Paw Paw, Illinois Weather Forecast Discussion

526
FXUS63 KLOT 080741
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
241 AM CDT Mon Sep 8 2025
.KEY MESSAGES...
- Gradual warming trend this week, with a return to normal
  temperatures midweek and above normal temperatures by the
  weekend.
&&
.DISCUSSION...
Issued at 240 AM CDT Mon Sep 8 2025
Through Tuesday:
Dry and gradually warming weather is expected into Tuesday, to
start the new week.
Early morning surface analysis depicts 1026 mb high pressure
ridge axis across IL/IN/MI, resulting in mainly clear skies and
calm or light/variable surface winds. Excellent conditions for
strong radiational cooling will likely allow for a few of our
typical cold spots (such as Rochelle) to dip into the upper 30s
again early this morning, and there may be some patch shallow
ground fog development in spots away from the Chicago metro
prior to sunrise.
A gradual warm-up is expected to begin today, as modest warm
advection develops downstream of a couple of mid-level short
waves approaching from the Plains and upper Midwest. This will
induce modest south-southwest winds in the 925-850 mb layer,
bringing warmer air into the region through the period. Low-
level thermal fields support highs in the low-mid 70s (warmest
northwest of I-55 across northern IL) by this afternoon under
mostly sunny skies, though light south-southeast surface winds
will support a weak southeasterly lake breeze along the IL shore
from Chicago northward. The only cloud cover of note is
expected to be some thin cirrus increasing from the west later
today, and perhaps a brief period of some patchy mid-level
clouds glancing northwest/far northern IL in association with
the stronger warm advection axis from IA into WI (currently seen
in GOES IR imagery over northeast IA). Other than a continued
increase in thin high clouds tonight, dry and quiet conditions
will continue, with light south-southeast winds and overnight
lows from the low-mid 50s in the Chicago area, to the low- mid
40s away from the metro.
The pair of mid-level short waves slowly move into the area
Tuesday, though the primary return moisture axis continues to be
focused well west and northwest of the forecast area, from the
Plains into the upper Mississippi Valley and northern Great
Lakes region. Other than some thicker mid/high level clouds
especially in the afternoon across the northwest half of the
forecast area, dry weather is expected to persist along with a
continued moderation in temperatures. With persistent warm
advection, low level thermal fields should support highs a
little closer to average for this time of year ranging from the
mid-upper 70s. Once again, a weak southeasterly lake breeze may
limit immediate shoreline areas to the lower 70s along the
Illinois Lake Michigan shore.
Ratzer
Tuesday Night through Sunday:
A low-amplitude wave shifting southeast from the western
Canadian prairie provinces will loosely phase with a small wave
over Wyoming today before becoming increasingly sheared over the
northern Great Lakes Tuesday into Wednesday. The southern wave
may experience some localized convective enhancement over the
central Great Plains this evening, but ultimately drift ENE
across the forecast area Tuesday night into Wednesday morning.
How quick the wave exits to the east late Tuesday night or
Wednesday will depend on the amount of phasing with the northern
wave. Modest mid-level ascent will be sufficient for the
generation of precip aloft, but with a rather dry airmass
located below 10kft, precip potential should be fairly low
during this time. Expectations are for isolated showers or
sprinkles over primarily the north half of the CWA, though most
locations should remain dry.
By late this week, the broader North American pattern will
transition to hybrid Omega/Rex blocking anchored by a strong
mid- level ridge centered southwest of Hudson Bay. Our area will
remain somewhat removed from the Canadian ridge, with a greater
focus on the trajectory of a high-latitude wave currently near
Anchorage to round the building ridge over central Canada and
track southward toward the Great Lakes region this weekend. This
could bring a period or two of showers and possibly a few
storms with a stalling cold front somewhere over the western
Great Lakes, though as can be expected with blocking in place,
timing and location of individual members from ensemble and
deterministic guidance show widely varying solutions. With that
said, the area will likely be on the periphery of the low-level
thermal ridge and stronger southwest flow and keep some or all
of the forecast area capped. This set-up would also yield a warm
weekend with highs well into the 80s to perhaps touching 90 in
some locations, though the regional dry spell over the past few
weeks and seasonal decline in evapotranspiration should keep dew
points out of more uncomfortable levels.
Kluber
&&
.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1219 AM CDT Mon Sep 8 2025
VFR conditions are expected through the period, though MIFG
cannot be ruled out for DPA/GYY/RFD early this morning. S winds
around 5 knots at ORD/MDW will shift SSW by sunrise, partly in
response to a strong land breeze developing offshore. Outlying
locations will remain calm through sunrise. SSW winds up to
around 10 knots are then expected today. A weak lake breeze will
likely wash out east of ORD/MDW early this evening, but a
broader SSE/SE wind shift will still occur by mid-evening and
persist well into the early morning hours on Tuesday.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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NWS LOT Office Area Forecast Discussion