Ottawa, Illinois Weather Forecast Discussion

788
FXUS63 KLOT 141701
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1201 PM CDT Sun Sep 14 2025
.KEY MESSAGES...
- Areas of fog this morning mainly outside of urban areas, some
  fog could be locally dense.
- Generally warm and dry conditions are expected through midweek.
- Temperatures turn more seasonable toward the end of the week
  with periodic shower and storm chances returning.
&&
.DISCUSSION...
Issued at 321 AM CDT Sun Sep 14 2025
Today through Saturday...
An upper ridge continues to build into the Great Lakes this
morning which has allowed cloud cover over northern IL and
northwest IN to scatter out. As a result temperatures have
fallen on par with our mid-60s dew points which is allowing fog
to develop across the area. While the most dense fog is
currently residing in southern WI (as of 250 AM), satellite
trends are showing the fog oozing into far northern IL.
Therefore, expect fog coverage to increase through daybreak,
especially near the IL-WI line and area river valleys, with some
localized pockets of sub-mile visibilities possible.
Fog will erode from sunrise through mid-morning leaving a sunny
and seasonably warm afternoon on tap. While temperatures in the
mid-80s are expected (upper 80s to near 90 possible near and
west of I-39), persistent easterly winds today will keep
readings notably cooler within a few miles of the lake where
highs look to top out in the mid-70s to near 80. Another clear
night is expected tonight with temperatures cooling into the low
to mid-60s, but the lowering dew points should limit any fog
development.
Heading into the work week, the previously advertised REX block
upper pattern is expected to remain in place with ridging over
the Great Lakes and troughing over the central and southeast
CONUS. Therefore, tranquil weather conditions will prevail
through at least the middle of the week with temperatures
remaining above average as well. Given that winds on Monday
through Wednesday should favor more of a southeasterly direction
highs should be warmer than today with readings into the upper
80s to near 90 each afternoon. However, the light wind fields
should allow daily lake breezes to develop and usher in cooler
air near the lake where highs look to remain in the mid-70s to
lower 80s.
As we get into the later half of the week, guidance continues to
show the REX block breaking down as the central CONUS trough begins
to deepen and gets shoved east by several shortwaves ejecting
out of the Pacific northwest and trying to phase with it.
Despite the rather good agreement on the pattern evolution,
there remains notable difference in where exactly the deepening
trough and its associated shortwaves will track in relation to
northern IL and northwest IN which will obviously dictate the
coverage of any precipitation. That said, it seems reasonable
that chances for showers and thunderstorms should increase from
late Thursday through next weekend where 20-40% POPs have been
maintained. In addition to the rain chances, temperatures also
look to return towards more typical mid to late September
readings during this period.
Yack
&&
.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1201 PM CDT Sun Sep 14 2025
There are no significant aviation weather concerns anticipated
through the period.
High pressure will remain dominant across the Great Lakes region
through the period. This will continue to foster light easterly
winds and overall quiet weather conditions. Accordingly, aside
from a low (20-30%) chance for a couple hour period of MVFR
VSBYs in BR late tonight at RFD, VFR conditions are anticipated
through the period.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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