Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

633
FXUS63 KILX 221100
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
500 AM CST Sat Feb 22 2025

.KEY MESSAGES...

- Temperatures steadily warm into early next week, with highs
  reaching the 50s Monday through Wednesday, which is about 10
  degrees above normal for late February.

- There is a low chance (20-30%) for light rain Monday night north
  of I-70, with a better chance (30-50%) for light rain showers
  across central/se IL on Wednesday and Wednesday evening as a
  cold front moves through.

&&

.DISCUSSION...
Issued at 300 AM CST Sat Feb 22 2025

The 09Z/3 am surface map shows 1035 mb modified arctic high
pressure over WV and ridging sw across the Ohio river valley and
into the mid MS river valley and to northeast Texas. A weak
positive titled upper level trof was over central MO into
northeast OK and spreading some mid/high clouds into areas south
of I-72 past few hours. Broken to overcast stratocumulus clouds
(bases 4-7k ft) was over sw half of MO into AR. Cold temperatures
were in the teens over CWA with Galesburg down to 10F (Wind chill
2 below). Wind chills were mostly in the single digits from
Quincy to Decatur to Mattoon north.

Expansive area of high pressure to drift off the NC coast during
this afternoon while ridging westward across the Gulf Coast states
into east Texas. Meanwhile the weak upper level trof to track
eastward into the mid MS river valley by mid morning and into the
central Appalachians by mid afternoon. The mid/high clouds over
southern half of CWA early this morning to diminish during
mid/late morning from west to east as trof passes by to our south.
Ample sunshine expected across CWA this afternoon and will be the
3rd consecutive day with a fair amount of sunshine over central
IL. Mixing up to 2.5-3k ft this afternoon supports sw wind gusts
to 18-24 mph over central IL, and lower in southeast IL. Highs in
the mid 30s over central IL, and will be a week since last
Saturday that much of central IL last got above freezing.

Fair skies tonight, though some increasing mid/high clouds from
the nw late especially from I-74 north as next upper level trof
moves se into the upper MS river valley. Lows in the lower 20s
with some upper teens possible near the Indiana border. The short
wave trof passing to our north on Sunday to bring a period of
partly to mostly cloudy skies to central IL Sunday morning and
trending mostly sunny during Sunday afternoon. A stronger southern
stream system affects the lower MS river valley Sunday keeping
its rain south of TN. SW winds continue warming Sunday with highs
in the mid to upper 40s.

IL remains in a WNW upper level flow early next week and stays
between systems to our north and south on Sunday night and Monday
with continued warming. Clouds increase overnight Sunday night
with milder lows in the lower 30s, and early February was last
time we had lows that mild. Partly to mostly cloudy skies Monday
with breezy sw winds gusting 20-30 mph. Mild highs in the mid 50s
with upper 50s possible from Springfield west/sw.

A northern stream short wave off Pacific Northwest to track into
the upper MS river valley by sunset Monday, and bring a weak cold
front se through IL during overnight Mon night. NBM continues low
pops (20-30%) north of I-70 Mon night and qpf amounts less than a
tenth inch if they occur. GFS and GEM models keeps its qpf north
of central IL, while Ecmwf has qpf over much of CWA Monday night.
Lows Mon night in the mid to upper 30s. Partly to mostly sunny
skies return on Tue with mild highs in the lower to mid 50s
central IL (coolest north of I-74) and upper 50s in southeast IL.
WNW winds on Tue but more of a Pacific air mass versus Canadian
air mass behind the cold front that passes through overnight Mon
night.

A stronger northern stream short wave dives down into IL on Wed
with its cold front pushing se through area Wed afternoon. NBM
pops are still in the 30-50% range Wed and Wed evening (slight
pops se IL Wed morning and across area overnight Wed night into
Thu morning. Breezy sw winds ahead of the front Wed keeps mild
temps in the 50s (lower 50s northern CWA and upper 50s se IL). The
Gulf moisture is still cutoff off from this system to qpf amounts
remain fairly light around tenth inch or less with higher qpf east
and se of IL. Breezy nw winds on Thu with cooler highs in the
upper 40s to near 50F, which is still a bit above normal. GFS,
Ecmwf and GEM models continue to show a deepening upper level
trof into the eastern US Thu and could keep more clouds around GFS
and Ecmwf even show light qpf Thu afternoon/evening. Strong upper
level trof shifts east toward the Atlantic Coast Friday with IL
in a NW mid/upper level flow and still having highs in the upper
40s/lower 50s. Strong low pressure moving into the northern Great
Lakes Fri night into next Sat to push a cold front se through IL
by Sat morning, with temps trending cooler during next weekend.

The Climate Prediction Center (CPC) 8-14 Day Outlook for March
1-7th has 40-45% chance of below normal temperatures over central
and eastern IL and 50-70% chance below normal over central/eastern
Great Lakes and New England.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 500 AM CST Sat Feb 22 2025

Winds to be southwest through the forecast with a period of higher
speeds and gusts near 20 kt from late morning through late
afternoon. VFR skies with SCT mid level clouds.

25

&&

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

$$