From:  Brett Crapser <cmdrcody@nospampharowtcom.invalid>
Date:  08 Oct 2024 01:50:02 Hong Kong Time
Newsgroup:  news.alt119.net/chi.weather
Subject:  

Mon Oct 07 Meteorology for Chicago

NNTP-Posting-Host:  null

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1227 PM CDT Mon Oct 7 2024

KEY MESSAGES...

- Dry weather continues through the week, with temperatures
  trending above average through Friday.

- A shift towards more typical October temperatures looks to
  occur weekend into next week.

&&

DISCUSSION...
Issued at 252 AM CDT Mon Oct 7 2024

Through Tuesday:

Evening upper air analysis and current GOES water vapor imagery
depict a deep upper trough over eastern Canada and the
Northeastern U.S., and a broad upper ridge across the western
CONUS. The upper trough to our east will deepen further today,
as a strong mid-level short wave digs southeast across the
northern Great Lakes region. At the surface, 1026 mb high
pressure centered across the Plains and mid-Missouri Valley will
drift east-southeast into the mid- Mississippi Valley by this
evening. This pattern will sustain weak low-level cold advection
on dry northwest flow into the forecast area today, with mostly
sunny skies and lighter winds. It will be somewhat cooler this
afternoon, with high temps generally in the mid to upper 60s,
which is right around average for this time of year. Coolest
locations will likely be near the Lake Michigan shore in
northwest Indiana, where onshore winds will produce some modest
lake cooling. The dry air mass will again produce afternoon
relative humidity values in the 20-25 percent range which will
still result in a slightly elevated grass/brush fire threat,
though with lighter winds in the 10-15 mph, there is less danger
of rapid spreading as there was with the gusty winds yesterday.

The surface high will settle across the IA/MO/western IL region
tonight, with light winds and mainly clear skies allowing temps
to settle into the lower 40s in most areas away from the city
and into the upper 30s in our typically cooler locations. Could
be a little patchy frost in some of those coolest spots. Upper
pattern remains largely similar through Tuesday, though low
level thermal advection becomes more neutral which should
support a little moderation in daytime temperatures under
continued sunny skies. Afternoon highs Tuesday should reach the
lower 70s across much of the area, with a few mid-70s possible
across our western counties. A weak lake breeze may bring some
slight lake cooling later in the afternoon along both the IL/IN
shores.

Ratzer


Tuesday Night through Sunday:

The upper-trough, and associated upper low currently over the
Hudson Bay, is expected to remain stalled across the eastern
Great Lakes and northeast CONUS through weeks end. At the same
time, an upper- ridge is expected to build across the central
CONUS and slowly meander into the Upper Midwest and western
Great Lakes by Friday. Since our area is expected to be
sandwiched between these two features our stretch of tranquil
weather is expected to persist with virtually no chances for
rain over the next 7 days. Furthermore, the building ridge will
also gradually increase the mid- level warm advection through
the week which will keep temperatures in the near to above
normal category for early October with highs generally in the
mid-upper 70s and lows in the mid-40s and 50s. Though, some
locations could see highs nearing the 80 degree mark on Friday.

However, guidance does depict a couple of shortwave troughs
digging into the Great Lakes this weekend which should flatten
the aforementioned ridge and bring us a chance at some more
seasonable temperatures. While the first of these two shortwaves
is forecast to pass more into eastern MI and the northeast, it
does look to force a cold front through at least portions of
northern IL Friday night into the day on Saturday. Depending on
how far the front makes it on Saturday could result in a
gradient in temperatures across our area with locales north of
the front possibly seeing highs in the 60s while those to the
south see readings in the upper 70s to near 80. Though where
exactly this gradient occurs remains unclear at this range.
Regardless, the second and arguably strong of the two shortwaves
is forecast to pivot into the Great Lakes late in the day on
Saturday into the day on Sunday. This second wave should fully
push the aforementioned front through northern IL and northwest
IN and result in more typical October temperatures for Sunday
and into next week.

While guidance has been consistently trying to showcase some
rain occurring with the shortwaves and front, the trajectory for
moisture return ahead of these features looks rather limited
for our area. Therefore, I suspect that the bulk of any rainfall
that occurs Saturday and Sunday will likely end up more into
Lower MI and points east where the better moisture return is
forecast. So while our official forecast does have some slight
chance (15-20%) POPs in our eastern CWA, most areas should
remain dry through the weekend and into next week.

Yack

&&

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1227 PM CDT Mon Oct 7 2024

VFR conditions with passing cirrus are expected through the
period. WNW to NNW winds will remain around 10 knots or less.

Kluber

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 4 PM CDT this afternoon for Gary to
     Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$