695
FXUS63 KDVN 221904
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
204 PM CDT Wed May 22 2024

.KEY MESSAGES...

- Dry conditions for most today, with seasonable temperatures
  and comfortable humidity.

- Active weather returns by Friday and again early next week
  with increasing shower and thunderstorm chances. There is a
  Marginal Risk (level 1 of 5) for severe weather on Friday.

- The Cedar, Iowa, Skunk, and the Wapsi rivers are expected to
  rise with some sites going into flood in the next 3-4 days
  due to the recent 2-5 inch rainfall upstream.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 1205 PM CDT Wed May 22 2024

A beautiful early afternoon was unfolding across all of eastern
Iowa, northwest Illinois and far northeast Missouri; a nice
welcome after yesterday`s active weather. Skies featured mostly
sunny skies with temperatures as of noon ranging from the mid
60s to near 70. It was breezy as well with west to northwest
winds gusting around 20-30 MPH.

15z surface analysis showed a strong surface low just north of the
arrowhead of Minnesota, with high pressure in place across the
central Plains. The pressure gradient between the low and high was
rather tight and, along with deep boundary layer mixing, was
responsible for our gusty winds early this afternoon.

Over the next 24 hours, our weather will be influenced by the the
surface high as it slowly moves across the Plains into the mid-
Mississippi River Valley. Gusty winds will subside late this
afternoon and evening, becoming light & variable tonight into much
of Thursday. Skies will feature only a few clouds, allowing for more
of a diurnal swing to our temperatures compared to previous
days. Look for lows tonight in the low to mid 50s (some upper
40s possible in valleys and low-lying areas), with highs
Thursday recovering into the upper 70s to lower 80s ahead of
strengthening ridging aloft.

Will make note of a low chance of a shower or storm along and
north of the Hwy 30 corridor this afternoon with a lobe of CVA
moving through the area. However, this is low confidence given a
lack of moisture in place across the area.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 159 PM CDT Wed May 22 2024

Thursday night through Friday night...

Our next chance of showers and thunderstorms arrives early Friday
into the evening as a cold front moves across the Midwest. This will
be in tandem with a negatively tilted shortwave and increasing
diffluence aloft, increasing overall lift. Deep layer shear will be
high in the 35-50 kt range with CAPE climbing into the 1500-2500
J/kg range, increasing potential for organized convection. Storms
will also be capable of producing heavy rain as PWATs climb into the
1.25-1.50" range. Unfortunately, guidance is not in agreement of
timing of the front this far out, and confidence on pinpointing where
storms will fire is low. This is why there is a rather broad Level 1
(marginal) risk of severe thunderstorms for this period, which at
time includes all of the DVN CWA.

Saturday...

High pressure will provide a dry start to the holiday weekend. Look
for near normal highs in the low to mid 70s, and lows Saturday
morning in the upper 40s to mid 50s.

Saturday Night Through Memorial Day...

Active weather returns as we head into Memorial Day with several
shortwaves on track to move across the area. Ensembles including
the NBM paint higher chances (50-70%) Saturday night with good
agreement amongst deterministic guidance on more widespread
showers and storms. Exact details on storm hazards at this time
are low, though heavy rain is possible with a robust Gulf
connection and PWATs climbing above 1.50" across portions of the
area. Chances lower head into early next week but remain
persistent through Tuesday (30-50%). Expect more details in the
coming days.

With the potential for precipitation, temperatures look to hold
around or just below normal for Memorial Day.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1205 PM CDT Wed May 22 2024

VFR conditions are expected for the upcoming TAF period. Gusty
west to northwest winds around 20-25 kts will become light &
variable with high pressure moving in this evening.

&&

.HYDROLOGY...
Issued at 115 PM CDT Wed May 22 2024

Watch/Warning Changes this Morning:

Upgraded the North Skunk River at near Sigourney to Major flood and
added the English River at Kalona to a warning with a secondary
crest into Minor. Also went to a warning for minor flood category
for the Wapsi at Anamosa.

Discussion:

Rainfall in the past 24 to 36 hours was highest in the Iowa and
Skunk river basins near their headwaters where radar estimates and
automated gauges reported 2 to 5 inches. The Cedar and Wapsi also
received 1.5 to 3 inches in the upper portions of the basins.
Because of this, the Iowa River at Marengo and the Skunk River near
Sigourney have the best chances of reaching solid Moderate Flood by
the end of the week. In fact with a projected run-off boost, there
was enough confidence to upgrade the North Skunk to Major flood
category. But still the idea that these sites will likely see some
attenuation in the routed flow upstream and expect some changes to
the forecast in the coming days. Because of this, confidence is
lower at some other sites in reaching the currently modeled flood
crest and Flood Watches were either continued or held off for one
more shift to assess. A few examples are the potential crest into
the Major category on the Wapsi near De Witt, and maintain the watch
for the Cedar River at Conesville for now. Oakville on the Iowa
River may eventually need a watch with crest projections near the
flood stage by late Monday night.

&&

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

&&

$$

SHORT TERM...Speck
LONG TERM...Speck
AVIATION...Speck
HYDROLOGY...12