802
FXUS63 KDVN 181049
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
549 AM CDT Wed Sep 18 2024

.KEY MESSAGES...

- Above normal temperatures continue through Saturday.

- Active weather returns to the area Thursday night through
  early next week. Confidence remains low in the timing of rain
  chances.

- There is low risk of severe thunderstorms west of a Manchester
  to Fairfield Iowa line late Thursday afternoon into the
  evening.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 218 AM CDT Wed Sep 18 2024

Tranquil weather continues across eastern Iowa, northwest
Illinois and far northeast Missouri through Wednesday night.
Temperatures at 2 AM range from 53 degrees at Macomb to 61
degrees at Dubuque and Fairfield.

At 500 MB, we continue to sit west of ridging centered over the
eastern Great Lakes and a closed low anchored along the spine
of the central Appalachians. This will bring quiet weather
to the area through the period. High temperatures today will be
very similar to the last several days and generally be in the
mid to upper 80s. A 250 MB jet streak associated with a closed
500 MB low over Montana is forecast to move into Minnesota
Wednesday night and  may lead to increasing cloud cover
Wednesday night as showers and storms develop to our west and
move into central Iowa overnight. This will lead to slightly
warmer low temperatures Wednesday night with temperatures
dropping into the lower 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 218 AM CDT Wed Sep 18 2024

The breakdown of the synoptic pattern that has been with us for
several days begins on Thursday as the Rex Block to our east
finally weakens and moves eastward and ridging across Texas
rebounds northward across the Plains. This will be shortlived as
a disturbance passing to our north will bring the risk of
showers and storms to the area Thursday night. There is a
substantial instability gradient across Iowa with quickly decreasing
values as you to move into eastern Iowa and northwest Illinois.
Models also show deep layer shear of around 30 knots. If storms
develop to our west and move into our area they look to be
weakening as they move into the lower instability environment.
There are timing differences between the models and that could
play a role in the severe threat. For now, SPC has a Marginal or
level 1 out of 5 Risk of severe storms west of a Manchester to
Fairfield line. The main threats will be hail and damaging
winds.

Active weather continues Friday into early next with zonal west
to east flow across North America. There are two closed 500 MB
lows that will bring chances of showers and storms to the area
during this time period. The first passes to our north Saturday
into Saturday night. The second will lift from the southern
High Plains and cross the area Sunday into early next week.
Models continue to disagree on the timing and placement of these
storms and any interaction between the two late this weekend
into early next week. This continues to result in broad brush
POPS across the area through the period. This will also result
in cooler high temperatures especially Sunday into early next
week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 544 AM CDT Wed Sep 18 2024

There were no changes to the TAFs for this issuance. High
pressure continues to bring quiet weather to the area. Cirrus
is forecast to slowly spread across the area today.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Cousins
LONG TERM...Cousins
AVIATION...Cousins