National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KILX 201751
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1251 PM CDT Sat Apr 20 2024

.KEY MESSAGES...

- Morning low temperatures through Monday will bottom out in the
  30s, posing a threat to sensitive vegetation.

- Our next chance for showers and storms arrives Monday night into
  Tuesday.

- A more active period with showers and storms is shaping up for
  late in the week into next weekend.

&&

.UPDATE...
Issued at 1040 AM CDT Sat Apr 20 2024

Updated the forecast with ending of freeze warning at 8 am over
Knox, Stark and Marshall counties. Updated sky cover and wind
grids along with central IL TAFs to increase the stratocumulus
cloud cover that is increasing/developing from the north. NW winds
have also increased a bit quicker during this morning with gusts
20-28 mph between 8-10 am. A northern stream mid/upper level trof
along the Quebec/Ontario province line extends back into WI/MI
this morning and is helping produce the scattered to broken
stratocumulus clouds with bases of 4-6k ft north of Lincoln.
Latest CAMs show these lower clouds drifting se over central and
se IL during this afternoon with sunny skies over central and
southern CWA becoming partly to mostly cloudy too for a time
during this afternoon and into mid evening. Temps currently in the
lower 40s in cloudier areas of northern CWA and upper 40s to near
50F in southeast IL, to only climb into the lower 50s central IL
and mid 50s southeast IL by mid afternoon. Areas north of Peoria
will struggle to reach 50F and breezy nw winds gusting 20-30 mph
to make it feel cooler again today.

07

&&

.DISCUSSION...
Issued at 305 AM CDT Sat Apr 20 2024

A ~1034 mb surface high is centered over the northern Plains early
this morning with surface ridging extending eastward into the
Midwest states. A subtle trough axis has crossed over into Indiana,
with northwest winds turning light on the backside of that. Mid-
level clouds have largely scattered out, setting the stage for
decent radiational cooling the remainder of this morning.
Temperatures as of 3 am range from the middle 30s to 40s with the
coolest values from Galesburg to Lacon. Temperatures should drop a
few more degrees through about sunrise, allowing some patchy frost
to form mainly north of I-72. A Freeze Warning remains in effect for
Knox, Marshall, and Stark counties where the HREF has 70%+
probabilities for 32 degree temperatures or lower.

The surface high will sink into the central Plains today, keeping
things dry and cool once again. A few subtle shortwaves will spread
low to mid-level moisture across the area this afternoon, turning
things partly cloudy. High temperatures will only be in the low to
middle 50s, which is about 10-15 degrees cooler than normal. A
better setup for efficient radiational cooling is expected tonight
as the pressure gradient slackens with the surface high nearing
closer. Some lingering moisture/clouds will be present to start the
night, but should thin out and sag south by or shortly after
midnight. Lows tonight will be the coldest of the weekend with
temperatures looking to bottom out in the 30s. Widespread frost will
likely develop once clouds exit, posing a threat to any sensitive
vegetation. Frost and Freeze headlines will be needed tonight and
possibly again Sunday night. Precautions should be taken to protect
any vegetation that may become damaged from the cold.

The surface high shifts into the southeast US by the start of the
new week, with southerly return flow setting up on the backside of
it. Temperatures will rebound back to near normal values both Monday
and Tuesday before a brief midweek cool down. An area of low
pressure emanating from the Pacific Northwest will dive into the
Great Lakes Region, sending a cold front through the area Monday
night into Tuesday. Rain chances return with the frontal passage,
though lack of moisture should prevent widespread storms and severe
weather for that matter. A more active weather pattern looks to be
shaping up for late in the week/next weekend with longer range
guidance showing a powerful system bringing widespread showers and
storms to the central US.

NMA

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1250 PM CDT Sat Apr 20 2024

VFR conditions are forecast to prevail across the central Illinois
terminals through 18Z/1 pm Sunday. Mid/upper level trof pivoting
se through central IL this afternoon to bring broken stratocumulus
clouds with bases around 5k ft, and getting into DEC and CMI next
hour and into SPI during mid afternoon. These VFR clouds should
scatter out later this evening/early overnight. 1034 mb Canadian
high pressure near the MT/SD border continues to ridge into the
Central Plains and sw IL and is maintaining enough pressure
gradient to generate NW wind gusts 20-25 kts today. These winds to
diminish to 4-8 kts at WNW to NW direction. These winds pick up
toward 10 kts during mid/late Sunday morning with gusts 15-20 kts
possible by midday Sunday.

07

&&

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

$$