696
FXUS63 KILX 101508
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1008 AM CDT Wed Jul 10 2024

.KEY MESSAGES...

- Heat and humidity will build back into the region this weekend
  into early next work week, with a greater than 70% chance for heat
  indices over 100 degrees Sunday west of I-55 and area-wide on
  Monday. This would increase the risk for heat-related illness in
  vulnerable populations and those attempting strenuous
  activities outdoors.

- Sporadic chances (generally 20-30%) for thunderstorms will
  exist this evening through the weekend. While severe weather is
  not expected through Thursday, severe potential becomes more
  uncertain Friday and beyond.

&&

.UPDATE...
Issued at 1008 AM CDT Wed Jul 10 2024

Fairly tranquil across the area as opposed to this time yesterday,
with mostly sunny skies and temperatures in the mid to upper 70s.
Main concern today is with scattered convection developing, as a
shortwave swings out of Iowa. Morning high-res models do show a
band of showers/storms forming in northeast Illinois along a weak
boundary/lake breeze which may approach the I-74 corridor toward
mid afternoon. However, activity with the shortwave should begin
crossing the Iowa border toward 5-6 pm and spread southeast.
Latest SPC Day1 outlook introduced a level 1 severe risk knocking
on our doorstep, though the severe activity should be pulse-like
and storms arrive in our area in a more inopportune time frame.

Recent updates focused on updating precipitation trends.
Temperature still look on track for highs in the lower 80s.

Geelhart


&&

.DISCUSSION...
Issued at 151 AM CDT Wed Jul 10 2024

The back edge of an area of rain continues to lift through the
region this morning as the remnant circulation from post-tropical
Beryl lifts northeast across extreme eastern IL and western IN.
This should clear the ILX CWA in just a few hours, and we`ll
likely be able to end the Flood Watch early. However, around this
time gusty northwest winds are expected to materialize across
areas near and east of I-57 - strongest in Vermilion and Edgar
Counties. Global models continue to advertise peak gusts around
30-35 mph, while CAMs (maybe due to better resolution of boundary
layer processes?) suggest a brief window of 40-50+ mph gusts near
the IN/IL border between 4 and 10am. Even though the CAMs may be
overdoing things, trees in full leaf and wet soils suggest that,
if winds reach the HREF mean of 45 mph, they perhaps would result
in some localized tree damage. We`ll continue to highlight this
through the SPS and graphics for most areas east of I-57 but a
Wind Advisory for Vermilion and Edgar Counties; we`ll be closely
monitoring observations to see whether this advisory might need to
be expanded to include more counties (chiefly Champaign).

Later this afternoon and evening, a piece of mid level energy will
dive toward the region from the northwest, bringing a 30% chance for
showers and thunderstorms after roughly 5 pm. Steep low level lapse
rates contributing to 1000-1500 J/kg (per HREF mean, which is
perhaps on the low side, if anything) SBCAPE will result in some
gusty (locally surpassing 40 mph) surface winds from the feistier
cells, though these storms should be shallow and hence won`t be hail
or prolific lightning producers. In other news, high res guidance
continues to climb for forecast highs, with the 00z HRRR now
bringing highs to the 85 to 87 degF range across areas west of the
IL River. This could be overdone given evapotranspiration after the
recent rains (which maintains more moist low levels and hence
shallower mixing), but even so it`ll be warm and muggy enough to
feel uncomfortable during the afternoon and evening ahead of any
showers/storms.

Tomorrow, it`s looking like subsidence behind the shortwave
responsible for this evening/tonight`s storms will help limit storm
development, though we can`t promise a clear day. Like HREF`s
mean, NAM forecast soundings show around 1000 J/kg of SBCAPE
developing during the afternoon when once again steep low level
lapse rates and abundant dry mid level air could foster some gusty
winds from the strongest cells, but, like today, the risk for
severe weather is going to be low (less than 5%).

Friday through the weekend, a ridge will slowly expand into the
region from the west, while subtle shortwave disturbances rippling
along its periphery will keep precip chances around. We`ll have to
watch for severe potential with these storms, particularly any that
get going in the afternoon and consequently have favorable
environmental low-level mixing to bring strong winds to the surface.
At this time, however, pinning down the timing and precise location
when and where severe weather will occur Friday night-Sunday is like
scoring a darts` bullseye blindfolded. This should get easier as
time goes on, but in general these MCSs are not easy to predict, as
each one will require a boundary on which to form, which would be
laid out by prior convection.

Outside of storms, it`ll be quite warm by Sunday and Monday when
surface dew points are forecast to climb into the mid 70s to 80+
and temps reach the low (to locally mid) 90s. A Heat Advisory, issued
when heat indices are expected to climb to 105 or higher, will
likely (60-80% chance) be needed to highlight this potential at
least one day Sunday-Tuesday, but it`s way too early to issue one
at this point given low confidence (for any given day) driven by
convective potential.

Bumgardner

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 544 AM CDT Wed Jul 10 2024

VFR conditions are expected to continue through the forecast
period, although HREF suggests 30-50% chances for MVFR ceilings
east of the IL River during the 12-15z (7-10am) time frame this
morning. Broken ceilings around 5kft are forecast to develop by
early afternoon as surface heating leads to widespread cu, with
widely scattered showers and storms arriving from the west after
around 22z/5pm. Confidence is quite low in whether lightning will
impact a terminal, but didn`t quite feel comfortable without a
PROB30 to highlight the risk, especially at SPI and PIA where the
chances seem highest.

Bumgardner

&&

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

$$