Decatur, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

290
FXUS63 KILX 221146
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
546 AM CST Sun Dec 22 2024

.KEY MESSAGES...

- Breezy southerly winds will advect more seasonal temperatures
  back into the area today.

- Several chances for precipitation remain possible this week
  with a series of frontal systems, including a low chance (20%)
  for patchy freezing drizzle late tonight into early Monday
  morning.

- Temperatures will gradually warm through the week week, with
  highs by Thursday/Friday looking to be 10-15 degrees above
  normal for late December.

&&

.DISCUSSION...
Issued at 332 AM CST Sun Dec 22 2024

Surface analysis early this morning shows a ~1034 high centered over
the Great Lakes Region with ridging extending south from there into
the Gulf Coast states. The high will shift further east today,
allowing southerly return flow to ramp up over central Illinois.
Breezy south winds with gusts upwards of 20-25 mph will advect
warmer temperatures northward, expected to approach our seasonal
normals in the middle to upper 30s.

The pattern becomes more unsettled starting Monday as several
frontal systems bring precipitation chances through the week. The
first is tied to an upper shortwave trough that will swing toward
the Great Lakes Region on Monday. A surface low will track from the
Northern Plains into Wisconsin by midday Monday, sending a cold
front across the area by the afternoon hours. Strong warm air
advection ahead of the front late tonight into Monday morning will
develop, with forecast soundings showing the lowest 2 km of the
column becoming saturated beneath a stout warm nose. This paired
with upward omega/lift out ahead of the shortwave would suggest the
development of drizzle until better mid-level moisture arrives with
the front. Although temperatures will be non-diurnally warming
overnight, there is a low chance for a patchy freezing drizzle
near/north of I-74 into east-central Illinois where surface
temperatures will be near freezing.

The cold front will stall out near the Ohio Valley Monday night with
a slight chance for rain lingering in southeast Illinois. Several
chances for precipitation will be seen through the remainder of
the holiday week as a series of upper disturbances track from the
Southern Plains into the Ohio Valley Tuesday into Christmas Day,
Thursday night into Friday, and another by the weekend. There will
be dry periods outside of the main waves, but minor timing and
placement differences has kept the mention of at least low end
PoPs present through the extended period. Milder weather will
support rain as the primary precipitation type with these systems
as temperatures gradually climb each day, reaching the 50s by the
end of the week. Normal temperatures for this time of the year
typically sit in the middle to upper 30s which would be a +10-15
degree departure. Total precipitation amounts have increased from
previous forecasts with total amounts looking to range from
0.5-1", most of this coming with the more potent late week system.

NMA

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 546 AM CST Sun Dec 22 2024

Mid-level stratus should gradually erode later this morning with
high clouds filtering in behind it. South winds will be breezy
today, approaching gusts of 20-25 kts. Winds remain elevated
overnight as a low-level jet develops ahead of an approaching
system. There is a low chance (20%) for drizzle or patchy freezing
drizzle to develop at northern airfields after 09Z Monday morning,
but confidence remains too low to mention in the TAFs. If drizzle
does materialize, ceilings and visbys will likely fall to MVFR or
IFR.

NMA

&&

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

$$