794
FXUS63 KLOT 031643
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1143 AM CDT Thu Oct 3 2024

.KEY MESSAGES...

- A period of scattered showers is possible late tonight into
  early Friday morning, though no significant rainfall is
  anticipated.

- While a series of cold fronts will move through the region
  through the weekend, at or above average temperatures are
  expected to prevail.

- Elevated risk for brush and field fires on Sunday due to dry
  and breezy conditions behind a cold front.

&&

.DISCUSSION...
Issued at 251 AM CDT Thu Oct 3 2024

Through Friday:

Sunny skies and light southerly winds are expected across most of
the area today in advance of an approaching cold front sliding
south across southern WI. This will thus foster another rather
pleasant day for the area as afternoon inland temperatures top out
well into the 70s. However, cooler (but still pleasant) conditions
will be developing through the afternoon along the northeastern
IL lakeshore areas as light winds promote the development and
inland progression of a lake breeze enhancement to the cold
front.

This afternoon`s cold front will settle southward into central
parts of IL and IN tonight as surface high pressure slides
eastward across the Upper Midwest. In the wake of the cold frontal
passage and to the south of the Upper Midwest high, a
strengthening surface pressure gradient is expected to drive a
period of breezy 10 to 20 mph) north-northeasterly winds tonight
into Friday morning. These winds should gradually ease through the
day on Friday as the center of the high slides across Lake
Michigan.

There are also increasing signals that a band of high based
showers will develop and shift southward across our area late
tonight in tandem with the passage of a mid-level impulse and an
associated generated band of low-to-mid level frontogenesis. This
certainly does not look to be a big rain maker for the area, as
the impulse will remain rather progressive. We will also have a
good amount of low-level dry air to overcome initially.
Nevertheless, it appears a period of scattered showers will move
across the area roughly between 4 am and 10 am Friday morning. We
have thus added a mention for scattered showers to the public
forecast. Fortunately, the threat of thunder will be low in our
area with this activity, though better chances will exist just to
our southwest across parts of southern IA and adjacent areas of
northern MO and west central IL.

The threat of rain showers will end by mid to late morning.
Thereafter, we are expecting decreasing cloud cover for the
afternoon. Northeasterly winds on Friday will favor cooler, but
still pleasant afternoon temperatures. Readings are expected to
rang from the upper 60s along the lakeshore, to the lower 70s
inland.

KJB


Friday Night through Wednesday:

High pressure will begin exiting to the east on the heels of a
potent mid-level wave across the far northern Great Plains by
Saturday. Southerly winds gusting to 30 mph will advect a ribbon
of 925 hPa temps of 20C+ amid mostly sunny skies, pushing max
temps into the low 80s. This will also result in a potentially
elevated fire weather day for portions of the area. This (and
expected poor RH recovery Saturday night) will set the stage for
heightened fire weather concerns on Sunday (see below).

Prominent forcing from the trough will likely remain to the
north Saturday night before a cold front crosses the area early
Sunday. Guidance has trended slightly south with precip, with
the edge of an EML plume possibly brushing northeast Illinois
and northwest Indiana. Precip still looks unlikely, but given
the potential for isolated strong elevated storms, have opted to
include some slight chance to low-end chance PoPs late Saturday
night.

The potential for a critical fire weather day for brush and
field fires continues to increase on Sunday as post-frontal
westerly winds gusting 20-30mph usher in a very dry airmass
behind the cold front. Have continued to lower NBM dew points by
several degrees behind the front, with forecast RH values
solidly 25-30% across much of the forecast area. After the past
couple dry days and little to no rain for the past week, RAWS
data indicates fine fuels have exhibited substantial drying.
With harvesting also underway, the spread of brush and field
fires will be of increased concern.

Appreciable rain looks unlikely next week with sprawling high
pressure being replaced by a stout mid-level ridge mid to late
week. Temps will run near normal to above normal through this
period.

Kluber

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1142 AM CDT Thu Oct 3 2024

The only aviation weather concerns are timing a lake breeze wind
shift at the Chicago-area terminals this afternoon, and a low
potential for a few sprinkles/light showers early Friday
morning.

Light south-southwesterly winds will turn northeasterly with the
passage of a lake breeze this afternoon at the Chicago-area
sites. A reinforcing/secondary cold front will then move across
the region this evening and overnight with some northeasterly
breezes, thickening cloud cover, and a small chance (20-30%) for
a few light showers or sprinkles through about mid-morning
Friday. Any thunder threat looks to remain mainly south and west
of the c90 TRACON. VFR conditions and northeast winds will then
prevail through the rest of the TAF period.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 3 AM to 1 PM CDT Friday for the IL
     and IN nearshore waters.

&&

$$

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