957
FXUS63 KDVN 100209
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
909 PM CDT Thu May 9 2024

.KEY MESSAGES...

- Showers will end from north to south this evening.

- Strong gusty winds are possible in thunderstorms Friday
  night.

- Warm next week with increasing chances of shower and storms.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 221 PM CDT Thu May 9 2024

An elongated trough at 500 MB stretches from Colorado into the
Great Lakes and sits across eastern Iowa and northwest Illinois
early this afternoon. There are widespread to scattered rain
showers across the area early this afternoon. Isolated
thunderstorms have remained to the northwest of the area.
Temperatures across the area are in the upper 50s to lower 60s.

The elongated trough is forecast to sink south of the area
tonight bring rain to an end from north to south between 7 PM
and 1 AM. Im the wake of this storm system, the flow aloft will
become northwesterly with shortwave ridging building into the
area Thursday night into Friday morning. This will bring quiet
weather to the area during that period. The only fly in the
ointment is that models do show lots of low level moisture in
the area. The question is will there be enough for patchy fog or
maybe light drizzle across the area. This will be dependent on
how much clearing occurs tonight. Low temperatures on Friday
morning will be in the mid to upper 40s across the area. High
temperatures on Friday will be in the mid to upper 60s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 221 PM CDT Thu May 9 2024

Friday night: Northwest flow aloft across the area as a strong
shortwave troughs digs from the Upper Midwest into eastern Iowa
and northwest Illinois late Friday afternoon into Friday
evening. This will also bring a cold front across the area
Friday night. Model soundings ahead of this wave show limited
instability with inverted V forecast soundings. Models show a
line of scattered line of showers and storms developing to our
northwest and giving southeastward across the area Friday night.
Inverted V soundings coupled with less moisture across the area
indicate that gusty winds will be the main threat. Severe
weather is not anticipated at this time.

Saturday: A very pleasant day is in store weak high pressure
building into the area. Highs will be around 70.

Sunday through Wednesday: Active period again with periodic
rounds of showers and thunderstorms as another deep trough
comes out of the Rockies and into the middle of the country.
However, way too early to determine severe threats or rainfall
amounts. Highs will be well into the 70s to around 80.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 625 PM CDT Thu May 9 2024

Upper low moving across eastern Iowa into northern Illinois will
keep scattered SHRA through at least 06z/10 and possibly to
near 12z/10. Conditions vary from IFR to VFR with VFR/MVFR being
predominate. Overall conditions through 12z/10 will be mainly
MVFR/VFR as the SHRA end. After 12z/10 the widespread MVFR/VFR
conditions will slowly improve to VFR as the upper low slowly
moves east into the Great Lakes.

&&

.HYDROLOGY...
Issued at 846 PM CDT Thu May 9 2024

Changes...

The flood watch for the Wapsipinicon River near De Witt
has been changed to a flood warning.

Discussion:

The Cedar, Iowa and Wapsipinicon Rivers continue to rise as a
result of the rainfall over the past 30 hours. The forecast for
De Witt has not changed much over the past 24 hours, thus
confidence has increased that it will reach flood stage within
the next 24 hours.

The overall situation with the Cedar and Iowa Rivers is more
uncertain. While there is a better accounting of the overall
runoff compared to 24 hours ago, the forecast for Marengo on the
Iowa river is just barely above flood stage. Since the flood
crest will gradually attenuate due to gravity as it moves
downstream, there is a 30 to 40 percent chance that the crest at
Marengo may occur just below flood stage.

On the Cedar River near Conesville the flood crest will also
attenuate as it moves downstream. However, the crest is further
above flood stage which means there is a 50 percent chance of
reaching flood stage.

Rainfall over the next 72 hours and where it occurs will be the
deciding factor as to whether or not the Cedar and Iowa Rivers
will reach flood stage near Conesville and at Marengo
respectively. If the rainfall is lighter than expected then
river forecasts may be lowered. However, if rainfall is heavier
than expected then river forecasts may be raised.

&&

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

&&

$$

SHORT TERM...Cousins
LONG TERM...Haase
AVIATION...08
HYDROLOGY...08