018
FXUS63 KILX 281602
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1102 AM CDT Sun Apr 28 2024

.KEY MESSAGES...

- Flood Watch remains in effect for locations along and north of a
  Rushville to El Paso line through 10 am. Between 1 and 2 inches
  of rain has fallen since Saturday evening, and up to 1 inch of
  additional rain is possible by mid morning. This heavy rainfall
  may lead to flash flooding.

- Another round of strong to potentially severe thunderstorms
  expected this evening. Highest severe probabilities will be
  focused west of I-55.

- Breezy south winds will gust between 30 and 40 mph again today.
  There is a 30-60% chance of wind gusts greater than 40 mph this
  morning east of the IL river and north of I-70.

&&

.UPDATE...
Issued at 1102 AM CDT Sun Apr 28 2024

15z/10am surface analysis shows a 1004mb low over Kansas with a
cold front extending southward into Texas. A band of convection
ahead of the storm system driven largely by the nocturnal low-
level jet continues to rapidly dissipate along the Mississippi
River this morning. Models have a good handle on the current
trends and suggest a period of dry weather across central Illinois
through mid-afternoon before widely scattered showers/storms begin
to develop along/west of I-55 after 20z/3pm. As the cold front
slowly approaches from the west and the nocturnal jet once again
strengthens after dark, showers and thunderstorms will become more
widespread across the Illinois River Valley this evening...with
the convection spreading eastward across all of central Illinois
overnight. Severe weather risk looks to remain low given only
modest MUCAPEs of 1000J/kg or less: however, a few of the cells
could produce gusty winds/hail west of I-55 through midnight.

Barnes

&&

.DISCUSSION...
Issued at 400 AM CDT Sun Apr 28 2024

Large MCS affected parts of central and nw IL since Saturday
evening brought a few strong to severe storms Sat evening along
with heavy rains to areas from I-55 nw where some areas had 1 to 2
inches with locally 2-3 inch amounts over the IL river valley.
Continued the flood watch until 10 am from Schuyler, Mason,
Tazewell and Woodford counties nw where up to an additional 1 inch
of rain possible before showers and thunderstorms diminish. Radar
loop does show a weakening trend of this convection as outflow
boundary has raced ahead of the convection and approaching Gibson
City, Decatur and Taylorville. South winds 8-18 mph and few gusts
18-28 mph was keeping mild temps in the 60s with Galesburg and
Macomb down to 59F.

Latest CAMs show convection diminishing over the IL river valley
by mid morning, and lasting longer over far NW CWA into late
morning. May be able to cancel the flood watch over the IL river
valley a few hours early if this weakening trend continues. Much
of area east of I-55 will be dry most of today along with breezy
south winds gusting back up to 30-40 mph. Warm highs ranging from
the mid 70s over nw CWA to 80-85F in southeast IL where more
sunshine possible.

1003 mb low pressure over north central KS to lift northeast
toward the upper MS river valley during overnight while pulling a
cold front eastward toward far west central IL by dawn Monday.
Around a 50 kt SSW to SW low level jet over IL tonight along with
PW values peaking 1.5-1.7 inches to likely develop another band of
shower and thunderstorms moving over the IL river valley this
evening and into eastern/se IL overnight. SPC day1 outlook
continues marginal risk of severe storms tonight, with slight risk
southwest of Macomb and Springfield for large hail and damaging
winds this evening. There is a 2% to less than 5% risk of
tornadoes west of highway 51. Instability is not as high today as
yesterday with CAPES less than 1000 j/kg, though wind shear
becomes stronger at 30-40 kts western CWA this afternoon and
evening. Lows overnight mostly in the lower 60s with mid 60s near
the Indiana border where rain chances arrive later tonight.

Low pressure to lift north of WI by late Mon afternoon and pulling
a weakening cold front eastward across IL. This shifts the greater
chances of showers and a few thunderstorms into eastern/se IL on
Monday. SPC day2 keeps marginal risk of severe storms Monday well
south of IL as instability is even weaker than today. Highs Monday
mostly in the lower 70s with breezy sw winds gusting 20-30 mph.
Have a chance of showers lingering in southeast IL Monday evening,
otherwise dry Monday night and Tuesday as weak high pressure
settles into the area. Nice weather on Tuesday with ample
sunshine, lighter winds and mild highs in the mid to upper 70s
along with drier dewpoints in the low to mid 50s. A good day for
outdoor activities.

Dry weather will be short lived unfortunately as a wx system off
the Pacific Northwest Coast tracks eastward into the upper MS
river valley by midnight Tue night. This brings a chance of
showers and isolated thunderstorms into the IL river valley Tue
evening and into rest of central IL overnight Tue night, while
southeast IL se of I-70 mostly stays dry Tue night. SPC Day3
outlook has marginal to slight risk of severe storms Tue
afternoon and Tue evening west of IL over central/western Iowa and
nw MO. Briefly dry over CWA Wed morning as the northern stream
system exits. But quickly on its heels is a disturbance ejecting
out of the central high plains with a warm front lifting northward
into central IL Wed afternoon. This will bring more chances of
showers and thunderstorms from Wed afternoon into Wed night. A
better chance of convection on Thu and Thu night and diminishing
from the west during Friday as cold front pushes eastward over IL.
Will need to watch for risk of strong to possibly severe storms
from Wed afternoon into Thu evening though stronger instability
appears to be sw of central IL. Warm highs Wed and Thu in the
lower 80s over much of the area. Highs Fri in the upper 60s and
lower 70s in central IL and mid 70s in southeast IL.

The Climate Prediction Center (CPC) 6-10 Day outlook for May 3-7
has a 40-50% chance of above normal temperatures over central and
southeast IL, with a 35-40% chance of above normal precipitation.
So the mild and unsettled weather pattern looks to continue
through the 1st week of May.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 555 AM CDT Sun Apr 28 2024

An area of showers and isolated thunderstorms was along and nw of
the IL river early this morning, and the latest CAMs show this
convection near the PIA airport before diminishing later this
morning. MVFR ceilings and vsbys possible into mid morning over
central IL and even have 200 foot ceiling at BMI with 3 mile vsby.
Isolated convection possible later this afternoon and early
evening especially IL river valley. More widespread showers and a
few thunderstorms to spread eastward over central IL between
03Z-05Z and diminish from the west between 09-11Z with MVFR
conditions possible. As for winds, continued LLWS at DEC and CMI
until 13-14Z with 2k ft sw winds 45 kts. At the surface south to
SSW winds will increase to 16-23 kts between 13-15Z and gust 27-34
kts. SSW winds diminish some this evening but still gusting up to
around 25 kts tonight.

07

&&

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

$$