683
FXUS63 KDVN 242332
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
632 PM CDT Fri May 24 2024

.KEY MESSAGES...

- Strong to severe storms are possible through early evening as a cold
front moves through the area.

- Another round of strong to severe storms are expected late
  Saturday night into Sunday.

- Northwest flow developing after the weekend will bring
  seasonal temperatures but the active weather pattern will
  continue.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 257 PM CDT Fri May 24 2024

The cold front in central Iowa will move east during the late
afternoon and evening hours. Ahead of the front scattered
thunderstorms will be seen with the potential for severe storms.

The better severe risk generally looks to be along and south of a
line from Ottumwa, IA to Galesburg, IL. The primary risks look to be
damaging winds and hail. However, given the numerous boundaries from
the earlier storms, an isolated tornado cannot be ruled out.

The overall rain and severe risk will quickly come to an end once
the cold front moves through the area. Right now is appears the cold
front will be very close to the Mississippi by 7 PM with it east of
the area by 10-11 PM. Dry conditions will be seen after midnight.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 257 PM CDT Fri May 24 2024

Saturday night through Sunday night
Assessment...medium to high confidence on seeing thunderstorms.
Medium confidence for severe storms.

This time period will be interesting as what occurs Saturday night
will impact subsequent storm development Sunday afternoon.

Late Saturday night a respectable upper level disturbance in
combination with a strengthening surface low will likely result in
an organized thunderstorm complex moving into eastern Iowa and then
east of the Mississippi Sunday morning. Right now (as a rough
estimate) there may be a 35-40 percent chance that this storm
complex may produce severe storms.

Boundaries left over from this storm complex combined with strong
differential heating Sunday afternoon will result in another round
of strong to severe storms developing that will continue into Sunday
evening before ending.

The current SPC enhanced outlook south of I-80 looks reasonable
given the questions of storm evolution. Hail and wind appear to be
the primary severe risks but a brief tornado cannot be ruled out.

After sunset Sunday, storms will slowly dissipate during the evening
hours with a few isolated storms lingering past midnight.

Monday through Tuesday
Assessment...medium confidence

The global models vary considerably on timing and strength of
features, but agree that an upper level disturbance will move
through the area that may or may not include a weak frontal boundary.

As a result of the differences in timing and feature strength, the
model consensus has 20-30 percent chance of pops for Monday, a dry
Monday night and then 15-25 percent chance pops for Tuesday.
Temperatures should be close to normal.

Tuesday night through Thursday
Assessment...high confidence

The model consensus has dry conditions for the area as an upper
level high moves across the area. Temperatures look to be near or
slightly above normal.

Thursday night and Friday
Assessment...low to medium confidence

The model consensus has a 20-30 percent chance for rain as an upper
level disturbance moves through the area.

However, there are disagreements regarding the timing of the
disturbance. Interestingly, the deterministic runs of the global
models are mainly dry. The respective ensembles on the other hand
have several members with some precipitation.

Overall moisture availability will be the key as to whether or not
precipitation occurs. If overall moisture is less than what is
depicted by the models then there is a very real possibility that
dry conditions would be seen.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 628 PM CDT Fri May 24 2024

Cold front should move east of the Mississippi by 02z/25 which
will bring an end to the SHRA/TSRA. Ahead of the front expect
VFR conditions outside of SHRA/TSRA with pockets of MVFR/IFR
mainly due to SHRA/TSRA. After 03z/25 VFR conditions will be
seen as high pressure builds into the Midwest.

&&

.HYDROLOGY...
Issued at 1025 PM CDT Thu May 23 2024

The flood warning for the North Skunk River near Sigourney has
been upgraded to Major flood category. Routed water from a
sparse data area upstream where the heaviest rain fell a few
days prior has led to a rapid rise in the last 6 hours and is
now above Major flood stage. The forecast calls for a crest of
24.5 feet by Friday afternoon, but there is uncertainty in the
amount of water that remains to move through the reach and the
crest may need to be further adjusted.

The Wapsipinicon River near DeWitt was upgraded to a Flood
warning. Major flood stage is being forecast based on routed
flow, and is supported in output from the Hydrologic Ensemble
Forecast Service Model Simulation (HEFS), which places high
confidence on reaching Major Flood stage (12.5 feet). The
forecast has gone up this evening with a crest now over 13 feet
next week. This fits near the most likely range from HEFS of
12.8-13.1 feet. Some attenuation is possible as the routed
flow moves through the river system, but at the same time there
will be additional rounds of rain Friday and Sunday of which
could total over 1 to 2 inches. There will likely be changes to
the forecast in the coming days as the rain lays out and the
extent of the routed flow is better known, so stay tuned!

Routed water and additional rain through the weekend is leading
to rises on most other tributary rivers and the mainstem of
the Mississippi, especially south. Flood warnings or watches
are in effect for portions of the Cedar, Iowa, Skunk and
southern sections of the Mississippi river so please refer to
the latest Flood Statements and Flood Warnings for details.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08
HYDROLOGY...McClure