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000
FXUS63 KILX 230446
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1146 PM CDT Mon Apr 22 2024

.KEY MESSAGES...

- Rain chances return late tonight into Tuesday, with a 20% chance
  for an isolated thunderstorms Tuesday afternoon. Chance of
  showers lingers in southeast IL early Tue evening.

- Brief cool down for midweek with frost/freeze potential possible
  northeast of Lincoln late Wed night/early Thu morning. There is
  a 60-80% chance for air temperatures to fall below 37 degrees
  at sunrise Thursday from I-74 northeast.

- A warmer, more humid and active weather pattern arrives Friday
  through next Monday. Several chances for showers and
  thunderstorms exist late Thursday night through Monday
  including the potential for severe weather and heavy rains.

&&

.UPDATE...
Issued at 859 PM CDT Mon Apr 22 2024

01z/8pm surface analysis shows a cold front extending from
western Lake Superior southwestward to Kansas. Moisture is slowly
on the increase ahead of the boundary: however, the initial
airmass is quite dry...as evidenced by an impressive dry layer
below 500mb on the 00z KILX upper air sounding. Even though
scattered radar echoes have developed on the regional radar
mosaic across eastern Iowa into west-central Illinois, think the
very dry boundary layer will keep any very light precip from
reaching the ground through at least midnight. Have therefore
dropped slight PoPs prior to 06z/1am. Forecast soundings slowly
moisten from the top-down late tonight, suggesting scattered
shower development along/north of I-72 toward dawn. Overnight low
temperatures will range from the middle 40s near the Indiana
border where clouds will be slowest to increase...to the lower
50s in the Illinois River Valley.

Barnes

&&

.DISCUSSION...
Issued at 300 PM CDT Mon Apr 22 2024

Mid afternoon surface map shows a cold front from nw MN thru
southeastern Nebraska to 1002 mb low pressure in east central CO.
Breezy sw winds with gusts 20-30 mph have brought in milder temps
in the mid 60s over much of CWA while low RH values down to 20-30%.
We have greened up over CWA with fuel moisture levels high enough
to limit fire danger. Special weather statement was issued for
northern IL for elevated fire danger. Breezy SSW to SW winds to
continue tonight and with increasing clouds will have milder lows
in the upper 40s and lower 50s. Shower chances to increase over
northern/nw CWA during overnight as wx system from the upper
Midwest approaches, with likely pops north of I-72 by dawn Tue.
Shower chances continue to increase from nw to se during Tue and
have isolated thunderstorms possible by midday and Tue afternoon.
Have lingering chances of showers early Tue evening in southeast
IL before system exits. Rainfall amounts have come up a bit to
0.30 to 0.60 inches with locally higher amounts from I-72 north.
PW values peak from 1-1.2 inches on Tuesday. Clouds and rain
showers to keep temps down some on Tue with highs in the upper 50s
and lower 60s with mid 60s from highway 50 south and over Knox and
Stark counties where clouds decrease soon during Tue afternoon.
Clouds continue to decrease from the nw during Tue night with
cooler lows in the lower 40s, with areas along and ne of I-74
around 40F and mid 40s south of I-70.

High pressure settles into the upper MS river valley on Wed and
ridges southward over IL by Wed afternoon with partly to mostly
sunny skies, but cool north to NE winds. Highs Wed in the upper
50s and lower 60s with Lawrenceville near 65F. 1030 mb high
pressure builds into the Great Lakes Wed night while ridging sw
into central IL and to provide fair skies and ENE winds under 10
mph with cool lows in the mid to upper 30s central and ne CWA and
lower 40s sw CWA and southeast IL. Could see some patchy frost ne
of Lincoln by dawn Thu. Upper level ridge builds eastward over the
MS river valley by Thu afternoon, with mostly sunny skies and
increasing se winds by Thu afternoon bringing milder highs in the
mid to upper 60s.

Unsettled weather pattern then evolves over the region from Thu
night through early next week as a couple wx systems eject ne into
the Midwest from a deepening upper level trof over the Rockies.
The 1st one to bring a round of showers and thunderstorms later
Thu night and Friday. Increasing instability Fri afternoon with
CAPES rising above 250 j/kg in west central IL and good wind
shear over 30 kts to give a risk of strong to severe storms,
though best chance of these will be over far western IL/MS river
valley and areas westward late Fri afternoon and Fri night. Highs
Fri in the low to mid 70s while dewpoints climb to around 60F Fri
afternoon with breezy south winds gusting 25-35 mph.

Higher CAPES advect eastward over much of CWA by Sat afternoon and
with higher instability and good wind shear, may be more a of
threat of strong to severe storms. Though less of a lifting
mechanism around area on Saturday though still have likely
chances of convection around over much of area on Saturday. Breezy
SW winds Saturday brings warmer highs in the upper 70s and lower
80s with dewpoints in the 60s. A cold front approaches IL late
Sunday with continued chance of showers and thunderstorms and then
best chances of convection shift into eastern/se IL by Monday. PW
values rise to 1-1.5 inches overnight Thu night and remain in
that range through Sunday night and over eastern IL yet on Monday
so may see 1-3 inches of rain with locally higher amounts from
overnight Thu night into Monday. There are timing differences with
this cold front so stayed close to blended forecast. Highs Sunday
in the upper 70s to around 80F and low to mid 70s on Monday,
warmest in southeast IL. Ecmwf, GEM and GFS models show qpf
shifting east of IL next Monday night and Tue.

07

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1146 PM CDT Mon Apr 22 2024

Latest CAMs continue to spread showers into KPIA by 11z...then
further southeast to the I-72 terminals by around 14z. Main aviation
forecast challenge will be the development of MVFR ceilings.
Strongest lift/deepest moisture appears to develop mostly north of
I-72...with HRRR consistently dropping cloud bases to MVFR for a
4-6 hour period from mid-morning through early afternoon. As the
showers drop southeast of the TAF sites, have raised ceilings back
to low VFR at KPIA by 19z...then by 21z at KSPI/KDEC/KCMI. The
surface cold front will pass through central Illinois by late
afternoon/early evening, perhaps accompanied by additional
scattered showers. Have therefore held on to VCSH until the
boundary passes and skies clear after the 01z-04z time period.
Winds will initially be SW at 10-15kt, then will veer to NW and
decrease to less than 10kt after FROPA Tuesday evening.

Barnes

&&

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

$$