-57 corridor. Confidence of a storm impacting a
terminal is very low, so have opted not to include thunder at
this time. After a lull in precip chances after sunset, several
models suggest isolated convection once again firing along/east of
I-57 toward dawn Tuesday. Have carried VCSH at both KDEC and KCMI
to account for this possibility. Winds will initially be SW at
10-15kt with gusts of around 20kt. While the gusts will diminish
toward sunset, sustained SW winds of 10-15kt will continue through
the night. Gusts of 20kt or greater will resume by mid-morning
Tuesday.

Barnes

&&

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

$$