594
FXUS63 KDVN 190003
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
703 PM CDT Wed Sep 18 2024

.KEY MESSAGES...

- Above normal temperatures continue through Saturday.

- Active weather returns to the area Thursday through Monday.

- There is a SLGT risk of severe thunderstorms for portions of
  eastern IA Thursday late afternoon through the evening.

&&

.UPDATE...
Issued at 704 PM CDT Wed Sep 18 2024

Severe storms, especially supercells, are looking possible
tomorrow late afternoon into the evening before becoming more
linear/cluster in nature well after dark. The better forcing
during peak heating looks to be just west of our area so storms
should initiate west of the area. I am not convinced in the
timing that the CAMs suggest for us as they seem to be too late
with timing, as such we need to adjust potential threats from
this system. Soundings depict high bases with modest instability
at the sfc that becomes capped later in the day. They also
depict a well curved low level hodograph. While speed shear
isn`t all that impressive, the curvature of the soundings
strongly suggests low level rotation and overall supercell
nature of the storms. This is especially true as the deep layer
shear vector is perpendicular to the forcing, leading to
supercells. Large hail looks to be the main threat from these
storms. With the high bases, normally this will lead to a lower
tornado threat. However, if these supercell storms enter the
CWA as the LLJ ramps up we could see a quick 1 to 2 hour window
where a sneaky tornado threat could set up, especially across
the slight risk area. As such have adjusted messaging to include
this tornado.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 155 PM CDT Wed Sep 18 2024

Tonight: One more quiet night ahead with partly cloudy skies
with some cirrus clouds. Lows in the mid to upper 50s east to
the lower 60s west.

Thursday: After about 3 weeks of dry weather the pattern begins
to become much more active. We start out with a bang with SPC
highlighting portions of eastern IA in a SLGT risk (Level 2 of 5)
for portions of eastern IA, with a MRGL risk roughly to the MS
River. While isolated showers are possible on Thursday, the bulk
of the showers and storms, some severe, will arrive late in the
afternoon through the evening.

Severe potential:

A seasonably strong stacked low in southern Manitoba will send a
cold front southeast towards the forecast area. This will pull
very warm and increasing humid air into our area with highs in
the upper 80s to possibly lower 90s in a couple of spots.
Dewpoints will also increase well into the 60s ahead of the
front. Models show mid level winds from the west strengthening
to 40 kts during the afternoon and evening. Shear/instability
will be more than sufficient to support the potential for large
hail and damaging winds, with the activity weakening by late
evening with the loss of instability.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 155 PM CDT Wed Sep 18 2024

Active weather continues Friday through Monday 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 /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 651 PM CDT Wed Sep 18 2024

VFR conditions are expected through the next 24 hours. There is
a low chance, under 20% that showers could impact CID and DBQ in
the AM. Showers and storms will be weakening as they approach
the area so confidence in timing/occurrence is low.

&&

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

&&

$$

UPDATE...Gibbs
SHORT TERM...Haase
LONG TERM...Haase
AVIATION...Haase