057
FXUS63 KILX 160924
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
424 AM CDT Sun Jun 16 2024

.KEY MESSAGES...

- An extended heat wave is on tap this week across central and
  southeast IL, as hot and humid weather prevails. Heat index
  values will peak in the upper 90s to around 100 degrees this
  afternoon, and 100 to 105 degrees Monday afternoon. Afternoon
  heat indices are expected to be in the mid to upper 90s Tuesday
  through Saturday, and may reach back to around 100 late this
  week.

- Isolated thunderstorms are possible through Saturday, mainly
  during the afternoon and early evening hours. Severe weather
  risk will be low this work week over the area, though lightning
  hazards and gusty winds will exist.

&&

.DISCUSSION...
Issued at 400 AM CDT Sun Jun 16 2024

Predawn surface map shows 1024 mb high pressure over the
Adirondack and Catskill mountains of eastern NY state while a warm
front was over northeast MO and eastern Iowa and extending to 995
mb low pressure over north central SD. A few MCS`s with clusters
of showers and thunderstorms were over northeast KS, nw MO and
central Iowa into eastern MN and central/western WI. This
convection was lifting ne and mostly staying nw of IL, though
clipping far nw Jo Daviess county. Some cirrus clouds over the IL
river valley especially nw of the IL river, while rest of CWA is
clear. Temperatures at 330 am ranged from mid 60s near the Indiana
border/Wabash river to 70-75F from highway 51 west with our
larger cities of Peoria and Springfield at 75F.

The warm front is forecast to lift ne across central IL during
this morning with SSE winds shifting south to SSW with its passage
and a tropical air mass flowing into the area today. Strong upper
level high strengthens further over the southeast states and
ridging over the eastern parts of Ohio river valley and Great
Lakes. A few of the CAM members like the HRRR and HiResW- ARW
show isolated convection slipping nw parts of Knox and Stark
counties early this morning (between 12-14Z) and continued slight
chances there. The complex of storms over ne KS and nw MO lifts ne
and the HRRR shows some of this convection affecting areas from
the IL river nw late this afternoon and early evening. Introduced
slight chance of convection nw of IL river from 4-8 pm for this
possibility. Otherwise much of CWA will be dry today with breezy
south to SSW winds bringing in a hot and humid air mass for this
afternoon. Highs 92-96F today with dewpoints 65-70F giving peak
heat indices in the upper 90s to around 100F. Airnow.gov has
orange area (unhealthy for sensitive groups) today in the Wabash
river valley). Air quality alerts are in effect east of IL over
Indiana through this evening. Muggy lows tonight in the mid 70s
with some lower 70s near the Indiana border.

A 595 dm 500 mb high drifts northward over the mid Atlantic States
on Monday with some deeper gulf moisture lifting into parts of
central and especially east central and southeast IL by Monday
afternoon. This to develop isolated showers/thunderstorms Monday
afternoon with best chances near the Wabash river valley. Breezy
south to SSW winds bring another hot and humid day with highs in
the mid 90s and afternoon heat indices of 100-105F. This will be
close to heat advisory criteria of 105F and heat headlines may
eventually be needed for Monday afternoon plus depending on
duration and intensity of this weeks heat wave. Heat watches have
been posted in Ohio, eastern Indiana and southern half of lower MI
Monday afternoon thru Friday. Isolated convection to diminish in
southeast IL after sunset Monday evening. Muggy lows in the mid
70s Monday night across the CWA.

The strong subtropical ridge builds over the mid Atlantic states
and into New England on Tuesday and continues to stream moisture
from the western gulf of Mexico into IL. Diurnally driven
isolated convection expected again Tue afternoon and looks to be a
bit more coverage over CWA on that day. More cumulus clouds Tue
keeps temps a few degrees cooler than Monday with highs in the
lower 90s and afternoon heat indices in mid to upper 90s, and near
100F nw of the IL river where more sunshine expected Tue. Lows
Tue night in the low to mid 70s, with isolated convection
dissipating around sunset.

The 500 mb high strengthens to around 600 meters near NJ and
southern New England coast by Wed/Thu while riding back into IL
with 500 mb heights rising above 594 meters over CWA on Thu.
Isolated convection chances on Wed afternoon appear to be more
focused nw of I-55 and mainly nw of the IL river. Highs Wed 90-95F
and mid 90s on Thu and Fri and peak heat indices of 95-100F and
possibly getting above 100F on Thu and Fri. The strong upper
level ridge back into IL to keep the frontal boundary nw of IL
late this week along with better chances of convection.

Extended models show the subtropical ridge still affecting central
and southeast IL on Saturday and then retreating se on Sunday as a
weak trof digs over the northern states. Still differences with
models that far out on how this evolves but consensus has 20-30%
pops arriving Sat afternoon and Sat night (highest pops northern
CWA) and 30-40% pops next Sunday and temps starting to cool a few
degrees over central IL.

07

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1131 PM CDT Sat Jun 15 2024

Showers/storms west of the Mississippi River are expected to
largely track northwest of KPIA early Sunday morning, but may be
close enough to produce some brief ceilings around 5,000 feet
there. Overall, VFR conditions will be the rule the next 24
hours. Winds turn southerly and increase to 10-15 knots early
Sunday morning, and a few gusts near 20 knots or so can`t be ruled
out. Winds should drop off around sunset.

Geelhart

&&

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

&&

$$