199
FXUS63 KILX 041510
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1010 AM CDT Tue Jun 4 2024

.KEY MESSAGES...

- 2 rounds of storms and showers this afternoon into the overnight
  hours ahead of a passing cold front with another low threat for
  strong-to-severe storms.

- A brief dry period settles in before the potential for rain
  arrives again for the weekend (10-20% chance).

&&

.UPDATE...
Issued at 1010 AM CDT Tue Jun 4 2024

An upper low evident on 1430z/930am water vapor imagery over
northern Missouri will pivot northeastward...triggering increasing
rain chances as the day progresses. The airmass ahead of this
feature will be modestly unstable and weakly sheared, with SBCAPEs
progged to reach 1500-2000J/kg and 0-6km shear values of 25-30kt.
Given the enhanced lift provided by the low, showers and
thunderstorms will become more numerous by peak heating: however,
the overall severe weather risk will remain low. The 12z KILX
upper air sounding showed precipitable water of 1.41 and the NAM
suggest these values will rise into the 1.75-2.00 inch range this
afternoon...which is close to the 99th percentile for this time
of year. Since the atmosphere will be so heavily-laden with
moisture, think one of the greatest risks with any convection that
develops later today will be locally heavy downpours. Given ample
cloud cover and at least scattered thunderstorms, high temperatures
will be a few degrees cooler than yesterday...only reaching the
lower to middle 80s.

Barnes

&&

.DISCUSSION...
Issued at 250 AM CDT Tue Jun 4 2024

As a MCV passes through again today, more showers and thunderstorms
could pop up. Today, the shear looks healthier (25-35kts) than
yesterday. This could mean that the storms that do fire up could
live slightly longer. There is a threat of severe weather this
afternoon, with the main hazards being marginally severe hail and
locally damaging winds, but most storms will be of the typical
summer-time pop up storm genre. MCVs are known to be tricky and
could increase the severe threat. There is a 40-60% chance of
showers and thunderstorms this afternoon starting after 18z.
Coverage will be of the scattered nature for areas along and north
of I-70. SBCAPE values of 1500-2500 J/kg support the development of
these storms. The PWAT values this afternoon are 1.6-1.8, which
support that these showers/storms could produce locally heavy
downpours.

The first and second rounds appear to blend together around midnight
as the cold front enters the CWA from the west. The line of showers
and thunderstorms along the front will move through from 05z to 15z
tomorrow. Thunderstorm activity with this round may be limited due
to the convection earlier in the day, if the afternoon convection
pans out like the CAMs (NAM 3km, HRRR, ARW) are depicting. The
potential for a worked over environment to be in place could mean
that along the front there would only be stronger showers without
the presence of thunderstorms. As the line moves across central
Illinois, it breaks up as it passes the I-55 corridor. Many
locations east of I-57 could see no rain out of the overnight system
as it become more scattered.

Behind the cold front, we will see a short period of dry weather as
a high pressure builds over the region. Surface high temperatures
cool slightly but remain around the upper 70s. By Sunday, highs warm
back up to near or just above 80 degrees. There is a very small
chance for rain this weekend (saturday and Sunday), with POPs of 10-
20%, as MCSs are passing to our far south. There is the small chance
that one could drift just far enough north-northeast to affect
central and southeastern Illinois.

Copple

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 549 AM CDT Tue Jun 4 2024

To start out all sites will be VFR. By mid afternoon (20-22z), SH
and TS will move into the area along with some gustier winds out of
the south. Overnight tonight, a cold front will move through,
shifting the winds to out of the west and calming down. There is a
chance for showers and thunderstorms from this afternoon to tomorrow
morning until the cold front exits central Illinois. The exact
location and time for these showers/t`storms is uncertain, so a VCSH
has been carried through the TAF period. Ceilings will drop to MVFR
(PIA/SPI/BMI) or IFR (DEC/CMI) by tomorrow morning.

Copple

&&

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

$$