000
FXUS63 KILX 161502
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1002 AM CDT Tue Apr 16 2024

.KEY MESSAGES...

- Today will be a warm and breezy day with south to southeasterly
  wind gusts of 30-40 mph.

- Showers and thunderstorms are expected (>80% chance) to develop
  from mid-afternoon and last through the early evening hours. A
  threat for severe weather exists from 5 to 10 PM today mainly
  west- northwest of I-55 with a threat for all hazards (damaging
  winds, damaging hail, tornadoes).

- After another round of showers and thunderstorms Thursday
  afternoon into early Friday morning, a cooler and drier pattern
  will arrive this weekend. Overnight lows could threaten any
  sensitive vegetation.

&&

.UPDATE...
Issued at 1001 AM CDT Tue Apr 16 2024

At 945am, the pronounced gradient in dewpoint temps - upper 30s to
mid 40s north, and upper 50s to low 60s south - suggests a warm
front located somewhere near I-74. Short term guidance agrees this
will lift quickly north of our area between now and early afternoon,
leaving the ILX CWA squarely in the unseasonably humid warm sector.
The LLJ will weaken this afternoon, but should still provide enough
moisture transport and (20-30 kt 0-6km bulk) shear to support
scattered thunderstorm development shifting into the area by 3pm,
with a few of the feistier updrafts perhaps conducive to
marginally severe hail given steep mid-level lapse rates. Aside
from some short term updates to the sky forecast - most of the
area now blanketed by prolific low clouds associated with the warm
front - things remain on track.

Bumgardner

&&

.DISCUSSION...
Issued at 304 AM CDT Tue Apr 16 2024

The convection that was expected to develop overnight has not
materialized yet. As the night progresses, it is seeming that we may
not see much early this morning. The HRRR (05z) is showing nothing
developing until this afternoon. The NAM 3km (00z) is showing some
scattered showers this am north of I-72. One of the biggest
uncertainties with today severe threat this afternoon/evening was
the early convection and its effect on the stability of the
environment. Seeing as the convection has failed to occur thus far,
the capping in the environment won`t be as strong.

The highs today will reach the low 80s with dewpoints in the low to
mid 60s. Winds out of the S/SE will aid in additional WAA and
moisture transport, essentially feeding the environment. Winds today
(S/SE) and tomorrow (W) could gust from 30-40 mph at times as the
tight pressure gradient moves across the state.

Taking a look at some forecast soundings from the NAMNest and HRRR
models, the low level lapse rates are steep (~8.5 C/km) by the late
afternoon. The CAPE profile is long, skinny, and is showing around
1000-1500 J/kg SBCAPE. PWAT values range 1.2-1.5. Long, skinny CAPE
with decent PWAT values and pretty saturated soil could result in
localized flash flooding across central Illinois. WPC has us in a
marginal risk for the excessive rainfall outlook for today.

The steep lapse rates, decent SBCAPE, warm/moist air, and bulk shear
values near 60 knots spells trouble for areas west & northwest of I-
55 this afternoon into the early overnight hours. Timing for the
showers and thunderstorms to begin around 5pm this evening. This
will be an all hazards possible event (damaging wind/hail, and
isolated tornadoes). SPC has the enhanced risk (level 3/5) still
clipping Knox to Schuyler counties, with a slight (level 2/5) for
the rest of the CWA for today. The 10% hatched tor risk still clip
Knox to Schuyler counties, along with the 30% hatched hail risk.
There is a 15% wind risk for all of central Illinois. The main
convection/showers should be out of the area by midnight, but some
isolated showers could linger a while longer. The cold front is
expected to pass through the CWA tomorrow morning.

SPC has removed most of the risk from central and southeastern
Illinois for tomorrow, but it still clips far eastern and
southeastern Illinois. This is for any lingering convection that
could be taking its time exiting tomorrow morning. After 7am, POPs
drop down to <20% for far eastern Illinois.

The second cold front of the week will make its move on Thursday.
This one isn`t expected to pack a punch precipitation wise, but
temperature wise is a different story. The above normal temperatures
are to come to an end on Thursday. The highs for the weekend will
drop below normal hovering in the upper 50s. Then will begin to warm
back up for the new week. Weather will be dry for the weekend, so
the big story will be the cold overnight temperatures that are
possible. Lows will drop down into the 30s for Friday night through
Monday morning. This could threaten any sensitive vegetation, as we
are now in the growing season.

Copple

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 558 AM CDT Tue Apr 16 2024

Conditions are expected to deteriorate as the day progresses. A
strong storm system is set to move through central Illinois today
bringing thunderstorms and gusty (30kt), southerly winds along with
it. The storms are timed to be at SPI by 23z and should exit CMI by
midnight. Ceilings are forecast to drop within stronger t`storms
that may move through this evening. Visbys could possibly drop as
well with any stronger rainfall within the showers/t`storms.

Copple

&&

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

$$